• Spring Boot 4.web开发


    web开发

    thymeleaf、web定制、容器定制
    代码地址
    ssh git@gitee.com:Ding_DangMao/learn-spring-bot.git

    1. 简介

    使用Spring Boot

    1. 创建 springboot应用,选中我们需要的模块。
    2. spring boot已经默认将这些场景配置好了,只需要在配置文件中指定少量配置就可以运行起来
    3. 编写自己业务代码

    自动配置原理?

    这个常见 spring boot帮我们配置了什么?能不能修改?能修改那些配置?能不能扩展?XXX

    XxxAutoConfiguration 帮我们给容器中自动配置组件
    XxxProperties 配置类来封装配置文件的内容

    2. spring boot静态资源的映射规则

    • spring boot的 mvc配置都在 WebMvcAutoConfiguration.java里面
    //添加资源映射 WebMvcAutoConfiguration类中【这个方法】
    public void addResourceHandlers(ResourceHandlerRegistry registry) {
    	if (!this.resourceProperties.isAddMappings()) {
    		logger.debug("Default resource handling disabled");
    	} else {
    		Integer cachePeriod = this.resourceProperties.getCachePeriod();
    		if (!registry.hasMappingForPattern("/webjars/**")) {
    			this.customizeResourceHandlerRegistration(registry.addResourceHandler(new String[]{"/webjars/**"}).addResourceLocations(new String[]{"classpath:/META-INF/resources/webjars/"}).setCachePeriod(cachePeriod));
    		}
    
    		String staticPathPattern = this.mvcProperties.getStaticPathPattern();
    		if (!registry.hasMappingForPattern(staticPathPattern)) {
    			this.customizeResourceHandlerRegistration(registry.addResourceHandler(new String[]{staticPathPattern}).addResourceLocations(this.resourceProperties.getStaticLocations()).setCachePeriod(cachePeriod));
    		}
    	}
    }
    ----------原理---------
    //ResourceProperties 可以设置静态资源有关的参数,缓存时间等。
    @ConfigurationProperties(
        prefix = "spring.resources",
        ignoreUnknownFields = false
    )
    public class ResourceProperties implements ResourceLoaderAware {}
    
    // /** 可以访问当前项目任何资源
    public String getStaticPathPattern() {
    	return this.staticPathPattern; // this.staticPathPattern = "/**";
    }
    
    public String[] getStaticLocations() {
    	return this.staticLocations;
    }
    this.staticLocations = RESOURCE_LOCATIONS;
    static {
    	RESOURCE_LOCATIONS = new String[CLASSPATH_RESOURCE_LOCATIONS.length + SERVLET_RESOURCE_LOCATIONS.length];
    	System.arraycopy(SERVLET_RESOURCE_LOCATIONS, 0, RESOURCE_LOCATIONS, 0, SERVLET_RESOURCE_LOCATIONS.length);
    	System.arraycopy(CLASSPATH_RESOURCE_LOCATIONS, 0, RESOURCE_LOCATIONS, SERVLET_RESOURCE_LOCATIONS.length, CLASSPATH_RESOURCE_LOCATIONS.length);
    }
    CLASSPATH_RESOURCE_LOCATIONS = new String[]{"classpath:/META-INF/resources/", "classpath:/resources/", "classpath:/static/", "classpath:/public/"};
    SERVLET_RESOURCE_LOCATIONS = new String[]{"/"};
    
    1. 所有 /webjars/** 的资源都去 classpath:/META-INF/resources/webjars/ 找资源;
      webjars:以 jar包的方式引入静态资源,
      image
      localhost:8080/webjars/jquery/3.3.1/jquery.js 拿到jquery文件
      	在访问的时候只需要写webjars下面资源的名称即可
          <!--引入 jquery-web-jar-->
          <dependency>
              <groupId>org.webjars</groupId>
              <artifactId>jquery</artifactId>
              <version>3.3.1</version>
          </dependency>
      
    2. /** 可以访问当前项目的任何资源,如果没人处理默认从【静态资源的文件夹】
      "classpath:/META-INF/resources/",
      "classpath:/resources/",
      "classpath:/static/",
      "classpath:/public/"
      "/" 当前项目的根路径
      
      localhost:8080/abc ===>去静态资源文件里面找abc
    3. 欢迎页映射,静态资源文件夹下的所有 index.html 页面,被 /** 映射。
      localhost:8080/ 默认找index页面
    //配置欢迎页映射 WebMvcAutoConfiguration类中【这个方法】
    @Bean
    public WebMvcAutoConfiguration.WelcomePageHandlerMapping welcomePageHandlerMapping(ResourceProperties resourceProperties) {
    	return new WebMvcAutoConfiguration.WelcomePageHandlerMapping(resourceProperties.getWelcomePage(), this.mvcProperties.getStaticPathPattern());
    }
    -----------原理------------
    public Resource getWelcomePage() {
    	String[] var1 = this.getStaticWelcomePageLocations();
    	int var2 = var1.length;
    	return null;
    }
    private String[] getStaticWelcomePageLocations() {
    	String[] result = new String[this.staticLocations.length];
    	//staticLocations 上面有
    	for(int i = 0; i < result.length; ++i) {
    		String location = this.staticLocations[i];
    		if (!location.endsWith("/")) {
    			location = location + "/";
    		}
    
    		result[i] = location + "index.html";
    	}
    	return result;
    }
    
    public String getStaticPathPattern() {
    	return this.staticPathPattern;//this.staticPathPattern = "/**";
    }
    
    1. 所有的 **/favicon.ioc 都是在静态资源文件下找
    //浏览器打开左上角的图标配置 WebMvcAutoConfiguration类中【这个方法】
    @Configuration
    @ConditionalOnProperty(
    	value = {"spring.mvc.favicon.enabled"},
    	matchIfMissing = true
    )
    public static class FaviconConfiguration {
    	private final ResourceProperties resourceProperties;
    
    	public FaviconConfiguration(ResourceProperties resourceProperties) {
    		this.resourceProperties = resourceProperties;
    	}
    
    	@Bean
    	public SimpleUrlHandlerMapping faviconHandlerMapping() {
    		SimpleUrlHandlerMapping mapping = new SimpleUrlHandlerMapping();
    		mapping.setOrder(-2147483647);
    		mapping.setUrlMap(Collections.singletonMap("**/favicon.ico", this.faviconRequestHandler()));
    		//所有 **/favicon.ico
    		return mapping;
    	}
    
    	@Bean
    	public ResourceHttpRequestHandler faviconRequestHandler() {
    		ResourceHttpRequestHandler requestHandler = new ResourceHttpRequestHandler();
    		requestHandler.setLocations(this.resourceProperties.getFaviconLocations());
    		return requestHandler;
    	}
    }
    ----------原理--------------
    List<Resource> getFaviconLocations() {
    	List<Resource> locations = new ArrayList(this.staticLocations.length + 1);
    }
    String[] staticLocations; //和上面一样,
    

    3. 模板引擎

    jsp,velocity,freemarker,thymeleaf
    image
    spring boot 推荐的 thymeleaf,语法简单,功能更强大

    3.1 引入 thymeleaf

    <!--引入thymeleaf 版本不用管,当前我引入的 springboot1.5.9默认版本2.1.6-->
    <dependency>
    	<groupId>org.springframework.boot</groupId>
    	<artifactId>spring-boot-starter-thymeleaf</artifactId>
    </dependency>
    <!--我们需要切换版本-->
    
    <properties> 顺序这个标签在上面
    	<!--主程序-->
    	<thymeleaf.version>3.0.11.RELEASE</thymeleaf.version>
    	<!--布局功能的支持程序  如果是:版本3主程序 layout2以上版本-->
    	<!--例如:thymeleaf2 和 layout1 适配  【layout2.0.0以上支持 thymeleaf3以上版本】-->
    	<thymeleaf-layout-dialect.version>2.3.0</thymeleaf-layout-dialect.version>
    </properties>
    

    3.2 thymeleaf 使用

    @ConfigurationProperties(
        prefix = "spring.thymeleaf"
    )
    public class ThymeleafProperties {
        private static final Charset DEFAULT_ENCODING = Charset.forName("UTF-8");
        private static final MimeType DEFAULT_CONTENT_TYPE = MimeType.valueOf("text/html");
        public static final String DEFAULT_PREFIX = "classpath:/templates/"; //默认的视图前缀
        public static final String DEFAULT_SUFFIX = ".html"; //默认的视图后缀
    	//只要我们把 html页面放在 /templates/,thymeleaf 就自动渲染了
        private boolean checkTemplate = true;
        private boolean checkTemplateLocation = true;
        private String prefix = "classpath:/templates/"; 
        private String suffix = ".html";	
        private String mode = "HTML5";
        private Charset encoding;
        private MimeType contentType;
        private boolean cache;
        private Integer templateResolverOrder;
        private String[] viewNames;
        private String[] excludedViewNames;
        private boolean enabled;
    }
    
    1. 导入 thymeleaf的名称空间
      <html lang="en" xmlns:th="http://www.thymeleaf.org">
      
    2. 使用 thymeleaf 语法
      <!DOCTYPE html>
      <html lang="en" xmlns:th="http://www.thymeleaf.org">
      <head>
      	<meta charset="UTF-8">
      	<title>Title</title>
      </head>
      <body>
      <h2>成功</h2>
      <!--th:text="" 将div里面的文本内容设置为 指定的值-->
      <div th:text="${hello}">
      	这是显示欢迎信息
      </div>
      </body>
      </html>
      

    3.3 语法规则

    1. th:text :改变当前元素里面的文本内容
      th :任意html属性,来替换原生属性的值
      image
    2. 我们能写的表达式
    Simple expressions: # 表达式语法
    	Variable Expressions: ${...}
    		1. 获取对象的属性,调用方法
    		2. 使用内置对象
    			#ctx : the context object.
    			#vars: the context variables.
    			#locale : the context locale.
    			#request : (only in Web Contexts) the HttpServletRequest object.
    			#response : (only in Web Contexts) the HttpServletResponse object.
    			#session : (only in Web Contexts) the HttpSession object.
    			#servletContext : (only in Web Contexts) the ServletContext object.
    			
    			$(session.size())
    		3. 内置的一些工具对象
    			#execInfo : information about the template being processed.
    			#messages : methods for obtaining externalized messages inside variables expressions, in the same way as they
    			would be obtained using #{…} syntax.
    			#uris : methods for escaping parts of URLs/URIs
    			Page 20 of 106
    			#conversions : methods for executing the configured conversion service (if any).
    			#dates : methods for java.util.Date objects: formatting, component extraction, etc.
    			#calendars : analogous to #dates , but for java.util.Calendar objects.
    			#numbers : methods for formatting numeric objects.
    			#strings : methods for String objects: contains, startsWith, prepending/appending, etc.
    			#objects : methods for objects in general.
    			#bools : methods for boolean evaluation.
    			#arrays : methods for arrays.
    			#lists : methods for lists.
    			#sets : methods for sets.
    			#maps : methods for maps.
    			#aggregates : methods for creating aggregates on arrays or collections.
    			#ids : methods for dealing with id attributes that might be repeated (for example, as a result of an iteration).
    			
    	Selection Variable Expressions: *{...} 选择表达式【和 ${}在功能上是一样的】
    		补充,配合 th:object=${session.user}
    		<div th:object="${session.user}">
    			<p>Name: <span th:text="*{firstName}">Sebastian</span>.</p>
    			<p>Surname: <span th:text="*{lastName}">Pepper</span>.</p>
    			<p>Nationality: <span th:text="*{nationality}">Saturn</span>.</p>
    		</div>
    		
    	Message Expressions: #{...} 获取国际化内容的
    	Link URL Expressions: @{...} 定义url连接的
    		@{/order/process(execId=${execId},execType='FAST')}
    		
    	Fragment Expressions: ~{...} 片段引用表达式
    		<div th:insert="~{commons :: main}">...</div>
    Literals 字面量
    	Text literals: 'one text' , 'Another one!' ,…
    	Number literals: 0 , 34 , 3.0 , 12.3 ,…
    	Boolean literals: true , false
    	Null literal: null
    	Literal tokens: one , sometext , main ,…
    Text operations: 文本操作
    	String concatenation: +
    	Literal substitutions: |The name is ${name}|
    Arithmetic operations: 数学运算
    	Binary operators: + , - , * , / , %
    	Minus sign (unary operator): -
    Boolean operations: boolean运算
    	Binary operators: and , or
    	Boolean negation (unary operator): ! , not
    Comparisons and equality: 比较运算
    	Comparators: > , < , >= , <= ( gt , lt , ge , le )
    	Equality operators: == , != ( eq , ne )
    Conditional operators: 条件运算(三元运算也支持)
    	If-then: (if) ? (then)
    	If-then-else: (if) ? (then) : (else)
    	Default: (value) ?: (defaultvalue)
    Special tokens: 特别的字符
    	No-Operation: _
    

    练习

    @Controller //代表当前类是一个控制器
    public class HelloController {
    
        @ResponseBody //hello 发送出去需要依赖 responseBody
        @RequestMapping("/hello") //处理请求
        public String Hello() {
            return "hello world";
        }
    
        /**
         * 查出一些数据,在页面展示
         *
         * @return
         */
        @RequestMapping("/success")
        public String success(Map<String, Object> map) {
            // classpath:/templates/
            map.put("hello", "<h1>你好</h1>");
            map.put("users", Arrays.asList("张三", "李四", "王五"));
            return "success";
        }
    }
    
    <!DOCTYPE html>
    <html lang="en" xmlns:th="http://www.thymeleaf.org">
    <head>
        <meta charset="UTF-8">
        <title>Title</title>
    </head>
    <body>
    <h2>成功</h2>
    <!--th:text="" 将div里面的文本内容设置为 指定的值-->
    <div th:text="${hello}" th:id="${hello}" th:clas="${hello}">
        这是显示欢迎信息
    </div>
    
    <hr>
    <div th:text="${hello}"></div>
    <div th:utext="${hello}"></div>
    <hr>
    <!-- th:each 每次遍历都会生成当前这个标签-->
    <h4 th:text="${user}" th:each="user:${users}"></h4>
    <hr>
    <!-- 英式符号写在里会转移,所以记录中文
    【【美元符{...}】】 ,双中括号,就是 th:text 会转义
    【(美元符{...})】 ,中括号小括号,就是 th:utext 不会转义
    -->
    <h4>
        <span th:each="user:${users}">[[${user}]]</span>
    </h4>
    
    </body>
    </html>
    

    image

    4. spring mvc自动配置

    地址 https://docs.spring.io/spring-boot/docs/2.5.6/reference/htmlsingle/#features.developing-web-applications.spring-mvc

    Spring MVC Auto-configuration
    Spring Boot 自动配置好了 springMVC
    以下是 spring boot对springMVC的默认配置

    • Inclusion of ContentNegotiatingViewResolver and BeanNameViewResolver beans.

      • 自动配置了 ViewResolver【视图解析器:根据方法的返回值的到视图对象 view】,视图对象决定如何渲染【转发重定向】
      • ContentNegotiatingViewResolver:组合所有的视图解析器的
      • 如何定制,我们可以自己给容器种添加一个视图解析器,自动的将其组合进来
    • Support for serving static resources, including support for WebJars (covered later in this document).

      • 静态资源文件夹路径,webjars
    • 自动注册了 Converter, GenericConverter, and Formatter beans.

      • Converter 转换器;public String hello(User user);类型转换使用 Converter
      • Formatter 格式化器;2017。12.17=Data;
        @Bean
        @ConditionalOnProperty(
            prefix = "spring.mvc",
            name = {"date-format"}//在文件中配置日期格式化规则
        )
        public Formatter<Date> dateFormatter() {
        	//日期格式化组件
            return new DateFormatter(this.mvcProperties.getDateFormat());
        }
        
        自己添加的格式化转换器,我们只需要放在容器中即可
    • Static Faviccon support (see below) favicon.ico

    • Support for HttpMessageConverters (covered later in this document).

      • HttpMessageConverters:springmvc用来转换 http请求和响应的:user-login
      • HttpMessageConverters 是从容器中确定的;底层就是获取所有的 httpMessageConverter
        自己给容器中添加 httpMessageConverter,只需要将自己的组件注册容器中【@Bean,@Component】
    • Automatic registration of MessageCodesResolver (covered later in this document).

      • 定义错误代码生成规则
    • Static index.html support. 静态首页访问的

    • Automatic use of a ConfigurableWebBindingInitializer bean (covered later in this document).

      • 我们也可以配置一个 ConfigurableWebBindingInitializer【它是从容器中拿的】来替换默认配置,添加到容器中
      • 初始化 WebDataBinder;请求数据 == JavaBean
    • spring-boot-autoconfigure-1.5.10.RELEASE.jar!orgspringframeworkoot autoconfigureweb 自动配置web的所有场景

    • If you want to keep those Spring Boot MVC customizations and make more MVC customizations (interceptors, formatters, view controllers, and other features), you can add your own @Configuration class of type WebMvcConfigurer but without @EnableWebMvc.

    • If you want to provide custom instances of RequestMappingHandlerMapping, RequestMappingHandlerAdapter, or ExceptionHandlerExceptionResolver, and still keep the Spring Boot MVC customizations, you can declare a bean of type WebMvcRegistrations and use it to provide custom instances of those components.

    • If you want to take complete control of Spring MVC, you can add your own @Configuration annotated with @EnableWebMvc, or alternatively add your own @Configuration-annotated DelegatingWebMvcConfiguration as described in the Javadoc of @EnableWebMvc.

    4.1 spring mvc auto-configuration

    4.2 扩展 spring mvc

        <mvc:view-controller path="/hello" view-name="success"/>
        <mvc:interceptors>
            <mvc:interceptor>
                <mvc:mapping path="/hello"/>
                <bean></bean>
            </mvc:interceptor>
        </mvc:interceptors>
    

    编写一个配置类 【@Configuration】,是WebMvcConfigurerAdapter类型;不能标注 @EnableWebMvc
    既保留了所有的自动配置,也能用我们扩展的配置

     * 使用 WebMvcConfigurerAdapter可以来扩展 springmvc的功能
     */
    @Configuration
    public class MyMvcConfig extends WebMvcConfigurerAdapter {
        @Override
        public void addViewControllers(ViewControllerRegistry registry) {
    //        super.addViewControllers(registry);
            //浏览器发送请求 /cainiao 来到 success页面
            registry.addViewController("/cainiao").setViewName("success");
        }
    }
    

    image
    image
    原理

    1. WebMvcAutoConfiguration 是springmvc的自动配置类
    2. 在做其他自动配置时会导入:@Import(EnableWebMvcConfiguration.class)
      @Configuration
      @Import({WebMvcAutoConfiguration.EnableWebMvcConfiguration.class})
      @EnableConfigurationProperties({WebMvcProperties.class, ResourceProperties.class})
      public static class WebMvcAutoConfigurationAdapter extends WebMvcConfigurerAdapter {}
      
      ----------原理-----------
      @Configuration
      public static class EnableWebMvcConfiguration extends DelegatingWebMvcConfiguration {}
      
      @Configuration
      public class DelegatingWebMvcConfiguration extends WebMvcConfigurationSupport {
      
      	private final WebMvcConfigurerComposite configurers = new WebMvcConfigurerComposite();
      
      	//从容器中 获取所有的 webmvcconfigurer
      	@Autowired(required = false) //自动装配,
      	public void setConfigurers(List<WebMvcConfigurer> configurers) {
      		if (!CollectionUtils.isEmpty(configurers)) {
      			this.configurers.addWebMvcConfigurers(configurers);
      		}
      	}
      	//一个参考实现 将所有的 WebMvcConfigurer相关配置都来一起调用。
      	@Override
      	protected void addViewControllers(ViewControllerRegistry registry) {
      		this.configurers.addViewControllers(registry);
      	}
      }
      @Override
      public void addViewControllers(ViewControllerRegistry registry) {
      	for (WebMvcConfigurer delegate : this.delegates) {
      		delegate.addViewControllers(registry);
      	}
      }
      
    3. 容器中所有的 WebMvcConfigurer都会一起起作用
    4. 我们的配置类也会被调用;效果,springmvc的自动配置和我们的扩展配置都会起作用。

    4.3 全面接管 spring mvc

    • spring boot对springmvc的自动配置不需要,所有都是我们自己配,所有的 springmvc的自动配置都失效了。我们需要在配置类中添加 @EnableWebMvc 即可 。
      原理
    • 为什么加上 @EnableWebMvc自动配置就就失效了,
    @Retention(RetentionPolicy.RUNTIME)
    @Target(ElementType.TYPE)
    @Documented
    @Import(DelegatingWebMvcConfiguration.class) enablewebmvc 的核心
    public @interface EnableWebMvc {
    }
    
    @Configuration
    public class DelegatingWebMvcConfiguration extends WebMvcConfigurationSupport {
    }
    
    @Configuration
    @ConditionalOnWebApplication
    @ConditionalOnClass({ Servlet.class, DispatcherServlet.class,
    		WebMvcConfigurerAdapter.class })
    //主要因为这个 容器中没有这个 bean的时候,这个自动配置类才生效
    @ConditionalOnMissingBean(WebMvcConfigurationSupport.class)
    @AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE + 10)
    @AutoConfigureAfter({ DispatcherServletAutoConfiguration.class,
    		ValidationAutoConfiguration.class })
    public class WebMvcAutoConfiguration {}
    
    • @EnableWebMvc 将 WebMvcConfigurationSupport 组件导入进来。
    • 导入的 WebMvcConfigurationSupport只是springmvc的基本功能。

    5. 如何修改 spring boot的默认配置

    模式

    1. spring boot在自动配置很多组件的时候,想看容器中有没有用户字节配置的【@Bean,@Component】如果有就用用户配置的,如果没有,才自动配置。如果有些组件可以有多个【viewResolver】将用户配置和自己配置的组合起来。
    2. 在 spring boot会有非常多的 xxConfigurer帮助我们进行扩展配置
    3. 在 spring boot中会有很多的 xxCustomizer帮助我们进行定制配置

    6. RestfulCRUD

    1. 默认访问首页
    /**
     * @author shkstart
     * @create 2021-10-26 19:31
     * 使用 WebMvcConfigurerAdapter可以来扩展 springmvc的功能
     */
    //@EnableWebMvc
    @Configuration
    public class MyMvcConfig extends WebMvcConfigurerAdapter {
        @Override
        public void addViewControllers(ViewControllerRegistry registry) {
    //        super.addViewControllers(registry);
            //浏览器发送请求 /cainiao 来到 success页面
            registry.addViewController("/cainiao").setViewName("success");
        }
    
        //所有的 WebMvcConfigurerAdapter组件会一起起作用
        @Bean //将组建注册在容器中
        public WebMvcConfigurerAdapter getWebMvcConfigurerAdapter() {
            return new WebMvcConfigurerAdapter() {
                @Override
                public void addViewControllers(ViewControllerRegistry registry) {
                    registry.addViewController("/").setViewName("login");
                    registry.addViewController("/index.html").setViewName("login");
                }
            };
        }
    }
    

    6.1 默认访问首页

    6.2 国际化

    1. 编写国际化配置文件
    2. 使用 ResourceBundleMessageSource 管理国际化资源文件
    3. 在页面使用 fmt:message 取出国际化内容

    步骤

    1. 编写国际化配置文件,抽取页面需要显示的国际化消息
      image
    2. spring boot自动配置好了管理国际化资源文件的组件
    @Configuration
    @ConditionalOnMissingBean(value = MessageSource.class, search = SearchStrategy.CURRENT)
    @AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE)
    @Conditional(ResourceBundleCondition.class)
    @EnableConfigurationProperties
    @ConfigurationProperties(prefix = "spring.messages")
    public class MessageSourceAutoConfiguration {
    	/**
    	 * Comma-separated list of basenames, each following the ResourceBundle convention.
    	 * Essentially a fully-qualified classpath location. If it doesn't contain a package
    	 * qualifier (such as "org.mypackage"), it will be resolved from the classpath root.
    	 */
    	private String basename = "messages";
    	//我们的配置文件可以直接放在类路径下叫 message.properties
    	
    	//管理国际化资源文件的 source
    	@Bean
    	public MessageSource messageSource() {
    		ResourceBundleMessageSource messageSource = new ResourceBundleMessageSource();
    		if (StringUtils.hasText(this.basename)) {
    			//设置国际化资源文件的基础名【去掉国家代码的】
    			messageSource.setBasenames(StringUtils.commaDelimitedListToStringArray(
    					StringUtils.trimAllWhitespace(this.basename)));
    		}
    		if (this.encoding != null) {
    			messageSource.setDefaultEncoding(this.encoding.name());
    		}
    		messageSource.setFallbackToSystemLocale(this.fallbackToSystemLocale);
    		messageSource.setCacheSeconds(this.cacheSeconds);
    		messageSource.setAlwaysUseMessageFormat(this.alwaysUseMessageFormat);
    		return messageSource;
    	}
    }
    
    #application.properties 文件
    指定国际化文件的的路径
    spring.messages.basename=i181.login
    
    1. 去页面获取国际化的值
      使用 #{} 获取值【login.html,index.html换成了login.html】
    <!DOCTYPE html>
    <html lang="en" xmlns:th="http://www.thymeleaf.org">
    <head>
        <meta charset="UTF-8">
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
        <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
        <meta name="description" content="">
        <meta name="author" content="">
        <title>Signin Template for Bootstrap</title>
        <!-- Bootstrap core CSS -->                         <!--@语法 会自动引入项目路径-->
        <link href="asserts/css/bootstrap.min.css" th:href="@{/webjars/bootstrap/4.0.0/css/bootstrap.css}" rel="stylesheet">
        <!-- Custom styles for this template -->
        <link href="asserts/css/signin.css" th:href="@{/asserts/css/signin.css}" rel="stylesheet">
    </head>
    
    <body class="text-center">
    <form class="form-signin" action="dashboard.html" th:action="@{/user/login}" method="post">
        <img class="mb-4" src="asserts/img/bootstrap-solid.svg" th:href="@{/asserts/img/bootstrap-solid.svg}" alt=""
             width="72" height="72">
        <h1 class="h3 mb-3 font-weight-normal" th:text="#{login.tip}">Please sign in</h1>
        <!--做一个判断-->
        <p style="color: red" th:text="${msg}" th:if="${not #strings.isEmpty(msg)}"></p>
        <label class="sr-only" th:text="#{login.username}">Username</label>
        <input type="text" class="form-control" th:placeholder="#{login.username}" placeholder="Username" required=""
               name="username" autofocus="">
        <label class="sr-only" th:text="#{login.password}">Password</label>
        <input type="password" class="form-control" th:placeholder="#{login.password}" placeholder="Password"
               name="password" required="">
        <div class="checkbox mb-3">
            <label>
                <input type="checkbox" value="remember-me"> [[#{login.remember}]] <!-- Remember me-->
            </label>
        </div>
        <button class="btn btn-lg btn-primary btn-block" type="submit" th:text="#{login.btn}">Sign in</button>
        <p class="mt-5 mb-3 text-muted">© 2017-2018</p>
        <a class="btn btn-sm" th:href="@{/index.html(l='zh_CN')}">中文</a>
        <a class="btn btn-sm" th:href="@{/index.html(l='en_US')}">English</a>
    </form>
    
    </body>
    
    </html>
    

    乱码问题解决
    image

    #application.properties 文件
    #i18n 乱码问题
    spring.messages.encoding=utf-8
    

    image

    效果:根据浏览器语言设置的信息切换了国际化

    • 原理:
      国际化 Locale【区域信息对象】LocaleResolver【获取区域对象】
      	@Bean
      	@ConditionalOnMissingBean
      	@ConditionalOnProperty(prefix = "spring.mvc", name = "locale")
      	public LocaleResolver localeResolver() {
      		if (this.mvcProperties
      				.getLocaleResolver() == WebMvcProperties.LocaleResolver.FIXED) {
      			return new FixedLocaleResolver(this.mvcProperties.getLocale());
      		}
      		AcceptHeaderLocaleResolver localeResolver = new AcceptHeaderLocaleResolver();
      		localeResolver.setDefaultLocale(this.mvcProperties.getLocale());
      		return localeResolver;
      	}
      // 默认的就是根据请求头带来的区域信息获取 locale进行国际化
      
      image
      image
    1. 点击连接切换国际化【自己编写一个 LocaleResolver 加到容器中
      <!--login.html-->
      <p class="mt-5 mb-3 text-muted">© 2017-2018</p>
      <a class="btn btn-sm" th:href="@{/index.html(l='zh_CN')}">中文</a>
      <a class="btn btn-sm" th:href="@{/index.html(l='en_US')}">English</a>
      
      import org.springframework.util.StringUtils;
      import org.springframework.web.servlet.LocaleResolver;
      import javax.servlet.http.HttpServletRequest;
      import javax.servlet.http.HttpServletResponse;
      import java.util.Locale;
      
      /**
       * 可以在连接上携带区域信息
       */
      public class MyLocaleResolver implements LocaleResolver {
      
      	//解析区域信息的
      	@Override
      	public Locale resolveLocale(HttpServletRequest request) {
      		String l = request.getParameter("l");
      		//获取到就根据获取到的,没有,默认的
      		Locale locale = Locale.getDefault();
      		if (!StringUtils.isEmpty(l)) {
      			String[] split = l.split("_");
      			//第一参数,语言代码,第二个,国家代码
      			locale = new Locale(split[0], split[1]);
      			System.out.println("使用自定义的 local");
      		}
      		return locale;
      	}
      
      	@Override
      	public void setLocale(HttpServletRequest request, HttpServletResponse response, Locale locale) {
      
      	}
      }
      
      //名字 localeResolver 指明一下 否则会使用spring boot默认的
      @Bean(name = "localeResolver")
      public LocaleResolver localResolver() {
          return new MyLocaleResolver();
      }
      

    6.3 登录

    "开发技巧"

    • 开发期间模板页面修改以后,要实时生效
      1. 禁用模板引擎的缓存
        #禁用掉模板缓存
        spring.thymeleaf.cache=false
        
      2. 修改页面完成以后 ctrl + f9 重新加载页面
    • 登录错误消息的显示
      <!--做一个判断-->
      <p style="color: red" th:text="${msg}" th:if="${not #strings.isEmpty(msg)}"></p>
      

    6.4 拦截器进行检查

    /**
     * @author shkstart
     * @create 2021-10-27 21:02
     * 拦截器:登录检查
     */
    
    public class LoginHandlerInterceptor implements HandlerInterceptor {
        //目标方法执行执行
        @Override
        public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
    
            Object user = request.getSession().getAttribute("loginUser");
            if (user == null) {
                //未登录,返回登录页面
                request.setAttribute("msg", "你没有权限");
                request.getRequestDispatcher("/index.html").forward(request, response);
            } else {
                //已登录,放行请求
                return true;
            }
            return false;
        }
    
        @Override
        public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
    
        }
    
        @Override
        public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
    
        }
    }
    

    image

        //所有的 WebMvcConfigurerAdapter组件会一起起作用
        @Bean //将组建注册在容器中
        public WebMvcConfigurerAdapter getWebMvcConfigurerAdapter() {
            return new WebMvcConfigurerAdapter() {
                //视图控制器
                @Override
                public void addViewControllers(ViewControllerRegistry registry) {
                    registry.addViewController("/").setViewName("login");
                    registry.addViewController("/index.html").setViewName("login");
                    registry.addViewController("/main.html").setViewName("dashboard");
                }
    
                //注册连接器的
                @Override
                public void addInterceptors(InterceptorRegistry registry) {
                    //静态资源: *.css *.js [spring boot已经做好了静态资源映射]
                    registry.addInterceptor(new LoginHandlerInterceptor())
                            // /** 拦截任意目录下的所有请求
                            .addPathPatterns("/**").excludePathPatterns("/index.html", "/user/login");
                }
            };
        }
    

    6.5 crud-员工列表

    实现要求:

    1. restfulCRUD;crud满足 rest风格
      url:/资源名称/资源标识 ===》http请求方式区分对资源 crud操作
    普通CRUD(uri来区分操作) RestfulCRUD
    查询 getEmp emp--GET
    添加 addEmp?xxx emp-Post
    修改 updateEmp?id=xxx&xx=xx emp/{id}---PUT
    删除 deleteEmp?id=1 emp/{id}---DELETE
    1. 实验的请求架构:
    # 请求url 请求方式
    查询所有员工 emps GET
    查询某个员工(来到修改页面 epm/{id} GET
    来到添加页面 emp1 GET
    添加员工 emp POST
    来到修改页面(查询出员工进行信息回显 emp/{id} GET
    修改员工 emp PUT
    删除员工 emp/{id} DELETE
    1. 员工列表

    thymeleaf 公共页面元素抽取

    thymeleaf 公共页面元素抽取

    1. 抽取公共页面
    <div th:foragment="copy">
    	&copy;2011 the good thymes virtual grocery
    </div>
    
    2. 引入公告片段
    <div th:insert="~{footer :: copy}"></div>
    ~{templatename::select} 模板名::选择器
    ~{templatename::fragmentname} 模板名::片段名
    或者
    <div th:insert="footer :: copy"></div>
    
    3. 默认效果
    insert 的功能片段在 div标签中
    如果使用 th:insert 等属性进行引入,可以不用写 ~{}
    行内写法可以加上:[[~{}]]  [(~{})]
    

    三种引入片段的 th属性

    1. th:insert 将公共的片段整个插入到声明引入的元素中
    2. th:replace 将声明引入的元素替换为公共片段
    3. th:inlude 将被引入的片段的内容包含进这个标签中
    <footer th:fragment="copy">
    &copy; 2021 the good thymes virtual grocery
    </footer>
     
    引入方式
    <div th:insert="footer::copy"></div>
    <div th:replace="footer::copy"></div>
    <div th:include="footer::copy"></div>
    
    效果
    <div>
    	<footer>
    	&copy; 2021 the good thymes virtual grocery
    	</footer>
    </div>
    <footer>  
    &copy; 2021 the good thymes virtual grocery
    </footer>
    <div>
    	&copy; 2021 the good thymes virtual grocery
    </div>
    

    引入片段的时候传入参数

    <div th:fragment="frga(onevar,twovar)">
    	<p th:text"${onevar}+'-'+${twovar}">
    	</p>
    </div>
    
    <div th:replace="::frag(${value1},${value2})"></div>
    <div th:replace="::frga(onevar=${value1},twovar=${value2})"></div>
    或者
    <div th:fragment="frag"></div>
    
    <div th:replace="::frag(onevar=$(value1),twovar=${value2})">  </div>
    

    6.6 curd-员工添加

                    <form th:action="@{/emp}" method="post">
                        <div class="form-group">
                            <label for="exampleFormControlInput1">Last Name</label>
                            <input name="lastName" type="text" class="form-control" id="exampleFormControlInput1"
                                   placeholder="zhangsan">
                        </div>
                        <div class="form-group">
                            <label>Email</label>
                            <input name="email" type="email" class="form-control" placeholder="name@example.com">
                        </div>
                        <div class="form-group">
                            <label>Gender</label>
                            <div class="form‐check form‐check‐inline">
                                <input class="form‐check‐input" type="radio" name="gender" value="1">
                                <label class="form‐check‐label">男</label>
                            </div>
                            <div class="form‐check form‐check‐inline">
                                <input class="form‐check‐input" type="radio" name="gender" value="0">
                                <label class="form‐check‐label">女</label>
                            </div>
                        </div>
                        <div class="form-group">
                            <label>department</label>
                            <select multiple class="form-control" name="department.id">
                                <option th:value="${dept.id}" th:each="dept:${depts}"
                                        th:text="${dept.getDepartmentName()}"></option>
                            </select>
                        </div>
                        <div class="form-group">
                            <label>Birth</label>
                            <input name="birth" type="text" class="form-control" placeholder="yyyy/MM/dd">
                        </div>
                        <button type="submit" class="btn btn-primary">添加</button>
                    </form>
    
    • 提交的数据格式不对:生日,日期【默认没有配是斜线】
      2012-12-21、2012/12/23、2012.12.12
      日期的格式化,springmvc将页面提交的值需要转为指定的类型
      2012-12-12 === date 类型转换,格式化
      默认日期是按照 / 的方式
      WebMvcAutoConfiguration 类中配置了一个类
      	@Bean
      	@ConditionalOnProperty(prefix = "spring.mvc", name = "date-format")
      	public Formatter<Date> dateFormatter() {
      		return new DateFormatter(this.mvcProperties.getDateFormat());
      	}
      
      public String getDateFormat() {
      	return this.dateFormat;
      }
      /**
       * Date format to use (e.g. dd/MM/yyyy).
       */
      private String dateFormat;
      
    • springboot 的 application.properties文件修改 mvc默认的解析格式
      #直接指定一下 mvc的日期解析格式
      spring.mvc.date-format=yyyy-MM-dd
      

    转发原理

    //redirect 表示重定向到一个地址,forward 表示转发到一个地址 /代表当前路径
            
    原理:ThymeleafViewResolver extends AbstractCachingViewResolver implements Ordered
    该类属性
    String REDIRECT_URL_PREFIX = "redirect:";
    String FORWARD_URL_PREFIX = "forward:";
    该类方法
    protected View createView(final String viewName, final Locale locale) throws Exception {
    	RedirectView view = new RedirectView
    }
    
    RedirectView类的该方法
    protected void renderMergedOutputModel(Map<String, Object> model, HttpServletRequest request,
    		HttpServletResponse response) throws IOException {
    	sendRedirect(request, response, targetUrl, this.http10Compatible);
    }
    
    protected void sendRedirect(HttpServletRequest request, HttpServletResponse response,
    		String targetUrl, boolean http10Compatible) throws IOException {
    	response.sendRedirect(encodedURL); //重定向
    }
    

    6.7 crud-员工修改

    <!DOCTYPE html>
    <!-- saved from url=(0052)http://getbootstrap.com/docs/4.0/examples/dashboard/ -->
    <html lang="en" xmlns:th="http://www.thymeleaf.org">
    
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
        <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
        <meta name="description" content="">
        <meta name="author" content="">
    
        <title>Dashboard Template for Bootstrap</title>
        <!-- Bootstrap core CSS -->
        <link href="asserts/css/bootstrap.min.css" rel="stylesheet" th:href="@{/webjars/bootstrap/4.0.0/css/bootstrap.css}">
    
        <!-- Custom styles for this template -->
        <link href="asserts/css/dashboard.css" rel="stylesheet" th:href="@{/asserts/css/dashboard.css}">
        <style type="text/css">
            /* Chart.js */
    
            @-webkit-keyframes chartjs-render-animation {
                from {
                    opacity: 0.99
                }
                to {
                    opacity: 1
                }
            }
    
            @keyframes chartjs-render-animation {
                from {
                    opacity: 0.99
                }
                to {
                    opacity: 1
                }
            }
    
            .chartjs-render-monitor {
                -webkit-animation: chartjs-render-animation 0.001s;
                animation: chartjs-render-animation 0.001s;
            }
        </style>
    </head>
    
    <body>
    <!--引入抽取的 topbar-->
    <!--模版名:会使用 thymeleaf的前后缀配置规则进行解析-->
    <div th:replace="commons/bar::topbar"></div>
    
    <div class="container-fluid">
        <div class="row">
            <!--引入侧边栏-->
            <div th:replace="commons/bar::#sidebar(activeUri='emps')"></div>
            <main role="main" class="col-md-9 ml-sm-auto col-lg-10 pt-3 px-4">
                <div class="table-responsive">
                    <!--需要区分员工修改还是添加-->
    
                    <form th:action="@{/emp}" method="post">
                        <!--发送put 请求修改数据
                        1. springmvc 配置 HiddenHttpMethodFilter【springboot自动配置好的】
                        2. 页面创建一个 post表单
                        3. 创建一个 input项,name="_method"; 值就是我们指定的请求
                        -->
                        <input type="hidden" name="_method" value="put" th:if="${emp!=null}"/>
                        <input type="hidden" name="id" th:if="${emp!=null}" th:value="${emp.id}">
    
                        <div class="form-group">
                            <label for="exampleFormControlInput1">Last Name</label>
                            <input name="lastName" type="text" class="form-control" id="exampleFormControlInput1"
                                   placeholder="zhangsan" th:value="${emp!=null}?${emp.lastName}">
                        </div>
                        <div class="form-group">
                            <label>Email</label>
                            <input name="email" type="email" class="form-control" placeholder="name@example.com"
                                   th:value="${emp!=null}?${emp.email}" }>
                        </div>
                        <div class="form-group">
                            <label>Gender</label>
                            <div class="form‐check form‐check‐inline">
                                <input class="form‐check‐input" type="radio" name="gender" value="1"
                                       th:checked="${emp!=null}?${emp.gender==1}">
                                <label class="form‐check‐label">男</label>
                            </div>
                            <div class="form‐check form‐check‐inline">
                                <input class="form‐check‐input" type="radio" name="gender" value="0"
                                       th:checked="${emp!=null}?${emp.gender==0}">
                                <label class="form‐check‐label">女</label>
                            </div>
                        </div>
                        <div class="form-group">
                            <label>department</label>
                            <select multiple class="form-control" name="department.id">
                                <option th:value="${dept.id}" th:each="dept:${depts}"
                                        th:text="${dept.getDepartmentName()}"
                                        th:selected="${emp!=null}?${dept.id==emp.department.id}"></option>
                            </select>
                        </div>
                        <div class="form-group">
                            <label>Birth</label>
                            <input th:value="${emp!=null}?${#dates.format(emp.birth,'yyyy-MM-dd HH:mm')}" name="birth"
                                   type="text"
                                   class="form-control"
                                   placeholder="yyyy-MM-dd">
                        </div>
                        <button type="submit" class="btn btn-primary" th:text="${emp!=null}?'修改':'添加'">添加</button>
                    </form>
    
                </div>
            </main>
        </div>
    </div>
    
    <!-- Bootstrap core JavaScript
    ================================================== -->
    <!-- Placed at the end of the document so the pages load faster -->
    <script type="text/javascript" src="asserts/js/jquery-3.2.1.slim.min.js"
            th:src="@{/asserts/js/jquery-3.2.1.slim.min.js}"></script>
    <script type="text/javascript" src="asserts/js/popper.min.js" th:src="@{/asserts/js/popper.min.js}"></script>
    <script type="text/javascript" src="asserts/js/bootstrap.min.js" th:src="@{asserts/js/bootstrap.min.js/}"></script>
    
    <!-- Icons -->
    <script type="text/javascript" src="asserts/js/feather.min.js" th:src="@{/asserts/js/feather.min.js}"></script>
    <script>
        feather.replace()
    </script>
    
    <!-- Graphs -->
    <script type="text/javascript" src="asserts/js/Chart.min.js" th:src="@{/asserts/js/Chart.min.js}"></script>
    <script>
        var ctx = document.getElementById("myChart");
        var myChart = new Chart(ctx, {
            type: 'line',
            data: {
                labels: ["Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"],
                datasets: [{
                    data: [15339, 21345, 18483, 24003, 23489, 24092, 12034],
                    lineTension: 0,
                    backgroundColor: 'transparent',
                    borderColor: '#007bff',
                    borderWidth: 4,
                    pointBackgroundColor: '#007bff'
                }]
            },
            options: {
                scales: {
                    yAxes: [{
                        ticks: {
                            beginAtZero: false
                        }
                    }]
                },
                legend: {
                    display: false,
                }
            }
        });
    </script>
    </body>
    </html>
    

    6.8 crud-员工删除

    • 示例
    <form action="subsccribe.html" th:attr="action=@{/subscribe}">
    	<inplut type="text" name="email"/>
    	<inplut type="submit" value="Subscribe!" th:attr="value=#{subscribe.submit}"/>
    </form>
    
    • 代码
    <!--这样写页面表单显示别扭 【升级】-->
    <!--<form th:action="@{/emp/}+${emp.id}" method="post">
    	<input type="hidden" name="_method" value="delete">
    	<button class="btn btn-sm btn-danger" type="submit">删除</button>
    </form>-->
    <!--【升级】-->
    <button th:attr="del_uri=@{/emp/}+${emp.id}" class="btn btn-sm btn-danger deleteBtn">删除
    </button>
    <script>
        $(".deleteBtn").click(function () {
            //删除当前员工
            let attr = $(this).attr("del_uri"); //获取当前自定义属性名值
            $("#deleteEmpForm").attr("action", attr).submit();
        })
    </script>
    

    7. 错误处理机制

    7.1 spring boot默认的错误处理机制

    • 默认效果

      1. 【浏览器】返回一个默认的错误页面
        image
        浏览器发送的请求的请求头
        image
      2. 如果是其他客户端,默认响应一个 json数据
        image
        image
    • 原理:可以参照 ErrorMvcAutoConfiguration,错误处理的自动配置

      DefaultErrorAttributes 
      	帮我们在页面共享信息 【timestamp、status、error、exception、message、errors】
      	@Override
      	public Map<String, Object> getErrorAttributes(RequestAttributes requestAttributes,
      			boolean includeStackTrace) {
      		Map<String, Object> errorAttributes = new LinkedHashMap<String, Object>();
      		errorAttributes.put("timestamp", new Date());
      		addStatus(errorAttributes, requestAttributes);
      		addErrorDetails(errorAttributes, requestAttributes, includeStackTrace);
      		addPath(errorAttributes, requestAttributes);
      		return errorAttributes;
      	}
      
      BasicErrorController  处理默认的 /error 请求
      	@RequestMapping("${server.error.path:${error.path:/error}}")
      	public class BasicErrorController extends AbstractErrorController
      	
      	@RequestMapping(produces = "text/html")  产生 html类型的数据;浏览器发送的请求来到这个方法处理
      	public ModelAndView errorHtml(HttpServletRequest request,
      			HttpServletResponse response) {
      		HttpStatus status = getStatus(request);
      		Map<String, Object> model = Collections.unmodifiableMap(getErrorAttributes(
      				request, isIncludeStackTrace(request, MediaType.TEXT_HTML)));
      		response.setStatus(status.value());
      		// 去哪个页面作为错误页面;包含页面地址和页面内容
      		ModelAndView modelAndView = resolveErrorView(request, response, status, model);
      		return (modelAndView == null ? new ModelAndView("error", model) : modelAndView);
      	}
      
      	@RequestMapping
      	@ResponseBody 产生的是 json的数据;其他客户端来到这个方法处理
      	public ResponseEntity<Map<String, Object>> error(HttpServletRequest request) {
      		Map<String, Object> body = getErrorAttributes(request,
      				isIncludeStackTrace(request, MediaType.ALL));
      		HttpStatus status = getStatus(request);
      		return new ResponseEntity<Map<String, Object>>(body, status);
      	}
      	//resolveErrorView 包含的内容【响应的页面】
      	protected ModelAndView resolveErrorView(HttpServletRequest request,
      			HttpServletResponse response, HttpStatus status, Map<String, Object> model) {
      		//得到所有的  ModelAndView 异常视图解析器得到 modelAndView
      		for (ErrorViewResolver resolver : this.errorViewResolvers) {
      			ModelAndView modelAndView = resolver.resolveErrorView(request, status, model);
      			if (modelAndView != null) {
      				return modelAndView;
      			}
      		}
      		return null;
      	}
      
      ErrorPageCustomizer 错误的定制页面
      		@Value("${error.path:/error}")
      		private String path = "/error"; 系统出现错误以后来到 error请求处理【web.xml注册的错误页面规则】
      		
      DefaultErrorViewResolver 
      	@Override
      	public ModelAndView resolveErrorView(HttpServletRequest request, HttpStatus status,
      			Map<String, Object> model) {
      		ModelAndView modelAndView = resolve(String.valueOf(status), model);
      		if (modelAndView == null && SERIES_VIEWS.containsKey(status.series())) {
      			modelAndView = resolve(SERIES_VIEWS.get(status.series()), model);
      		}
      		return modelAndView;
      	}
      
      	private ModelAndView resolve(String viewName, Map<String, Object> model) {
      		//默认 springboot可以去找到一个页面 error/404
      		String errorViewName = "error/" + viewName;
      		// 如果模板引擎可以解析这个地址就用模板引擎解析
      		TemplateAvailabilityProvider provider = this.templateAvailabilityProviders
      				.getProvider(errorViewName, this.applicationContext);
      		if (provider != null) {
      			//模板引擎可用的情况下返回到 errorViewName指定的视图地址
      			return new ModelAndView(errorViewName, model);
      		}
      		//模板引擎不可以的情况下调用这个方法,
      		return resolveResource(errorViewName, model);
      	}
      
      	private ModelAndView resolveResource(String viewName, Map<String, Object> model) {
      		for (String location : this.resourceProperties.getStaticLocations()) {
      			//在静态资源资源文件下找 errorViewName对应的页面 error/404.html
      			try {
      				Resource resource = this.applicationContext.getResource(location);
      				resource = resource.createRelative(viewName + ".html");
      				if (resource.exists()) {
      					return new ModelAndView(new HtmlResourceView(resource), model);
      				}
      			}
      			catch (Exception ex) {
      			}
      		}
      		return null;
      	}
      

      步骤:

      1. 一但系统出现 4xx或者 5xx之类的错误,ErrorPageCustomizer就会生效(定制错误的响应规则), 就会来到 /error 请求;就会被 BasicErrorController处理。
      2. 响应页面;去哪个页面是由 DefaultErrorViewResolver 解析得到的

    7.2 如果定制错误响应

    一. 如何定制错误页面

    1. 有模板引擎的情况下:error/状态码;【将错误的页面命名为 错误状态码.html 放在模板引擎下的 error文件夹下】,发生此状态码的错误就会来到对应的页面。
      我们可用使用 4xx和 5xx作为此错误页面的文件名来匹配这种类型的所有错误,精确优先【优先寻找精确的状态码.html】
      页面能获取的信息:
      • timestamp:时间戳
      • status:状态码
      • error:错误提示
      • exception:异常消息
      • message:异常信息
      • errors: jsr303 数据校验的错误都在这里
      1. 没有模板引擎(模板引擎找不到这个错误页面),静态资源文件夹下找
      2. 以上都没有错误页面,就是默认来到 spring boot默认的错误提示页面

    二. 如何定制错误的 json数据

    1. 自定义异常处理与返回定制 json数据
      /**
       * @create 2021-10-30 22:00
       * 自定义异常处理器
       */
      @ControllerAdvice
      public class MyExceptionHandler {
      	@ResponseBody //浏览器客户端返回的都是 json数据
      	@ExceptionHandler(UserNotExistException.class)
      	public Map<String, Object> handleException(Exception e) {
      		HashMap<String, Object> map = new HashMap<>();
      		map.put("code", "user.notexist");
      		map.put("message", e.getMessage());
      		return map;
      	}
      }
      
    2. 转发到 error进行自适应效果处理
      @ControllerAdvice
      public class MyExceptionHandler {
      	@ExceptionHandler(UserNotExistException.class)
      	public String handleException(Exception e, HttpServletRequest request) {
      		HashMap<String, Object> map = new HashMap<>();
      		//传入字节的状态码 4xx 5xx,否则就不会进入定制的错误页面的解析流程
      		/*
      		 * Integer statusCode = (Integer) request.getAttribute("javax.servlet.error.status_code");
      		 * */
      		request.setAttribute("javax.servlet.error.status_code", 500);
      		map.put("code", "user.notexist");
      		map.put("message", e.getMessage());
      		return "forward:/error";
      	}
      }
      

    image

    三.将我们定制数据携带出去

    • 出现错误以后,会来到 /error 请去,会被 BasicErrorController处理,响应出去可以获取的数据是由 getErrorAttribute得到的(是AbstractErrorController【ErrorController】规定的方法
    1. 完全来编写一个 ErrorController的实现类,【或者编写 AbstractErrorController的子类】放在容器中
    2. 页面上能用的数据,或者是 json返回能用的数据都是通过 errorAttributes.getErrorAttributes 得到。
      容器中 DefaultErrorAttributes.getErrorAttributes();默认进行数据处理的。
      自定义 ErrorAttributes
      /**
       * @author shkstart
       * @create 2021-10-31 17:21
       * 给容器中加入我们字节的ErrorAttributes
       */
      @Component
      public class MyErrorAttributes extends DefaultErrorAttributes {
      	@Override
      	public Map<String, Object> getErrorAttributes(RequestAttributes requestAttributes, boolean includeStackTrace) {
      		Map<String, Object> map = super.getErrorAttributes(requestAttributes, includeStackTrace);
      		map.put("company", "cainiao");
      		return map;
      	}
      }
      
      image
    • 最终的效果:响应是自适应的,可以通过定制 ErrorAttributes改变需要返回的内容。
      image
      image
      image
      image

    8. 配置嵌入式 servlet容器

    • SpringBoot默认使用 Tomcat作为嵌入式的 Servlet容器
      image
    • 问题?

    8.1 如何定制和修改 servlet容器的相关配置

    • 如何定制和修改 Servlet容器的相关配置
      • 修改和 server有相关的配置【ServerProperties也是 implement EmbeddedServletContainerCustomizer】
        server.prot=8081
        server.context-path=/crud
        server.tomcat.uri-encoding=utf-8
        
        #通用的 servlet容器设置
        server.xxx
        #tomcat的设置
        server.tomcat.xxx
        
      • 编写一个 EmbeddedServletContainerCustomizer:嵌入式的 servlet容器定制器,来修改Servlet容器的配置
        @Bean
        public EmbeddedServletContainerCustomizer embeddedServletContainerCustomizer() {
        	//定制嵌入式的 servlet容器相关的规则
        	return new EmbeddedServletContainerCustomizer() {
        		@Override
        		public void customize(ConfigurableEmbeddedServletContainer container) {
        			container.setPort(8083);
        		}
        	};
        }
        

    8.2 注册 servlet三大组件【servlet,filter,listener】

    • 由于 springboot默认是以 jar包的方式启动嵌入式的 servlet容器来启动 spring boot的文本应用,没有 web.xml文件
    • 注册三大组件用以下方式
      • ServletRegistrationBean
        @Bean
        public ServletRegistrationBean myServlet() {
        	ServletRegistrationBean registrationBean =
        			new ServletRegistrationBean(new MyServlet(), "/myServlet");
        	registrationBean.setLoadOnStartup(1);
        	return registrationBean;
        }
        
      • FilterRegistrationBean
        @Bean
        public FilterRegistrationBean myFilter() {
        	FilterRegistrationBean registrationBean = new FilterRegistrationBean();
        	registrationBean.setFilter(new MyFilter());
        	registrationBean.setUrlPatterns(Arrays.asList("/hello", "/myServlet"));
        	return registrationBean;
        }
        
      • ServletListenerRegistrationBean
        @Bean
        public ServletListenerRegistrationBean myListener() {
        	return new ServletListenerRegistrationBean<MyListener>(new MyListener());
        }
        
    • spring boot帮我们自动配置 springmvc的时候,自动的注册 springmvc的的前端控制器;DispatcherServlet
      	@Bean(name = DEFAULT_DISPATCHER_SERVLET_REGISTRATION_BEAN_NAME)
      	@ConditionalOnBean(value = DispatcherServlet.class, name = DEFAULT_DISPATCHER_SERVLET_BEAN_NAME)
      	public ServletRegistrationBean dispatcherServletRegistration(
      			DispatcherServlet dispatcherServlet) {
      		ServletRegistrationBean registration = new ServletRegistrationBean(
      				dispatcherServlet, this.serverProperties.getServletMapping());
      		//默认拦截 / 所有请求;包括静态资源,但是不会拦截 jsp请求, /* 会拦截 jsp
      		//可以通过 server.servletPath来修改 springmvc前端控制器默认拦截的请求路径
      		registration.setName(DEFAULT_DISPATCHER_SERVLET_BEAN_NAME);
      		registration.setLoadOnStartup(
      				this.webMvcProperties.getServlet().getLoadOnStartup());
      		if (this.multipartConfig != null) {
      			registration.setMultipartConfig(this.multipartConfig);
      		}
      		return registration;
      	}
      

    8.3 替换为其他嵌入式 servlet容器

    image

    • 默认支持:tomcat(默认) , jetty(长连接 web聊天) , undertow(不支持jsp,并发性能好)
          <!--引入web模块 spring-boot-starter :springboot场景启动器,帮我们导入了web模块正常运行所依赖的 jar包-->
          <dependency>
              <groupId>org.springframework.boot</groupId>
              <artifactId>spring-boot-starter-web</artifactId>
              <exclusions>
                  <exclusion>
                      <artifactId>spring-boot-starter-tomcat</artifactId>
                      <groupId>org.springframework.boot</groupId>
                  </exclusion>
              </exclusions>
          </dependency>
          <!--引入其他的 servlet容器 jetty-->
          <dependency>
              <artifactId>spring-boot-starter-jetty</artifactId>
              <groupId>org.springframework.boot</groupId>
          </dependency>
      

    8.4 嵌入式 servlet容器自动配置原理

    • EmbeddedServletContainerAutoConfiguration,嵌入式的 servlet容器自动配置
    @AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE)
    @Configuration
    @ConditionalOnWebApplication
    @Import(BeanPostProcessorsRegistrar.class)
    // 导入 BeanPostProcessorsRegistrar :后置处理器的注册器(spring注解版)
    //给容器中导入组件,导入了 EmbeddedServletContainerCustomizerBeanPostProcessor
    //后置处理器:bean初始化前(创建完对象,还没赋值)执行初始化工作。
    public class EmbeddedServletContainerAutoConfiguration {
    	@Configuration
    	@ConditionalOnClass({ Servlet.class, Tomcat.class })//判断当前是否引入了 tomcat依赖
    	//判断当前容器没有用户直接定义 EmbeddedServletContainerFactory;嵌入式的 servlet容器工厂,作用:创建嵌入式的 servlet容器
    	@ConditionalOnMissingBean(value = EmbeddedServletContainerFactory.class, search = SearchStrategy.CURRENT)//
    	public static class EmbeddedTomcat {
    
    		@Bean
    		public TomcatEmbeddedServletContainerFactory tomcatEmbeddedServletContainerFactory() {
    			return new TomcatEmbeddedServletContainerFactory();
    		}
    
    	}
    }
    
    #EmbeddedServletContainerAutoConfiguration 类中 原理
    	/**
    	 * Nested configuration if Tomcat is being used.
    	 */
    	@Configuration
    	@ConditionalOnClass({ Servlet.class, Tomcat.class })
    	@ConditionalOnMissingBean(value = EmbeddedServletContainerFactory.class, search = SearchStrategy.CURRENT)
    	public static class EmbeddedTomcat {
    
    		@Bean
    		public TomcatEmbeddedServletContainerFactory tomcatEmbeddedServletContainerFactory() {
    			return new TomcatEmbeddedServletContainerFactory();
    		}
    
    	}
    
    	/**
    	 * Nested configuration if Jetty is being used.
    	 */
    	@Configuration
    	@ConditionalOnClass({ Servlet.class, Server.class, Loader.class,
    			WebAppContext.class })
    	@ConditionalOnMissingBean(value = EmbeddedServletContainerFactory.class, search = SearchStrategy.CURRENT)
    	public static class EmbeddedJetty {
    
    		@Bean
    		public JettyEmbeddedServletContainerFactory jettyEmbeddedServletContainerFactory() {
    			return new JettyEmbeddedServletContainerFactory();
    		}
    
    	}
    
    	/**
    	 * Nested configuration if Undertow is being used.
    	 */
    	@Configuration
    	@ConditionalOnClass({ Servlet.class, Undertow.class, SslClientAuthMode.class })
    	@ConditionalOnMissingBean(value = EmbeddedServletContainerFactory.class, search = SearchStrategy.CURRENT)
    	public static class EmbeddedUndertow {
    
    		@Bean
    		public UndertowEmbeddedServletContainerFactory undertowEmbeddedServletContainerFactory() {
    			return new UndertowEmbeddedServletContainerFactory();
    		}
    
    	}
    
    1. EmbeddedServletContainerFactory 嵌入式 Servlet 容器工厂,
    public interface EmbeddedServletContainerFactory {
    	//获取嵌入式的 servlet容器
    	EmbeddedServletContainer getEmbeddedServletContainer(
    			ServletContextInitializer... initializers);
    }
    

    image
    2. EmbeddedServletContainer 嵌入式的 servlet容器
    image
    3. 以 TomcatEmbeddedServletContainerFactory tomcat工厂类中的这个重写的方法

    	@Override
    	public EmbeddedServletContainer getEmbeddedServletContainer(
    			ServletContextInitializer... initializers) {
    		// 创建一个 tomcat
    		Tomcat tomcat = new Tomcat();
    		// 配置 tomcat的基本环节
    		File baseDir = (this.baseDirectory != null ? this.baseDirectory
    				: createTempDir("tomcat"));
    		tomcat.setBaseDir(baseDir.getAbsolutePath());
    		Connector connector = new Connector(this.protocol);
    		tomcat.getService().addConnector(connector);
    		customizeConnector(connector);
    		tomcat.setConnector(connector);
    		tomcat.getHost().setAutoDeploy(false);
    		configureEngine(tomcat.getEngine());
    		for (Connector additionalConnector : this.additionalTomcatConnectors) {
    			tomcat.getService().addConnector(additionalConnector);
    		}
    		prepareContext(tomcat.getHost(), initializers);
    		// 将配置好的 tomcat传入进去,返回一个 EmbeddedServletContainer;并且启动 tomcat服务器
    		return getTomcatEmbeddedServletContainer(tomcat);
    	}
    
    1. 我们对嵌入式容器的配置修改是怎么生效的?
    # application.properties 文件
    ServerProperties 该文件、EmbeddedServletContainerCustomizer 嵌入式ServletContainer编辑器
    

    EmbeddedServletContainerCustomizer:定制器帮我们修改了 servlet容器的配置?怎么修改?
    5. 容器中导入了 EmbeddedServletContainerCustomizerBeanPostProcessor

    EmbeddedServletContainerCustomizerBeanPostProcessor 类中
    	//初始化之前
    	@Override
    	public Object postProcessBeforeInitialization(Object bean, String beanName)
    			throws BeansException {
    		//如果当初初始化的是一个 ConfigurableEmbeddedServletContainer类型组件
    		//就调该方法
    		if (bean instanceof ConfigurableEmbeddedServletContainer) {
    			postProcessBeforeInitialization((ConfigurableEmbeddedServletContainer) bean);
    		}
    		return bean;
    	}
    
    	private void postProcessBeforeInitialization(
    			ConfigurableEmbeddedServletContainer bean) {
    		//获取所有的定制器,调用每一个定制器的 customize方法
    		//给每一个属性赋值(端口号、访问路径)
    		for (EmbeddedServletContainerCustomizer customizer : getCustomizers()) {
    			//getCustomizers 拿到所有的定制器
    			customizer.customize(bean);
    		}
    	}
    
    	private Collection<EmbeddedServletContainerCustomizer> getCustomizers() {
    		if (this.customizers == null) {
    			// Look up does not include the parent context
    			//从 ioc容器中获取嵌入式容器的组件
    			this.customizers = new ArrayList<EmbeddedServletContainerCustomizer>(
    					this.beanFactory
    						//从容器中获取所有该类型的组件
    						//EmbeddedServletContainerCustomizer
    						//定制 servlet容器,给容器中添加一个
    						//EmbeddedServletContainerCustomizer类型的组件
    							.getBeansOfType(EmbeddedServletContainerCustomizer.class,
    									false, false)
    							.values());
    			Collections.sort(this.customizers, AnnotationAwareOrderComparator.INSTANCE);
    			this.customizers = Collections.unmodifiableList(this.customizers);
    		}
    		return this.customizers;
    	}
    //ServerProperties 也是定制器
    

    image
    image
    总结

    1. springboot根据导入的依赖情况,给容器中添加响应的 EmbeddedServletContainerFactory【TomcatEmbeddedServletContainerFactory】
    2. 容器中某个组件要创建对象就会惊动后置处理器;
      EmbeddedServletContainerCustomizerBeanPostProcessor
      image
      只要是嵌入式的 Servlet容器工厂,后置处理处理器就可以工作了
    3. 后置处理器,从容器中获取所有的 EmbeddedServletContainerCustomizer(嵌入式servlet容器定制器)调用定制器的定制方法。

    8.5 嵌入式 servlet容器启动原理

    • 声明时候创建嵌入式的 Servlet容器工厂?什么时候获取嵌入式的 Servlet容器并启动 Tocmat
    1. 获取 spring boot应用启动运行 run()方法
      image

    2. refreshContext(context); spring boot属性 ioc容器【创建 ioc容器对象并初始化容器中的每一个组件】
      如果是 web应用创建:AnnotationConfigEmbeddedWebApplicationContext,否则:AnnotationConfigApplicationContext
      image

    3. refresh(context); 刷新刚才创建号的 ioc容器
      image

    @Override
    public void refresh() throws BeansException, IllegalStateException {
    synchronized (this.startupShutdownMonitor) {
    // Prepare this context for refreshing.
    prepareRefresh();

    		// Tell the subclass to refresh the internal bean factory.
    		ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
    
    		// Prepare the bean factory for use in this context.
    		prepareBeanFactory(beanFactory);
    
    		try {
    			// Allows post-processing of the bean factory in context subclasses.
    			postProcessBeanFactory(beanFactory);
    
    			// Invoke factory processors registered as beans in the context.
    			invokeBeanFactoryPostProcessors(beanFactory);
    
    			// Register bean processors that intercept bean creation.
    			registerBeanPostProcessors(beanFactory);
    
    			// Initialize message source for this context.
    			initMessageSource();
    
    			// Initialize event multicaster for this context.
    			initApplicationEventMulticaster();
    
    			// Initialize other special beans in specific context subclasses.
    			onRefresh();
    
    			// Check for listener beans and register them.
    			registerListeners();
    
    			// Instantiate all remaining (non-lazy-init) singletons.
    			finishBeanFactoryInitialization(beanFactory);
    
    			// Last step: publish corresponding event.
    			finishRefresh();
    		}
    
    		catch (BeansException ex) {
    			if (logger.isWarnEnabled()) {
    				logger.warn("Exception encountered during context initialization - " +
    						"cancelling refresh attempt: " + ex);
    			}
    
    			// Destroy already created singletons to avoid dangling resources.
    			destroyBeans();
    
    			// Reset 'active' flag.
    			cancelRefresh(ex);
    
    			// Propagate exception to caller.
    			throw ex;
    		}
    
    		finally {
    			// Reset common introspection caches in Spring's core, since we
    			// might not ever need metadata for singleton beans anymore...
    			resetCommonCaches();
    		}
    	}
    }
    ```
    
    1. onRefresh(); web的ioc容器 重写 onRefresh()方法
    2. web ioc容器会创建嵌入式的 servlet容器:createEmbeddedServletContainer();
    3. 获取嵌入式的 servlet容器工厂
      EmbeddedServletContainerFactory containerFactory = getEmbeddedServletContainerFactory();
      从 ioc容器中获取 EmbeddedServletContainerFactory组件
      TomcatEmbeddedServletContainerFactory 创建对象,惊动了后置处理器,后置处理器获取所有的定制器对象来获取定制 servlet容器的相关配置。
    4. 使用容器工程获取嵌入式的 servlet容器
      this.embeddedServletContainer = containerFactory
      .getEmbeddedServletContainer(getSelfInitializer());
    5. 嵌入式的 servlet容器创建对象并启动 servlet容器
      先启动嵌入式的 servlet容器,在将 ioc容器中剩下没有创建出的对象获取出来
      ioc容器启动创建嵌入式的 servlet容器

    9. 使用外置的 servlet容器

    • 嵌入式 servlet容器
      优点:简单,便携
      缺点:默认不支持 jsp,优化定制比较复杂【使用定制器 ServerProperties,自定义 EmbeddedServletContainerCustomizer】,自己编写 servlet容器工厂【EmbeddedServletContainerFacotry】
    • 外置的 servlet容器:外面安装 tomcat--应用war包的方式打包。

    9.1 步骤

    1. 必须创建一个 war项目
    2. 将嵌入式的 tomcat指定为 provided
          <dependency>
              <groupId>org.springframework.boot</groupId>
              <artifactId>spring-boot-starter-tomcat</artifactId>
              <scope>provided</scope>
          </dependency>
      
    3. 必须编写一个 SpringBootServletInitializer 的子类,并调用 configure方法
      public class ServletInitializer extends SpringBootServletInitializer{
      	@Override
      	protected SpringApplicationBuilder configure(SpringApplicationBuilder application){
      		//传入spring boot主程序
      		return application.sources(SpringBoot04WebJspApplication.class);
      	}
      }
      
    4. 启动服务器就可以使用了

    9.2 原理

    jar包:执行 SpringBoot 主内的 main方法,启动 ioc容器,创建嵌入式的 servlet容器
    war包:启动服务器,服务器启动 springboot应用,启动ioc容器。

    • 在 servlet3.0 的时候定义了一个规范
      在 servlet3.0 pdf文件中的 8.2.4 章节 Shared libraries / runtimes pluggability
      规则:
      1. 服务器【web应用启动】会创建当前 web应用里面每一个 jar包里面 ServletContainerinitializer实例
      2. ServletContainerinitializer 的实现的 jar包妨碍 META-INF/services文件夹下,有一个名为 javax.servlet.ServletContainerInitializer,内容就是 ServletContainerinitializer的实现类的全类名。
      3. 还可以使用 @HandlesTypes 注解,作用就是:在应用启动的时候加载我们感性的类。
        流程
    1. 启动 tomcat

    2. 在 spring的 web模块里面有这个文件
      spring-web-4.3.13.RELEASE.jar!META-INFservicesjavax.servlet.ServletContainerInitializer
      image

    3. SpringServletContainerInitializer 将 @HandlesTypes(WebApplicationInitializer.class)这个类型的类传入到 onStartup方法的 Set《Class《?》》为这些 WebApplicationInitializer类型的类创建对象,

    4. 每一个 WebApplicationInitializer都调用直接的 onStartup方法
      image

    5. 相当于我们的 SpringBootServletInitializer的类会被创建对象,并执行 onStartup方法并执行

    6. SpringBootServletInitializer实例执行 onStartup 的时候会 createRootApplicationContext;创建容器

      protected WebApplicationContext createRootApplicationContext(
      		ServletContext servletContext) {
      	//1. 创建 SpringApplicationBuilder构建器
      	SpringApplicationBuilder builder = createSpringApplicationBuilder();
      	StandardServletEnvironment environment = new StandardServletEnvironment();
      	environment.initPropertySources(servletContext, null);
      	builder.environment(environment);
      	builder.main(getClass());
      	ApplicationContext parent = getExistingRootWebApplicationContext(servletContext);
      	if (parent != null) {
      		this.logger.info("Root context already created (using as parent).");
      		servletContext.setAttribute(
      				WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, null);
      		builder.initializers(new ParentContextApplicationContextInitializer(parent));
      	}
      	builder.initializers(
      			new ServletContextApplicationContextInitializer(servletContext));
      	builder.contextClass(AnnotationConfigEmbeddedWebApplicationContext.class);
      	//调用 configure方法,子类重写了这个方法,传入spring boot主类的主程序
      	builder = configure(builder);
      	//使用 builder 创建一个spring应用
      	SpringApplication application = builder.build();
      	if (application.getSources().isEmpty() && AnnotationUtils
      			.findAnnotation(getClass(), Configuration.class) != null) {
      		application.getSources().add(getClass());
      	}
      	Assert.state(!application.getSources().isEmpty(),
      			"No SpringApplication sources have been defined. Either override the "
      					+ "configure method or add an @Configuration annotation");
      	// Ensure error pages are registered
      	if (this.registerErrorPageFilter) {
      		application.getSources().add(ErrorPageFilterConfiguration.class);
      	}
      	//启动 spring
      	return run(application);
      }
      
    7. spring的应用就启动了并创建 ioc容器

      public ConfigurableApplicationContext run(String... args) {
      	StopWatch stopWatch = new StopWatch();
      	stopWatch.start();
      	ConfigurableApplicationContext context = null;
      	FailureAnalyzers analyzers = null;
      	configureHeadlessProperty();
      	SpringApplicationRunListeners listeners = getRunListeners(args);
      	listeners.starting();
      	try {
      		ApplicationArguments applicationArguments = new DefaultApplicationArguments(
      				args);
      		ConfigurableEnvironment environment = prepareEnvironment(listeners,
      				applicationArguments);
      		Banner printedBanner = printBanner(environment);
      		context = createApplicationContext();
      		analyzers = new FailureAnalyzers(context);
      		prepareContext(context, environment, listeners, applicationArguments,
      				printedBanner);
      		
      		// 刷新 ioc容器
      		refreshContext(context);
      		afterRefresh(context, applicationArguments);
      		listeners.finished(context, null);
      		stopWatch.stop();
      		if (this.logStartupInfo) {
      			new StartupInfoLogger(this.mainApplicationClass)
      					.logStarted(getApplicationLog(), stopWatch);
      		}
      		return context;
      	}
      	catch (Throwable ex) {
      		handleRunFailure(context, listeners, analyzers, ex);
      		throw new IllegalStateException(ex);
      	}
      }
      

    先是启动 servlet容器,在启动 springboot应用

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  • 原文地址:https://www.cnblogs.com/zk2020/p/15438858.html
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