springboot情操陶冶-web配置(一)

承接前文springboot情操陶冶-@SpringBootApplication注解解析，在前文讲解的基础上依次看下web方面的相关配置

环境包依赖

在pom.xml文件中引入web依赖，炒鸡简单，如下

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>

上述的三行依赖代码便完成了对web环境的配置，此时可以直接运行main()方法

package com.example.demospringbootweb;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class DemoSpringbootWebApplication {

    public static void main(String[] args) {
        SpringApplication.run(DemoSpringbootWebApplication.class, args);
    }
}

默认服务是挂载在Tomcat容器中，端口为8080。所以可以通过该链接直接访问http://127.0.0.1:8080便可得到以下页面(未配置index页面的效果)

应用端口和上下文配置

本文将在上文的基础山讲解端口和上下文路径的具体配置以及解析。现附上简单的步骤操作

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创建application-servlet.properties文件，专门用于配置应用服务

#server application config
server.port=9001
server.servlet.context-path=/demoWeb

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在application.properties文件中指定激活的profile，用于使上述文件生效

spring.profiles.active=servlet

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为了使界面变得稍微友好，引入index.html文件，放置于static目录下，如下

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继续运行对应的main()函数，便可访问http://127.0.0.1:9001/demoWeb，得到以下结果

源码剖析

关于Tomcat等容器的配置，springboot采用了EmbeddedWebServerFactoryCustomizerAutoConfiguration和ServletWebServerFactoryAutoConfiguration两个类便完成了。笔者针对这两个类进行简单的分析

EmbeddedWebServerFactoryCustomizerAutoConfiguration

直接查看其内部源码，如下

@Configuration
@EnableConfigurationProperties(ServerProperties.class)
public class EmbeddedWebServerFactoryCustomizerAutoConfiguration {
	@ConditionalOnClass({ Tomcat.class, UpgradeProtocol.class })
	public static class TomcatWebServerFactoryCustomizerConfiguration {

		@Bean
		public TomcatWebServerFactoryCustomizer tomcatWebServerFactoryCustomizer(
				Environment environment, ServerProperties serverProperties) {
			return new TomcatWebServerFactoryCustomizer(environment, serverProperties);
		}

	}

	/**
	 * Nested configuration if Jetty is being used.
	 */
	@Configuration
	@ConditionalOnClass({ Server.class, Loader.class, WebAppContext.class })
	public static class JettyWebServerFactoryCustomizerConfiguration {

		@Bean
		public JettyWebServerFactoryCustomizer jettyWebServerFactoryCustomizer(
				Environment environment, ServerProperties serverProperties) {
			return new JettyWebServerFactoryCustomizer(environment, serverProperties);
		}

	}

	/**
	 * Nested configuration if Undertow is being used.
	 */
	@Configuration
	@ConditionalOnClass({ Undertow.class, SslClientAuthMode.class })
	public static class UndertowWebServerFactoryCustomizerConfiguration {

		@Bean
		public UndertowWebServerFactoryCustomizer undertowWebServerFactoryCustomizer(
				Environment environment, ServerProperties serverProperties) {
			return new UndertowWebServerFactoryCustomizer(environment, serverProperties);
		}

	}
}

主要是引入了ServerProperties配置类，样例中的server.port/server.servlet.context-path便是保存在ServerProperties对象中的，其是读取spring上下文环境中的以server为开头的属性，具体的属性用户可自行查看源码。

由上述的简单代码得知该自动配置类主要根据classpath环境创建不同的应用容器，默认springboot集成的都是tomcat。我们此处只关注下TomcatWebServerFactoryCustomizer类，下文中会有所提及

ServletWebServerFactoryAutoConfiguration

具体的ServletWebServer容器配置是通过ServletWebServerFactoryAutoConfiguration来创建的，由于代码过长笔者分为几个部分来讲解

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头上注解先瞧一发

@Configuration
@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE)
@ConditionalOnClass(ServletRequest.class)
@ConditionalOnWebApplication(type = Type.SERVLET)
@EnableConfigurationProperties(ServerProperties.class)
@Import({ ServletWebServerFactoryAutoConfiguration.BeanPostProcessorsRegistrar.class,
		ServletWebServerFactoryConfiguration.EmbeddedTomcat.class,
		ServletWebServerFactoryConfiguration.EmbeddedJetty.class,
		ServletWebServerFactoryConfiguration.EmbeddedUndertow.class })
public class ServletWebServerFactoryAutoConfiguration {
}

要想本自动配置生效则必须classpath环境中存在ServletRequest.class等servlet环境依赖类，这一般引入开头的starter-web版块便基本满足了

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创建webServerFactory个性化配置类

	@Bean
	public ServletWebServerFactoryCustomizer servletWebServerFactoryCustomizer(
			ServerProperties serverProperties) {
		return new ServletWebServerFactoryCustomizer(serverProperties);
	}

	@Bean
	@ConditionalOnClass(name = "org.apache.catalina.startup.Tomcat")
	public TomcatServletWebServerFactoryCustomizer tomcatServletWebServerFactoryCustomizer(
			ServerProperties serverProperties) {
		return new TomcatServletWebServerFactoryCustomizer(serverProperties);
	}

这两个bean类和上文中的TomcatWebServerFactoryCustomizer很相似，但仔细阅读源码之后便发现其实这只是tomcat配置的分工处理，小结如下

• TomcatWebServerFactoryCustomizer 配置tomcat的主要信息，包含remoteIpValue、connector(最大/最小可接收线程、最大可接收头部大小等等)、uriEncoding、connectionTimeout、maxConnection等属性
• TomcatServletWebServerFactoryCustomizer 配置tomcat的额外信息，redirectContextRoot(是否在请求根上下文时转发，true则转发路径为/demoWeb/)和useRelativeRedirects(是否使用相对路径)等路径跳转问题处理
• ServletWebServerFactoryCustomizer 主要配置tomcat的servlet的信息，包含端口、上下文路径、应用名、Session配置、Servlet携带的初始变量等等

通过上述的三个bean类便基本完成了基本的tomcat配置，其都是WebServerFactoryCustomizer接口的实现类，那么是被谁来统一调用以完成上述的配置呢？

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1.首先引入了WebServerFactory工厂类，此点可直接看由上述@Import引入的EmbeddedTomcat分析可得

	@Configuration
	@ConditionalOnClass({ Servlet.class, Tomcat.class, UpgradeProtocol.class })
	@ConditionalOnMissingBean(value = ServletWebServerFactory.class, search = SearchStrategy.CURRENT)
	public static class EmbeddedTomcat {
		@Bean
		public TomcatServletWebServerFactory tomcatServletWebServerFactory() {
			return new TomcatServletWebServerFactory();
		}

	}

创建了TomcatServletWebServerFactory的tomcat容器，其余的web容器读者可自行分析

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2.最后通过beanPostProcessor接口来完成相应的容器初始化
由@Import引入的BeanPostProcessorsRegistrar类，注册了webServerFactoryCustomizerBeanPostProcessor类来完成相应的tomcat个性化配置

    // 初始化上述的WebServerFactory对象前操作
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        if (bean instanceof WebServerFactory) {
            this.postProcessBeforeInitialization((WebServerFactory)bean);
        }

        return bean;
    }

	// 调用所有实现了WebServerFactoryCustomizer接口的对象
    private void postProcessBeforeInitialization(WebServerFactory webServerFactory) {
        ((Callbacks)LambdaSafe.callbacks(WebServerFactoryCustomizer.class, this.getCustomizers(), webServerFactory, new Object[0]).withLogger(WebServerFactoryCustomizerBeanPostProcessor.class)).invoke((customizer) -> {
            customizer.customize(webServerFactory);
        });
    }
	
	// 查找当前bean工厂中所有类型为WebServerFactoryCustomizer接口对象集合
    private Collection<WebServerFactoryCustomizer<?>> getCustomizers() {
        if (this.customizers == null) {
            this.customizers = new ArrayList(this.getWebServerFactoryCustomizerBeans());
            this.customizers.sort(AnnotationAwareOrderComparator.INSTANCE);
            this.customizers = Collections.unmodifiableList(this.customizers);
        }

        return this.customizers;
    }

    private Collection<WebServerFactoryCustomizer<?>> getWebServerFactoryCustomizerBeans() {
        return this.beanFactory.getBeansOfType(WebServerFactoryCustomizer.class, false, false).values();
    }

具体的解析见上述的代码注释，其实也很简单并一目了然，所以如果用户想在tomcat上再作个性化的需求，可自行实现WebServerFactoryCustomizer接口并注册至bean工厂即可

@Configuration
public MyWebServerFactoryCustomizer implements WebServerFactoryCustomizer<ConfigurableServletWebServerFactory>{
	@Override
	public void customize(ConfigurableServletWebServerFactory factory) {
		PropertyMapper map = PropertyMapper.get().alwaysApplyingWhenNonNull();
		// do personal binding
	}
}

小结

本文只讲述tomcat的相关配置，并举例说明了其port/contextPath的应用配置，更多的配置读者可采用springboot实现的带server前缀的配置以及自行实现WebServerFactoryCustomizer接口去实现