自制Springboot Starter

1. 新建Spring boot项目

   <parent>
     <groupId>org.springframework.boot</groupId>
     <artifactId>spring-boot-starter-parent</artifactId>
     <version>2.7.0</version>
     <relativePath/> <!-- lookup parent from repository -->
   </parent>
   <groupId>com.example</groupId>
   <artifactId>web-filter-log-boot-starter</artifactId>
   <dependency>
     <groupId>org.springframework.boot</groupId>
     <artifactId>spring-boot-starter-web</artifactId>
   </dependency>
   

2. 定义一个web过滤器，验证Spring boot starter是否生效

   // Filter
   public class LogFilter implements Filter {
   
       private Logger logger = LoggerFactory.getLogger(LogFilter.class);
   
       @Override
       public void init(FilterConfig filterConfig) throws ServletException {
           System.err.println("logFilter init...");
           logger.info("logFilter init...");
       }
   
       @Override
       public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
           HttpServletRequest httpServletRequest = (HttpServletRequest) servletRequest;
           logger.info("uri: {} is working.", httpServletRequest.getRequestURI());
           filterChain.doFilter(servletRequest,servletResponse);
       }
   
       @Override
       public void destroy() {
           logger.info("logFilter destroy...");
       }
   }
   

   // 配置Filter生效
   public class LogFilterRegistrationBean extends FilterRegistrationBean<LogFilter> {
       public LogFilterRegistrationBean() {
           super();
           this.setFilter(new LogFilter());
           this.addUrlPatterns("/*");
           this.setName("LogFilter");
           this.setOrder(1);
       }
   }
   

   定义自动配置类

   // 自动配置类
   @Configuration
   @ConditionalOnClass({LogFilterRegistrationBean.class, LogFilter.class})
   public class LogFilterAutoConfiguration {
       @Bean
       @ConditionalOnMissingBean(LogFilterRegistrationBean.class)
       public LogFilterRegistrationBean logFilterRegistrationBean() {
           return new LogFilterRegistrationBean();
       }
   }
   

3. 定义注解，使用注解将使该starter配置生效

   @Target(ElementType.TYPE)
   @Retention(RetentionPolicy.RUNTIME)
   @Import(EnableLogFilterImportSelector.class)
   public @interface EnableLogFilter {
   
   }
   

4. 定义EnableLogFilterImportSelector用于从spring.factories加载starter自动配置类

   public class EnableLogFilterImportSelector implements DeferredImportSelector, BeanClassLoaderAware, EnvironmentAware {
   
       private ClassLoader beanClassLoader;
       private Class annotationClass = EnableLogFilter.class;
   
       @Override
       public String[] selectImports(AnnotationMetadata importingClassMetadata) {
   
           var attributes =
                   AnnotationAttributes.fromMap(importingClassMetadata
                           .getAnnotationAttributes(annotationClass.getName(), true));
           List<String> factories = new ArrayList<>(
                   new LinkedHashSet<>(SpringFactoriesLoader.loadFactoryNames(this.annotationClass, this.beanClassLoader)));
           return factories.toArray(new String[factories.size()]);
       }
   
       @Override
       public void setEnvironment(Environment environment) {
   
       }
   
       @Override
       public void setBeanClassLoader(ClassLoader classLoader) {
           this.beanClassLoader = classLoader;
       }
   }
   

5. 在resources/META-INF中添加spring.factories

   com.example.annotation.EnableLogFilter=com.example.config.LogFilterAutoConfiguration
   

6. 使用starter

   <dependency>
     <groupId>com.example</groupId>
     <artifactId>web-filter-log-boot-starter</artifactId>
   </dependency>
   

   在启动类上添加EnableLogFilter注解，使starter自动配置生效

   @SpringBootApplication
   @EnableLogFilter
   public class DemoBootApplication {
   
       public static void main(String[] args) {
           SpringApplication.run(DemoBootApplication.class, args);
       }
   
   }