SpringBoot 配置 Servlet、Filter、Listener

SpringBoot 配置 Servlet、Filter、Listener

在SpringBoot应用中，嵌入式的 Servlet 3.0+ 容器不会直接使用 ServletContainerInitializer 和 WebApplicationInitializer，即通过以上两个接口实现的 Servlet、Filter、Listener 配置都是无效的，这是为了防止第三方代码的设计损坏应用程序，原文如下

Embedded servlet containers will not directly execute the Servlet 3.0+ javax.servlet.ServletContainerInitializer interface, or Spring’s org.springframework.web.WebApplicationInitializer interface. This is an intentional design decision intended to reduce the risk that 3rd party libraries designed to run inside a war will break Spring Boot applications.

If you need to perform servlet context initialization in a Spring Boot application, you should register a bean that implements the org.springframework.boot.context.embedded.ServletContextInitializer interface. The single onStartup method provides access to the ServletContext, and can easily be used as an adapter to an existing WebApplicationInitializer if necessary.

综上，可以采取以下配置

配置策略一：ServletContextInitializer

由官方原文可知，我们可以使用替代方案：ServletContextInitializer，示例如下

@Configuration public class GoServletContextInitializer implements ServletContextInitializer { @Override public void onStartup(ServletContext servletContext) throws ServletException { //配置 Log4j Config Listener servletContext.setInitParameter("log4jConfigLocation", "classpath:config/properties/log4j.properties"); servletContext.addListener(Log4jConfigListener.class); //配置 CharacterEncodingFilter FilterRegistration.Dynamic characterEncodingFilter = servletContext.addFilter("characterEncodingFilter", CharacterEncodingFilter.class); characterEncodingFilter.setInitParameter("encoding", "UTF-8"); characterEncodingFilter.setInitParameter("forceEncoding", "true"); characterEncodingFilter.addMappingForUrlPatterns( EnumSet.of(DispatcherType.REQUEST, DispatcherType.FORWARD, DispatcherType.INCLUDE), false, "/*"); //配置 statViewServlet StatViewServlet statViewServlet = new StatViewServlet(); ServletRegistration.Dynamic dynamic = servletContext.addServlet( "statViewServlet", statViewServlet); dynamic.setLoadOnStartup(2); dynamic.addMapping("/druid/*"); } }

亲测，即使将 Spring Boot 打包成 war，并部署到 Tomcat 8.5，这份配置也是有效的

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配置策略二：ServletContextInitializer 的延伸

请看类继承体系

原理：最下边的三个子类会自动在运行时注册 Servlet、Listener、Filter（一定要将其定义为 Spring 容器的 Bean）

ServletRegistrationBean：在Servlet容器初始化时，向 ServletContext 注册一个自定义的 ServletServletListenerRegistrationBean：在Servlet容器初始化时，向 ServletContext 注册一个自定义的 ServletContextListenerAbstractFilterRegistrationBean：（模板方法模式）通过模板方法 getFilter()，将 Filter 的构建过程延迟到子类，并在Servlet容器初始化时，向 ServletContext 注册该 Filter。开发者可以定义一个子类来重写该模板方法，以配置一个自定义的 Filter。

Servlet 配置示例

@Configuration public class ServletConfig { //配置 StatViewServlet @Bean public ServletRegistrationBean servletRegistration0() { ServletRegistrationBean registration = new ServletRegistrationBean(new StatViewServlet()); registration.addUrlMappings("/druid/*"); registration.setLoadOnStartup(0); return registration; } }

Filter 配置示例

@Configuration public class FilterConfig { //配置 CharacterEncodingFilter @Bean public FilterRegistrationBean filterRegistration1() { FilterRegistrationBean registration = new FilterRegistrationBean(new CharacterEncodingFilter()); registration.addUrlPatterns("/*"); Map<String, String> initParameters = Maps.newHashMap(); initParameters.put("encoding", "UTF-8"); initParameters.put("forceEncoding", "true"); registration.setInitParameters(initParameters); return registration; } }

Listener 配置示例

@Configuration public class ListenerConfig { //配置 RequestContextListener @Bean public ServletListenerRegistrationBean<RequestContextListener> listenerRegistration3() { return new ServletListenerRegistrationBean<>( new RequestContextListener()); } }

转载于:https://www.cnblogs.com/pomer-huang/p/9639322.html