https://blog.csdn.net/qq_38709999/article/details/99986797
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
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 Servlet
- ServletListenerRegistrationBean:在Servlet容器初始化时,向 ServletContext 注册一个自定义的 ServletContextListener
- AbstractFilterRegistrationBean:(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());
}
}
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需求:springboot 启动后自动执行某些代码,初始化数据,并将数据放到 servletContext 中。 首先,不可使用 ServletContextListener 即不能用 @WebListener ,因为 servlet 容器初始化后,spring 并未初始化完毕,不能使用 @Autowired 注入 spring 的对象。 推荐使用 ApplicationListener:启动项目, spring 加载完毕后,才执行该 ApplicationListener,并且该 Listener 中可以使用 spring 的内容。 @Component public class SettingDataInitListener implements ApplicationListener<ContextRefreshedEvent> { @Override public void onApplicationEvent(ContextRefreshedEvent contextRefreshedEvent) { // 将 ApplicationContext 转化为 WebApplicationContext WebApplicationContext webApplicationContext = (WebApplicationContext)contextRefreshedEvent.getApplicationContext(); // 从 webApplicationContext 中获取 servletContext ServletContext servletContext = webApplicationContext.getServletContext(); // servletContext设置值 servletContext.setAttribute("key", "value"); }
需求:springboot 启动后自动执行某些代码,初始化数据,并将数据放到 servletContext 中。
首先,不可使用 ServletContextListener 即不能用 @WebListener ,因为 servlet 容器初始化后,spring 并未初始化完毕,不能使用 @Autowired 注入 spring 的对象。
推荐使用 ApplicationListener:启动项目, spring 加载完毕后,才执行该 ApplicationListener,并且该 Listener 中可以使用 spring 的内容。
-
@Component
-
public class SettingDataInitListener implements ApplicationListener<ContextRefreshedEvent> {
-
@Override
-
public void onApplicationEvent(ContextRefreshedEvent contextRefreshedEvent) {
-
// 将 ApplicationContext 转化为 WebApplicationContext
-
WebApplicationContext webApplicationContext =
-
(WebApplicationContext)contextRefreshedEvent.getApplicationContext();
-
// 从 webApplicationContext 中获取 servletContext
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ServletContext servletContext = webApplicationContext.getServletContext();
-
// servletContext设置值
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servletContext.setAttribute("key", "value");
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}
原文地址:https://www.cnblogs.com/kelelipeng/p/11412138.html