Web三大组件的注册——Servlet、Filter、Listener(监听三大作用域： ServletContext、HttpSession、ServletRequest )

Web三大组件的注册

Servlet

@WebServlet(“/user.action”)

</servlet>

<servlet-mapping>

</servlet-mapping>

Filter

@WebFilter()

</filter>

<filter-mapping>

</filter-mapping>

Listener

@WebListener

<listener-class></listener-class>

</listener>

UserServlet.java

package com.sxt.controller;import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;public class UserServlet extends HttpServlet {@Overridepublic void init(ServletConfig config) throws ServletException {String env = config.getInitParameter("env");String hello = config.getInitParameter("hello");System.out.println(env+"  "+hello);}@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {this.doPost(req,resp);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {System.out.println("hello--UserServlet");}
}

 /*** 创建UserServlet*/@Bean("userServlet")@ConditionalOnClass(value = {UserServlet.class})public UserServlet userServlet(){return new UserServlet();}/*** 注册UserServlet*/@Bean@ConditionalOnBean(value = {UserServlet.class})public ServletRegistrationBean<UserServlet> servletRegistrationBeanUserServlet(UserServlet userServlet){
//    public ServletRegistrationBean<UserServlet> servletRegistrationBeanUserServlet(){
//        UserServlet userServlet=new UserServlet();//创建注册器对象ServletRegistrationBean<UserServlet> registrationBean=new ServletRegistrationBean<>();//注入ServletregistrationBean.setServlet(userServlet);//设置参数registrationBean.addInitParameter("env","UTF-8");registrationBean.addInitParameter("hello","你好");//设置映射registrationBean.addUrlMappings("/user1.action","/user2.action");return registrationBean;}

AppFilter.java

package com.sxt.controller;import javax.servlet.*;
import java.io.IOException;public class AppFilter implements Filter {@Overridepublic void init(FilterConfig filterConfig) throws ServletException {String env = filterConfig.getInitParameter("env");String hello = filterConfig.getInitParameter("hello");System.out.println(env+"  "+hello);}@Overridepublic void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {System.out.println("doFilter");chain.doFilter(request,response);}@Overridepublic void destroy() {}
}

/*** 创建Filter*/@Bean("appFilter")@ConditionalOnClass(value = {AppFilter.class})public AppFilter appFilter(){return new AppFilter();}/*** 注册Filter*/@Bean@ConditionalOnBean(value = {AppFilter.class})public FilterRegistrationBean<AppFilter> filterFilterRegistrationBeanAppFilter(AppFilter appFilter){//创建注册器FilterRegistrationBean<AppFilter> registrationBean=new FilterRegistrationBean<>();//注入filterregistrationBean.setFilter(appFilter);//设置参数registrationBean.addInitParameter("env","filter-UTF-8");registrationBean.addInitParameter("hello","filter-你好");//设置映射
//        registrationBean.addUrlPatterns("/*");registrationBean.addServletNames("userServlet");return registrationBean;}

Listener的分类

监听三大作用域

ServletContext

|--ServletContextListener ServletContextAttributeListener

HttpSession

|--HttpSessionListner HttpSessionAttributeListener

ServletRequest

|--ServletReqeustListener ServletRequestAttributeListener

AppListener.java

package com.sxt.controller;import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;public class AppListener implements ServletContextListener {@Overridepublic void contextInitialized(ServletContextEvent sce) {System.out.println("contextInitialized");}@Overridepublic void contextDestroyed(ServletContextEvent sce) {}
}

package com.sxt.config;import com.sxt.controller.AppListener;
import lombok.Data;
import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.web.servlet.ServletListenerRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.stereotype.Component;@Configuration
@Component
@ConfigurationProperties(prefix = "web")
@Data
public class WebConfig {private Boolean applistenerEnable=true;/*** 创建Listener*/@Bean@ConditionalOnClass(value = {AppListener.class})public AppListener appListener(){return new AppListener();}@Bean@ConditionalOnBean(value = {AppListener.class})public ServletListenerRegistrationBean<AppListener> servletListenerRegistrationBeanAppListener(AppListener listener){//创建注册器ServletListenerRegistrationBean<AppListener> bean=new ServletListenerRegistrationBean<AppListener>();//注入listenerbean.setListener(listener);bean.setEnabled(applistenerEnable);return bean;}
}

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