（020）Spring Boot之Servlet、过滤器（Filter）、监听器（Listener）
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IT文章
•
2025-01-14 13:40:31
分别有两种方法实现Servlet、过滤器（Filter）、监听器（Listener）
先贴出pom.xml
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<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.edu.spring</groupId>
<artifactId>springboot_web</artifactId>
<version>1.0.0</version>
<name>springboot_web</name>
<!-- FIXME change it to the project's website -->
<url>http://www.example.com</url>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.0.4.RELEASE</version>
</parent>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.source>1.8</maven.compiler.source>
<maven.compiler.target>1.8</maven.compiler.target>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
</dependencies>
</project>
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方法一，使用注解，（WebServlet、WebFilter、WebListener是Servlet3.0的注解）
（1）Servlet使用@ServletComponentScan+@WebServlet。举例如下：
UserServlet.java
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package com.edu.spring.springboot;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("/user.do")
public class UserServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
resp.getWriter().print("user servlet");
}
}
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App.java
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package com.edu.spring.springboot;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.servlet.ServletComponentScan;
@ServletComponentScan
@SpringBootApplication
public class App
{
public static void main(String[] args) {
SpringApplication.run(App.class, args);
}
}
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浏览器输入：http://127.0.0.1:8080/user.do，验证结果如下：
（2）Filter使用@ServletComponentScan+@WebFilter。举例如下：
LogFilter.java
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package com.edu.spring.springboot;
import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;
@WebFilter("/user.do")
public class LogFilter implements Filter {
@Override
public void destroy() {
// TODO Auto-generated method stub
}
@Override
public void doFilter(ServletRequest arg0, ServletResponse arg1,
FilterChain arg2) throws IOException, ServletException {
// TODO Auto-generated method stub
System.out.println("income log filter "+arg0.getRemoteHost());
arg2.doFilter(arg0, arg1);
}
@Override
public void init(FilterConfig arg0) throws ServletException {
// TODO Auto-generated method stub
}
}
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App.java
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package com.edu.spring.springboot;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.servlet.ServletComponentScan;
@ServletComponentScan
@SpringBootApplication
public class App
{
public static void main(String[] args) {
SpringApplication.run(App.class, args);
}
}
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浏览器输入：http://127.0.0.1:8080/user.do，验证结果如下：
（3）Listener使用@ServletComponentScan+@WebListener。举例如下：
MyContextListener.java
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package com.edu.spring.springboot;
import java.time.LocalDateTime;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.annotation.WebListener;
@WebListener
public class MyContextListener implements ServletContextListener {
@Override
public void contextDestroyed(ServletContextEvent arg0) {
// TODO Auto-generated method stub
}
@Override
public void contextInitialized(ServletContextEvent arg0) {
// TODO Auto-generated method stub
System.out.println("start at "+LocalDateTime.now().toString());
}
}
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App.java
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package com.edu.spring.springboot;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.servlet.ServletComponentScan;
@ServletComponentScan
@SpringBootApplication
public class App
{
public static void main(String[] args) {
SpringApplication.run(App.class, args);
}
}
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启动结果如下：
方法二，分别创建3个bean：ServletRegistrationBean、FilterRegistrationBean、ServletListenerRegistrationBean
servlet对应ServletRegistrationBean；Filter对应FilterRegistrationBean；Listenner对应ServletListenerRegistrationBean。请看代码：
UserServlet.java
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package com.edu.spring.springboot;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("/user.do")
public class UserServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
resp.getWriter().print("user servlet");
}
}
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LogFilter.java
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package com.edu.spring.springboot;
import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;
@WebFilter("/user.do")
public class LogFilter implements Filter {
@Override
public void destroy() {
// TODO Auto-generated method stub
}
@Override
public void doFilter(ServletRequest arg0, ServletResponse arg1,
FilterChain arg2) throws IOException, ServletException {
// TODO Auto-generated method stub
System.out.println("income log filter "+arg0.getRemoteHost());
arg2.doFilter(arg0, arg1);
}
@Override
public void init(FilterConfig arg0) throws ServletException {
// TODO Auto-generated method stub
}
}
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MyContextListener.java
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package com.edu.spring.springboot;
import java.time.LocalDateTime;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.annotation.WebListener;
@WebListener
public class MyContextListener implements ServletContextListener {
@Override
public void contextDestroyed(ServletContextEvent arg0) {
// TODO Auto-generated method stub
}
@Override
public void contextInitialized(ServletContextEvent arg0) {
// TODO Auto-generated method stub
System.out.println("start at "+LocalDateTime.now().toString());
}
}
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ServletConfig.java。创建bean，并且装配到spring容器中
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package com.edu.spring.springboot;
import java.util.Arrays;
import org.springframework.boot.SpringBootConfiguration;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.boot.web.servlet.ServletListenerRegistrationBean;
import org.springframework.boot.web.servlet.ServletRegistrationBean;
import org.springframework.context.annotation.Bean;
@SpringBootConfiguration
public class ServletConfig {
@Bean
public ServletRegistrationBean createBookServlet(){
ServletRegistrationBean servlet= new ServletRegistrationBean(new UserServlet(),"/user.do");
return servlet;
}
@Bean
public FilterRegistrationBean createEchoFilter(){
FilterRegistrationBean filter=new FilterRegistrationBean();
filter.setFilter(new LogFilter());
filter.setUrlPatterns(Arrays.asList("/user.do"));
return filter;
}
@Bean
public ServletListenerRegistrationBean<MyContextListener> createStartedUpListener(){
ServletListenerRegistrationBean<MyContextListener> servletRegistrationBean=new ServletListenerRegistrationBean(new MyContextListener());
return servletRegistrationBean;
}
}
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App.java
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package com.edu.spring.springboot;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class App
{
public static void main(String[] args) {
SpringApplication.run(App.class, args);
}
}
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启动并验证结果如下：
浏览器输入：http://127.0.0.1:8080/user.do ，验证Servlet
验证Filter
