springboot开发之配置Servlet三大组件（Servlet、Filter、Listener）

1、首先我们自己定义三大组件：MyServlet.java、MyFilter.java、MyListener.java

MyServlet.java

package com.gong.springbootcurd.servlet;

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 MyServlet extends HttpServlet {
    //处理get请求
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req,resp);
    }
    //处理post请求
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.getWriter().write("hello world");
    }
}

MyFilter.java

package com.gong.springbootcurd.filter;

import javax.servlet.*;
import java.io.IOException;

public class MyFilter implements Filter{
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        System.out.println("myfilter process");
        filterChain.doFilter(servletRequest,servletResponse);;
    }

    @Override
    public void destroy() {

    }
}

MyListener.java

package com.gong.springbootcurd.listener;

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

public class MyListener implements ServletContextListener {
    @Override
    public void contextInitialized(ServletContextEvent sce) {
        System.out.println("contextInitialized..web应用启动了");
    }

    @Override
    public void contextDestroyed(ServletContextEvent sce) {
        System.out.println("contextDestroyed..web应用关闭了");
    }
}

（2）我们自定义注册三大组件的文件：MyServletConfig.java

package com.gong.springbootcurd.config;

import com.gong.springbootcurd.filter.MyFilter;
import com.gong.springbootcurd.listener.MyListener;
import com.gong.springbootcurd.servlet.MyServlet;
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;
import org.springframework.context.annotation.Configuration;

import javax.servlet.Filter;
import javax.servlet.Servlet;
import javax.servlet.ServletContextListener;
import java.util.Arrays;

@Configuration
public class MyServletConfig {
    //注册三大组件
    @Bean
    public ServletRegistrationBean myServlet(){
        ServletRegistrationBean<Servlet> registrationBean = new ServletRegistrationBean<>(
                new MyServlet(),"/myServlet"
        );
        registrationBean.setLoadOnStartup(1);
        return registrationBean;
    }
    @Bean
    public FilterRegistrationBean myFilter(){
        FilterRegistrationBean<Filter> registrationBean = new FilterRegistrationBean<>();
        registrationBean.setFilter(new MyFilter());
        registrationBean.setUrlPatterns(Arrays.asList("/hello","/myServlet"));
        return registrationBean;
    }
    @Bean
    public ServletListenerRegistrationBean myListener(){
        ServletListenerRegistrationBean<MyListener> registrationBean = new ServletListenerRegistrationBean<MyListener>(new MyListener());
        return registrationBean;
    }
}

我们启动服务器，并输入localhost:8080/curd/myServlet，可以看到：

MyServlet起作用了。

在控制台：

MyListener起作用了，MyFilter也起作用 

点击紫色框中按钮关闭服务：

MyListener其作用了。