6. Servlet入门 - Servlet概述

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">

    <!-- servlet标签给Tomcat配置Servlet程序 -->
    <servlet>
        <!--servlet-name标签 Servlet程序起一个别名（一般是类名） -->
        <servlet-name>HelloServlet</servlet-name>
        <!--servlet-class是Servlet程序的全类名-->
        <servlet-class>com.test01.HelloServlet</servlet-class>
    </servlet>

    <!--servlet-mapping标签给servlet程序配置访问地址-->
    <servlet-mapping>
        <!--servlet-name标签的作用是告诉服务器，我当前配置的地址给哪个Servlet程序使用-->
        <servlet-name>HelloServlet</servlet-name>
        <!--
            url-pattern标签配置访问地址
               / 斜杠在服务器解析的时候，表示地址为：http://ip:port/工程路径
               /hello 表示地址为：http://ip:port/工程路径/hello
        -->
        <url-pattern>/hello</url-pattern>
    </servlet-mapping>

</web-app>

<!--form表单请求-->
<form action="http://localhost:8080/06_servlet/hello" method="get">
    <input type="submit">
</form>

@Override
public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException, IOException {
    System.out.println("3. service 方法：hello servlet被访问了！");
    // 类型转换（因为它有getMethod()方法）
    HttpServletRequest httpServletRequest = (HttpServletRequest) servletRequest;
    // 获取请求的方式
    String method = httpServletRequest.getMethod();
    System.out.println("请求的方法：" + method);
}

package com.test01;

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

/**
 * @author Aron.li
 * @date 2020/11/10 23:34
 */
public class HelloServlet implements Servlet {

    public HelloServlet() {
        System.out.println("1. HelloServlet构造方法");
    }

    @Override
    public void init(ServletConfig servletConfig) throws ServletException {
        System.out.println("2. init 初始化方法");
    }

    @Override
    public ServletConfig getServletConfig() {
        return null;
    }

    /**
     * 实现 service 方法，专门用来处理请求和响应
     * @param servletRequest
     * @param servletResponse
     * @throws ServletException
     * @throws IOException
     */
    @Override
    public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException, IOException {
        System.out.println("3. service 方法：hello servlet被访问了！");
        // 类型转换（因为它有getMethod()方法）
        HttpServletRequest httpServletRequest = (HttpServletRequest) servletRequest;
        // 获取请求的方式
        String method = httpServletRequest.getMethod();
        System.out.println("请求的方法：" + method);
        // 根据method分发执行不同的方法
        if ("GET".equals(method)){
            this.doGET();
        }else if ("POST".equals(method)){
            this.doPOST();
        }
    }
    /**
     * 处理GET方法
     */
    public void doGET(){
        System.out.println("处理GET方法");
    }
    /**
     * 处理POST方法
     */
    public void doPOST(){
        System.out.println("处理POST方法");
    }

    @Override
    public String getServletInfo() {
        return null;
    }

    @Override
    public void destroy() {
        System.out.println("4. destroy 销毁方法！");
    }
}

public class HelloServlet2 extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doGet(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}

<!-- 配置HelloServlet2   -->
<servlet>
    <servlet-name>HelloServlet2</servlet-name>
    <servlet-class>com.test01.HelloServlet2</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>HelloServlet2</servlet-name>
    <url-pattern>/hello2</url-pattern>
</servlet-mapping>

<!-- 配置HelloServlet3  -->
<servlet>
    <servlet-name>HelloServlet3</servlet-name>
    <servlet-class>com.test01.HelloServlet3</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>HelloServlet3</servlet-name>
    <url-pattern>/hello3</url-pattern>
</servlet-mapping>