HelloServlet初始化

1。新建一个空maven项目，删掉src文件夹。

2.在pom.xml里建中加入依赖关系

    <dependencies>
    <!-- https://mvnrepository.com/artifact/javax.servlet/javax.servlet-api -->
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>javax.servlet-api</artifactId>
        <version>3.1.0</version>
    </dependency>

    <!-- https://mvnrepository.com/artifact/javax.servlet.jsp/javax.servlet.jsp-api -->
    <dependency>
        <groupId>javax.servlet.jsp</groupId>
        <artifactId>javax.servlet.jsp-api</artifactId>
        <version>2.3.3</version>
    </dependency>
    </dependencies>

3.建立子项目

4. Maven环境优化

• web子项目的web.xml替换以下代码（来自tomcat的webapp）

<?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"
  metadata-complete="true">

</web-app>

• 　　将maven的结构搭建完整，新建java,resources 文件夹并标记。

5编写一个servlet程序。

编写一个普通类，实现servlet接口，这里我们直接继承HttpServlet

package com.yin.servlet;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;

public class HelloServlet extends HttpServlet {

    //GET和PUT只是请求实现的不同方式，业务逻辑都一样，可以互相调用
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        req.getInputStream();

        PrintWriter writer=resp.getWriter();//响应流
        writer.println("Hello YinSong!");

    }

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

　　6.编写Servlet的映射，web.xml添加以下代码

    <servlet>
        <servlet-name>hello</servlet-name>
        <servlet-class>com.yin.servlet.HelloServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>hello</servlet-name>
        <url-pattern>/hello</url-pattern>
    </servlet-mapping>

7.配置Tomcat