通过继承 HttpServlet 实现 Servlet 程序
一般在实际项目开发中，都是使用继承 HttpServlet 类的方式去实现 Servlet 程序。
1、编写一个类去继承 HttpServlet 类
2、根据业务需要重写 doGet 或 doPost 方法
3、到 web.xml 中的配置 Servlet 程序的访问地址
package top.qaqaq.P127;
import jakarta.servlet.ServletException;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import java.io.IOException;
/**
* @author RichieZhang
* @create 2022-12-04 下午 8:33
*/
public class HelloServlet2 extends HttpServlet {
/**
* doGet() 在get请求的时候调用
* @param req
* @param resp
* @throws ServletException
* @throws IOException
*/
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// super.doGet(req, resp);
System.out.println("HelloServlet2 的doGet方法");
}
/**
* doPost() 在post请求的时候调用
* @param req
* @param resp
* @throws ServletException
* @throws IOException
*/
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// super.doPost(req, resp);
System.out.println("HelloServlet2 的doPost方法");
}
}
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<!-- <form action="http://localhost:8080/JavaWeb_Code_Servlet/hello" method="get">-->
<!-- -->
<!-- <input type="submit">-->
<!-- </form>-->
<form action="http://localhost:8080/JavaWeb_Code_Servlet/hello3" method="post">
<input type="submit">
</form>
</body>
</html><?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>top.qaqaq.P122.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>
<servlet>
<servlet-name>HelloServlet2</servlet-name>
<servlet-class>top.qaqaq.P127.HelloServlet2</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>HelloServlet2</servlet-name>
<url-pattern>/hello2</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>HelloServlet3</servlet-name>
<servlet-class>top.qaqaq.P128.HelloServlet3</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>HelloServlet3</servlet-name>
<url-pattern>/hello3</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>HelloServlet4</servlet-name>
<servlet-class>top.qaqaq.P130.HelloServlet4</servlet-class>
<!-- init-param是初始化参数 -->
<init-param>
<!-- 是参数名 -->
<param-name>username</param-name>
<!-- 是参数值 -->
<param-value>root</param-value>
</init-param>
<!-- init-param是初始化参数 -->
<init-param>
<!-- 是参数名 -->
<param-name>url</param-name>
<!-- 是参数值 -->
<param-value>jdbc:mysql://localhost:3306/test</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>HelloServlet4</servlet-name>
<url-pattern>/hello4</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>HelloServlet5</servlet-name>
<servlet-class>top.qaqaq.P131.HelloServlet5</servlet-class>
<!-- init-param是初始化参数 -->
<init-param>
<!-- 是参数名 -->
<param-name>username</param-name>
<!-- 是参数值 -->
<param-value>root2</param-value>
</init-param>
<!-- init-param是初始化参数 -->
<init-param>
<!-- 是参数名 -->
<param-name>url</param-name>
<!-- 是参数值 -->
<param-value>jdbc:mysql://localhost:3306/test2</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>HelloServlet5</servlet-name>
<url-pattern>/hello5</url-pattern>
</servlet-mapping>
</web-app>