javaWEB总结(9):自定义HttpServlet

时间：2021-07-14 02:53:19

前言:我们知道 MyHttpServlet是MyGenericServlet的子类，MyHttpServlet会继承父类的方法，可是却很少去追问MyHttpServlet中的doGet方法和doPost方法是如何进行判断的，本文主要做一个小例子，进一步理解HttpServlet。有些代码前文多次用到，这里不再叙述。

1.项目结构

javaWEB总结(9):自定义HttpServlet

2.web.xml

<?xml version="1.0" encoding="UTF-8"?>

<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">

    <display-name>javaWeb_09</display-name>

    <welcome-file-list>

        <welcome-file>login.jsp</welcome-file>

    </welcome-file-list>

    <servlet>

        <servlet-name>myHttpServletExtends</servlet-name>

        <servlet-class>com.dao.chu.MyHttpServletExtends</servlet-class>

    </servlet>

    <servlet-mapping>

        <servlet-name>myHttpServletExtends</servlet-name>

        <url-pattern>/myHttpServletExtends</url-pattern>

    </servlet-mapping>

</web-app>

3.login.jsp

<%@ page language="java" contentType="text/html; charset=utf-8"

    pageEncoding="utf-8"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<title>登陆页</title>

</head>

<body>

	<form action="myHttpServletExtends" method="post">

		用户名：<input type="text" name="user">

		<br><br>

		密码  <input type="password" name="password">

		<br><br>

		<!-- 一组信息 -->

		interesting:

		<input type="checkbox" name="interesting" value="reading">Reading

		<input type="checkbox" name="interesting" value="writing">Writing

		<input type="checkbox" name="interesting" value="football">Football

		<input type="checkbox" name="interesting" value="game">Game

		<input type="checkbox" name="interesting" value="shopping">Shopping

		<input type="checkbox" name="interesting" value="party">Party

		<input type="checkbox" name="interesting" value="TV">TV

		<br><br>

		<input type="submit" value="提交">

	</form>

</body>

</html>

4.MyGenericServlet

package com.dao.chu;

import java.util.Enumeration;

import javax.servlet.Servlet;

import javax.servlet.ServletConfig;

import javax.servlet.ServletContext;

import javax.servlet.ServletException;

import javax.servlet.ServletRequest;

import javax.servlet.ServletResponse;

/**

 *

 * <p>

 * Title: MyGenericServlet

 * </p>

 * <p>

 * Description: 自定义MyGenericServlet

 * </p>

 */

public abstract class MyGenericServlet implements Servlet, ServletConfig {

	// ServletConfig对象，在init方法执行后赋值

	private ServletConfig servletConfig;

	/**

	 * 实现Servlet的方法

	 */

	@Override

	public void destroy() {

	}

	@Override

	public String getServletInfo() {

		return "";

	}

	// ServletConfig对象的get方法

	@Override

	public ServletConfig getServletConfig() {

		return servletConfig;

	}

	@Override

	public void init(ServletConfig servletConfig) throws ServletException {

		this.servletConfig = servletConfig;

		init();

	}

	// 空的init函数，用来给子类继承，防止覆盖init(ServletConfig servletConfig)方法引起的错误

	public void init() {

	}

	//抽象方法，必需被子类实现

	@Override

	public abstract void service(ServletRequest servletRequest,

			ServletResponse servletResponse);

	/**

	 * 实现ServletConfig的方法

	 */

	@Override

	public String getServletName() {

		return getServletConfig().getServletName();

	}

	@Override

	public ServletContext getServletContext() {

		return getServletConfig().getServletContext();

	}

	@Override

	public String getInitParameter(String paramString) {

		return getServletConfig().getInitParameter(paramString);

	}

	@Override

	public Enumeration<String> getInitParameterNames() {

		return getServletConfig().getInitParameterNames();

	}

}

5.MyHttpServlet

package com.dao.chu;

import javax.servlet.ServletRequest;

import javax.servlet.ServletResponse;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

/**

 *

 * <p>

 * Title: MyHttpServlet

 * </p>

 * <p>

 * Description:自定义 HttpServlet

 * </p>

 */

public abstract class MyHttpServlet extends MyGenericServlet {

	private static final String METHED_GET="GET";

	private static final String METHED_POST="POST";

	@Override

	public void service(ServletRequest servletRequest,

			ServletResponse servletResponse) {

		try {

			// 强转类型

			HttpServletRequest request = (HttpServletRequest) servletRequest;

			HttpServletResponse response = (HttpServletResponse) servletResponse;

			// 调用service(HttpServletRequest,HttpServletResponse)方法

			service(request, response);

		} catch (Exception e) {

			e.printStackTrace();

		}

	}

	protected void service(HttpServletRequest httpServletRequest,

			HttpServletResponse httpServletResponse) {

		// 根据请求方式,决定使用的方法

		String method = httpServletRequest.getMethod();

		if (method.equalsIgnoreCase(METHED_GET)) {

			doGet(httpServletRequest, httpServletResponse);

		} else if (method.equalsIgnoreCase(METHED_POST)) {

			doPost(httpServletRequest, httpServletResponse);

		}

	}

	protected void doPost(HttpServletRequest httpServletRequest,

			HttpServletResponse httpServletResponse) {

	}

	protected void doGet(HttpServletRequest httpServletRequest,

			HttpServletResponse httpServletResponse) {

	}

}

6.MyHttpServletExtends

package com.dao.chu;

import java.io.IOException;

import java.io.PrintWriter;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

/**

 *

 * <p>

 * Title: MyHttpServletExtends

 * </p>

 * <p>

 * Description: 继承MyHttpServletExtends的类

 * </p>

 */

public class MyHttpServletExtends extends MyHttpServlet {

	/**

	 * Post请求方式

	 */

	@Override

	public void doPost(HttpServletRequest httpServletRequest,

			HttpServletResponse httpServletResponse) {

		try {

			PrintWriter out = httpServletResponse.getWriter();

			out.print("hello Post");

		} catch (IOException e) {

			e.printStackTrace();

		}

	}

	/**

	 * Get请求方式

	 */

	@Override

	public void doGet(HttpServletRequest httpServletRequest,

			HttpServletResponse httpServletResponse) {

		try {

			PrintWriter out = httpServletResponse.getWriter();

			out.print("hello Get");

		} catch (IOException e) {

			e.printStackTrace();

		}

	}

}

7.页面请求提交后，可以根据判断的请求方式到相应的方法中执行:

javaWEB总结(9):自定义HttpServlet

javaWEB总结(9):自定义HttpServlet

javaWEB总结(9):自定义HttpServlet

所以HttpServlet中重载了service方法，主要作用是根据请求类型调用相应的doXXX方法。

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