java servlet简单使用

最新推荐文章于 2023-03-30 20:42:57 发布

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本文展示了如何使用Java Servlet开发一个简单的考试系统，包括HTML表单、POST请求及成绩计算。同时，详细解释了请求转发和请求作用域的概念，通过FirstServlet和SecondServlet实现登录并展示学号和姓名的过程。

开发一个简单的考试系统，在HTML页面中建立一个表单，通过POST方法传递参数，题目类型包括单选题、多选题和填空题，要求程序给出考试成绩。页面参考如图1，请在下方贴上question.html的源码及其运行效果。

图1 运行效果
在这里插入图片描述

源码：

<!DOCTYPE html>
<html>
  <head>
    <title>question.html</title>
    <meta name="content-type" content="text/html" charset=UTF-8>
  </head>
  
  <body>
 	<a>请回答下面问题: </a>
 	<form action="" method="post">
 		<table>
 			<tr><td>1.Windows操作系统是那家公司产品？
 				<input type="radio" name="cooperation" value="apple">apple公司
				<input type="radio" name="cooperation" value="ibm">IBM公司
				<input type="radio" name="cooperation" value="microsoft">Microsoft公司		
 			</td></tr>
 			<tr><td>2.下列设计语言，那些事面向对象的？
 				<input type="checkbox" name="language" value="java">java语言
				<input type="checkbox" name="language" value="c">c语言
				<input type="checkbox" name="language" value="c++">c++语言		
 			</td></tr>
 			<tr><td>3.编写Servlet程序应该继承那个类？
 				<input type="text" name="impClass" size="20' vlaue=" ">
 			</td></tr>
 			<tr><td>4.下图是那种编程语言的图标？
 				<input type="checkbox" name="language" value="c++">c++
 				<input type="checkbox" name="language" value="python">python
 				<input type="checkbox" name="language" value="java">java
 				<br>
 				<img src="img/javalogo.png">	
 			</td></tr>
 			<td>
 				交卷请单击<input type="submit" name="submit" value="提交">
 				重新交卷请单击<input type="reset" name="reset" value="重置">
 			</td>
 		
 		</table>
 	</form>
  </body>
</html>

2）在src目录中创建com.demo包，然后创建ExamServlet.java文件。当在question.html页面中单击“交卷”按钮时，根据用户答案，给出最终成绩。结果如图2所示。请在下方贴出ExamServlet.java代码。

图2 运行效果
在这里插入图片描述
代码：

package com.demo;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;

import javax.jws.WebService;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet(urlPatterns = "/quetionForm")
public class ExamServlet extends HttpServlet{
	

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

	
	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		
		resp.setContentType("text/html;charset=UTF-8");
		PrintWriter out = resp.getWriter();
		String cooperation = req.getParameter("cooperation");
//		out.println("1 "+cooperation);
 		String language1 = req.getParameter("language1");
 		String language2 = req.getParameter("language2");
 		String language3 = req.getParameter("language3");
//		out.println(" 2 "+language1);
 		String impClass = req.getParameter("impClass");
//		out.println(" 3 "+impClass);
 		String languagelogo = req.getParameter("languagelogo");
//		out.println("4 "+languagelogo);
		
		
 	    int sum = 0;
 	    try {
			if(cooperation.equals("Microsoft"))
	 			sum += 25;
	 		if(language1.equals("java") && language3.equals("c++") ){
	 			sum += 25;
	 			if(language2 != null)
	 				sum -= 25;
	 		}
	 		if(impClass.equals("HttpServlet"))
	 			sum += 25;
	 		if(languagelogo.equals("java"))
	 			sum += 25;
 	    	} catch (Exception e) {
				out.print("请选择正确的答案");
		}
 			
// 		out.println("cooperation ==> "+cooperation +"\n"+
// 				"language ==> "+ language  + "\n"+
// 				"impClass ==> "+ impClass +  "\n"+
// 				"languagelogo ==> "+ languagelogo + "\n"
// 				+ "sum = "+sum);
		
		
		out.println("<!DOCTYPE>");
		out.println("<HTML>");
		out.println("  <HEAD><TITLE>result</TITLE></HEAD>");
		out.println("  <BODY>");
		out.print("     ");
		out.println("result == " +sum);
		out.println("  </BODY>");
		out.println("</HTML>");
		out.flush();
		out.close();
		
	}
}

任务2 学习请求转发与请求作用域
完成下面的综合应用。程序运行首先显示一个页面，输入学号和姓名后，单击“登录”按钮，控制转发到FirstServlet，在其中检索出学号和姓名信息，创建一个Student对象并将它存储到请求作用域中，将控制转发到SecondServlet，在其中从请求作用域检索出Student对象并显示学号和姓名，同时显示一个链接。参考效果如图3.

图3 运行效果
在这里插入图片描述

源码：

FirstServlet


package com.demo;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;
import java.util.List;

import javax.json.Json;
import javax.json.JsonArray;
import javax.json.JsonObject;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet("/login")
public class FirstServlet extends HttpServlet {


	private static final long serialVersionUID = 1L;
	

	public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		this.doPost(request, response);
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		
		response.setContentType("text/html;charset=UTF-8");
		PrintWriter out = response.getWriter();
		String id = request.getParameter("id");
		String name = request.getParameter("name");	
		request.setAttribute("stu",new Student(id, name));
		System.out.println("成功 == "+ id +"  ==  "+name);    
	    request.getRequestDispatcher("/SecondServlet.do").forward(request, response);
		out.flush();
		out.close();
	}

}

SecondServlet

package com.demo;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;
import java.util.regex.Pattern;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet("/getMethod")
public class SecondServlet extends HttpServlet {

	

	private static final long serialVersionUID = 1L;

	public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		response.setContentType("text/html;charset=utf-8");
		PrintWriter out = response.getWriter();
		
		Student stu  = (Student) request.getAttribute("stu");
		String id = stu.getId();
		String name = stu.getName();
		out.println("<!DOCTYPE>");
		out.println("<HTML>");
		out.println("  <HEAD><TITLE>result</TITLE></HEAD>");
		out.println("  <BODY>");
		out.print(" 学号: "+id + "<br> ");
		out.print(" 姓名: "+name + "<br> ");
		out.print("<div><a href=\"http://localhost:8080/demo/login.jsp\">返回输入首页 </a></div>");
		out.println("  </BODY>");
		out.println("</HTML>");
	
		out.flush();
		out.close();
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		this.doGet(request, response);
	}

}


<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
login.jsp

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
    
    <title>ForwordJsp.jsp</title>
	<meta http-equiv="description" content="This is my page" chartset="utf-8">
  </head>
  
  <body>
    this is students form: <br>
     <form action="FirstServlet.do" >
     	 学号:<input name="id" value=" "><br><br>
	        姓名:<input name="name" value=" "><br><br>
	  	<a> &nbsp;&nbsp;&nbsp;</a>
	    <button type="submit">登录</button>  
	  	<a> &nbsp;&nbsp;&nbsp;&nbsp;</a>
	    <button type="reset" >取消</button>
     </form>
  </body>
  
  
</html>