寫在前面：
因爲這學期博主修的課太多了，所以一直沒怎麼更新。
很驚喜，因爲之前發的學生信息管理系統多了很多人flow我，也有很多人通過QQ聯繫我，希望能幫忙解決一些問題，我也是盡力去幫忙。
前兩天有位同學跟我說爲什麼沒有修改功能，我自己看了一下，確實是沒有，也答應他這兩天要補充一下，所以有了這篇博客。
正文：
思路：在原來顯示列表頁面“添加學生”按鈕旁添加一個“修改”按鈕，
點擊按鈕跳轉到修改頁面，修改頁面填寫信息後，發送到後臺servlet處理，
處理完成後，再轉會顯示列表頁面。
1）添加“修改按鈕”
源碼如下：
<input type="button" value="修改"
onclick="javascrtpt:window.location.href = 'editStu.jsp'">
2）編輯修改頁面
這一步只需要在原來addStu.jsp頁面上做一些簡單的修改，我直接貼上截圖和源碼，可以自己對比下區別
源碼：
<!--這裏是pages文件夾裏的addStu.jsp-->
<%@page contentType="text/html" pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<meta name="viewport" content="width=device-width,initial-scale=1.0,
minimum-scale=1.0, maximum-scale=1.0, user-scalable=no"/>
<title>修改學生信息</title>
</head>
<body>
<h2 align="center">請輸入要修改學生信息</h2>
<div style="width:100%;text-align:center">
<form action="../editServlet">
<table border=1 style="margin:auto">
<tr>
<td>學號：</td>
<td><input type="text" name="stuid" id="stuid"></td>
</tr>
<tr>
<td>姓名：</td>
<td><input type="text" name="stuname" id="stuname"></td>
</tr>
<tr>
<td>性別：</td>
<td><input type="text" name="stusex" id="stusex"></td>
</tr>
<tr>
<td>年齡：</td>
<td><input type="text" name="stuage" id="stuage"></td>
</tr>
<tr>
<td>年級：</td>
<td><input type="text" name="stugrade" id="stugrade"></td>
</tr>
<tr>
<td>個人簡介：</td>
<td><input type="text" name="stuintroduce" id="stuintroduce"></td>
</tr>
<tr>
<td colspan="2">
<input type="submit" value="提交">
</td>
</tr>
</table>
</form>
</div>
</body>
</html>
3）在後臺的editServlet頁面做處理（和數據庫交互）
這一步依然是拷貝addServlet的代碼，做一些簡單的修改 比如說SQL語句 即可
源碼如下：
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package p1;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
*
* @author Administrator
*/
public class editServlet extends HttpServlet {
/**
* Processes requests for both HTTP <code>GET</code> and <code>POST</code>
* methods.
*
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
try (PrintWriter out = response.getWriter()) {
String driver="com.mysql.jdbc.Driver";
String url="jdbc:mysql://localhost:3306/test?characterEncoding=utf-8";
String usr="root";
String password="root";
try{
Class.forName(driver);
Connection conn=DriverManager.getConnection(url,usr,password);
String sqlString="UPDATE stulist SET name = ?, sex = ?, age = ?, grade = ?, introduce = ? WHERE id = ?";
PreparedStatement pstmt=conn.prepareStatement(sqlString);
int id = Integer.parseInt(request.getParameter("stuid"));
String name = request.getParameter("stuname");
String sex = request.getParameter("stusex");
int age = Integer.parseInt(request.getParameter("stuage"));
String grade = request.getParameter("stugrade");
String introduce = request.getParameter("stuintroduce");
pstmt.setString(1, name);
pstmt.setString(2, sex);
pstmt.setInt(3, age);
pstmt.setString(4, grade);
pstmt.setString(5, introduce);
pstmt.setInt(6, id);
pstmt.executeUpdate();
}catch(Exception e){
System.err.println("error:"+e);
}
response.sendRedirect("pages/displayStuList.jsp");
}
}
// <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
/**
* Handles the HTTP <code>GET</code> method.
*
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
processRequest(request, response);
}
/**
* Handles the HTTP <code>POST</code> method.
*
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
processRequest(request, response);
}
/**
* Returns a short description of the servlet.
*
* @return a String containing servlet description
*/
@Override
public String getServletInfo() {
return "Short description";
}// </editor-fold>
}
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