首先说一下数据库更新操作的语句讲解：
我们想要修改数据库中的值需要写sql语句，然后为其中复制的一些是上面我们通过String定义好的，那么怎样写这样的sql语句呢？
讲解：
update users set username=”+username+”,password=”+password+”,email=”+email+”,grade=”+grade+” where userId=”+userId中的字段。
比如username如果是字符串的话，要加单引号update users set username=’”+username+”’…
所以我这里的写法应该是：
String sql ="update user set username ='"+username+"',password='"+passwd+"',sex = '"+sex+"',age = '"+age+"'where id = 1";
理解了上面的语句开始写编辑用户的界面：
前端用户编辑界面代码:
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title></title>
<style>
.addVip {
/*border: 1px solid black;*/
width: 100%;
height: 1000px;
background-color: #F0F3F4;
padding-top: 50px;
padding-left: 50px;
}
.rform {
/*border: 1px solid black;*/
width: 800px;
height: 600px;
margin-top: 20px;
margin-left: 150px;
border-color: #E2E8EA;
background-color: #FFFFFF;
}
.top1 {
/*border: 1px solid black;*/
width: 800px;
height: 50px;
margin-top: -20px;
background-color: #F6F8F8;
}
.top1 p {
padding-top: 10px;
font-family: "隶书";
font-size: 20px;
padding-left: 5px;
}
.rif {
/*border: 1px solid black;*/
width: 400px;
height: 420px;
margin-left: 250px;
margin-top: 70px;
color: #979797;
}
textarea {
margin-left: 80px;
margin-top: -30px;
}
.password input {
width: 250px;
height: 20px;
}
.name input {
width: 250px;
height: 20px;
}
.birthday input {
width: 250px;
height: 20px;
}
.home input {
width: 250px;
height: 20px;
}
.phone input {
width: 250px;
height: 20px;
}
.data1 p {
padding-left: 40px;
margin-top: -6px;
}
.home1 p {
padding-left: 45px;
margin-top: -2px;
}
.tijiao {
margin-left: 60px;
}
.tijiao button {
/*border: 1px solid black;*/
width: 70px;
height: 40px;
border-color: #23B7E5;
background-color: #23B7E5;
color: white;
}
</style>
</head>
<body>
<div class="addVip">
<div class="rform">
<div class="top1">
<p>信息修改</p>
</div>
<div class="rif">
<form action="edit" name="" method="post">
<div class="name">
<p>ID: <input name="id" type="text"/>
</p>
</div>
<div class="name">
<p>
用户名:<input name="username" type="text"/>
</p>
</div>
<div class="birthday">
<p>
<div class="data1">
</div>
</p>
</div>
<div class="home">
<p>
密码: <input name="password" type="text"/>
</p>
</div>
<div class="sex">
<p>
性别:
<input type="radio" name="sex" value="男"/>男
<input type="radio" name="sex" value="女"/>女
</p>
</div>
<div class="home">
<p>
年龄: <input name="age" type="text"/>
</p>
</div>
<div class="tijiao">
<button type="submit">修改</button>
</div>
</form>
</div>
</div>
</div>
</body>
</html>
后端功能实现：
还是固定的步骤，连接好数据库然后sql语句进行操作，只不过这里需要edit.jsp界面的form表单action设置成edit然后后端@WebServlet("/edit")这样写：
package com.ftz.Demo.web;
import com.ftz.Demo.util.DBUtil;
import lombok.SneakyThrows;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.sql.Connection;
import java.sql.Statement;
/**
* @author ${范涛之}
* @Description
* @create 2021-12-09 1:26
*/
@WebServlet("/edit")
public class EditServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
super.doGet(req, resp);
}
@SneakyThrows
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
req.setCharacterEncoding("UTF-8");
//设置服务器端以UTF-8编码进行输出
resp.setCharacterEncoding("UTF-8");
//设置浏览器以UTF-8编码进行接收,解决中文乱码问题
resp.setContentType("text/html;charset=UTF-8");
Integer id = Integer.valueOf(req.getParameter("id"));
String username = req.getParameter("username");
String passwd = req.getParameter("password");
String sex = req.getParameter("sex");
Integer age = Integer.valueOf(req.getParameter("age"));
System.out.println(username+passwd+sex+age);
Connection connection = DBUtil.getConnection();
String sql ="update user set username ='"+username+"',password='"+passwd+"',sex = '"+sex+"',age = '"+age+"'where id = '"+id+"'";
Statement statement = connection.createStatement();
int temp = statement.executeUpdate(sql);
resp.sendRedirect("/user");
// req.getRequestDispatcher("user").forward(req,resp);
}
}
编辑功能写好之后就是最难的用户界面回显功能：这里我们前端会用到JSTL传值。然后我们首先在后端写一个查询用户的方法，在DAO层：
/**
* 查询全部数据
*
* @throws SQLException
*/
public List<User> findall() throws SQLException {
Connection connection = null;
PreparedStatement preparedStatement = null;
ResultSet resultSet = null;
connection = DBUtil.getConnection();
String sql = "select * from user ";
preparedStatement = connection.prepareStatement(sql);
resultSet = preparedStatement.executeQuery();
List<User> list = new ArrayList();
while (resultSet.next()) {
User user = new User();
user.setId(Integer.valueOf(resultSet.getString(1)));
user.setUsername(resultSet.getString(2));
user.setPassword(resultSet.getString(3));
user.setSex(resultSet.getString(4));
user.setAge(Integer.valueOf(resultSet.getString(5)));
list.add(user);
}
System.out.println(list.size());
return list;
}
在UserServlet层写：
public void userEdit(HttpServletRequest request,HttpServletResponse response) throws SQLException {
UserDao userDao = new UserDao();
List<User> findall = userDao.findall();
for (User user : findall) {
System.out.println(user);
}
request.setAttribute("all", findall);
}
在最前面调用一下：
// 用户编辑
userEdit(request, response);
request.getRequestDispatcher("user.jsp").forward(request,response);
前端JSTL：
运行截图:
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