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终于凑齐增删改查四个宝喽

时间：2022-10-25 14:11:34浏览次数：54  
标签：凑齐 preparedStatement name 改查 public connection 增删 id String

表依旧是上上次的表~

然后是目录结构

 

 

 然后……贴代码！

package Bean;

public class Bean {

    String id;
    String name;
    public Bean() {
        // TODO Auto-generated constructor stub
    }
    public String getId() {
        return id;
    }
    public void setId(String id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Bean(String id, String name) {
        super();
        this.id = id;
        this.name = name;
    }

}




package DBUtil;

import java.sql.*;

public class DBUtil {
    private static Connection connection;
    private static String url="jdbc:mysql://localhost:3306/test?useSSL=false&allowPublicKeyRetrieval=true&serverTimezone=UTC";
    private static String user="root";//用户名
    private static String pass="mysql26331";//密码

    static {
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
    public static Connection getConnection(){
        try {
            connection= DriverManager.getConnection(url,user,pass);
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return connection;
    }
    public static void close(Connection connection, Statement statement, ResultSet resultSet){
        try {
            if (connection!=null) {
                connection.close();
            }
            if (statement!=null){
                statement.close();
            }
            if (resultSet!=null){
                resultSet.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    public static void close(PreparedStatement preparedStatement, Connection connection) {
        // TODO Auto-generated method stub
        try {
            preparedStatement.close();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        try {
            connection.close();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    public static void close(PreparedStatement preparedstatement, Connection connection, ResultSet rs) {
        // TODO Auto-generated method stub
        try {
            rs.close();
        } catch (SQLException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }
        try {
            preparedstatement.close();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        try {
            connection.close();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

}




package Dao;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import Bean.Bean;
import DBUtil.DBUtil;

public class Dao {

    //增删改是差不多的操作，查询相对特殊一点

    public static void add(String id, String name) {
        // TODO Auto-generated method stub
        Connection connection=null;
        PreparedStatement preparedStatement=null;
        connection= DBUtil.getConnection();
        String sql="insert into inf(id,name) values (?,?)";
        try{
            preparedStatement=connection.prepareStatement(sql);
            preparedStatement.setString(1,id);//就是把id替代sql的第一个问号，id由前端传过来
            preparedStatement.setString(2,name);
            System.out.print("信息传输成功");
            int flag = preparedStatement.executeUpdate();
            if(flag != 0) {
                System.out.print("信息添加成功");
            } else {
                System.out.print("信息添加失败");
            }
            preparedStatement.close();
            connection.close();
        }catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally {
            DBUtil.close(preparedStatement,connection);
        }
    }

    public static void delete(String id, String name) {
        // TODO Auto-generated method stub
        Connection connection=null;
        PreparedStatement preparedStatement=null;
        try {
            connection= DBUtil.getConnection();
            //这里一定要注意！！！这里和查找操作不同，from前边没有*
            String sql="delete from  inf where id=?";
            preparedStatement=connection.prepareStatement(sql);
            //寻找到需要删除的数据，执行删除指令
            preparedStatement.setString(1,id);
            int flag = preparedStatement.executeUpdate();
            if(flag != 0) {
                System.out.print("信息删除成功");
            } else {
                System.out.print("信息删除失败");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            DBUtil.close(connection,preparedStatement,null);
        }
    }

    public static void change(String id, String name) {
        // TODO Auto-generated method stub
        Connection connection=null;
        PreparedStatement preparedStatement=null;
        try {
            connection= DBUtil.getConnection();
            //这里也算是一个小小的踩坑点吧，通过id查找，set后边就不要添加id=?了，不然下边也要对应得进行修改
            //sql中有几个？就要写几个preparedStatement.setString
            String sql="update inf set name=? where id=?";
            preparedStatement=connection.prepareStatement(sql);
            preparedStatement.setString(1,name);
            preparedStatement.setString(2,id);

            int flag = preparedStatement.executeUpdate();
            if(flag != 0) {
                System.out.print("信息修改成功");
            } else {
                System.out.print("信息修改失败");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            DBUtil.close(connection,preparedStatement,null);
        }
    }

    public static Bean found(String id) {
        // TODO Auto-generated method stub
        Connection connection=null;
        PreparedStatement preparedStatement=null;
        ResultSet resultSet=null;
        Bean bb = null;
        try {
            connection= DBUtil.getConnection();
            String sql="select * from  inf where id=?";
            preparedStatement=connection.prepareStatement(sql);
            preparedStatement.setString(1,id);
            resultSet = preparedStatement.executeQuery();
            while (resultSet.next()){
                String id2=resultSet.getString(1);
                String name=resultSet.getString(2);
                bb = new Bean(id2, name);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            DBUtil.close(connection,preparedStatement,resultSet);
        }
        return bb;
    }

}




package Servlet;

import java.io.IOException;

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 Dao.Dao;

/**
 * Servlet implementation class Servlet
 */
@WebServlet("/Servlet")
public class Servlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public Servlet() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        //response.getWriter().append("Served at: ").append(request.getContextPath());
        //防止乱码
        response.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");
        request.setCharacterEncoding("UTF-8");

        //判断前端传来的标记，以此执行相对应的增删改查操作
        String method=request.getParameter("method");
        //获取前端传来的数据
        if("add".equals(method)) {
            //获取前端传来的数据
            String id=request.getParameter("id");
            String name=request.getParameter("name");
            //调用add方法将数据添加进数据库
            Dao.add(id,name);
        } else if("delete".equals(method)) {
            //获取前端传来的数据
            String id=request.getParameter("id");
            String name=request.getParameter("name");
            //调用delete方法删除数据库相关信息
            Dao.delete(id,name);
        } else if("change".equals(method)) {
            //获取前端传来的数据
            String id=request.getParameter("id");
            String name=request.getParameter("name");
            //调用change方法修改数据库相关信息
            Dao.change(id,name);
        } else if("found".equals(method)) {
            //获取前端传来的数据
            String id=request.getParameter("id");
            //调用found方法查询数据库相关信息
            request.setAttribute("Bean",Dao.found(id));
            request.getRequestDispatcher("show.jsp").forward(request,response);
        }

    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        this.doGet(request, response);
    }

}




<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<%@ page import ="java.sql.*"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>主界面</title>
<body>
<center>
<p style="height: 20px; border: 1px solid red;text-align: center;">主界面</p>

<button type="submit" value="add" onclick="window.location.href='add.jsp'">增加信息</button>
<br><br>
<button type="submit" value="delete" onclick="window.location.href='delete.jsp'">删除信息</button>
<br><br>
<button type="submit" value="change" onclick="window.location.href='change.jsp'">修改信息</button>
<br><br>
<button type="submit" value="found" onclick="window.location.href='found.jsp'">查询信息</button>
<br><br>
</center>
</body>
</html>




<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<%@ page import ="java.sql.*"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>添加</title>
</head>
<body>
<center>
<form action="Servlet" method="post">

<p style="height: 20px; border: 1px solid red;text-align: center;">添加</p>

<p>请输入id：<input type="text" name="id"><p/>
<p>请输入姓名：<input type="text" name="name"><p/>

<input type="hidden" name="method" value="add"/>
<input type="submit" name="submit" value="添加">

</form>

</center>
</body>
</html>




<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<%@ page import ="java.sql.*"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>删除</title>
</head>
<body>
<center>
<form action="Servlet" method="post">

<p style="height: 20px; border: 1px solid red;text-align: center;">删除</p>

<p>请输入id：<input type="text" name="id"><p/>
<p>请输入姓名：<input type="text" name="name"><p/>

<input type="hidden" name="method" value="delete"/>
<input type="submit" name="submit" value="删除">

</form>

</center>
</body>
</html>




<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<%@ page import ="java.sql.*"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>修改</title>
</head>
<body>
<center>
<form action="Servlet" method="post">

<p style="height: 20px; border: 1px solid red;text-align: center;">修改</p>

<p>请输入id：<input type="text" name="id"><p/>
<p>请输入姓名：<input type="text" name="name"><p/>

<input type="hidden" name="method" value="change"/>
<input type="submit" name="submit" value="修改">

</form>

</center>
</body>
</html>




<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<%@ page import ="java.sql.*"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>查找</title>
</head>
<body>
<center>
<form action="Servlet" method="post">

<p style="height: 20px; border: 1px solid red;text-align: center;">查询</p>
<%--
        通过学号查询
        --%>
<p>请输入id：<input type="text" name="id"><p/>

<p>请输入姓名：<input type="text" name="name"><p/>

<input type="hidden" name="method" value="found"/>
<input type="submit" name="submit" value="查询">

</form>

</center>
</body>
</html>




<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<%@ page import ="java.sql.*"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>展示</title>
</head>
<body>
<center>
<form action="Servlet" method="post">
        id：${Bean.id}<br/>
        姓名：${Bean.name}<br/>
<input type="hidden" name="method" value="change"/>
<%--
<br><br>
<button type="submit" value="change" onclick="window.location.href='change.jsp'">修改</button>
<br><br>
          --%>

</form>
</center>
</body>
</html>

标签：凑齐,preparedStatement,name,改查,public,connection,增删,id,String
From： https://www.cnblogs.com/yansans/p/16824661.html

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