数据库的增删改查

最新推荐文章于 2025-03-30 19:19:17 发布

北京德润科技孙潘迪

最新推荐文章于 2025-03-30 19:19:17 发布

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本文链接：https://blog.youkuaiyun.com/u013402595/article/details/20768367

本文介绍了一个使用Java实现的简单登录系统数据访问层（DAO）的设计与实现，包括连接数据库、按用户名查找记录、更新记录、查看所有记录、添加新记录及删除记录等功能。

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package com.caidan;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;

public class DengLuDAO {

private static final String URL = "jdbc:mysql://localhost:3306/denglu";
private static final String USER = "root";
private static final String PASSWORD = "0208";
//连接数据库
public static Connection getConnection() {
Connection con = null;
try {
System.out.println("正在连接数据库");
con = DriverManager.getConnection(URL, USER, PASSWORD);
System.out.println("数据库连接成功");
} catch (SQLException ex) {

System.out.println("数据库连接失败");
ex.printStackTrace();
}
return con;

}
//按名字查找
public Denglu chazhao(String name) {
String sql = "select * from denglu1 where name='" + name + "'";
Denglu denglu = null;
try (Connection con = getConnection();
Statement stem = con.createStatement();
ResultSet rs = stem.executeQuery(sql)) {

while (rs.next()) {
denglu = new Denglu();
denglu.setName(rs.getString("name"));
denglu.setPassword(rs.getString("password"));

}
} catch (SQLException ex) {
ex.printStackTrace();
}
return denglu;
}

//修改
public void update(Denglu denglu) {
String sql1 = "update denglu1 set password='"+ denglu.getPassword() +"',name='" + denglu.getName()
+ "'where id=" + denglu.getId();

try (Connection con =getConnection();
Statement stem = con.createStatement();) {
int result = stem.executeUpdate(sql1);
if (result > 0) {
System.out.println("修改成功");
} else {
System.out.println("修改失败");
}

} catch (SQLException ex) {
ex.printStackTrace();
}
}

//查看全部
public java.util.List<Denglu> findAll() {
java.util.List<Denglu> denglu1 = new ArrayList<>();
String sql = "select * from denglu1";
try (Connection con = getConnection();
Statement stem = con.createStatement();
ResultSet re = stem.executeQuery(sql)) {
while (re.next()) {
Denglu denglu = new Denglu();
denglu.setId(re.getInt("id"));
denglu.setName(re.getString("name"));

denglu.setPassword(re.getString("password"));
denglu1.add(denglu);
}

} catch (SQLException ex) {

}
return denglu1;
}

//添加咖啡信息

public void add(Denglu denglu) {
String sql = "insert into denglu1 values("
+ denglu.getId() + ",'"
+ denglu.getName() + "','"
+ denglu.getPassword() + "')";
try (Connection con = getConnection();
Statement stem = con.createStatement();) {
int result = stem.executeUpdate(sql);
if (result > 0) {
System.out.println("添加成功");
} else {
System.out.println("添加失败");
}

} catch (SQLException ex) {
ex.printStackTrace();
}
}


public void remove(String dengluName) {
String sql2 = "delete from denglu1 where name='" + dengluName + "'";
try (Connection con = getConnection();
Statement stem = con.createStatement();) {
int result = stem.executeUpdate(sql2);
if (result > 0) {
System.out.println("删除成功");
} else {
System.out.println("删除失败");
}

} catch (SQLException ex) {
ex.printStackTrace();

}
}



//按照名称查询指定信息
public Denglu find(String dengluName) {
String sql4 = "select id,name,password from denglu1 where name='" + dengluName + "'";
Denglu denglu = null;
try (Connection con =getConnection();
Statement stem = con.createStatement();) {
ResultSet re = stem.executeQuery(sql4);
while (re.next()) {
denglu= new Denglu();

denglu.setId(re.getInt("id"));
denglu.setName(re.getString("name"));
denglu.setPassword(re.getString("password"));

}

} catch (SQLException ex) {
ex.printStackTrace();
}
return denglu;
}

}