MySql-数据库增删改查-封装类直接调用-2022-12-27

1、新建文件 db.properties

driver = com.mysql.jdbc.Driver
url = jdbc:mysql://localhost:3306/jdbcstudy?useUnicode=true&characterEncoding=utf8&useSSL=false
username = root
password = 123456

2、写工具类 JdbcUtils

package com.kuang.lesson02.utils;

import java.io.InputStream;
import java.sql.*;
import java.util.Properties;

public class JdbcUtils {

    private static String driver = null;
    private static String url = null;
    private static String username = null;
    private static String password = null;
    //读取配置文件
    static {
        try{
            InputStream in = JdbcUtils.class.getClassLoader().getResourceAsStream("db.properties");
            Properties properties = new Properties();
            properties.load(in);

            driver = properties.getProperty("driver");
            url = properties.getProperty("url");
            username = properties.getProperty("username");
            password = properties.getProperty("password");

            //驱动只用加载一次
            Class.forName(driver);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    //获取连接
    public static Connection getConnection() throws SQLException {
         return DriverManager.getConnection(url,username,password);

    }

    //释放连接资源
    public static void release(Connection conn, Statement st, ResultSet rs){
        if (rs!=null){
            try{
                rs.close();
            }catch (SQLException e){
                e.printStackTrace();
            }
        }
        if (st!=null){
            try{
                st.close();
            }catch (SQLException e){
                e.printStackTrace();
            }
        }
        if (conn!=null){
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

    }
}

3、增，删，改，查调用

package com.kuang.lesson02;

import com.kuang.lesson02.utils.JdbcUtils;
import jdk.nashorn.internal.scripts.JD;

import javax.swing.plaf.nimbus.State;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class TestInsert {

    public static void main(String[] args) {

        Connection conn = null;
        Statement st = null;
        ResultSet rs =null;

        try {
            conn = JdbcUtils.getConnection();
            st = conn.createStatement();
            String sql = "INSERT INTO users (`id`,`NAME`,`PASSWORD`,`email`,`birthday`)" +
                    "VALUES (4,'LRR','123456','288@qq.com','1988-01-02')";
            int i = st.executeUpdate(sql);
            if(i>0){
                System.out.println("插入成功");
            }

        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            JdbcUtils.release(conn,st,rs);
        }


    }
}

查询和其他三个不一样

package com.kuang.lesson02;

import com.kuang.lesson02.utils.JdbcUtils;

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

public class TestQuery {
    public static void main(String[] args) {
        Connection conn = null;
        Statement st = null;
        ResultSet rs =null;

        try {
            conn = JdbcUtils.getConnection();
            st = conn.createStatement();
            String sql = "SELECT * FROM users WHERE id = 1";
            rs = st.executeQuery(sql);  //查询完毕返回结果集
            while (rs.next()){
                System.out.println(rs.getString("NAME"));
            }

        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            JdbcUtils.release(conn,st,rs);
        }
    }
}