Java连接Mysql数据库详细代码

数据库连接类：

package util;

import java.sql.*;

/**
 * TODO
 *
 * @author 
 * @date 2020/12/10 9:07
 */
public class DBUtil {
    private final static String DRIVER = "com.mysql.jdbc.Driver";    //某个MySQL版本是com.mysql.cj.jdbc.Driver
    private final static String URL = "jdbc:mysql://localhost:3306/db_test?CharacterEncoding=utf-8";    //db_test是数据库名
    private final static String USERNAME = "root";     //用户名
    private final static String PASSWORD = "27348915Ljh";  //密码

    private static Connection conn = null;
    private static PreparedStatement ps = null;
    private static ResultSet rs = null;

    //加载驱动
    static {
        try {
            Class.forName(DRIVER);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }

    /**
     *
     *  获取连接
     * @param
     * @author 
     * @date 2020/12/10
     */
    public static Connection getConn(){
        try {
            conn = DriverManager.getConnection(URL,USERNAME,PASSWORD);
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }
        return conn;
    }

    /**
     *
     *  关闭连接
     * @param
     * @author 
     * @date 2020/12/10
     */
    public static void close(){
        try {
            if(rs != null)  rs.close();
            if (ps != null)  ps.close();
            if (conn != null)  conn.close();
        }catch (Exception e){
            e.printStackTrace();
        }
    }

    /**
     *
     * 查询数据库
     * @param sql
     * @param objects
     * @author 
     * @date 2020/12/10
     */
   public static ResultSet executeQuery(String sql,Object... objects){
        conn = getConn();
       try {
           ps = conn.prepareStatement(sql);
           for (int i = 0; i < objects.length; i++) {
               ps.setObject((i+1), objects[i]);
           }
           rs = ps.executeQuery();
       } catch (Exception e) {
           e.printStackTrace();
       }
       return rs;
   }

   /**
    * 
    * 数据库增、删、改
    * @param sql
    * @param objects
    * @author 
    * @date 2020/12/10
    */
   public static int executeUpdate(String sql,Object... objects){
       conn = getConn();
       int result = 0;
       try {
           ps = conn.prepareStatement(sql);
           for (int i = 0; i < objects.length; i++) {
               ps.setObject((i+1), objects[i]);
           }
           result = ps.executeUpdate();
       }catch (Exception e){
           e.printStackTrace();
       }finally {
           close();
       }
       return result;
   }


	//测试数据库是否连接成功，写入项目时可注释
	public static void main(String[] args) {
        System.out.println(getConn()); 
        //输出类似：com.mysql.jdbc.JDBC4Connection@2b71fc7e ，则连接成功
    }
}

数据库操作

示例：

 /**
     * Products 是实体类
     * 问号是需要替换的内容
     *  根据商品Id查询商品是否存在
     * @param productsId
     * @author 
     * @date 2020/12/10
     */
    public Products queryById(int productsId){
        Products products = new Products();
        String sql = "select * from products where id = ?";    //products 是数据库表
        ResultSet rs = DBUtil.executeQuery(sql,productsId);
        try {
            if (rs.next()){
                products.setId(rs.getInt("id"));
                products.setName(rs.getString("name"));
                products.setPrice(rs.getInt("price"));
                products.setNums(rs.getInt("nums"));
            }
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            DBUtil.close();
        }
        return products;
    }

    /**
     * 增、删、改返回值类型是int ，值是数据库更新数据的条数
     *  修改商品信息
     * @param products
     * @author 
     * @date 2020/12/10
     */
    public boolean update(Products products){
        String sql = "update products set nums = ? where id = ?";
        return DBUtil.executeUpdate(sql, products.getNums(),products.getId()) > 0;
    }