封装JDBCUtils工具类。

/**
 * @program: HelloWorld
 * @description: JDBC工具类
 * @author: fish
 * @create: 2019-12-07 18:36
 **/
public class JDBCUtils {
        /**
        * @Description: 获取数据库连接
        * @Param: 
        * @return: 
        * @Author: fish
        * @Date: 6:55 PM 2019/12/7
        */ 
    public static Connection getConnection() throws Exception{
        Connection conn = null;
        //1.读取配置文件中的4个基本信息
        InputStream is = ClassLoader.getSystemClassLoader().getResourceAsStream("jdbc.properties");
        Properties pros = new Properties();
        pros.load(is);

        String user = pros.getProperty("user");
        String password = pros.getProperty("password");
        String url = pros.getProperty("url");
        String driverClass = pros.getProperty("driverClass");

        //2.加载驱动
        Class.forName(driverClass);

        //3.获取连接
        conn = DriverManager.getConnection(url,user,password);
        return conn;
    }
/**
* @Description: 关闭连接和Statement的操作
* @Param: 
* @return: 
* @Author: fish
* @Date: 6:59 PM 2019/12/7
*/ 
    public static void closeResource(Connection conn, Statement ps){
        try {
            if (ps!=null)
                ps.close();
        }catch (SQLException e)
        {
            e.printStackTrace();
        }
        try{
            if (conn!=null )
                conn.close();
        }catch (SQLException e)
        {
            e.printStackTrace();;
        }
    }
}

实现数据库的修改操作。

public class PreparedStatementUpdateTest {
    //修改customers表中的一条记录
    @Test
    public void testUpdate(){
        Connection conn = null;
        PreparedStatement ps = null;
        try{
            //1.获取数据库的连接
            conn = JDBCUtils.getConnection();
            //2.预编译sql语句，返回PreparedStatement的实例
            String sql = "update customers set name = ? where id = ?";
            ps = conn.prepareStatement(sql);
            //3.填充占位符
            ps.setObject(1,"莫扎特");
            ps.setObject(2,13);
            //4.执行
            ps.execute();
        }catch (Exception e)
        {
            e.printStackTrace();
        }finally {
            //5.资源的关闭
            JDBCUtils.closeResource(conn,ps);
            System.out.println("执行完毕！");
        }
    }
}

封装通用的增删改操作

//通用的增删改操作
    public void update(String sql,Object ...args){//sql中占位符的个数与可变形参的个数相同
        Connection conn = null;
        PreparedStatement ps = null;
        try{
            //1.获取数据库的连接
            conn = JDBCUtils.getConnection();
            //2.预编译sql语句,返回PreparedStatement的实例
            ps = conn.prepareStatement(sql);
            //3.填充占位符
            for (int i = 0;i<args.length;i++)
            {
                ps.setObject(i+1,args[i]);
            }
            //4.执行
            ps.execute();
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            //5.资源的关闭
            JDBCUtils.closeResource(conn,ps);
            System.out.println("执行完毕！");
        }
    }
    public class PreparedStatementUpdateTest {
    @Test
    public void testCommonUpdate(){
        String sql = "delete from customers where id = ?";
        update(sql,3);
    }
}

Snip20191207_1.png

数据库中的表名若和数据库关键字相同，则在sql语句中要给表名加``(键盘中1左边的键)，如order。否则报错。You have an error in your SQL syntax,check the manual that corresponds to your MySQL server version for the right syntax to use near...

String sql = "update 'order' set order_name = ? where order_id = ?";
update(sql,"DD","2");