MySQL 基础 14 JDBC的CRUD操作之Prepared

1.1保存操作

    @Test
    /**
     * 保存操作
     */
    public void demo1(){
        Connection conn = null;
        PreparedStatement pstmt = null;
        try{
            // 获得连接:
            conn = JDBCUtils.getConnection();
            // 编写SQL语句:
            String sql = "insert into user values (null,?,?,?,?)";
            // 预编译SQL:
            pstmt = conn.prepareStatement(sql);
            // 设置参数:
            pstmt.setString(1, "eee");
            pstmt.setString(2, "abc");
            pstmt.setString(3, "旺财");
            pstmt.setInt(4, 32);
            // 执行SQL
            int num = pstmt.executeUpdate();
            if(num > 0){
                System.out.println("保存成功！");
            }
        }catch(Exception e){
            e.printStackTrace();
        }finally{
            JDBCUtils.release(pstmt, conn);
        }
    }

1.2 修改操作

@Test
    /**
     * 修改操作
     */
    public void demo2(){
        Connection conn = null;
        PreparedStatement pstmt = null;
        try{
            // 获得连接:
            conn = JDBCUtils.getConnection();
            // 编写SQL语句:
            String sql = "update user set username = ?,password =?,nickname=?,age = ? where id = ?";
            // 预编译SQL:
            pstmt = conn.prepareStatement(sql);
            // 设置参数:
            pstmt.setString(1, "abc");
            pstmt.setString(2, "1234");
            pstmt.setString(3, "旺旺");
            pstmt.setInt(4, 23);
            pstmt.setInt(5, 6);
            // 执行SQL：
            int num = pstmt.executeUpdate();
            if(num > 0){
                System.out.println("修改成功！");
            }
        }catch(Exception e){
            e.printStackTrace();
        }finally{
            JDBCUtils.release(pstmt, conn);
        }
    }

1.3 删除操作

@Test
    /**
     * 删除操作
     */
    public void demo3(){
        Connection conn = null;
        PreparedStatement pstmt  = null;
        try{
            // 获得连接：
            conn = JDBCUtils.getConnection();
            // 编写SQL语句:
            String sql = "delete from user where id = ?";
            // 预编译SQL
            pstmt = conn.prepareStatement(sql);
            // 设置参数:
            pstmt.setInt(1, 4);
            // 执行SQL:
            int num = pstmt.executeUpdate();
            if(num > 0){
                System.out.println("删除成功！");
            }
        }catch(Exception e){
            e.printStackTrace();
        }finally{
            JDBCUtils.release(pstmt, conn);
        }
    }

1.4 查询操作

@Test
    /**
     * 查询操作
     */
    public void demo4(){
        Connection conn = null;
        PreparedStatement pstmt = null;
        ResultSet rs = null;
        try{
            // 获得连接:
            conn = JDBCUtils.getConnection();
            // 编写SQL:
            String sql = "select * from user";
            // 预编译SQL:
            pstmt = conn.prepareStatement(sql);
            // 设置参数:
            // 执行SQL:
            rs = pstmt.executeQuery();
            // 遍历结果集:
            while(rs.next()){
                System.out.println(rs.getInt("id")+" "+rs.getString("username")+" "+rs.getString("password")+" "+rs.getString("nickname"));
            }
        }catch(Exception e){
            e.printStackTrace();
        }finally{
            JDBCUtils.release(rs, pstmt, conn);
        }
    }