MyBatis參考文檔：

中文版：http://www.mybatis.org/mybatis-3/zh/index.html
英文版：http://www.mybatis.org/mybatis-3/

工具

JDK 1.6及以上版本
MyBatis 3.30版本
MySQL 6.3版本
Eclipse4 及以上版本
Apache Maven 構(gòu)建工具

項目源碼下載地址：https://github.com/JFAlex/MyBatis/tree/master/MyBatis_No.3/alex

update用法

一個簡單的通過主鍵更新數(shù)據(jù)的UPDATE的列子：
在UserMapper接口中添加一個修改的方法：

public int updateById(SysUser sysUser);

這里的sysUser就是新的數(shù)據(jù)對象，然后在XML文件中添加響應(yīng)的映射數(shù)據(jù):

    <update id="updateById">
        update sys_user set user_name = #{userName},
        user_password = #{userPassword},
        user_email = #{userEmail}, user_info =
        #{userInfo}, head_img = #{headImg
        , jdbcType=BLOB}, create_time =
        #{createTime,jdbcType=TIMESTAMP}
        where id = #{id}
    </update>

下面再在UserMapperTest測試類中添加一個測試方法：

    @Test
    public void testUpateById(){
        // 獲取SqlSession
                SqlSession sqlSession = getSqlSession();

                // 獲取UserMapper接口
                try {
                    UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
                    
                    //根據(jù)數(shù)據(jù)庫中的用戶的ID,查詢出用戶數(shù)據(jù)
                    SysUser user = userMapper.selectById(3L);
                    
                    System.out.println("修改前數(shù)據(jù)為：" + user);
                    
                    //修改用戶數(shù)據(jù)
                    user.setUserName("update");
                    user.setUserPassword("12345678");
                    user.setUserEmail("mybatis@my.test");
                    user.setUserInfo("update data");
                    //正常情況下應(yīng)該存入一張圖片
                    user.setHeadImg(new byte[]{1,2,3});
                    user.setCreateTime(new Date());
                    
                    //將新建的對象插入數(shù)據(jù)庫中，特別注意這里的返回值result是執(zhí)行的SQL影響的行數(shù)
                    int result = userMapper.updateById(user);
                    System.out.println("修改成功數(shù)據(jù)條數(shù)為：" + result);
                    
                    //修改后再次獲取用戶數(shù)據(jù)
                    SysUser user2 = userMapper.selectById(3L);
                    System.out.println("修改后數(shù)據(jù)為：" + user2);
                }catch(Exception e){
                    e.printStackTrace();
                } finally {
                    //為了不對其他的測試造成影響，此處進行數(shù)據(jù)回滾
                    //由于默認的sqlSessionFactory.openSession()是不會自動提交的舌涨，因此如果不手動進行commit操作，數(shù)據(jù)也不會寫入數(shù)據(jù)庫
                    sqlSession.rollback();
                    // 關(guān)閉SqlSession
                    sqlSession.close();
                }
    }

測試方法首先從數(shù)據(jù)庫中根據(jù)id獲取出一個已經(jīng)存在的用戶的信息扔字，然后對查詢出來的數(shù)據(jù)進行修改囊嘉，當然不能修改主鍵id的值，然后調(diào)用修改的接口革为，將修改后的數(shù)據(jù)更新扭粱，最后在執(zhí)行一個根據(jù)id獲取用戶信息，即為修改后的用戶信息震檩。

右鍵單擊測試類焊刹，在Run As選項中選擇JUnit Test執(zhí)行測試。測試通過恳蹲，控制臺將會打印如下日志：

DEBUG [main] - Opening JDBC Connection
DEBUG [main] - Created connection 1665404403.
DEBUG [main] - Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@63440df3]
DEBUG [main] - ==>  Preparing: select * from sys_user where id = ? 
DEBUG [main] - ==> Parameters: 3(Long)
TRACE [main] - <==    Columns: id, user_name, user_password, user_email, user_info, head_img, create_time
TRACE [main] - <==        Row: 3, insert, 123456, mybatis@my.test, <<BLOB>>, <<BLOB>>, 2017-08-15 10:01:41.0
DEBUG [main] - <==      Total: 1
修改前數(shù)據(jù)為：SysUser [id=3, userName=insert, userPassword=123456, userEmail=mybatis@my.test, userInfo=insert data, headImg=[1, 2, 3], createTime=Tue Aug 15 10:01:41 CST 2017]
DEBUG [main] - ==>  Preparing: update sys_user set user_name = ?, user_password = ?, user_email = ?, user_info = ?, head_img = ?, create_time = ? where id = ? 
DEBUG [main] - ==> Parameters: update(String), 12345678(String), mybatis@my.test(String), update data(String), java.io.ByteArrayInputStream@51c8530f(ByteArrayInputStream), 2017-08-15 14:44:13.635(Timestamp), 3(Long)
DEBUG [main] - <==    Updates: 1
修改成功數(shù)據(jù)條數(shù)為：1
DEBUG [main] - ==>  Preparing: select * from sys_user where id = ? 
DEBUG [main] - ==> Parameters: 3(Long)
TRACE [main] - <==    Columns: id, user_name, user_password, user_email, user_info, head_img, create_time
TRACE [main] - <==        Row: 3, update, 12345678, mybatis@my.test, <<BLOB>>, <<BLOB>>, 2017-08-15 14:44:14.0
DEBUG [main] - <==      Total: 1
修改后數(shù)據(jù)為：SysUser [id=3, userName=update, userPassword=12345678, userEmail=mybatis@my.test, userInfo=update data, headImg=[1, 2, 3], createTime=Tue Aug 15 14:44:14 CST 2017]
DEBUG [main] - Rolling back JDBC Connection [com.mysql.jdbc.JDBC4Connection@63440df3]
DEBUG [main] - Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@63440df3]
DEBUG [main] - Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@63440df3]
DEBUG [main] - Returned connection 1665404403 to pool.

我們還可以通過設(shè)置UPDATE語句中的WHERE條件虐块，來修改一條或者多條數(shù)據(jù)，基本的UPDATE用法就這么簡單嘉蕾。

delete用法

delete同update相似贺奠，我們通過主鍵來完成刪除數(shù)據(jù)。
在UserMapper接口中添加方法：

public int deleteById(Long id);

根據(jù)主鍵刪除數(shù)據(jù)時错忱，如果主鍵只有一個字段儡率，那么就可以像這個方法一樣使用一個參數(shù)，這個方法對應(yīng)的UserMapper.xml中的代入如：

    <update id="updateById">
        update sys_user set user_name = #{userName},
        user_password = #{userPassword},
        user_email = #{userEmail}, user_info =
        #{userInfo}, head_img = #{headImg
        , jdbcType=BLOB}, create_time =
        #{createTime,jdbcType=TIMESTAMP}
        where id = #{id}
    </update>

如果我們修改UserMapper接口中方法中傳遞的參數(shù)以清，如下：

public int deleteById(SysUser sysUser);

我們XML中的代碼不需要進行任何修改儿普，也是可以正確執(zhí)行的。
然后在測試類UserMapperTest中添加一個測試方法：

@Test
    public void testDeleteById(){
        // 獲取SqlSession
        SqlSession sqlSession = getSqlSession();

        // 獲取UserMapper接口
        try {
            UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
            
            //根據(jù)數(shù)據(jù)庫中的用戶的ID,查詢出用戶數(shù)據(jù)
            SysUser user1 = userMapper.selectById(1L);
            SysUser user2 = userMapper.selectById(2L);
            //此時還能夠查詢出數(shù)據(jù)
            System.out.println("執(zhí)行刪除前："+user1);
            System.out.println("執(zhí)行刪除前："+user2);
            
            //執(zhí)行刪除
            int result1 = userMapper.deleteById(1L);
            
            int result2 = userMapper.deleteById(user2);
            
            System.out.println("刪除id=1數(shù)據(jù)條數(shù)：" + result1);
            System.out.println("刪除id=2數(shù)據(jù)條數(shù)：" + result2);
            
            SysUser user11 = userMapper.selectById(1L);
            SysUser user22 = userMapper.selectById(2L);
            //此時還能夠查詢出數(shù)據(jù)
            System.out.println("執(zhí)行刪除后："+user11);
            System.out.println("執(zhí)行刪除后："+user22);
        }catch(Exception e){
            e.printStackTrace();
        } finally {
            //為了不對其他的測試造成影響掷倔，此處進行數(shù)據(jù)回滾
            //由于默認的sqlSessionFactory.openSession()是不會自動提交的眉孩，因此如果不手動進行commit操作，數(shù)據(jù)也不會寫入數(shù)據(jù)庫
            sqlSession.rollback();
            // 關(guān)閉SqlSession
            sqlSession.close();
        }
    }

右鍵單擊測試類，在Run As選項中選擇JUnit Test執(zhí)行測試浪汪。測試通過巴柿，控制臺將會打印如下日志：

DEBUG [main] - Opening JDBC Connection
DEBUG [main] - Created connection 1665404403.
DEBUG [main] - Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@63440df3]
DEBUG [main] - ==>  Preparing: select * from sys_user where id = ? 
DEBUG [main] - ==> Parameters: 1(Long)
TRACE [main] - <==    Columns: id, user_name, user_password, user_email, user_info, head_img, create_time
TRACE [main] - <==        Row: 1, admin, 123456, admin@mybais.alex, <<BLOB>>, <<BLOB>>, 2017-08-09 15:26:52.0
DEBUG [main] - <==      Total: 1
DEBUG [main] - ==>  Preparing: select * from sys_user where id = ? 
DEBUG [main] - ==> Parameters: 2(Long)
TRACE [main] - <==    Columns: id, user_name, user_password, user_email, user_info, head_img, create_time
TRACE [main] - <==        Row: 2, test, 123456, test@mybais.alex, <<BLOB>>, <<BLOB>>, 2017-08-09 15:27:30.0
DEBUG [main] - <==      Total: 1
執(zhí)行刪除前：SysUser [id=1, userName=admin, userPassword=123456, userEmail=admin@mybais.alex, userInfo=管理員, headImg=null, createTime=Wed Aug 09 15:26:52 CST 2017]
執(zhí)行刪除前：SysUser [id=2, userName=test, userPassword=123456, userEmail=test@mybais.alex, userInfo=測試用戶, headImg=null, createTime=Wed Aug 09 15:27:30 CST 2017]
DEBUG [main] - ==>  Preparing: delete from sys_user where id = ? 
DEBUG [main] - ==> Parameters: 1(Long)
DEBUG [main] - <==    Updates: 1
DEBUG [main] - ==>  Preparing: delete from sys_user where id = ? 
DEBUG [main] - ==> Parameters: 2(Long)
DEBUG [main] - <==    Updates: 1
刪除id=1數(shù)據(jù)條數(shù)：1
刪除id=2數(shù)據(jù)條數(shù)：1
DEBUG [main] - ==>  Preparing: select * from sys_user where id = ? 
DEBUG [main] - ==> Parameters: 1(Long)
DEBUG [main] - <==      Total: 0
DEBUG [main] - ==>  Preparing: select * from sys_user where id = ? 
DEBUG [main] - ==> Parameters: 2(Long)
DEBUG [main] - <==      Total: 0
執(zhí)行刪除后：null
執(zhí)行刪除后：null
DEBUG [main] - Rolling back JDBC Connection [com.mysql.jdbc.JDBC4Connection@63440df3]
DEBUG [main] - Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@63440df3]
DEBUG [main] - Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@63440df3]
DEBUG [main] - Returned connection 1665404403 to pool.

項目源碼下載地址：https://github.com/JFAlex/MyBatis/tree/master/MyBatis_No.3/alex

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