Mybatis中Insert插入后返回主键id值

向右看齐 2022-05-27 07:40 320阅读 0赞

*   *  Mybatis中Insert插入后返回主键id值
        
         *  Mapper的接口:
         *  方法1：
         *  方法2：

## Mybatis中Insert插入后返回主键id值 ##

[PostgreSQL如何设置自增序列可以点这里][PostgreSQL]:

### Mapper的接口: ###

public interface ThesisMapper {
        int insertSelective(Thesis record);
    }

无论什么情况下，interface接口中的int返回的都是影响的条数(可以用来识别成功插入与否)，  
而返回的自增长主键id值，Mybatis利用反射机制，自动帮我们回填到了Model实体类当中了。我们可以利用model.getId()来获取id值。  
(当然，再insert之前，我们用getId()来获取是返回null的)

两种方法:

都是在 mapper.xml文件中

### 方法1： ###

<insert id="insertSelective" parameterType="site.gaoyisheng.pojo.Thesis" useGeneratedKeys="true" keyProperty="id">
            insert into public.XXX
            <trim prefix="(" suffix=")" suffixOverrides=",">
                <if test="type != null">
                    type,
                </if>
                <if test="type != null">
                    ....,
                </if>
            </trim>
            <trim prefix="values (" suffix=")" suffixOverrides=",">
                <if test="type != null">
                    #{type,jdbcType=VARCHAR},
                </if>
                <if test="type != null">
                    #{...},
                </if>
            </trim>
        </insert>

其中:  
**useGeneratedKeys=”true”** 表明自增主键值  
**keyProperty=”id”** 用来标识主键colum是’id’

### 方法2： ###

<insert id="insertSelective" parameterType="site.gaoyisheng.pojo.Thesis"
                 useGeneratedKeys="true" keyProperty="id">
            <selectKey resultType="int" keyProperty="id" order="BEFORE">
                 select currval("自增序列的名称") as id
            </selectKey>
    
            insert into public.XXX
            <trim prefix="(" suffix=")" suffixOverrides=",">
                <if test="type != null">
                    type,
                </if>
                <if test="type != null">
                    ....,
                </if>
            </trim>
            <trim prefix="values (" suffix=")" suffixOverrides=",">
                <if test="type != null">
                    #{type,jdbcType=VARCHAR},
                </if>
                <if test="type != null">
                    #{...},
                </if>
            </trim>
        </insert>

其中，

<selectKey resultType="int" keyProperty="id" order="BEFORE">
                 select currval("自增序列的名称") as id
    </selectKey>

**currval(“自增序列的名称”)**是PostgreSQL的序列函数，  
在MySQL或者oracle中，函数这样用:

MySQL、SQLserver中：

<selectKey resultType="_long" keyProperty="id" order="AFTER">
        select @@IDENTITY as id
      </selectKey>

oracle:

<selectKey keyProperty="id" resultType="_long" order="BEFORE">
        select CAST(RANDOM * 100000 as INTEGER) a FROM SYSTEM.SYSDUMMY1
      </selectKey>

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附录:

--------------------

参考资料:

[https://blog.csdn.net/timo1160139211/article/details/78193816][https_blog.csdn.net_timo1160139211_article_details_78193816]  
[https://blog.csdn.net/sinat\_30474567/article/details/51395247][https_blog.csdn.net_sinat_30474567_article_details_51395247]  
[https://blog.csdn.net/hardworking0323/article/details/51105136][https_blog.csdn.net_hardworking0323_article_details_51105136]

[PostgreSQL]: https://blog.csdn.net/timo1160139211/article/details/78191470
[https_blog.csdn.net_timo1160139211_article_details_78193816]: https://blog.csdn.net/timo1160139211/article/details/78193816
[https_blog.csdn.net_sinat_30474567_article_details_51395247]: https://blog.csdn.net/sinat_30474567/article/details/51395247
[https_blog.csdn.net_hardworking0323_article_details_51105136]: https://blog.csdn.net/hardworking0323/article/details/51105136