java 高级 -- selectKey

傷城~ 2023-06-15 04:49 11阅读 0赞

## java 高级 – selectKey ##

前言，在开发过程中，有时候插入一条数据，那么对于Dto的主键id进行赋值需要写两条逻辑，这样有些复杂，有没有快速插入数据并且Dto获取到Id的办法，有，就是selectKey

架构  
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![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDU1MDQ5MA_size_16_color_FFFFFF_t_70 1]

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDU1MDQ5MA_size_16_color_FFFFFF_t_70 2]

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## 调用dao层进行插入DTO ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDU1MDQ5MA_size_16_color_FFFFFF_t_70 3]

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDU1MDQ5MA_size_16_color_FFFFFF_t_70 4]

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<insert id="insertSelectKey">
        <selectKey keyProperty="id" order="AFTER" resultType="java.lang.Integer">
          SELECT LAST_INSERT_ID()
        </selectKey>
    
        insert into user_info
        <trim prefix="(" suffix=")" suffixOverrides="," >
          <if test="id != null" >
            id,
          </if>
          <if test="name != null" >
            name,
          </if>
          <if test="gender != null" >
            gender,
          </if>
          <if test="age != null" >
            age,
          </if>
          <if test="telphone != null" >
            telphone,
          </if>
          <if test="registerMode != null" >
            register_mode,
          </if>
          <if test="thirdPartyId != null" >
            third_party_id,
          </if>
        </trim>
        <trim prefix="values (" suffix=")" suffixOverrides="," >
          <if test="id != null" >
            #{ id,jdbcType=INTEGER},
          </if>
          <if test="name != null" >
            #{ name,jdbcType=VARCHAR},
          </if>
          <if test="gender != null" >
            #{ gender,jdbcType=TINYINT},
          </if>
          <if test="age != null" >
            #{ age,jdbcType=INTEGER},
          </if>
          <if test="telphone != null" >
            #{ telphone,jdbcType=VARCHAR},
          </if>
          <if test="registerMode != null" >
            #{ registerMode,jdbcType=VARCHAR},
          </if>
          <if test="thirdPartyId != null" >
            #{ thirdPartyId,jdbcType=VARCHAR},
          </if>
        </trim>
      </insert>

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## 正文 关于 SELECTKEY ##

selectKey 会将 SELECT LAST\_INSERT\_ID()的结果放入到传入的model的主键里面

keyProperty 对应的model中的主键的属性名，这里是 userdto 中的id，因为它跟数据库的主键对应

order AFTER 表示 SELECT LAST\_INSERT\_ID() 在insert执行之后执行,多用与自增主键，

BEFORE 表示 SELECT LAST\_INSERT\_ID() 在insert执行之前执行，这样的话就拿不到主键了，

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