有时候在开发中需要向表中插入自增ID，这个时候领域模型如果想要获取该ID的值，就需要在相应的mapper文件中添加useGeneratedKeys="true" keyProperty="id"。

<insert id="insertSelective" parameterType="com.huayun.mall.dataobject.UserDO"  
useGeneratedKeys="true" keyProperty="id">
    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=BIT},
      </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>

useGeneratedKeys 取值范围true、false 默认值是：false。 含义：设置是否使用JDBC的getGenereatedKeys方法获取主键并赋值到keyProperty设置的领域模型属性中

keyProperty 取id的key值

设置完以后我们就可以在前端获取到该自增ID的值
userModel.setId(userDO.getId());