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());
