<update id="update" parameterType="map" >
update user
<set>
<if test="user.name!=null">name=#{user.name},</if>
<if test="user.age!=null">age=#{user.age},</if>
<if test="user.gender!=null">gender=#{user.gender},</if>
<if test="user.phone!=null">phone=#{user.phone},</if>
<if test="user.username!=null">username=#{user.username},</if>
<if test="user.password!=null">password=#{user.password},</if>
</set>
where id=#{id}
</update>
多个参数用map
update没有返回结果不能设置resultType