Mybatis执行插入语句后并返回主键ID问题

 <insert id="insertUser" parameterType="com.crush.mybatisplus.entity.User">
     INSERT  INTO tb_user (username,password) VALUES(#{username},#{password});
     <selectKey resultType="java.lang.Long" order="AFTER" keyProperty="id">
         SELECT LAST_INSERT_ID()
     </selectKey>
 </insert>

@Override
 public Long insert(User user) {
     return  userMapper.insertUser(user)>0?user.getId():null;
 }

<insert id="insertUser2" parameterType="com.crush.mybatisplus.entity.User">
     <selectKey keyProperty="id" order="BEFORE" resultType="String">
         select uuid()
     </selectKey>
     INSERT INTO tb_user (id,username,password) VALUES(#{id},#{username},#{password});
 </insert>

 @PostMapping("/add3")
 public Object add3(@RequestBody User user){
     return tbUserService.save(user)==true?user.getId():"插入失败";
 }

 @PostMapping("/add3")
 public Object add3(@RequestBody User user){
     tbUserService.save(user);
     System.out.println("执行完插入后的User："+user);
     return user.getId();
 }
 

 @Insert(value = "INSERT INTO t_XXXX" +
         "XXX,XXX,XXX " +
         "VALUES (XXX,XXX,XXX)")
 @SelectKey(statement="select LAST_INSERT_ID()",keyProperty = "id",before = false,resultType = Long.class)
 Integer testInsert1(MessageMould messageMould);