AJAX——请求正确完成,但执行了错误函数

我有一个来自服务器的AJAX请求,它在数据库中保存了一个用户:

JavaScript

u.first_name = "chaabaoui";
u.last_name = "aymene";
u.mot_de_passe = "123";
u.type = 0;
u.email = "ekka@gmail.com";         
$.ajax({
    url : "http://localhost:8080/utilisateurs/addUser",
    headers: { 
        'Accept': 'application/json',
        'Content-Type': 'application/json' 
    },
    type : "POST",
    data : JSON.stringify(u),
    dataType : "application/json",
    success : function(response) {
                  console.log("the request is done,");
                  if(response == "true") {
                      console.log("and the user was saved");
                  } else {
                      console.log("but the user was not saved");
                  }
              },
    error : function(error) {
                console.log("the request was failed ", error);
            },
    complete : function(xhr , status) {
                   console.log("the requeste is complete");
               }
});

问题用户被保存到数据库中,但会显示来自错误功能的错误消息(“请求失败”),而不是成功消息。我需要知道这里出了什么问题。最重要的是,为什么不执行成功消息?

提前谢谢你。