即使在发布之后，弹簧引导字段也始终为空

Question

我有一个LoginCredential 课程：

public class LoginCredential {
    @Id @GeneratedValue Long userID;
    String eMail;
    String passwordHash;
    @OneToOne(mappedBy = "loginCredential", fetch = FetchType.LAZY)
    User user;
    LoginCredential(){}
    public LoginCredential(String eMail, String passwordHash, User user) 
    {
        this.eMail = eMail;
        this.passwordHash = passwordHash;
        this.user = user;
    }
}

然后我有User 类：

public class User {
    @Id @GeneratedValue Long userID;
    @OneToOne(fetch = FetchType.LAZY,targetEntity = LoginCredential.class)
    @JoinColumn(name = "userID",referencedColumnName = "userID")
    @JsonIgnore
    private LoginCredential loginCredential;
    public User(){}
    public User(String eMail)
    {
          this.eMail=eMail;
    }
    public User(String eMail, LoginCredential loginCredential) {
        this.eMail = eMail;
        this.loginCredential = loginCredential;
    }
}

在我的系统中，首先创建了一个LoginCredential 的实例。

但对我来说，问题是在我创建该实例之后，user 字段仍然是null。

如何解决？

由于它们是一对一映射的，还有其他方法吗？

我试过这个：{"email":"test@gmail.com","passwordHash":"a665a45920422f9d417e4867efdc4fb8a04a1f3fff1fa07e998e86f7f7a27ae3","user":{"userID":801,"email":"test@gmail.com"}}

我在前端使用的方法，在我的react.js 应用程序中：

createUserAndCredential = () => {

  var xhr = new XMLHttpRequest();
  xhr.open('POST', 'http://localhost:8080/login/');
  xhr.setRequestHeader("Content-Type", "application/json");
  xhr.send(JSON.stringify({
    email: this.state.email,
    passwordHash: this.state.passwordHash
  }));
  let that = this;
  xhr.onreadystatechange = function() {
    if (this.readyState === 4 && this.status === 200) {
      console.log(this.responseText);
      /*
      console.log(this.responseText);
      console.log(that.state.newLoginCredential);
      */

      that.state.newLoginCredential = this.responseText.toString();


      var xhr1 = new XMLHttpRequest();
      xhr1.open('POST', 'http://localhost:8080/user/');
      xhr1.setRequestHeader("Content-Type", "application/json");
      console.log(that.state.newLoginCredential);

      let user = JSON.stringify({
        email: that.state.email,
        loginCredential: JSON.parse(that.state.newLoginCredential)
      });

      //console.log(loginCredential);

      xhr1.send(user);

    } else if (this.readyState !== 4 && this.status !== 200) {
      console.log(this.status);
    }
  };
};

<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.6.3/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.6.3/umd/react-dom.production.min.js"></script>

这给了我这个警告：

已解决 [org.springframework.http.converter.HttpMessageNotReadableException：JSON 解析错误：无法构造 com.mua.cse616.Model.LoginCredential 的实例（尽管至少存在一个 Creator）：没有 String-argument 构造函数/工厂方法可从 String 反序列化值('{"email":"t7@gmail.com","passwordHash":"a665a45920422f9d417e4867efdc4fb8a04a1f3fff1fa07e998e86f7f7a27ae3"}');嵌套异常是 com.fasterxml.jackson.databind.exc.MismatchedInputException：无法构造 com.mua.cse616.Model.LoginCredential 的实例（尽管至少存在一个 Creator）：没有字符串参数构造函数/工厂方法可以从字符串值反序列化（'{"email" :"t7@gmail.com","passwordHash":"a665a45920422f9d417e4867efdc4fb8a04a1f3fff1fa07e998e86f7f7a27ae3"}') 在 [来源：（PushbackInputStream）；行：1，列：43]（通过引用链：com.mua.cse616.Model.User["loginCredential"])]

Answer 1

由于映射位于 User 一侧（mappedBy 驻留在那里），您必须保存它才能看到填充到 LoginCredential 的更改。但是您可以将父级中的更改定义为级联到子级：

@OneToOne(mappedBy = "loginCredential", fetch = FetchType.LAZY, cascade = CascadeType.ALL)

或者，如果您不想级联所有内容（例如删除）：

@OneToOne(mappedBy = "loginCredential", fetch = FetchType.LAZY, cascade = {CascadeType.PERSIST, CascadeType.MERGE})