javascript - 即使在发布后，Spring Boot 字段也始终为空

Question

我有一个 LoginCredential 类:

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，首先创建一个 LoginCredential 实例。

但对我来说，问题是在创建该实例后，user 字段仍为 null。

如何解决这个问题？

由于它们是一对一映射的，还有其他方法吗？

我已经尝试过:{"email":"test@gmail.com","passwordHash":"a665a45920422f9d417e4867efdc4fb8a04a1f3fff1fa07e998e86f7f7a27ae3","user":{"userID":801,"email":"test@ gmail.com"}}

我在前端的 react.js 应用程序中使用的方法:

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:

Resolved [org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: Cannot construct instance of com.mua.cse616.Model.LoginCredential (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value ('{"email":"t7@gmail.com","passwordHash":"a665a45920422f9d417e4867efdc4fb8a04a1f3fff1fa07e998e86f7f7a27ae3"}'); nested exception is com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot construct instance of com.mua.cse616.Model.LoginCredential (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value ('{"email":"t7@gmail.com","passwordHash":"a665a45920422f9d417e4867efdc4fb8a04a1f3fff1fa07e998e86f7f7a27ae3"}') at [Source: (PushbackInputStream); line: 1, column: 43] (through reference chain: com.mua.cse616.Model.User["loginCredential"])]

Answer 1

由于映射位于 User 一侧(mappedBy 驻留在此处)，因此您必须保存它才能看到填充到 LoginCredential 中的更改>。但是您可以定义父级中的更改以级联到子级:

@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})