直接自引用导致循环异常 [英] Direct self-reference leading to cycle exception

问题描述

我有类似这样的课程

public abstract class ElasticSearchValue<T> {

  private Long txId;
  private Long currentTxId;
  private T previous;

  public Long getTxId() {
    return txId;
  }

  public void setTxId(Long txId) {
    this.txId = txId;
  }

  public Long getCurrentTxId() {
    return currentTxId;
  }

  public void setCurrentTxId(Long currentTxId) {
    this.currentTxId = currentTxId;
  }

  public Object getPrevious() {
    return previous;
  }

  public void setPrevious(T previous) {
    this.previous = previous;
  }

}

还有一个扩展课程的班级上面

And a class that extends the class above

public class DailyActivity extends ElasticSearchValue<DailyActivity> {

  Long agentId;
  Date date;
  Long success;

  public Long getAgentId() {
    return agentId;
  }

  public void setAgentId(Long agentId) {
    this.agentId = agentId;
  }

  public Date getDate() {
    return date;
  }

  public void setDate(Date date) {
    this.date = date;
  }

  public Long getSuccess() {
    return success;
  }

  public void setSuccess(Long success) {
    this.success = success;
  }

  @Override
  public String toString() {
    return agentId + "_" + date.toString();
  }

}

现在，我有一个对象键入DailyActivity，当我尝试将其转换为json字符串时，我得到以下异常：

Now, I have an object of type DailyActivity and when I try to convert it into json string I get the following exception:

Caused by: com.fasterxml.jackson.databind.JsonMappingException: Direct self-reference leading to cycle (through reference chain: com.pr.analysis.DailyActivity["previous"])

我在google上寻找解决方案，但我得到的解决方案要求将jsonIgnore放到之前的值，这不是我打算做的。有人遇到过同样的问题吗？
谢谢

I have looked for solution on google but the solution which I get asks to put jsonIgnore to previous value which is not what I intent to do. Has anyone faced the same issue? Thanks

编辑
我知道课程中有一个循环，我问的是如何反序列化课程哪个有自引用？

EDIT I know there is a cycle in the class and I am asking how to deserialize the class which has a self reference?

推荐答案

在这种情况下，你需要用 @JsonManagedReference 和 @ JsonBackReference 像这样：

In this case you need to annotate the relationships with @JsonManagedReference and @JsonBackReference like this:

 @ManyToOne
 @JoinColumn(name = "company_id", referencedColumnName = "id")
 @JsonBackReference
 private Company company 

和

 @OneToMany(mappedBy="company")
 @JsonManagedReference
 private Set<Employee> employee = new HashSet<Employee>();

有一个很好的例子这里

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