Direct Self-Reference Leading to Cycle Exception
I Have a Class; Something Like the Following: Public Abstract Class Elasticsearchvalue { Private Long txId; Private Long currentTxId; Private T Previous...
I have a class; something like the following:
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;
}
}
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();
}
}
Now, I have an object of type DailyActivity, and when I try to convert it into a 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"])
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
EDIT I know there is a cycle in the class and I am asking how to deserialize the class which has a self reference?
6 Answers
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
And
@OneToMany(mappedBy="company")
@JsonManagedReference
private Set<Employee> employee = new HashSet<Employee>();
There is a nice example here
SerializationFeature has a property called FAIL_ON_SELF_REFERENCES default is true but you can set to false to skip this kind of exception.
ObjectMapper objectMapper = new ObjectMapper();
objectMapper.configure(SerializationFeature.FAIL_ON_SELF_REFERENCES, false);
If you are using SpringBoot you can simply add spring.jackson.serialization.fail-on-self-references=false
in your application.properties
The self-reference is here:
public class DailyActivity extends ElasticSearchValue<DailyActivity> {
You're saying DailyActivity is an ElasticSearchValue<DailyActivity>, which is by itself an ElasticSearchValue<ElasticSearchValue<DailyActivity>>, and this goes on infinitely...
Update: I would break that in two classes. Create DailyActivity without subclassing ElasticSearchValue:
public class DailyActivity {
// the same content as your class above
then create another class like:
public class ElacticDailyActivity extends ElasticSearchValue<DailyActivity> {
Try @JsonIdentityInfo annotation as given in this example. More details here
@JsonIdentityInfo(generator=ObjectIdGenerators.IntSequenceGenerator.class, property="@id")
public class Identifiable
{
public int value;
public Identifiable next;
}
Please refer to related question and a sensible way of handling this in my opinion.
In current case it would help to annotate 'previous' like below
@JsonIgnoreProperties({"previous"})//... along with other annotations
private T previous;
I guess somewhere in your code. The previous of some instance of DailyActivity point to itself.
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