gson.toJson() throws StackOverflowError and I dont have a circular dependency - spring-boot

Question

I am trying to generate a JSON
Gson gson = new Gson();
String json = gson.toJson(item);
But every time i try to I keep getting a stackoverflow error:
java.lang.StackOverflowError: null
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.write(ReflectiveTypeAdapterFactory.java:239)
at com.google.gson.Gson$FutureTypeAdapter.write(Gson.java:968)
at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.write(TypeAdapterRuntimeTypeWrapper.java:68)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.write(ReflectiveTypeAdapterFactory.java:112)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.write(ReflectiveTypeAdapterFactory.java:239)
at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.write(TypeAdapterRuntimeTypeWrapper.java:68)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.write(ReflectiveTypeAdapterFactory.java:112)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.write(ReflectiveTypeAdapterFactory.java:239)
at com.google.gson.Gson$FutureTypeAdapter.write(Gson.java:968)
at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.write(TypeAdapterRuntimeTypeWrapper.java:68)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.write(ReflectiveTypeAdapterFactory.java:112)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.write(ReflectiveTypeAdapterFactory.java:239)
It is caused when i try to convert DataTableResults class which contains a list of Transactions.class as its property field to a string.
The DataTableResult class looks like this :
public class DataTableResults<T> {
/** The draw. */
private String draw;
/** The records filtered. */
private String recordsFiltered;
/** The records total. */
private String recordsTotal;
/** The list of data objects. */
#SerializedName("data")
List<T> listOfDataObjects;
/**
* Gets the draw.
*
* #return the draw
*/
public String getDraw() {
return draw;
}
/**
* Sets the draw.
*
* #param draw the draw to set
*/
public void setDraw(String draw) {
this.draw = draw;
}
/**
* Gets the records filtered.
*
* #return the recordsFiltered
*/
public String getRecordsFiltered() {
return recordsFiltered;
}
/**
* Sets the records filtered.
*
* #param recordsFiltered the recordsFiltered to set
*/
public void setRecordsFiltered(String recordsFiltered) {
this.recordsFiltered = recordsFiltered;
}
/**
* Gets the records total.
*
* #return the recordsTotal
*/
public String getRecordsTotal() {
return recordsTotal;
}
/**
* Sets the records total.
*
* #param recordsTotal the recordsTotal to set
*/
public void setRecordsTotal(String recordsTotal) {
this.recordsTotal = recordsTotal;
}
/**
* Gets the list of data objects.
*
* #return the listOfDataObjects
*/
public List<T> getListOfDataObjects() {
return listOfDataObjects;
}
/**
* Sets the list of data objects.
*
* #param listOfDataObjects the listOfDataObjects to set
*/
public void setListOfDataObjects(List<T> listOfDataObjects) {
this.listOfDataObjects = listOfDataObjects;
}
}
while the Transactions.class looks like this
#Entity
#Table(name = "TRANS")
public class Transactions extends DefaultEntity {
public enum TRANSACTIONTYPE{WITHDRAW, DEPOSIT, WIN, LOSS}
#ManyToOne(targetEntity = User.class)
#JoinColumn(name="player")
private User player;
private double amount;
#Enumerated(EnumType.STRING)
private TRANSACTIONTYPE transactiontype;
private String referenceID;
private String detail;
private String token;
public TRANSACTIONTYPE getTransactiontype() {
return transactiontype;
}
public Transactions setTransactiontype(TRANSACTIONTYPE transactiontype) {
this.transactiontype = transactiontype;
return this;
}
public double getAmount() {
return amount;
}
public Transactions setAmount(double amount) {
this.amount = amount;
return this;
}
public String getReferenceID() {
return referenceID;
}
public Transactions setReferenceID(String referenceID) {
this.referenceID = referenceID;
return this;
}
public String getDetail() {
return detail;
}
public Transactions setDetail(String detail) {
this.detail = detail;
return this;
}
public String getToken() {
return token;
}
public Transactions setToken(String token) {
this.token = token;
return this;
}
public User getPlayer() {
return player;
}
public Transactions setPlayer(User player) {
this.player = player;
return this;
}
}
according to this post, it is supposed to be caused by a circular dependency, but in my case it is not cause i dont have one. What else could cause such error ?

Answer 1

You should remove extends DefaultEntity, you don't need it and may bring circular dependency.
Also you have a #ManyToOne relationship with User, that may cause circular dependency if User also have a reference to Transactions.
If you have it in both parts, you should exclude it from serialization with transient on one part at least.