Question

I have the following model:

public class CategoryModel {

    public String id;
    public String name;
    public String imageUrl;
    public CategoryModel parent;
    public List<CategoryModel> childrens = new ArrayList<CategoryModel>();
}

I am using Spring MVc + jackson to return Json.

My action build the following model and after the execution, i get stackoverflow exception.

List<CategoryModel> allCategories = new ArrayList<CategoryModel>(); 

CategoryModel model = new CategoryModel();
model.id = "1";
model.name = "category 1";

CategoryModel model1 = new CategoryModel();
model.id = "2";
model.name = "category 1.1";


model.childrens.add(model1);
model1.parent = model;

allCategories.add(model);

Any idea what’s my problem ?

this is the log file (part of it):

at
org.codehaus.jackson.map.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:446)
at
org.codehaus.jackson.map.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:150)
at
org.codehaus.jackson.map.ser.BeanSerializer.serialize(BeanSerializer.java:112)
at
org.codehaus.jackson.map.ser.std.StdContainerSerializers$IndexedListSerializer.serializeContents(StdContainerSerializers.java:122)
at
org.codehaus.jackson.map.ser.std.StdContainerSerializers$IndexedListSerializer.serializeContents(StdContainerSerializers.java:71)
at
org.codehaus.jackson.map.ser.std.AsArraySerializerBase.serialize(AsArraySerializerBase.java:86)
at
org.codehaus.jackson.map.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:446)
at
org.codehaus.jackson.map.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:150)
at
org.codehaus.jackson.map.ser.BeanSerializer.serialize(BeanSerializer.java:112)
at
org.codehaus.jackson.map.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:446)
at
org.codehaus.jackson.map.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:150)
at
org.codehaus.jackson.map.ser.BeanSerializer.serialize(BeanSerializer.java:112)
at
org.codehaus.jackson.map.ser.std.StdContainerSerializers$IndexedListSerializer.serializeContents(StdContainerSerializers.java:122)
at
org.codehaus.jackson.map.ser.std.StdContainerSerializers$IndexedListSerializer.serializeContents(StdContainerSerializers.java:71)
at
org.codehaus.jackson.map.ser.std.AsArraySerializerBase.serialize(AsArraySerializerBase.java:86)
at
org.codehaus.jackson.map.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:446)
at
org.codehaus.jackson.map.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:150)
at
org.codehaus.jackson.map.ser.BeanSerializer.serialize(BeanSerializer.java:112)
at
org.codehaus.jackson.map.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:446)
at
org.codehaus.jackson.map.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:150)
at
org.codehaus.jackson.map.ser.BeanSerializer.serialize(BeanSerializer.java:112)
at
org.codehaus.jackson.map.ser.std.StdContainerSerializers$IndexedListSerializer.serializeContents(StdContainerSerializers.java:122)
at
org.codehaus.jackson.map.ser.std.StdContainerSerializers$IndexedListSerializer.serializeContents(StdContainerSerializers.java:71)
at
org.codehaus.jackson.map.ser.std.AsArraySerializerBase.serialize(AsArraySerializerBase.java:86)
at
org.codehaus.jackson.map.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:446)
at
org.codehaus.jackson.map.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:150)
at
org.codehaus.jackson.map.ser.BeanSerializer.serialize(BeanSerializer.java:112)
at
org.codehaus.jackson.map.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:446)
at
org.codehaus.jackson.map.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:150)
at
org.codehaus.jackson.map.ser.BeanSerializer.serialize(BeanSerializer.java:112)
at
org.codehaus.jackson.map.ser.std.StdContainerSerializers$IndexedListSerializer.serializeContents(StdContainerSerializers.java:122)
at
org.codehaus.jackson.map.ser.std.StdContainerSerializers$IndexedListSerializer.serializeContents(StdContainerSerializers.java:71)
Caused by: java.lang.StackOverflowError

Answer 1

As drorb mentioned the cyclic reference is the problem. But instead of using the @JsonIgnore annotation you should use @JsonBackReference to indicate the cyclic reference. With this annotation Jackson is able to map to the correct parent when deserializing.