Svexo Svexo - 3 months ago 28
Java Question

Json (fasterxml) stackoverflow exception

When trying to serialize a Category I get a stackoverflow.

Exception


Warning: StandardWrapperValve[dispatcher]: Servlet.service() for
servlet dispatcher threw exception java.lang.StackOverflowError at
java.lang.ClassLoader.defineClass1(Native Method) at
java.lang.ClassLoader.defineClass(ClassLoader.java:760) at
org.apache.felix.framework.BundleWiringImpl$BundleClassLoader.findClass(BundleWiringImpl.java:2279)
at
org.apache.felix.framework.BundleWiringImpl.findClassOrResourceByDelegation(BundleWiringImpl.java:1501)
at
org.apache.felix.framework.BundleWiringImpl.access$400(BundleWiringImpl.java:75)
at
org.apache.felix.framework.BundleWiringImpl$BundleClassLoader.loadClass(BundleWiringImpl.java:1955)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357) at
com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:660)
at
com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:152)
at
com.fasterxml.jackson.databind.ser.impl.IndexedListSerializer.serializeContents(IndexedListSerializer.java:100)
at
com.fasterxml.jackson.databind.ser.impl.IndexedListSerializer.serializeContents(IndexedListSerializer.java:21)
at
com.fasterxml.jackson.databind.ser.std.AsArraySerializerBase.serialize(AsArraySerializerBase.java:183)
at
com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:541)
at
com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:644)
at
com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:152)


Category.java

@Entity
public class Category implements DataObject, Serializable {

@Id
@GeneratedValue
private Long id;
private String title;
private String description;

@ManyToOne @JsonIgnore
private Category parent;


@Override
public long getId() {
return id;
}

@Override
public void setId(long id) {
this.id = id;
}

public String getTitle() {
return title;
}

public void setTitle(String title) {
this.title = title;
}
public String getDescription() {
return description;
}

public void setDescription(String description) {
this.description = description;
}

public Category getParent() {
return null;//return parent;
}

public void setParent(Category parent) {
// this.parent = parent;
}

public boolean isMainCategory()
{
return true;// return this.parent == null;
}

/**
* Returns the chain of parent categories with the main category on index 0
* @return Chain of categories
*/
public List<Category> getParentChain()
{

List<Category> cats = new ArrayList<>();
Category current = this;
while(!current.isMainCategory())
{
cats.add(current);
current = current.getParent();
}
cats.add(current);
Collections.reverse(cats);
return cats;
}

@Override
public String toString()
{
return this.title;
}

@Override
public boolean equals(Object o)
{
if(!(o instanceof Category))return false;
Category c = (Category)o;

return c.title.equals(this.title);
}

@Override
public int hashCode()
{
return super.hashCode();
}
}


Rest Controller function

@RequestMapping(value="/{id}", method=RequestMethod.GET)
public ResponseEntity<Category> get(@PathVariable("id") long categoryId)
{
Category c = service.getCategoryRepository().ReadValue(categoryId);
if(c == null)
return new ResponseEntity<>(HttpStatus.NOT_FOUND);
return new ResponseEntity<>(c,HttpStatus.OK);
}


Note

Even when I replace
return new ResponseEntity<>(c,HttpStatus.OK);
with
return new ResponseEntity<>(new Category(),HttpStatus.OK);
I will get a stackoverflow whilist none of the fields contain a value.

It works fine with my other classes it's only this class that causes a stackoverflow.

Answer

Probably if you comment private Category parent; you will not have the StackOverflow. I've got the same problem in a project with circular dependencies.

The best way to solve this problem is to use the id of the parent instead of the Class like:

private Long parentId;

Edit:

The problem is with getParentChain() that is trying to be serialized. By adding @JsonIgnore before the method the problem was resolved.

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