A Solution to Hierarcy Cycle Problem with JSON: JSON Filter

When you have a cycle in your domain model, beacuse sometimes you realy need it*, then with Spring JsonView, indeed you may have same problem in different cases, while converting Java objects to JSON objects, you can get en error :

net.sf.json.JSONException: There is a cycle in the hierarchy!

with a following unusefull stack trace:)

First of all, think carefully fi you really do need this cycle in the dependency. If you don’t, remove it.
If you do, the you can use, JSON filters.

I will give an example code to show it. In the code, resulting JSON object will contain only id, name and description fields and values of the objects.




JsonConfig config = new JsonConfig();
config.setJsonPropertyFilter(new PropertyFilter() {
public boolean apply(Object source, String name, Object value) {
if ("name".equals(name) || "description".equals(name) || "id".equals(name)) {
return false;
}
return true;
}
});
List jsonObjects = new ArrayList();
for (Object object : objects) {
jsonObjects.add(JSONSerializer.toJSON(object, config));
}
//Here you have jsonObjects, do whatever you need.
...


This is a sample code. It depends on you how to use this in a proper way! :)

* Consider, you have an class X with composition Y, and in Y class, if you need all Xs referenced by Y, then you will probably have a property containing list of X. Then you have cycle! For example, Employee works on a Department, so Employee has a composition with Department, in Department you need all employees workin in this department.