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

Problem
I apply JPA(Java Persistence API) to do search via primary key, then it return an object to me. And I would like to covert this object to JSONObject, it show this error message.

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net.sf.json.JSONException: There is a cycle in the hierarchy! at net.sf.json.util.CycleDetectionStrategy$StrictCycleDetectionStrategy.handleRepeatedReferenceAsObject(CycleDetectionStrategy.java:97) at net.sf.json.JSONObject._fromBean(JSONObject.java:674) at net.sf.json.JSONObject.fromObject(JSONObject.java:181) at net.sf.json.JSONArray._processValue(JSONArray.java:2381) at net.sf.json.JSONArray.processValue(JSONArray.java:2412) Truncated. see log file for complete stacktrace

The code snippet as shown below


Root Cause
Because the entity you return has many-to-one relationship, so you need to filter them out.

Solution



Reference: http://json-lib.sourceforge.net/snippets.html