Occasional ConcurrentModificationException

[ajanata]

Feb 28, 2015 5:59:30 AM org.apache.catalina.core.StandardWrapperValve invoke SEVERE: Servlet.service() for servlet [net.socialgamer.cah.servlets.AjaxServlet] in context with path [/zy] threw exception java.util.ConcurrentModificationException at java.util.HashMap$HashIterator.nextEntry(HashMap.java:922) at java.util.HashMap$KeyIterator.next(HashMap.java:956) at java.util.AbstractCollection.toString(AbstractCollection.java:457) at org.json.simple.JSONValue.toJSONString(Unknown Source) at org.json.simple.JSONObject.toJSONString(Unknown Source) at org.json.simple.JSONObject.toJSONString(Unknown Source) at org.json.simple.JSONValue.toJSONString(Unknown Source) at org.json.simple.JSONObject.toJSONString(Unknown Source) at org.json.simple.JSONObject.toJSONString(Unknown Source) at org.json.simple.JSONValue.toJSONString(Unknown Source) at org.json.simple.JSONArray.toJSONString(Unknown Source) at org.json.simple.JSONValue.toJSONString(Unknown Source) at org.json.simple.JSONObject.toJSONString(Unknown Source) at org.json.simple.JSONObject.toJSONString(Unknown Source) at org.json.simple.JSONValue.toJSONString(Unknown Source) at net.socialgamer.cah.servlets.CahServlet.returnObject(CahServlet.java:218) at net.socialgamer.cah.servlets.CahServlet.returnData(CahServlet.java:188) at net.socialgamer.cah.servlets.AjaxServlet.handleRequest(AjaxServlet.java:99) at net.socialgamer.cah.servlets.CahServlet.doPost(CahServlet.java:116) at javax.servlet.http.HttpServlet.service(HttpServlet.java:646) at javax.servlet.http.HttpServlet.service(HttpServlet.java:727) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) at net.socialgamer.cah.CacheControlFilter.doFilter(CacheControlFilter.java:31) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408) at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1040) at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607) at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:313) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) at java.lang.Thread.run(Thread.java:745)