下面是报的异常：在网上搜了关于：There is a cycle in the hierarchy!，才知道原来是因为死循环造成的！解决了好久，没有成功，后台不得已请教老大，老大说是因为在使用JSONArray.fromObject()时，往list里去探，只要又关联就会一直往下探，直到出现了死循环状态。老大给的建议将想要的东西通过list遍历出来重新柱状成一个list，在返回jsp就可以了！下面贴出错误代码，和修改后的代码：

错误的代码：

 修改后的代码：

严重: Servlet.service() for servlet [spring] in context with path [] threw exception [Request processing failed; nested exception is net.sf.json.JSONException: There is a cycle in the hierarchy!] with root cause
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:657)
    at net.sf.json.JSONObject.fromObject(JSONObject.java:172)
    at net.sf.json.AbstractJSON._processValue(AbstractJSON.java:274)
    at net.sf.json.JSONObject._processValue(JSONObject.java:2655)
    at net.sf.json.JSONObject.processValue(JSONObject.java:2721)
    at net.sf.json.JSONObject.setInternal(JSONObject.java:2736)
    at net.sf.json.JSONObject.setValue(JSONObject.java:1424)
    at net.sf.json.JSONObject.defaultBeanProcessing(JSONObject.java:765)
    at net.sf.json.JSONObject._fromBean(JSONObject.java:699)
    at net.sf.json.JSONObject.fromObject(JSONObject.java:172)
    at net.sf.json.AbstractJSON._processValue(AbstractJSON.java:274)
    at net.sf.json.JSONArray._processValue(JSONArray.java:2513)
    at net.sf.json.JSONArray.processValue(JSONArray.java:2538)
    at net.sf.json.JSONArray.addValue(JSONArray.java:2525)
    at net.sf.json.JSONArray._fromCollection(JSONArray.java:1056)
    at net.sf.json.JSONArray.fromObject(JSONArray.java:123)
    at net.sf.json.AbstractJSON._processValue(AbstractJSON.java:240)
    at net.sf.json.JSONObject._processValue(JSONObject.java:2655)
    at net.sf.json.JSONObject.processValue(JSONObject.java:2721)
    at net.sf.json.JSONObject.setInternal(JSONObject.java:2736)
    at net.sf.json.JSONObject.setValue(JSONObject.java:1424)
    at net.sf.json.JSONObject.defaultBeanProcessing(JSONObject.java:765)
    at net.sf.json.JSONObject._fromBean(JSONObject.java:699)
    at net.sf.json.JSONObject.fromObject(JSONObject.java:172)
    at net.sf.json.AbstractJSON._processValue(AbstractJSON.java:274)
    at net.sf.json.JSONObject._processValue(JSONObject.java:2655)
    at net.sf.json.JSONObject.processValue(JSONObject.java:2721)
    at net.sf.json.JSONObject.setInternal(JSONObject.java:2736)
    at net.sf.json.JSONObject.setValue(JSONObject.java:1424)
    at net.sf.json.JSONObject.defaultBeanProcessing(JSONObject.java:765)
    at net.sf.json.JSONObject._fromBean(JSONObject.java:699)
    at net.sf.json.JSONObject.fromObject(JSONObject.java:172)
    at net.sf.json.AbstractJSON._processValue(AbstractJSON.java:274)
    at net.sf.json.JSONArray._processValue(JSONArray.java:2513)
    at net.sf.json.JSONArray.processValue(JSONArray.java:2538)
    at net.sf.json.JSONArray.addValue(JSONArray.java:2525)
    at net.sf.json.JSONArray._fromCollection(JSONArray.java:1056)
    at net.sf.json.JSONArray.fromObject(JSONArray.java:123)
    at net.sf.json.JSONArray.fromObject(JSONArray.java:105)
    at com.hnzy.web.controller.AdminController.setDeptCascading(AdminController.java:198)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205)
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:133)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:97)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:967)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:901)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.shiro.web.servlet.ProxiedFilterChain.doFilter(ProxiedFilterChain.java:61)
    at org.apache.shiro.web.servlet.AdviceFilter.executeChain(AdviceFilter.java:108)
    at org.apache.shiro.web.servlet.AdviceFilter.doFilterInternal(AdviceFilter.java:137)
    at org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125)
    at org.apache.shiro.web.servlet.ProxiedFilterChain.doFilter(ProxiedFilterChain.java:66)
    at org.apache.shiro.web.servlet.AbstractShiroFilter.executeChain(AbstractShiroFilter.java:449)
    at org.apache.shiro.web.servlet.AbstractShiroFilter$1.call(AbstractShiroFilter.java:365)
    at org.apache.shiro.subject.support.SubjectCallable.doCall(SubjectCallable.java:90)
    at org.apache.shiro.subject.support.SubjectCallable.call(SubjectCallable.java:83)
    at org.apache.shiro.subject.support.DelegatingSubject.execute(DelegatingSubject.java:387)
    at org.apache.shiro.web.servlet.AbstractShiroFilter.doFilterInternal(AbstractShiroFilter.java:362)
    at org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125)
    at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:346)
    at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:262)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:475)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:651)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:500)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:754)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1376)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:745)