Net. SF. JSON. jsonexception: there is a cycle in the hierarchy! Error Solution

Hibernate is prone to this problem, mainly because of the cascading relationship of pojo class attributes. For example, employees and departments have department attributes in the employee table, and there is an employee set in the department table. In this way, the nested reference problem exists and this exception is thrown.

The solution is simple. You can use the setexcludes function to remove cascading attributes when converting each object into a JSON object, as shown below:

　

1 // get all Departments 2 // return the JSON object string 3 Public String getalldep () {4 List list = deptdao. findall (); 5 jsonconfig Config = new jsonconfig (); 6 config. setexcludes (New String [] {"EMPs"}); // remove the EMPs attribute 7 string JSON = jsonarray. fromobject (list, config ). tostring (); 8 return JSON; 9} 10 11 // get all employees 12 Public String getallemp (int id) {13 list = empdao. findbyproperty ("dept. deptid ", ID); 14 jsonconfig Config = new jsonconfig (); 15 config. setexcludes (New String [] {"Dept"}); // remove the dept attribute 16 string JSON = jsonarray. fromobject (list, config ). tostring (); 17 return JSON; 18}

 

 

The Exception Code is as follows:

Severe: servlet. Service () for servlet springmvc threw exceptionnet. 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: 857) at net. SF. JSON. jsonobject. fromobject (jsonobject. java: 192) at net. SF. JSON. jsonobject. _ processvalue (jsonobject. java: 2774) at net. SF. JSON. jsonobject. _ setinternal (jsonobject. java: 2798) at net. SF. JSON. jsonobject. setvalue (jsonobject. java: 1507) at net. SF. JSON. jsonobject. _ frombean (jsonobject. java: 940) at net. SF. JSON. jsonobject. fromobject (jsonobject. java: 192) at net. SF. JSON. jsonarray. _ processvalue (jsonarray. java: 2557) at net. SF. JSON. jsonarray. processvalue (jsonarray. java: 2588) at net. SF. JSON. jsonarray. addvalue (jsonarray. java: 2575) at net. SF. JSON. jsonarray. _ fromcollection (jsonarray. java: 1082) at net. SF. JSON. jsonarray. fromobject (jsonarray. java: 145) at net. SF. JSON. jsonobject. _ processvalue (jsonobject. java: 2749) at net. SF. JSON. jsonobject. _ setinternal (jsonobject. java: 2798) at net. SF. JSON. jsonobject. setvalue (jsonobject. java: 1507) at net. SF. JSON. jsonobject. _ frombean (jsonobject. java: 940) at net. SF. JSON. jsonobject. fromobject (jsonobject. java: 192) at net. SF. JSON. jsonarray. _ processvalue (jsonarray. java: 2557) at net. SF. JSON. jsonarray. processvalue (jsonarray. java: 2588) at net. SF. JSON. jsonarray. addvalue (jsonarray. java: 2575) at net. SF. JSON. jsonarray. _ fromcollection (jsonarray. java: 1082) at net. SF. JSON. jsonarray. fromobject (jsonarray. java: 145) at com. service. empservice. getalldep (empservice. java: 31) at com. service. empservice $ fastclassbycglib $ fef4bb53. invoke (<generated>) at net. SF. cglib. proxy. methodproxy. invoke (methodproxy. java: 149) at Org. springframework. AOP. framework. cglib2aopproxy $ cglibmethodinvocation. invokejoinpoint (cglib2aopproxy. java: 700) at Org. springframework. AOP. framework. reflectivemethodinvocation. proceed (reflectivemethodinvocation. java: 149) at Org. springframework. transaction. interceptor. transactioninterceptor. invoke (transactioninterceptor. java: 106) at Org. springframework. AOP. framework. reflectivemethodinvocation. proceed (reflectivemethodinvocation. java: 171) at Org. springframework. AOP. interceptor. exposeinvocationinterceptor. invoke (exposeinvocationinterceptor. java: 89) at Org. springframework. AOP. framework. reflectivemethodinvocation. proceed (reflectivemethodinvocation. java: 171) at Org. springframework. AOP. framework. cglib2aopproxy $ dynamicadvisedinterceptor. intercept (cglib2aopproxy. java: 635) at com. service. empservice $ enhancerbycglib $8fce1d77. getalldep (<generated>) at com. action. depaction. getalldept (depaction. java: 22) at Sun. reflect. nativemethodaccessorimpl. invoke0 (native method) at Sun. reflect. nativemethodaccessorimpl. invoke (nativemethodaccessorimpl. java: 57) at Sun. reflect. delegatingmethodaccessorimpl. invoke (delegatingmethodaccessorimpl. java: 43) at java. lang. reflect. method. invoke (method. java: 601) at Org. springframework. web. BIND. annotation. support. handlermethodinvoker. doinvokemethod (handlermethodinvoker. java: 413) at Org. springframework. web. BIND. annotation. support. handlermethodinvoker. invokehandlermethod (handlermethodinvoker. java: 134) at Org. springframework. web. servlet. MVC. annotation. annotationmethodhandleradapter. invokehandlermethod (annotationmethodhandleradapter. java: 310) at Org. springframework. web. servlet. MVC. annotation. annotationmethodhandleradapter. handle (annotationmethodhandleradapter. java: 297) at Org. springframework. web. servlet. dispatcherservlet. dodispatch (dispatcherservlet. java: 875) at Org. springframework. web. servlet. dispatcherservlet. doservice (dispatcherservlet. java: 809) at Org. springframework. web. servlet. frameworkservlet. processrequest (frameworkservlet. java: 571) at Org. springframework. web. servlet. frameworkservlet. doget (frameworkservlet. java: 501) at javax. servlet. HTTP. httpservlet. service (httpservlet. java: 690) at javax. servlet. HTTP. httpservlet. service (httpservlet. java: 803) at Org. apache. catalina. core. applicationfilterchain. internaldofilter (applicationfilterchain. java: 290) at Org. apache. catalina. core. applicationfilterchain. dofilter (applicationfilterchain. java: 206) at Org. springframework. orm. hibernate3.support. opensessioninviewfilter. dofilterinternal (opensessioninviewfilter. java: 198) at Org. springframework. web. filter. onceperrequestfilter. dofilter (onceperrequestfilter. java: 76) at Org. apache. catalina. core. applicationfilterchain. internaldofilter (applicationfilterchain. java: 235) at Org. apache. catalina. core. applicationfilterchain. dofilter (applicationfilterchain. java: 206) at Org. apache. catalina. core. standardwrappervalve. invoke (standardwrappervalve. java: 230) at Org. apache. catalina. core. standardcontextvalve. invoke (standardcontextvalve. java: 175) at Org. apache. catalina. core. standardhostvalve. invoke (standardhostvalve. java: 128) at Org. apache. catalina. valves. errorreportvalve. invoke (errorreportvalve. java: 104) at Org. apache. catalina. core. standardenginevalve. invoke (standardenginevalve. java: 109) at Org. apache. catalina. connector. coyoteadapter. service (coyoteadapter. java: 261) at Org. apache. coyote. http11.http11processor. process (http11processor. java: 844) at Org. apache. coyote. http11.http11protocol $ http11connectionhandler. process (http11protocol. java: 581) at org.apache.tomcat.util.net. jioendpoint $ worker. run (jioendpoint. java: 447) at java. lang. thread. run (thread. java: 722)