当jpa尝试从数据库提取对象时出现此错误。
错误：路径为[]的上下文中servlet [dispatcherServlet]的Servlet.service（）引发了异常错误[处理程序调度失败;嵌套异常错误为java.lang.StackOverflowError]，其根本原因为

UserController在此情况下，getUsers方法不起作用并导致错误

@RestController
@RequestMapping("user")
public class UserController {

    private final Logger log = LoggerFactory.getLogger(UserController.class);

    @Autowired
    private UserService userService;

    @Autowired
    private RoleService roleService;

    @PostMapping("/add")
    public MessageDto addUser(@RequestBody UserDto userDto)
    {
        log.info("Post call have been received at user/add with DTO " + userDto);
                                             //Set<UserRoleDomain>
        UserDomain userDomain = userService.mapUserDtoToDomain(userDto);
        return userService.add(userDomain, roleService.add(userDomain));
    }

    @GetMapping("/get/{userName}")
    public UserDto getUsers(@PathVariable("userName") String userName)
    {
        log.info("Get call have been received at user/get/ "+userName);
        return userService.getById(userName);
    }

}

用户服务

@Service
@Transactional
public class UserService {

    private final Logger log = LoggerFactory.getLogger(UserService.class);

    @Autowired
    private ObjectMapper objectMapper;

    @Autowired
    private UserRepository userRepository;

    @Autowired
    private RoleRepository roleRepository;

    @Autowired
    private UserRoleRepository userRoleRepository;

    public MessageDto add(UserDomain userDomain , Set<UserRoleDomain> userRoles)
    {
            // UserDomain userDomain = mapUserDtoToDomain(userDto);
            if( userRepository.findByUserName(userDomain.getUserName())!=null) // causing error
            {
                String responseMessage = "User is already register with name ! "+userDomain.getUserName();
                MessageDto messageDto = new MessageDto(responseMessage);
                log.info(responseMessage);
                return messageDto;
            }
            else {

                for (UserRoleDomain userRoleDomain: userRoles) {
                    System.out.println("result : "+userRoleDomain.getRoleDomain());
                    roleRepository.save(userRoleDomain.getRoleDomain());
                }

                userDomain.getUserRoleDomains().addAll(userRoles);
                userRepository.save(userDomain);
                String responseMessage = "User has been added with Id " + userDomain.getUserId();
                MessageDto messageDto = new MessageDto(responseMessage);
                log.info(responseMessage);
                return messageDto;
            }
    }

    public UserDto getById(String userName)
    {
       UserDomain userDomain =  userRepository.findByUserName(userName);
       return mapUserDomainToDto(userDomain);
    }

    public UserDomain mapUserDtoToDomain(UserDto userDto)
    {
        return objectMapper.convertValue(userDto , UserDomain.class);
    }

    public UserDto mapUserDomainToDto(UserDomain userDomain)
    {
        return objectMapper.convertValue(userDomain , UserDto.class);
    }

}

"这是我的终端"

2021-07-31 13:57:50.549  WARN 13691 --- [nio-8881-exec-1] o.h.e.loading.internal.LoadContexts      : HHH000100: Fail-safe cleanup (collections) : org.hibernate.engine.loading.internal.CollectionLoadContext@17f80723<rs=HikariProxyResultSet@763024380 wrapping Result set representing update count of -1>
2021-07-31 13:57:50.549  WARN 13691 --- [nio-8881-exec-1] o.h.e.loading.internal.LoadContexts      : HHH000100: Fail-safe cleanup (collections) : org.hibernate.engine.loading.internal.CollectionLoadContext@38b516d2<rs=HikariProxyResultSet@1651373951 wrapping Result set representing update count of -1>
2021-07-31 13:57:50.558 ERROR 13691 --- [nio-8881-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Handler dispatch failed; nested exception is java.lang.StackOverflowError] with root cause

java.lang.StackOverflowError: null
    at java.base/java.lang.String.indexOf(String.java:1578) ~[na:na]
    at java.base/java.lang.String.indexOf(String.java:1535) ~[na:na]
    at java.base/java.net.URLStreamHandler.parseURL(URLStreamHandler.java:143) ~[na:na]
    at java.base/sun.net.www.protocol.file.Handler.parseURL(Handler.java:67) ~[na:na]
    at java.base/java.net.URL.<init>(URL.java:674) ~[na:na]
    at java.base/java.net.URL.<init>(URL.java:541) ~[na:na]
    at java.base/jdk.internal.loader.URLClassPath$FileLoader.getResource(URLClassPath.java:1221) ~[na:na]
    at java.base/jdk.internal.loader.URLClassPath.getResource(URLClassPath.java:314) ~[na:na]
    at java.base/jdk.internal.loader.BuiltinClassLoader.findClassOnClassPathOrNull(BuiltinClassLoader.java:695) ~[na:na]
    at java.base/jdk.internal.loader.BuiltinClassLoader.loadClassOrNull(BuiltinClassLoader.java:621) ~[na:na]
    at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:579) ~[na:na]
    at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178) ~[na:na]
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521) ~[na:na]
    at com.mysql.cj.jdbc.ClientPreparedStatement.executeQuery(ClientPreparedStatement.java:1020) ~[mysql-connector-java-8.0.25.jar:8.0.25]
    at com.zaxxer.hikari.pool.ProxyPreparedStatement.executeQuery(ProxyPreparedStatement.java:52) ~[HikariCP-4.0.3.jar:na]
    at com.zaxxer.hikari.pool.HikariProxyPreparedStatement.executeQuery(HikariProxyPreparedStatement.java) ~[HikariCP-4.0.3.jar:na]
    at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.extract(ResultSetReturnImpl.java:57) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.getResultSet(AbstractLoadPlanBasedLoader.java:390) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.executeQueryStatement(AbstractLoadPlanBasedLoader.java:163) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.executeLoad(AbstractLoadPlanBasedLoader.java:104) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.loader.collection.plan.AbstractLoadPlanBasedCollectionInitializer.initialize(AbstractLoadPlanBasedCollectionInitializer.java:87) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.persister.collection.AbstractCollectionPersister.initialize(AbstractCollectionPersister.java:710) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.event.internal.DefaultInitializeCollectionEventListener.onInitializeCollection(DefaultInitializeCollectionEventListener.java:76) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.event.service.internal.EventListenerGroupImpl.fireEventOnEachListener(EventListenerGroupImpl.java:99) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.internal.SessionImpl.initializeCollection(SessionImpl.java:2163) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection$4.doWork(AbstractPersistentCollection.java:589) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:264) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:585) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection.read(AbstractPersistentCollection.java:149) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.collection.internal.PersistentSet.hashCode(PersistentSet.java:458) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at com.examportal.examportalapi.domain.RoleDomain.hashCode(RoleDomain.java:13) ~[classes/:na]
    at com.examportal.examportalapi.domain.UserRoleDomain.hashCode(UserRoleDomain.java:14) ~[classes/:na]
    at java.base/java.util.HashMap.hash(HashMap.java:339) ~[na:na]
    at java.base/java.util.HashMap.put(HashMap.java:607) ~[na:na]
    at java.base/java.util.HashSet.add(HashSet.java:220) ~[na:na]
    at java.base/java.util.AbstractCollection.addAll(AbstractCollection.java:352) ~[na:na]
    at org.hibernate.collection.internal.PersistentSet.endRead(PersistentSet.java:355) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.engine.loading.internal.CollectionLoadContext.endLoadingCollection(CollectionLoadContext.java:239) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.engine.loading.internal.CollectionLoadContext.endLoadingCollections(CollectionLoadContext.java:224) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.engine.loading.internal.CollectionLoadContext.endLoadingCollections(CollectionLoadContext.java:198) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.loader.plan.exec.process.internal.CollectionReferenceInitializerImpl.endLoading(CollectionReferenceInitializerImpl.java:154) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.loader.plan.exec.process.internal.AbstractRowReader.finishLoadingCollections(AbstractRowReader.java:253) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.loader.plan.exec.process.internal.AbstractRowReader.finishUp(AbstractRowReader.java:211) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.loader.plan.exec.process.internal.ResultSetProcessorImpl.extractResults(ResultSetProcessorImpl.java:96) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.executeLoad(AbstractLoadPlanBasedLoader.java:105) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.loader.collection.plan.AbstractLoadPlanBasedCollectionInitializer.initialize(AbstractLoadPlanBasedCollectionInitializer.java:87) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.persister.collection.AbstractCollectionPersister.initialize(AbstractCollectionPersister.java:710) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.event.internal.DefaultInitializeCollectionEventListener.onInitializeCollection(DefaultInitializeCollectionEventListener.java:76) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.event.service.internal.EventListenerGroupImpl.fireEventOnEachListener(EventListenerGroupImpl.java:99) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.internal.SessionImpl.initializeCollection(SessionImpl.java:2163) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection$4.doWork(AbstractPersistentCollection.java:589) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:264) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:585) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection.read(AbstractPersistentCollection.java:149) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.collection.internal.PersistentSet.hashCode(PersistentSet.java:458) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at com.examportal.examportalapi.domain.RoleDomain.hashCode(RoleDomain.java:13) ~[classes/:na]
    at com.examportal.examportalapi.domain.UserRoleDomain.hashCode(UserRoleDomain.java:14) ~[classes/:na]
    at java.base/java.util.HashMap.hash(HashMap.java:339) ~[na:na]
    at java.base/java.util.HashMap.put(HashMap.java:607) ~[na:na]
    at java.base/java.util.HashSet.add(HashSet.java:220) ~[na:na]
    at java.base/java.util.AbstractCollection.addAll(AbstractCollection.java:352) ~[na:na]
    at org.hibernate.collection.internal.PersistentSet.endRead(PersistentSet.java:355) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.engine.loading.internal.CollectionLoadContext.endLoadingCollection(CollectionLoadContext.java:239) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.engine.loading.internal.CollectionLoadContext.endLoadingCollections(CollectionLoadContext.java:224) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.engine.loading.internal.CollectionLoadContext.endLoadingCollections(CollectionLoadContext.java:198) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.loader.plan.exec.process.internal.CollectionReferenceInitializerImpl.endLoading(CollectionReferenceInitializerImpl.java:154) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.loader.plan.exec.process.internal.AbstractRowReader.finishLoadingCollections(AbstractRowReader.java:253) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.loader.plan.exec.process.internal.AbstractRowReader.finishUp(AbstractRowReader.java:211) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.loader.plan.exec.process.internal.ResultSetProcessorImpl.extractResults(ResultSetProcessorImpl.java:96) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.executeLoad(AbstractLoadPlanBasedLoader.java:105) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.loader.collection.plan.AbstractLoadPlanBasedCollectionInitializer.initialize(AbstractLoadPlanBasedCollectionInitializer.java:87) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.persister.collection.AbstractCollectionPersister.initialize(AbstractCollectionPersister.java:710) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.event.internal.DefaultInitializeCollectionEventListener.onInitializeCollection(DefaultInitializeCollectionEventListener.java:76) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.event.service.internal.EventListenerGroupImpl.fireEventOnEachListener(EventListenerGroupImpl.java:99) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.internal.SessionImpl.initializeCollection(SessionImpl.java:2163) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection$4.doWork(AbstractPersistentCollection.java:589) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:264) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:585) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection.read(AbstractPersistentCollection.java:149) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.collection.internal.PersistentSet.hashCode(PersistentSet.java:458) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at com.examportal.examportalapi.domain.RoleDomain.hashCode(RoleDomain.java:13) ~[classes/:na]
    at com.examportal.examportalapi.domain.UserRoleDomain.hashCode(UserRoleDomain.java:14) ~[classes/:na]
    at java.base/java.util.HashMap.hash(HashMap.java:339) ~[na:na]
    at java.base/java.util.HashMap.put(HashMap.java:607) ~[na:na]
    at java.base/java.util.HashSet.add(HashSet.java:220) ~[na:na]
    at java.base/java.util.AbstractCollection.addAll(AbstractCollection.java:352) ~[na:na]
    at org.hibernate.collection.internal.PersistentSet.endRead(PersistentSet.java:355) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.engine.loading.internal.CollectionLoadContext.endLoadingCollection(CollectionLoadContext.java:239) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.engine.loading.internal.CollectionLoadContext.endLoadingCollections(CollectionLoadContext.java:224) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.engine.loading.internal.CollectionLoadContext.endLoadingCollections(CollectionLoadContext.java:198) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.loader.plan.exec.process.internal.CollectionReferenceInitializerImpl.endLoading(CollectionReferenceInitializerImpl.java:154) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.loader.plan.exec.process.internal.AbstractRowReader.finishLoadingCollections(AbstractRowReader.java:253) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.loader.plan.exec.process.internal.AbstractRowReader.finishUp(AbstractRowReader.java:211) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.loader.plan.exec.process.internal.ResultSetProcessorImpl.extractResults(ResultSetProcessorImpl.java:96) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.executeLoad(AbstractLoadPlanBasedLoader.java:105) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.loader.collection.plan.AbstractLoadPlanBasedCollectionInitializer.initialize(AbstractLoadPlanBasedCollectionInitializer.java:87) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.persister.collection.AbstractCollectionPersister.initialize(AbstractCollectionPersister.java:710) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.event.internal.DefaultInitializeCollectionEventListener.onInitializeCollection(DefaultInitializeCollectionEventListener.java:76) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.event.service.internal.EventListenerGroupImpl.fireEventOnEachListener(EventListenerGroupImpl.java:99) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.internal.SessionImpl.initializeCollection(SessionImpl.java:2163) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection$4.doWork(AbstractPersistentCollection.java:589) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:264) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:585) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection.read(AbstractPersistentCollection.java:149) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.collection.internal.PersistentSet.hashCode(PersistentSet.java:458) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at com.examportal.examportalapi.domain.RoleDomain.hashCode(RoleDomain.java:13) ~[classes/:na]
    at com.examportal.examportalapi.domain.UserRoleDomain.hashCode(UserRoleDomain.java:14) ~[classes/:na]
    at java.base/java.util.HashMap.hash(HashMap.java:339) ~[na:na]
    at java.base/java.util.HashMap.put(HashMap.java:607) ~[na:na]
    at java.base/java.util.HashSet.add(HashSet.java:220) ~[na:na]
    at java.base/java.util.AbstractCollection.addAll(AbstractCollection.java:352) ~[na:na]
    at org.hibernate.collection.internal.PersistentSet.endRead(PersistentSet.java:355) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.engine.loading.internal.CollectionLoadContext.endLoadingCollection(CollectionLoadContext.java:239) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.engine.loading.internal.CollectionLoadContext.endLoadingCollections(CollectionLoadContext.java:224) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.engine.loading.internal.CollectionLoadContext.endLoadingCollections(CollectionLoadContext.java:198) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.loader.plan.exec.process.internal.CollectionReferenceInitializerImpl.endLoading(CollectionReferenceInitializerImpl.java:154) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.loader.plan.exec.process.internal.AbstractRowReader.finishLoadingCollections(AbstractRowReader.java:253) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.loader.plan.exec.process.internal.AbstractRowReader.finishUp(AbstractRowReader.java:211) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.loader.plan.exec.process.internal.ResultSetProcessorImpl.extractResults(ResultSetProcessorImpl.java:96) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.executeLoad(AbstractLoadPlanBasedLoader.java:105) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.loader.collection.plan.AbstractLoadPlanBasedCollectionInitializer.initialize(AbstractLoadPlanBasedCollectionInitializer.java:87) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.persister.collection.AbstractCollectionPersister.initialize(AbstractCollectionPersister.java:710) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.event.internal.DefaultInitializeCollectionEventListener.onInitializeCollection(DefaultInitializeCollectionEventListener.java:76) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.event.service.internal.EventListenerGroupImpl.fireEventOnEachListener(EventListenerGroupImpl.java:99) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.internal.SessionImpl.initializeCollection(SessionImpl.java:2163) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection$4.doWork(AbstractPersistentCollection.java:589) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:264) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:585) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection.read(AbstractPersistentCollection.java:149) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at org.hibernate.collection.internal.PersistentSet.hashCode(PersistentSet.java:458) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
    at com.examportal.examportalapi.domain.RoleDomain.hashCode(RoleDomain.java:13) ~[classes/:na]
    at com.examportal.examportalapi.domain.UserRoleDomain.hashCode(UserRoleDomain.java:14) ~[classes/:na]
    at java.base/java.util.HashMap.hash(HashMap.java:339) ~[na:na]
    at java.base/java.util.HashMap.put(HashMap.java:607) ~[na:na]
    at java.base/java.util.HashSet.add(HashSet.java:220) ~[na:na]