title: What is causing a unique constraint violation when using a SEQUENCE in Hibernate?
body: <p>I am using the code below to generate unique IDs for an <code>id</code> field. It was working fine until last week. I deleted some entities using the Hibernate interface and then it started giving a unique constraint violation exception when I try to insert new records.</p>
  
  <p>What might be causing this problem?</p>
  
  <pre><code>@SequenceGenerator(name = "ParamGenerator", sequenceName = "ParamSequence", allocationSize = 1)
  public class Param extends IdNameEntity&lt;Long&gt; {
  
      private static final long serialVersionUID = 1L;
  
      @Id
      @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "ParamGenerator")
      private Long id;
  </code></pre>
  
  <p>This is the delete method:</p>
  
  <pre><code>@Override
  public void delete(final T t) {
      getCurrentSession().delete(t);
  }
  </code></pre>
  
  <p>This is the error log:</p>
  
  <pre><code>2018-04-25 16:34:41 [http-nio-8081-exec-3] INFO  o.h.e.j.b.internal.AbstractBatchImpl - HHH000010: On release of batch it still contained JDBC statements
  2018-04-25 16:34:41 [http-nio-8081-exec-3] ERROR org.hibernate.internal.SessionImpl - HHH000346: Error during managed flush [could not execute statement]
  2018-04-25 16:34:41 [http-nio-8081-exec-3] ERROR o.a.c.c.C.[.[.[.[dispatcherServlet] - Servlet.service() for servlet [dispatcherServlet] in context with path [/admin_panel] threw exception [Request processing failed; nested exception is org.springframework.dao.DataIntegrityViolationException: could not execute statement; SQL [n/a]; constraint [XXXTTT_XXX.SYS_C00114023]; nested exception is org.hibernate.exception.ConstraintViolationException: could not execute statement] with root cause
  java.sql.SQLIntegrityConstraintViolationException: ORA-00001: unique constraint (XXXTTT_XXX.SYS_C00114023) violated
  
      at oracle.jdbc.driver.T4CTTIoer.processError(T4CTTIoer.java:447)
      at oracle.jdbc.driver.T4CTTIoer.processError(T4CTTIoer.java:396)
      at oracle.jdbc.driver.T4C8Oall.processError(T4C8Oall.java:951)
      at oracle.jdbc.driver.T4CTTIfun.receive(T4CTTIfun.java:513)
      at oracle.jdbc.driver.T4CTTIfun.doRPC(T4CTTIfun.java:227)
      at oracle.jdbc.driver.T4C8Oall.doOALL(T4C8Oall.java:531)
      at oracle.jdbc.driver.T4CPreparedStatement.doOall8(T4CPreparedStatement.java:208)
      at oracle.jdbc.driver.T4CPreparedStatement.executeForRows(T4CPreparedStatement.java:1046)
      at oracle.jdbc.driver.OracleStatement.doExecuteWithTimeout(OracleStatement.java:1336)
      at oracle.jdbc.driver.OraclePreparedStatement.executeInternal(OraclePreparedStatement.java:3613)
      at oracle.jdbc.driver.OraclePreparedStatement.executeUpdate(OraclePreparedStatement.java:3694)
      at oracle.jdbc.driver.OraclePreparedStatementWrapper.executeUpdate(OraclePreparedStatementWrapper.java:1354)
      at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:204)
      at org.hibernate.engine.jdbc.batch.internal.NonBatchingBatch.addToBatch(NonBatchingBatch.java:45)
      at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2921)
      at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:3421)
      at org.hibernate.action.internal.EntityInsertAction.execute(EntityInsertAction.java:89)
      at org.hibernate.engine.spi.ActionQueue.executeActions(ActionQueue.java:560)
      at org.hibernate.engine.spi.ActionQueue.executeActions(ActionQueue.java:434)
      at org.hibernate.event.internal.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:337)
      at org.hibernate.event.internal.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:39)
      at org.hibernate.internal.SessionImpl.flush(SessionImpl.java:1295)
      at org.hibernate.internal.SessionImpl.managedFlush(SessionImpl.java:468)
      at org.hibernate.internal.SessionImpl.flushBeforeTransactionCompletion(SessionImpl.java:3135)
      at org.hibernate.internal.SessionImpl.beforeTransactionCompletion(SessionImpl.java:2352)
      at org.hibernate.engine.jdbc.internal.JdbcCoordinatorImpl.beforeTransactionCompletion(JdbcCoordinatorImpl.java:485)
      at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl.beforeCompletionCallback(JdbcResourceLocalTransactionCoordinatorImpl.java:147)
      at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl.access$100(JdbcResourceLocalTransactionCoordinatorImpl.java:38)
      at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl$TransactionDriverControlImpl.commit(JdbcResourceLocalTransactionCoordinatorImpl.java:231)
      at org.hibernate.engine.transaction.internal.TransactionImpl.commit(TransactionImpl.java:65)
      at org.springframework.orm.hibernate5.HibernateTransactionManager.doCommit(HibernateTransactionManager.java:581)
      at org.springframework.transaction.support.AbstractPlatformTransactionManager.processCommit(AbstractPlatformTransactionManager.java:761)
      at org.springframework.transaction.support.AbstractPlatformTransactionManager.commit(AbstractPlatformTransactionManager.java:730)
      at org.springframework.transaction.interceptor.TransactionAspectSupport.commitTransactionAfterReturning(TransactionAspectSupport.java:504)
      at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:292)
      at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)
      at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
      at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:656)
      at roma.admin_panel.orm.dao.ParamDao$$EnhancerBySpringCGLIB$$91c61766.save(&lt;generated&gt;)
      at roma.admin_panel.orm.service.AbstractService.save(AbstractService.java:41)
      at roma.admin_panel.controller.ParamController.save(ParamController.java:59)
      at sun.reflect.GeneratedMethodAccessor121.invoke(Unknown Source)
      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:116)
      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:963)
      at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:897)
      at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
      at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:872)
      at javax.servlet.http.HttpServlet.service(HttpServlet.java:648)
      at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
      at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:230)
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
      at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
      at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:317)
      at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:127)
      at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:91)
      at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
      at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:114)
      at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
      at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:137)
      at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
      at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:111)
      at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
      at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:170)
      at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
      at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:63)
      at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
      at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:200)
      at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
      at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:116)
      at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
      at org.springframework.security.web.csrf.CsrfFilter.doFilterInternal(CsrfFilter.java:124)
      at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
      at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
      at org.springframework.security.web.header.HeaderWriterFilter.doFilterInternal(HeaderWriterFilter.java:64)
      at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
      at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
      at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:105)
      at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
      at org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:56)
      at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
      at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
      at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:214)
      at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:177)
      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:192)
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
      at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99)
      at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
      at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:105)
      at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
      at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:81)
      at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
      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:192)
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
      at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198)
      at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
      at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:474)
      at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
      at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
      at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
      at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:349)
      at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:783)
      at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
      at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:798)
      at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1434)
      at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
      at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
      at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
      at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
      at java.lang.Thread.run(Thread.java:748)
  </code></pre>