MySQLNonTransientConnectionException: Too many connections

Question

My Spring-MVC application sometimes crashes when navigating around the site, the error message I've gotten from the logs are found below. I have absolutely no idea of what is causing this and would be very thankful for any tips that'll lead me in the right direction.

    SEVERE: Servlet.service() for servlet HS threw exception com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Data source rejected establishment of connection,  message from server: "Too many connections"     at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)     at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)     at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)     at java.lang.reflect.Constructor.newInstance(Constructor.java:532)     at com.mysql.jdbc.Util.handleNewInstance(Util.java:407)     at com.mysql.jdbc.Util.getInstance(Util.java:382)     at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1013)     at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:987)     at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:982)     at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1116)     at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2338)     at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2371)     at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2163)     at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:794)     at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)     at sun.reflect.GeneratedConstructorAccessor56.newInstance(Unknown Source)     at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)     at java.lang.reflect.Constructor.newInstance(Constructor.java:532)     at com.mysql.jdbc.Util.handleNewInstance(Util.java:407)     at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:378)     at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:305)     at org.apache.commons.dbcp.DriverConnectionFactory.createConnection(DriverConnectionFactory.java:38)     at org.apache.commons.dbcp.PoolableConnectionFactory.makeObject(PoolableConnectionFactory.java:582)     at org.apache.commons.dbcp.BasicDataSource.validateConnectionFactory(BasicDataSource.java:1556)     at org.apache.commons.dbcp.BasicDataSource.createPoolableConnectionFactory(BasicDataSource.java:1545)     at org.apache.commons.dbcp.BasicDataSource.createDataSource(BasicDataSource.java:1388)     at org.apache.commons.dbcp.BasicDataSource.getConnection(BasicDataSource.java:1044)     at org.springframework.orm.hibernate3.LocalDataSourceConnectionProvider.getConnection(LocalDataSourceConnectionProvider.java:81)     at org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:446)     at org.hibernate.jdbc.ConnectionManager.getConnection(ConnectionManager.java:167)     at org.hibernate.jdbc.AbstractBatcher.prepareQueryStatement(AbstractBatcher.java:161)     at org.hibernate.loader.Loader.prepareQueryStatement(Loader.java:1577)     at org.hibernate.loader.Loader.doQuery(Loader.java:696)     at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:259)     at org.hibernate.loader.Loader.doList(Loader.java:2232)     at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2129)     at org.hibernate.loader.Loader.list(Loader.java:2124)     at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:401)     at org.hibernate.hql.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:363)     at org.hibernate.engine.query.HQLQueryPlan.performList(HQLQueryPlan.java:196)     at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1149)     at org.hibernate.impl.QueryImpl.list(QueryImpl.java:102)     at org.springframework.orm.hibernate3.HibernateTemplate$30.doInHibernate(HibernateTemplate.java:921)     at org.springframework.orm.hibernate3.HibernateTemplate$30.doInHibernate(HibernateTemplate.java:1)     at org.springframework.orm.hibernate3.HibernateTemplate.doExecute(HibernateTemplate.java:406)     at org.springframework.orm.hibernate3.HibernateTemplate.executeWithNativeSession(HibernateTemplate.java:374)     at org.springframework.orm.hibernate3.HibernateTemplate.find(HibernateTemplate.java:912)     at org.springframework.orm.hibernate3.HibernateTemplate.find(HibernateTemplate.java:904)     at se.hs.daos.UserDAOImpl.findByName(UserDAOImpl.java:42)     at se.hs.controllers.LoginController.checkPassword(LoginController.java:20)     at se.hs.pagecontrollers.LoginPageController.submitForm(LoginPageController.java:26)     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:616)     at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:176)     at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:426)     at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:414)     at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:790)     at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:719)     at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:644)     at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:560)     at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)     at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)     at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)     at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)     at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)     at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)     at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)     at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)     at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859)     at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588)     at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)     at java.lang.Thread.run(Thread.java:636) 

What my UserDaoImpl looks like:

package se.hs.daos;  import java.util.List;  import org.hibernate.SessionFactory; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; import org.springframework.orm.hibernate3.HibernateTemplate; import org.springframework.orm.hibernate3.support.HibernateDaoSupport;  import se.hs.models.User;  public class UserDAOImpl extends HibernateDaoSupport implements UserDAO {      private ApplicationContext context = new ClassPathXmlApplicationContext(             "classpath*:applicationContext.xml");     private SessionFactory sessionFactory = (SessionFactory) context             .getBean("mySessionFactory");     private HibernateTemplate hibernateTemplate = new HibernateTemplate(             sessionFactory, true);      public void saveUser(User user) {         hibernateTemplate.save(user);     }      public User getUserById(Integer id) {          User userFromDB = hibernateTemplate.get(User.class, id);         return userFromDB;     }      public void removeUser(User user) {         hibernateTemplate.delete(user);     }      public User findByName(String name) {          String query = "SELECT u.userId FROM User u WHERE u.userName='" + name                 + "'";          @SuppressWarnings("unchecked")         List<Integer> list = hibernateTemplate.find(query);          User userFromDB = null;          if (list.size() > 0) {             userFromDB = getUserById(list.get(0));         }          return userFromDB;     }  } 

UPDATE:

    exception  org.springframework.web.util.NestedServletException: Request processing failed; nested exception is org.springframework.jdbc.UncategorizedSQLException: Hibernate operation: Cannot release connection; uncategorized SQLException for SQL [???]; SQL state [null]; error code [0]; Already closed.; nested exception is java.sql.SQLException: Already closed.     org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:656)     org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:560)     javax.servlet.http.HttpServlet.service(HttpServlet.java:637)     javax.servlet.http.HttpServlet.service(HttpServlet.java:717) root cause  org.springframework.jdbc.UncategorizedSQLException: Hibernate operation: Cannot release connection; uncategorized SQLException for SQL [???]; SQL state [null]; error code [0]; Already closed.; nested exception is java.sql.SQLException: Already closed.     org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:83)     org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:80)     org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:80)     org.springframework.orm.hibernate3.HibernateAccessor.convertJdbcAccessException(HibernateAccessor.java:424)     org.springframework.orm.hibernate3.HibernateAccessor.convertHibernateAccessException(HibernateAccessor.java:410)     org.springframework.orm.hibernate3.HibernateTemplate.doExecute(HibernateTemplate.java:411)     org.springframework.orm.hibernate3.HibernateTemplate.executeWithNativeSession(HibernateTemplate.java:374)     org.springframework.orm.hibernate3.HibernateTemplate.save(HibernateTemplate.java:683)     se.hsr.daos.InfoTextDAOImpl.saveInfoText(InfoTextDAOImpl.java:26)     se.hsr.controllers.InfoTextController.saveInfoText(InfoTextController.java:31)     se.hsr.pagecontrollers.InfoTextPageController.submitForm(InfoTextPageController.java:35)     sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)     sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)     sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)     java.lang.reflect.Method.invoke(Method.java:616)     org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:176)     org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:426)     org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:414)     org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:790)     org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:719)     org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:644)     org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:560)     javax.servlet.http.HttpServlet.service(HttpServlet.java:637)     javax.servlet.http.HttpServlet.service(HttpServlet.java:717) root cause  java.sql.SQLException: Already closed.     org.apache.commons.dbcp.PoolableConnection.close(PoolableConnection.java:114)     org.apache.commons.dbcp.PoolingDataSource$PoolGuardConnectionWrapper.close(PoolingDataSource.java:191)     org.springframework.orm.hibernate3.LocalDataSourceConnectionProvider.closeConnection(LocalDataSourceConnectionProvider.java:95)     org.hibernate.jdbc.ConnectionManager.closeConnection(ConnectionManager.java:474)     org.hibernate.jdbc.ConnectionManager.aggressiveRelease(ConnectionManager.java:429)     org.hibernate.jdbc.ConnectionManager.afterStatement(ConnectionManager.java:304)     org.hibernate.jdbc.AbstractBatcher.closePreparedStatement(AbstractBatcher.java:572)     org.hibernate.jdbc.AbstractBatcher.closeStatement(AbstractBatcher.java:291)     org.hibernate.id.insert.AbstractReturningDelegate.releaseStatement(AbstractReturningDelegate.java:82)     org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:60)     org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2176)     org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2656)     org.hibernate.action.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:71)     org.hibernate.engine.ActionQueue.execute(ActionQueue.java:279)     org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:321)     org.hibernate.event.def.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:204)     org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:130)     org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:210)     org.hibernate.event.def.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:56)     org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:195)     org.hibernate.event.def.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:50)     org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:93)     org.hibernate.impl.SessionImpl.fireSave(SessionImpl.java:563)     org.hibernate.impl.SessionImpl.save(SessionImpl.java:551)     org.hibernate.impl.SessionImpl.save(SessionImpl.java:547)     org.springframework.orm.hibernate3.HibernateTemplate$12.doInHibernate(HibernateTemplate.java:686)     org.springframework.orm.hibernate3.HibernateTemplate$12.doInHibernate(HibernateTemplate.java:1)     org.springframework.orm.hibernate3.HibernateTemplate.doExecute(HibernateTemplate.java:406)     org.springframework.orm.hibernate3.HibernateTemplate.executeWithNativeSession(HibernateTemplate.java:374)     org.springframework.orm.hibernate3.HibernateTemplate.save(HibernateTemplate.java:683)     se.hsr.daos.InfoTextDAOImpl.saveInfoText(InfoTextDAOImpl.java:26)     se.hsr.controllers.InfoTextController.saveInfoText(InfoTextController.java:31)     se.hsr.pagecontrollers.InfoTextPageController.submitForm(InfoTextPageController.java:35)     sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)     sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)     sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)     java.lang.reflect.Method.invoke(Method.java:616)     org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:176)     org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:426)     org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:414)     org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:790)     org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:719)     org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:644)     org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:560)     javax.servlet.http.HttpServlet.service(HttpServlet.java:637)     javax.servlet.http.HttpServlet.service(HttpServlet.java:717) 

Answer 1

It means DB SQL server is running out of connections. Server has a configuration parameter that specifies how maximum allowed connections.

This usually indicates that connections are not being closed. Are you requesting Connection objects from Hibernate in your code?

In short term, you can just increase maximum connections till this problem is fixed.