MySQLNonTransientConnectionException: Too many connections

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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)