The project stopped working in Eclipse and in the log file it says

WARN JdbcServicesImpl: HHH000342: Could not obtain connection to query metadata : org.postgresql.Driver
DEBUG DepartmentFilter: /
WARN SqlExceptionHelper: SQL Error: 0, SQLState: null
ERROR SqlExceptionHelper: org.postgresql.Driver
ERROR ExceptionResolver: Exception caused by guest
org.springframework.orm.jpa.JpaSystemException: org.hibernate.exception.GenericJDBCException: Could not open connection; nested exception is javax.persistence.PersistenceException: org.hibernate.exception.GenericJDBCException: Could not open connection
 at org.springframework.orm.jpa.EntityManagerFactoryUtils.convertJpaAccessExceptionIfPossible(EntityManagerFactoryUtils.java:326)
 at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.translateExceptionIfPossible(AbstractEntityManagerFactoryBean.java:404)
 at org.springframework.dao.support.ChainedPersistenceExceptionTranslator.translateExceptionIfPossible(ChainedPersistenceExceptionTranslator.java:58)
 at org.springframework.dao.support.DataAccessUtils.translateIfNecessary(DataAccessUtils.java:213)
 at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:163)
 at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
 at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:202)
 at $Proxy48.getDepartments(Unknown Source)
 at csns.web.controller.IndexController.index(IndexController.java:43)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
 at java.lang.reflect.Method.invoke(Unknown Source)
 at org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:213)
 at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:126)
 at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:96)
 at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:617)
 at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:578)
 at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80)
 at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:923)
 at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:852)
 at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:882)
 at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:778)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
 at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330)
 at csns.web.filter.RegistrationFilter.doFilterInternal(RegistrationFilter.java:58)
 at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
 at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
 at csns.web.filter.DepartmentFilter.doFilterInternal(DepartmentFilter.java:63)
 at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
 at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
 at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:118)
 at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:84)
 at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
 at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:113)
 at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
 at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:103)
 at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
 at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:113)
 at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
 at org.springframework.security.web.authentication.rememberme.RememberMeAuthenticationFilter.doFilter(RememberMeAuthenticationFilter.java:139)
 at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
 at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:54)
 at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
 at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:45)
 at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
 at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:183)
 at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
 at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:105)
 at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
 at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:87)
 at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
 at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:192)
 at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:160)
 at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:346)
 at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:259)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
 at org.springframework.orm.jpa.support.OpenEntityManagerInViewFilter.doFilterInternal(OpenEntityManagerInViewFilter.java:147)
 at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
 at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
 at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
 at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
 at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
 at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
 at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:929)
 at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
 at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
 at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1002)
 at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:585)
 at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310)
 at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
 at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
 at java.lang.Thread.run(Unknown Source)
Caused by: javax.persistence.PersistenceException: org.hibernate.exception.GenericJDBCException: Could not open connection
 at org.hibernate.ejb.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1377)
 at org.hibernate.ejb.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1300)
 at org.hibernate.ejb.QueryImpl.getResultList(QueryImpl.java:266)
 at csns.model.academics.dao.jpa.DepartmentDaoImpl.getDepartments(DepartmentDaoImpl.java:70)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
 at java.lang.reflect.Method.invoke(Unknown Source)
 at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:309)
 at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:183)
 at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150)
 at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:155)
 ... 74 more
Caused by: org.hibernate.exception.GenericJDBCException: Could not open connection
 at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:54)
 at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:125)
 at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:110)
 at org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.obtainConnection(LogicalConnectionImpl.java:304)
 at org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.getConnection(LogicalConnectionImpl.java:169)
 at org.hibernate.engine.jdbc.internal.proxy.ConnectionProxyHandler.extractPhysicalConnection(ConnectionProxyHandler.java:82)
 at org.hibernate.engine.jdbc.internal.proxy.ConnectionProxyHandler.continueInvocation(ConnectionProxyHandler.java:138)
 at org.hibernate.engine.jdbc.internal.proxy.AbstractProxyHandler.invoke(AbstractProxyHandler.java:81)
 at $Proxy66.prepareStatement(Unknown Source)
 at org.hibernate.engine.jdbc.internal.StatementPreparerImpl$5.doPrepare(StatementPreparerImpl.java:147)
 at org.hibernate.engine.jdbc.internal.StatementPreparerImpl$StatementPreparationTemplate.prepareStatement(StatementPreparerImpl.java:166)
 at org.hibernate.engine.jdbc.internal.StatementPreparerImpl.prepareQueryStatement(StatementPreparerImpl.java:145)
 at org.hibernate.loader.Loader.prepareQueryStatement(Loader.java:1720)
 at org.hibernate.loader.Loader.executeQueryStatement(Loader.java:1697)
 at org.hibernate.loader.Loader.doQuery(Loader.java:832)
 at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:293)
 at org.hibernate.loader.Loader.doList(Loader.java:2382)
 at org.hibernate.loader.Loader.doList(Loader.java:2368)
 at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2198)
 at org.hibernate.loader.Loader.list(Loader.java:2193)
 at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:470)
 at org.hibernate.hql.internal.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:355)
 at org.hibernate.engine.query.spi.HQLQueryPlan.performList(HQLQueryPlan.java:195)
 at org.hibernate.internal.SessionImpl.list(SessionImpl.java:1248)
 at org.hibernate.internal.QueryImpl.list(QueryImpl.java:101)
 at org.hibernate.ejb.QueryImpl.getResultList(QueryImpl.java:257)
 ... 83 more
Caused by: java.sql.SQLException: org.postgresql.Driver
 at org.apache.tomcat.jdbc.pool.PooledConnection.connectUsingDriver(PooledConnection.java:254)
 at org.apache.tomcat.jdbc.pool.PooledConnection.connect(PooledConnection.java:182)
 at org.apache.tomcat.jdbc.pool.ConnectionPool.createConnection(ConnectionPool.java:699)
 at org.apache.tomcat.jdbc.pool.ConnectionPool.borrowConnection(ConnectionPool.java:631)
 at org.apache.tomcat.jdbc.pool.ConnectionPool.init(ConnectionPool.java:485)
 at org.apache.tomcat.jdbc.pool.ConnectionPool.<init>(ConnectionPool.java:143)
 at org.apache.tomcat.jdbc.pool.DataSourceProxy.pCreatePool(DataSourceProxy.java:116)
 at org.apache.tomcat.jdbc.pool.DataSourceProxy.createPool(DataSourceProxy.java:103)
 at org.apache.tomcat.jdbc.pool.DataSourceProxy.getConnection(DataSourceProxy.java:127)
 at org.hibernate.ejb.connection.InjectedDataSourceConnectionProvider.getConnection(InjectedDataSourceConnectionProvider.java:70)
 at org.hibernate.internal.AbstractSessionImpl$NonContextualJdbcConnectionAccess.obtainConnection(AbstractSessionImpl.java:281)
 at org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.obtainConnection(LogicalConnectionImpl.java:297)
 ... 105 more
Caused by: java.lang.ClassNotFoundException: org.postgresql.Driver
 at java.net.URLClassLoader$1.run(Unknown Source)
 at java.net.URLClassLoader$1.run(Unknown Source)
 at java.security.AccessController.doPrivileged(Native Method)
 at java.net.URLClassLoader.findClass(Unknown Source)
 at java.lang.ClassLoader.loadClass(Unknown Source)
 at java.lang.ClassLoader.loadClass(Unknown Source)
 at java.lang.Class.forName0(Native Method)
 at java.lang.Class.forName(Unknown Source)
 at org.apache.tomcat.jdbc.pool.PooledConnection.connectUsingDriver(PooledConnection.java:246)
 ... 116 more
DEBUG ExceptionResolver: Resolving exception from handler [public java.lang.String csns.web.controller.IndexController.index(org.springframework.ui.ModelMap)]: org.springframework.orm.jpa.JpaSystemException: org.hibernate.exception.GenericJDBCException: Could not open connection; nested exception is javax.persistence.PersistenceException: org.hibernate.exception.GenericJDBCException: Could not open connection
DEBUG ExceptionResolver: Resolving to default view 'exception/default' for exception of type [org.springframework.orm.jpa.JpaSystemException]
DEBUG ExceptionResolver: Exposing Exception as model attribute 'exception'

I tried looking up the errors, but the closest thing I could find was errors caused by missing drivers and I'm not sure how to fix this.

BelknapKristine wrote:

The project stopped working in Eclipse and in the log file it says

 ... 105 more
Caused by: java.lang.ClassNotFoundException: org.postgresql.Driver
 ...

I tried looking up the errors, but the closest thing I could find was errors caused by missing drivers and I'm not sure how to fix this.

So basically the postgresql jdbc library disappeared. If you changed pom.xml, revert it. You can also try cleaning the project:

• In the Servers view, remove csns2 from Tomcat, then right click on Tomcat and select "Clean...".
• In the menu Project -> Clean..., check csns2 and select "Clean selected projects".
• Try running the project again