I started to learn the Hibernate library and encountered this problem when running on Tomcate:

exception javax.servlet.ServletException: Servlet execution threw an exception org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) root cause java.lang.ExceptionInInitializerError logic.HibernateUtil.<clinit>(HibernateUtil.java:16) logic.DefaultTableDAO.getItems(DefaultTableDAO.java:38) servlet.TestServlet.doGet(TestServlet.java:36) javax.servlet.http.HttpServlet.service(HttpServlet.java:622) javax.servlet.http.HttpServlet.service(HttpServlet.java:729) org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) root cause org.hibernate.service.spi.ServiceException: Unable to create requested service [org.hibernate.engine.jdbc.env.spi.JdbcEnvironment] org.hibernate.service.internal.AbstractServiceRegistryImpl.createService(AbstractServiceRegistryImpl.java:267) org.hibernate.service.internal.AbstractServiceRegistryImpl.initializeService(AbstractServiceRegistryImpl.java:231) org.hibernate.service.internal.AbstractServiceRegistryImpl.getService(AbstractServiceRegistryImpl.java:210) org.hibernate.engine.jdbc.internal.JdbcServicesImpl.configure(JdbcServicesImpl.java:51) org.hibernate.boot.registry.internal.StandardServiceRegistryImpl.configureService(StandardServiceRegistryImpl.java:94) org.hibernate.service.internal.AbstractServiceRegistryImpl.initializeService(AbstractServiceRegistryImpl.java:240) org.hibernate.service.internal.AbstractServiceRegistryImpl.getService(AbstractServiceRegistryImpl.java:210) org.hibernate.boot.model.process.spi.MetadataBuildingProcess.handleTypes(MetadataBuildingProcess.java:352) org.hibernate.boot.model.process.spi.MetadataBuildingProcess.complete(MetadataBuildingProcess.java:111) org.hibernate.boot.model.process.spi.MetadataBuildingProcess.build(MetadataBuildingProcess.java:83) org.hibernate.boot.internal.MetadataBuilderImpl.build(MetadataBuilderImpl.java:418) org.hibernate.boot.internal.MetadataBuilderImpl.build(MetadataBuilderImpl.java:87) org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:691) org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:726) logic.HibernateUtil.<clinit>(HibernateUtil.java:14) logic.DefaultTableDAO.getItems(DefaultTableDAO.java:38) servlet.TestServlet.doGet(TestServlet.java:36) javax.servlet.http.HttpServlet.service(HttpServlet.java:622) javax.servlet.http.HttpServlet.service(HttpServlet.java:729) org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) root cause org.hibernate.HibernateException: Access to DialectResolutionInfo cannot be null when 'hibernate.dialect' not set org.hibernate.engine.jdbc.dialect.internal.DialectFactoryImpl.determineDialect(DialectFactoryImpl.java:100) org.hibernate.engine.jdbc.dialect.internal.DialectFactoryImpl.buildDialect(DialectFactoryImpl.java:54) org.hibernate.engine.jdbc.env.internal.JdbcEnvironmentInitiator.initiateService(JdbcEnvironmentInitiator.java:137) org.hibernate.engine.jdbc.env.internal.JdbcEnvironmentInitiator.initiateService(JdbcEnvironmentInitiator.java:35) org.hibernate.boot.registry.internal.StandardServiceRegistryImpl.initiateService(StandardServiceRegistryImpl.java:88) org.hibernate.service.internal.AbstractServiceRegistryImpl.createService(AbstractServiceRegistryImpl.java:257) org.hibernate.service.internal.AbstractServiceRegistryImpl.initializeService(AbstractServiceRegistryImpl.java:231) org.hibernate.service.internal.AbstractServiceRegistryImpl.getService(AbstractServiceRegistryImpl.java:210) org.hibernate.engine.jdbc.internal.JdbcServicesImpl.configure(JdbcServicesImpl.java:51) org.hibernate.boot.registry.internal.StandardServiceRegistryImpl.configureService(StandardServiceRegistryImpl.java:94) org.hibernate.service.internal.AbstractServiceRegistryImpl.initializeService(AbstractServiceRegistryImpl.java:240) org.hibernate.service.internal.AbstractServiceRegistryImpl.getService(AbstractServiceRegistryImpl.java:210) org.hibernate.boot.model.process.spi.MetadataBuildingProcess.handleTypes(MetadataBuildingProcess.java:352) org.hibernate.boot.model.process.spi.MetadataBuildingProcess.complete(MetadataBuildingProcess.java:111) org.hibernate.boot.model.process.spi.MetadataBuildingProcess.build(MetadataBuildingProcess.java:83) org.hibernate.boot.internal.MetadataBuilderImpl.build(MetadataBuilderImpl.java:418) org.hibernate.boot.internal.MetadataBuilderImpl.build(MetadataBuilderImpl.java:87) org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:691) org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:726) logic.HibernateUtil.<clinit>(HibernateUtil.java:14) logic.DefaultTableDAO.getItems(DefaultTableDAO.java:38) servlet.TestServlet.doGet(TestServlet.java:36) javax.servlet.http.HttpServlet.service(HttpServlet.java:622) javax.servlet.http.HttpServlet.service(HttpServlet.java:729) org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

I am using Tomcate 8.5.6, Java 8, Hibernate and postgresql 9.5.2. JDBC Driver 9.4-1201

Hibernate configuration

hibernate.cfg.xml

  <?xml version="1.0" encoding="UTF-8"?> <hibernate-configuration> <session-factory> <property name="hibernate.connection.url">jdbc:postgresql://localhost:5432/postgres</property> <property name="hibernate.connection.driver_class">org.postgresql.Driver</property> <property name="hibernate.connection.username">postgres</property> <property name="hibernate.connection.password">java1235</property> <property name="hibernate.connection.pool_size">1</property> <property name="hibernate.dialect">org.hibernate.dialect.PostgreSQLDialect</property> <property name="hibernate.cache.provider_class">org.hibernate.cache.internal.NoCachingRegionFactory</property> <property name="hibernate.show_sql">true</property> </session-factory> </hibernate-configuration>

HibernateUtil.java

 public class HibernateUtil { private static SessionFactory sessionFactory; static { try { sessionFactory = new Configuration().buildSessionFactory(); } catch (Throwable e){ throw new ExceptionInInitializerError(e); } } private HibernateUtil(){} public static SessionFactory getSessionFactory() { return sessionFactory; } }

The class in which I refer to the database

 package servlet; import logic.DefaultTable; import logic.DefaultTableDAO; import logic.Factory; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; import java.sql.SQLException; import java.util.ArrayList; import java.util.List; public class TestServlet extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { req.setCharacterEncoding("UTF-8"); List<Integer> list = new ArrayList<>(); list.add(1); list.add(1); list.add(1); list.add(1); list.add(1); Factory factory = Factory.getInstance(); DefaultTableDAO table = factory.getItemDao(); List<DefaultTable> items = null; try { items = table.getItems(); } catch (SQLException e) { e.printStackTrace(); } req.setAttribute("listItem", list); req.setAttribute("str", items.get(0).getPartName()); req.getRequestDispatcher("/WEB-INF/my_page.jsp").forward(req, resp); } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { resp.getWriter().write("NOOOOOOOOOOOOOOOOOO"); } }

web.xml

 <?xml version="1.0" encoding="UTF-8"?> <web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" version="3.1"> <servlet> <servlet-name>test</servlet-name> <servlet-class>servlet.TestServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>test</servlet-name> <url-pattern>/test/</url-pattern> </servlet-mapping> </web-app>

Logs from when accessing Tomcate servlet

 05-Nov-2016 15:44:39.412 INFO [main] org.apache.catalina.startup.Catalina.start Server startup in 846 ms 05-Nov-2016 15:44:46.519 INFO [http-nio-80-exec-1] org.hibernate.Version.logVersion HHH000412: Hibernate Core {5.2.4.Final} 05-Nov-2016 15:44:46.522 INFO [http-nio-80-exec-1] org.hibernate.cfg.Environment.<clinit> HHH000206: hibernate.properties not found 05-Nov-2016 15:44:46.524 INFO [http-nio-80-exec-1] org.hibernate.cfg.Environment.buildBytecodeProvider HHH000021: Bytecode provider name : javassist 05-Nov-2016 15:44:46.567 INFO [http-nio-80-exec-1] org.hibernate.annotations.common.reflection.java.JavaReflectionManager.<clinit> HCANN000001: Hibernate Commons Annotations {5.0.1.Final} 05-Nov-2016 15:44:46.730 WARN [http-nio-80-exec-1] org.hibernate.engine.jdbc.connections.internal.ConnectionProviderInitiator.initiateService HHH000181: No appropriate connection provider encountered, assuming application will be supplying connections 05-Nov-2016 15:44:46.733 WARN [http-nio-80-exec-1] org.hibernate.engine.jdbc.env.internal.JdbcEnvironmentInitiator.initiateService HHH000342: Could not obtain connection to query metadata : The application must supply JDBC connections org.hibernate.service.spi.ServiceException: Unable to create requested service [org.hibernate.engine.jdbc.env.spi.JdbcEnvironment] 05-Nov-2016 15:46:49.454 INFO [ContainerBackgroundProcessor[StandardEngine[Catalina]]] org.apache.catalina.core.StandardContext.reload Reloading Context with name [] has started 05-Nov-2016 15:46:49.986 INFO [ContainerBackgroundProcessor[StandardEngine[Catalina]]] org.apache.catalina.core.StandardContext.reload Reloading Context with name [] is completed org.hibernate.service.spi.ServiceException: Unable to create requested service [org.hibernate.engine.jdbc.env.spi.JdbcEnvironment]

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