Servlet和Hibernate -不会打开会话

Question

我有一个DAO类，它通过Hibernate与数据库连接：

public class ChartDAO {

public static ChartData getChartData(){
    Session session = null;
    List data;
    try {
        try {
            session = HibUtil.getSessionFactory().openSession();
            Transaction tx = session.beginTransaction();
            data = session.createQuery("FROM ChartData").list();
            tx.commit();
        } catch (Exception e) {
            e.printStackTrace();
            data = new ArrayList();
            data.add(new ChartData());
        }
    } finally {
        session.disconnect();
        session.close();
        try {
            HibUtil.close();
        } catch (Exception e){
            e.printStackTrace();
        }
    }
    ChartData chartData = (ChartData) data.get(0);
    return chartData;
}

public static void main(String[] args) throws Exception{
    ChartData cd = getChartData();
} 
}

当我运行调用getChartData()的main方法时，一切都运行正常(在调试器中签入-打开会话并检索数据)。

但是，当我试图从servlet调用相同的方法时，数据并没有被检索到。我检查了调试器-当尝试打开hibernate会话时，它“冻结”了一段时间，然后立即跳到“finally”块。

我做错了什么？

谢谢。

编辑:下面是我的HibUtil：

public class HibUtil {

private static ServiceRegistry serviceRegistry;
private static final SessionFactory sessionFactory;

static {
    try {
        Configuration configuration = new Configuration();
        configuration.configure();
        serviceRegistry = new StandardServiceRegistryBuilder().applySettings(configuration.getProperties()).build();
        sessionFactory = configuration.buildSessionFactory(serviceRegistry);
    } catch (Throwable ex) { 
        System.err.println("Initial SessionFactory creation failed." + ex);
        throw new ExceptionInInitializerError(ex);
    }
}

public static SessionFactory getSessionFactory() {
    return sessionFactory;
}

public static void close() throws Exception{
    if(serviceRegistry!= null) {
        StandardServiceRegistryBuilder.destroy(serviceRegistry);
    }
}
}

更新:这是我尝试从servlet调用方法时的Apache Tomcat日志：

mar 25, 2014 6:42:41 PM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet [DataProvider] in context with path [/SHJS] threw exception
java.lang.NullPointerException
    at org.mb.DataProvider.processRequest(DataProvider.java:53)
    at org.mb.DataProvider.doGet(DataProvider.java:83)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
    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:502)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1023)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
    at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:1852)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
    at java.lang.Thread.run(Thread.java:722)

Answer 1

使用会话创建连接

 Connection connection     = session.connection();

然后使用connection.as创建您的查询，因为您没有创建连接，所以它可能无法工作。您也可以像这样使用Annotation Configuration

private static SessionFactory buildSessionFactory() {
    try {
        // Create the SessionFactory from hibernate.cfg.xml
        return new AnnotationConfiguration().configure()
                .buildSessionFactory();
    } catch (Throwable ex) {
        System.err.println("Initial SessionFactory creation failed." + ex);
        throw new ExceptionInInitializerError(ex);
    }
}
public static SessionFactory getSessionFactory() {
    return sessionFactory;
}

把这个叫作

Session session  = HibernateUtil.getSessionFactory().openSession();

为了进行session.then事务，然后进行连接，因此on.this对我来说工作得很好，你可以尝试一下。

Answer 2

试试这个：

new Configuration().configure().buildSessionFactory();