Question

我正在尝试完成this Hibernate教程，但有一些名称和文件夹结构更改。我不确定我哪里出错了。我一直得到空指针异常。

enter image description here

客户经理

package fpg2.controller;


import fpg2.model.Customer;
import fpg2.util.HibernateUtil;
import java.util.List;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class CustomerManager {

    private static SessionFactory sf; 
    public static void main(String[] args) {
       try{
         // sf = new Configuration().configure().buildSessionFactory();
            SessionFactory sf = HibernateUtil.getSessionFactory();

       }catch (Throwable ex) { 
          System.err.println("Failed to create sessionFactory object." + ex);
          throw new ExceptionInInitializerError(ex); 
       }
    }

    public Customer add(Customer customer) {
//  SessionFactory sf = HibernateUtil.getSessionFactory();
    Session session = sf.getCurrentSession();
    if(session==null){
        session =sf.openSession();
    }
//  Session session = sf.openSession();
        session.beginTransaction();
        session.save(customer);
        session.getTransaction().commit();
        return customer;
    }
    public Customer delete(Long id) {
//        Session session = HibernateUtil.getSessionFactory().getCurrentSession();
    Session session = sf.getCurrentSession();
    if(session==null){
        session =sf.openSession();
    }
        session.beginTransaction();
        Customer customer = (Customer) session.load(Customer.class, id);
        if(null != customer) {
            session.delete(customer);
        }
        session.getTransaction().commit();
        return customer;
    }

    public List<Customer> list() {
//    Session session = HibernateUtil.getSessionFactory().getCurrentSession();
    Session session = sf.getCurrentSession();   
        session.beginTransaction();
        List<Customer> customers = null;
        try {

            customers = (List<Customer>)session.createQuery("from Customer").list();

        } catch (HibernateException e) {
            e.printStackTrace();
            session.getTransaction().rollback();
        }
        session.getTransaction().commit();
        return customers;
    }
}

Hibernate Utility

package fpg2.util;

import org.hibernate.HibernateException;
import org.hibernate.SessionFactory;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
//import org.hibernate.service.ServiceRegistry;
import org.hibernate.cfg.AnnotationConfiguration;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;


public class HibernateUtil {


    private static SessionFactory sessionFactory;
    private static ServiceRegistry serviceRegistry;

    private static SessionFactory configureSessionFactory() throws HibernateException {
    Configuration config = new Configuration().configure();
        serviceRegistry = new StandardServiceRegistryBuilder().applySettings(config.getProperties()).build();      
        sessionFactory = config.buildSessionFactory(serviceRegistry);
        return sessionFactory;

    }

    public static SessionFactory getSessionFactory() {
        return configureSessionFactory();

    }

//   private static final SessionFactory sessionFactory = buildSessionFactory();
// 
//    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;
//    }

}

配置文件

<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
        "http://hibernate.org/dtd/hibernate-configuration.dtd">

<hibernate-configuration>
    <session-factory>
        <property name="connection.driver_class">
            com.mysql.jdbc.Driver
        </property>
        <property name="connection.url">
            jdbc:mysql://localhost:8889/test_hibernate
        </property>
        <property name="connection.username">user</property>
        <property name="connection.password">password</property>
        <property name="connection.pool_size">1</property>
        <property name="dialect">
            org.hibernate.dialect.MySQLDialect
        </property>
        <property name="current_session_context_class">thread</property>
        <property name="cache.provider_class">
            org.hibernate.cache.NoCacheProvider
        </property>
        <property name="show_sql">true</property>
        <property name="hbm2ddl.auto">update</property>
        <mapping class="fpg2.model.Customer" />

    </session-factory>
</hibernate-configuration>

错误

java.lang.NullPointerException
    at fpg2.controller.CustomerManager.list(CustomerManager.java:72)
    at fpg2.view.CustomerAction.add(CustomerAction.java:48)
    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:606)
    at com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:450)
    at com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:289)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:252)
    at org.apache.struts2.interceptor.DeprecationInterceptor.intercept(DeprecationInterceptor.java:41)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    at org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:256)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    at com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:167)
    at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    at com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:265)
    at org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68)
    at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    at com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:138)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:254)
    at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:254)
    at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    at com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:191)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    at org.apache.struts2.interceptor.MultiselectInterceptor.intercept(MultiselectInterceptor.java:73)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    at org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:91)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    at org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:252)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    at com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:100)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    at com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:141)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    at com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:145)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    at com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:171)
    at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    at com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:139)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    at org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:164)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    at com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:193)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    at com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:189)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    at org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:54)
    at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:562)
    at org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:77)
    at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:99)
    at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1624)
    at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:550)
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:143)
    at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:568)
    at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:221)
    at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1112)
    at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:479)
    at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:183)
    at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1046)
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141)
    at org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:199)
    at org.eclipse.jetty.server.handler.HandlerCollection.handle(HandlerCollection.java:109)
    at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:97)
    at org.eclipse.jetty.server.Server.handle(Server.java:462)
    at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:281)
    at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:232)
    at org.eclipse.jetty.io.AbstractConnection$1.run(AbstractConnection.java:505)
    at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:607)
    at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:536)
    at java.lang.Thread.run(Thread.java:724)

Answer 1

您的代码在

处抛出NullPointerException

Session session = sf.getCurrentSession();

因此，唯一可能的解释是私有静态变量sf为空。因此，我们将检查sf初始化为非空值的位置。并且......它从未在任何地方初始化。

hibernate sessionfactory教程nullpointerexception

1 个答案: