当在Spring / Hibernate项目中需要访问数据库时，exceptionjava.lang.NullPointerException
我正在尝试在我的Spring应用程序中使用Hibernate进行Db访问。 在依赖关系出现问题（现已解决）后，我可以正常运行我的项目，并且它的第一页向我开放（这是一个登录页面）。 但是，当我将表单提交给服务器（此请求由弹簧控制器处理）时，我收到以下错误消息：
org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.NullPointerException org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:948) org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:838) javax.servlet.http.HttpServlet.service(HttpServlet.java:647) org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:812) javax.servlet.http.HttpServlet.service(HttpServlet.java:728) root cause java.lang.NullPointerException org.ligadesportiva.resources.HibernateConfig.restDataSource(HibernateConfig.java:38) org.ligadesportiva.resources.HibernateConfig.sessionFactory(HibernateConfig.java:28) org.ligadesportiva.data.UsuarioHome.(UsuarioHome.java:31) org.ligadesportiva.controller.controller.login(controller.java:36) 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:606) org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:176) org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:440) org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:428) org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:925) org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:856) org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:936) org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:838) javax.servlet.http.HttpServlet.service(HttpServlet.java:647) org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:812) javax.servlet.http.HttpServlet.service(HttpServlet.java:728) 这是处理请求的控制器的方法：
@RequestMapping(value="/login", method=RequestMethod.POST) public ModelAndView login(@RequestParam("username") String username, @RequestParam("password") String password) throws NoSuchAlgorithmException { MessageDigest md = MessageDigest.getInstance("MD5"); md.update(password.getBytes()); byte[] digest = md.digest(); Usuario temp = new Usuario(username, convertByteToHex(digest)); UsuarioHome tempHome = new UsuarioHome(); List lista = tempHome.findByExample(temp); if(lista.size() == 0) { ModelAndView mav = new ModelAndView(); mav.setViewName("usuario_login"); mav.addObject("message", "Não foi possivel efetuar o login"); return mav; } else { this.sessao = new Sessao(); ModelAndView mav = new ModelAndView(); mav.setViewName("usuario_start"); mav.addObject("usuario", temp); return mav; } }
这是我的HibernateConfig类：
package org.ligadesportiva.resources; import java.util.Properties; import javax.sql.DataSource; import org.apache.tomcat.dbcp.dbcp.BasicDataSource; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.ComponentScan; import org.springframework.context.annotation.Configuration; import org.springframework.context.annotation.PropertySource; import org.springframework.core.env.Environment; import org.springframework.dao.annotation.PersistenceExceptionTranslationPostProcessor; import org.springframework.orm.hibernate3.HibernateTransactionManager; import org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean; import org.springframework.transaction.annotation.EnableTransactionManagement; @Configuration @EnableTransactionManagement @PropertySource({ "classpath:database.properties" }) @ComponentScan({ "org.ligadesportiva.data" }) public class HibernateConfig { @Autowired private Environment env; @Bean public AnnotationSessionFactoryBean sessionFactory() { AnnotationSessionFactoryBean sessionFactory = new AnnotationSessionFactoryBean(); sessionFactory.setDataSource(restDataSource()); sessionFactory.setPackagesToScan(new String[] { "org.ligadesportiva.core" }); sessionFactory.setHibernateProperties(hibernateProperties()); return sessionFactory; } @Bean public DataSource restDataSource() { BasicDataSource dataSource = new BasicDataSource(); dataSource.setDriverClassName(env.getProperty("jdbc.driverClassName")); dataSource.setUrl(env.getProperty("jdbc.url")); dataSource.setUsername(env.getProperty("jdbc.user")); dataSource.setPassword(env.getProperty("jdbc.pass")); return dataSource; } @Bean public HibernateTransactionManager transactionManager() { HibernateTransactionManager txManager = new HibernateTransactionManager(); txManager.setSessionFactory(sessionFactory().getObject()); return txManager; } @SuppressWarnings("serial") Properties hibernateProperties() { return new Properties() { { setProperty("hibernate.hbm2ddl.auto", env.getProperty("hibernate.hbm2ddl.auto")); setProperty("hibernate.show_sql", env.getProperty("hibernate.show_sql")); setProperty("hibernate.dialect", env.getProperty("hibernate.dialect")); } }; } }
这是我的class级DAO（UsuarioHome.java）：
package org.ligadesportiva.data; // Generated 15/03/2014 09:34:19 by Hibernate Tools 3.4.0.CR1 import java.util.List; import javax.naming.InitialContext; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.hibernate.LockMode; import org.hibernate.SessionFactory; import org.hibernate.criterion.Example; import org.ligadesportiva.core.Usuario; /** * Home object for domain model class Usuario. * @see org.ligadesportiva.core.Usuario * @author Hibernate Tools */ public class UsuarioHome { private static final Log log = LogFactory.getLog(UsuarioHome.class); private HibernateConfig hibernateConfig = new HibernateConfig(); @Autowired private final SessionFactory sessionFactory = (SessionFactory) hibernateConfig.sessionFactory(); public void persist(Usuario transientInstance) { log.debug("persisting Usuario instance"); try { sessionFactory.getCurrentSession().persist(transientInstance); log.debug("persist successful"); } catch (RuntimeException re) { log.error("persist failed", re); throw re; } } public void attachDirty(Usuario instance) { log.debug("attaching dirty Usuario instance"); try { sessionFactory.getCurrentSession().saveOrUpdate(instance); log.debug("attach successful"); } catch (RuntimeException re) { log.error("attach failed", re); throw re; } } public void attachClean(Usuario instance) { log.debug("attaching clean Usuario instance"); try { sessionFactory.getCurrentSession().lock(instance, LockMode.NONE); log.debug("attach successful"); } catch (RuntimeException re) { log.error("attach failed", re); throw re; } } public void delete(Usuario persistentInstance) { log.debug("deleting Usuario instance"); try { sessionFactory.getCurrentSession().delete(persistentInstance); log.debug("delete successful"); } catch (RuntimeException re) { log.error("delete failed", re); throw re; } } public Usuario merge(Usuario detachedInstance) { log.debug("merging Usuario instance"); try { Usuario result = (Usuario) sessionFactory.getCurrentSession() .merge(detachedInstance); log.debug("merge successful"); return result; } catch (RuntimeException re) { log.error("merge failed", re); throw re; } } public Usuario findById(int id) { log.debug("getting Usuario instance with id: " + id); try { Usuario instance = (Usuario) sessionFactory.getCurrentSession() .get("org.ligadesportiva.data.Usuario", id); if (instance == null) { log.debug("get successful, no instance found"); } else { log.debug("get successful, instance found"); } return instance; } catch (RuntimeException re) { log.error("get failed", re); throw re; } } public List findByExample(Usuario instance) { log.debug("finding Usuario instance by example"); try { List results = sessionFactory.getCurrentSession() .createCriteria("org.ligadesportiva.data.Usuario") .add(Example.create(instance)).list(); log.debug("find by example successful, result size: " + results.size()); return results; } catch (RuntimeException re) { log.error("find by example failed", re); throw re; } } }
这是我的* -servlet.xml文件，我按照这里的说明声明了HibernateConfig： http ： //docs.spring.io/spring/docs/3.1.x/javadoc-api/org/springframework/context/ annotation / Configuration.html 。
有人可以看看这段代码有什么问题吗？
Spring IoC容器的基本规则是让Spring管理大多数（如果不是全部）依赖项和对象。
您的HibernateConfig类使用@Configuration注释。 这表明它应该由Spring管理 ，您在上下文文件中正确地执行了此操作
但是，你没有在任何地方使用它。 你也没有宣布UsuarioHome bean。 相反，您自己创建这些对象
UsuarioHome tempHome = new UsuarioHome(); // and private HibernateConfig hibernateConfig = new HibernateConfig();
您如何期望Spring处理它们？
浏览Spring IoC容器的文档，了解如何通过上下文配置管理这些依赖项。