sessionFactory.getCurrentSession（）导致的java.lang.NullPointerException异常

我正在用Spring和Hibernate制作一个Java webapp，但当我执行它时，出现了以下错误：

SEVERE: El Servlet.service() para el servlet [springapp] en el contexto con ruta [/appCracks] lanzó la excepción [Request processing failed; nested exception is java.lang.NullPointerException] con causa raíz
java.lang.NullPointerException
    at com.companyname.springapp.repository.UsuarioDaoImp.getTodosUsuariosList(UsuarioDaoImp.java:26)
    at com.companyname.springapp.service.SimpleAnonimoManager.identificarse(SimpleAnonimoManager.java:21)
    at com.companyname.springapp.web.IdentificarseFormController.onSubmit(IdentificarseFormController.java:46)
    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.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:174)
    at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:421)
    at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:409)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:771)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:716)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:644)
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:560)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:647)
    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:472)
    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:936)
    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:1004)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)

当我尝试获取会话时，错误在此行中：

    return this.sessionFactory.getCurrentSession().createQuery("from Usuario u order by u.id").list();

我在这里复制了该错误所涉及的类：

UsuarioDaoImp.java

package com.companyname.springapp.repository;

import java.util.List;

import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

import org.hibernate.SessionFactory;
import org.springframework.stereotype.Repository;
import org.springframework.transaction.annotation.Transactional;

import com.companyname.springapp.domain.Usuario;

@Repository(value = "usuarioDao")
public class UsuarioDaoImp implements UsuarioDao {

    private SessionFactory sessionFactory;

    public void setSessionFactory(SessionFactory sessionFactory) {
        this.sessionFactory = sessionFactory;
    }

    @Override
    @SuppressWarnings("unchecked")
    public List<Usuario> getTodosUsuariosList() {
        return this.sessionFactory.getCurrentSession()
                .createQuery("from Usuario u order by u.id")
                .list();
    }

    @Override
    public String encriptarContrasena(String contrasena) {
        return (String) this.sessionFactory.getCurrentSession()
                .createQuery("select SHA1(:c)")
                .setParameter ( "c", contrasena)
                .uniqueResult();
    }

    @Override
    public String getTipoUsuario(String usuario) {
        return (String) this.sessionFactory.getCurrentSession()
                .createQuery("select u.tipoUsuario from Usuario u where u.usuario = '" +
                usuario + "'")
                .uniqueResult();
    }


}

配置文件如下所示： app-config.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:mvc="http://www.springframework.org/schema/mvc"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd">

    <bean id="messageSource" class="org.springframework.context.support.ResourceBundleMessageSource">
        <property name="basename" value="messages"/>
    </bean>

    <!-- Scans the classpath of this application for @Components to deploy as beans -->
    <context:component-scan base-package="com.companyname.springapp.web" />

    <!-- Configures the @Controller programming model -->
    <mvc:annotation-driven/>

    <bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="viewClass" value="org.springframework.web.servlet.view.JstlView"></property>
        <property name="prefix" value="/jsp/"></property>
        <property name="suffix" value=".jsp"></property>        
    </bean>

</beans>

applicationContext.xml：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:p="http://www.springframework.org/schema/p"
    xmlns:tx="http://www.springframework.org/schema/tx"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
        http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.0.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd">


    <!-- holding properties for database connectivity /-->
    <context:property-placeholder location="classpath:jdbc.properties"/>

    <!-- enabling annotation driven configuration /-->
    <context:annotation-config/>

    <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
        <property name="driverClassName" value="${jdbc.driverClassName}"/>
        <property name="url" value="${jdbc.url}"/>
        <property name="username" value="${jdbc.username}"/>
        <property name="password" value="${jdbc.password}"/>
    </bean>

    <bean id="sessionFactory" class="org.springframework.orm.hibernate3.LocalSessionFactoryBean">
        <property name="dataSource" ref="dataSource"/>
        <property name="configLocation">
            <value>classpath:hibernate.cfg.xml</value>
        </property>
        <property name="configurationClass">
            <value>org.hibernate.cfg.AnnotationConfiguration</value>
        </property>
    </bean>

    <bean id="transactionManager" class="org.springframework.orm.hibernate3.HibernateTransactionManager">
        <property name="sessionFactory" ref="sessionFactory"/>
    </bean>

    <tx:annotation-driven transaction-manager="transactionManager"/>

    <!-- Scans the classpath of this application for @Components to deploy as beans -->
    <context:component-scan base-package="com.companyname.springapp.repository" />
    <context:component-scan base-package="com.companyname.springapp.service" />

</beans>

类路径：hibernate.cfg.xml
org.hibernate.cfg.AnnotationConfiguration

hibernate.cfg.xml：

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

<hibernate-configuration>
    <session-factory>
        <mapping class="com.companyname.springapp.repository.UsuarioDaoImp" />
    </session-factory>

</hibernate-configuration>

我还尝试映射数据库中的实体类Usuario.java，但我有同样的问题

问题是当我试图获得会话时。我被告知使用OpenSessionInViewFilter，并使用SessionFactoryUtil而不是SessionFactory，但我不知道如何使用它

---

有人能帮我吗？谢谢

您的sessionFactory尚未在UsuarioDaoImp中设置。尝试使用构造函数自动布线，而不是设置SessionFactory，例如

@Repository(value = "usuarioDao")
public class UsuarioDaoImp implements UsuarioDao {

    private final SessionFactory sessionFactory;

    @Autowired
    public UsuarioDaoImp(SessionFactory sessionFactory) {
        this.sessionFactory = sessionFactory;
    }

    ...

}

---

好啊谢谢它现在运行。但我有一个疑问。以前，我用EntityManager而不是SessionFactory制作了这个应用程序，我有很多内存问题，它每天都会因为java.lang.OutOfMemoryError:java堆空间而关闭。我询问并告诉我，问题是由于EntityManager造成的，我应该使用SessionFactory，但我不知道我是否使用得很好。用我现在做的这个，你知道我会不会有那个问题吗？这是一个很难说的问题！如果您坚持使用Hibernate，那么可以使用SessionFactory。

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

<hibernate-configuration>
    <session-factory>
        <mapping class="com.companyname.springapp.repository.UsuarioDaoImp" />
    </session-factory>

</hibernate-configuration>

@Repository(value = "usuarioDao")
public class UsuarioDaoImp implements UsuarioDao {

    private final SessionFactory sessionFactory;

    @Autowired
    public UsuarioDaoImp(SessionFactory sessionFactory) {
        this.sessionFactory = sessionFactory;
    }

    ...

}