NullPointerexception获取会话
我得到以下例外。它由于线
Session ss=session.getCurrentSession();
java.lang.NullPointerException
at com.mkyong.common.dao.UserDao.saveUser(UserDao.java:25)
at com.mkyong.common.controller.JSONController.getShopInJSON(JSONController.java:31)
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:601)
at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:176)
at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:426)
at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:414)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:790)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:719)
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:310)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:722)我的dao班如下。
package com.mkyong.common.dao;
import org.hibernate.SessionFactory;
import org.hibernate.Session;
import com.mkyong.common.model.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Repository;
public class UserDao {
private SessionFactory session;
public void setSessionFactory(SessionFactory session){
if(session == null){
throw new IllegalStateException();
}
this.session=session;
}
public int saveUser(User user) {
Session ss=session.getCurrentSession();
System.out.println(user.getUserName());
System.out.println(user.getPassword());
//Session ss=session.getCurrentSession();
ss.save(user);
return 1;
}
}
我的配置文件如下：
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:tx="http://www.springframework.org/schema/tx"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd
http://www.springframework.org/schema/tx
http://www.springframework.org/schema/tx/spring-tx-3.0.xsd">
<context:property-placeholder location="classpath:jdbc.properties" />
<context:component-scan base-package="com.mkyong.common.controller" />
<context:annotation-config/>
<mvc:annotation-driven />
<bean id="dataSource"
class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName" value="${database.driver}" />
<property name="url" value="${database.url}" />
<property name="username" value="${database.user}" />
<property name="password" value="${database.password}" />
</bean>
<bean id="SessionFactory"
class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean">
<property name="dataSource" ref="dataSource" />
<property name="annotatedClasses">
<list>
<value>com.mkyong.common.model.User</value>
</list>
</property>
<property name="hibernateProperties">
<props>
<prop key="hibernate.dialect">${hibernate.dialect}</prop>
<prop key="hibernate.show_sql">${hibernate.show_sql}</prop>
</props>
</property>
</bean>
<bean id="hibernateTransactionManager" class="org.springframework.orm.hibernate3.HibernateTransactionManager">
<property name="SessionFactory" ref="SessionFactory" />
</bean>
</beans>
您的session为null 。您在null上使用getCurrentSession 。因此，您在此处收到NullpointeException
您的会话不会注入您的DAO。 确保你的配置是正确的。
您可以通过两种方式注入会话工厂（只选择一种）
1）Xml声明在这里你将用这种方式在你的xml配置文件中声明你的userDAO bean：
<bean id="userDAO" class="com.mkyong.common.dao.UserDAO">
<property name="session" ref="SessionFactory" />
</bean>
当我的bean的id以大写字母开头时，我有时会遇到问题，所以我将通过“sessionFactory”重命名“SessionFactory”。
2）带注释
在这里，Spring将扫描所有声明的包
<context:component-scan base-package="com.foo.bar" />
并在com.foo.bar包中查找使用“@Repository”，“@Service”或“@Component”注解的Classes。 所以，您的类UserDAO应该注明“@Repository”以便找到并且您的包必须在组件扫描中进行扫描。 现在Spring会检测到你的userDAO bean，但没有看到任何要注入的bean，所以你必须使用“@Autowired”来注释SessionFactory字段，你的类必须如下所示：
@Repository
public class UserDao {
@Autowired
private SessionFactory session;
public void setSessionFactory(SessionFactory session){
if(session == null){
throw new IllegalStateException();
}
this.session=session;
}
...
你的配置文件如下所示：
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd
http://www.springframework.org/schema/tx
http://www.springframework.org/schema/tx/spring-tx-3.0.xsd">
<context:property-placeholder location="classpath:jdbc.properties" />
<context:component-scan base-package="com.mkyong.common.controller" />
<context:component-scan base-package="com.mkyong.common.dao" />
<context:annotation-config/>
<mvc:annotation-driven />
...
</beans>