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spring+hibernate 调用 DAO 报java.lang.NullPointerException异常,先谢谢了

2014-01-26 
applicationcontex.xml配置如下:?xml version1.0 encodingUTF-8?!DOCTYPE beans PUBLIC -//SPRIN

applicationcontex.xml配置如下:
  <?xml version="1.0" encoding="UTF-8"?>
  <!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">
 
  <beans>
 
  <bean name="/login" class="com.test.struts.action.LoginAction" singleton="false"></bean>
 
  <bean id="DataSource" class="org.apache.commons.dbcp.BasicDataSource">
  <property name="driverClassName">
  <value>com.mysql.jdbc.Driver</value>
  </property>
  <property name="url">
  <value>jdbc:mysql://localhost:3306/SAMPLEDB</value>
  </property>
  <property name="username">
  <value>root</value>
  </property>
  <property name="password">
  <value>123</value>
  </property>
  </bean>
  <bean id="SessionFactory" class="org.springframework.orm.hibernate3.LocalSessionFactoryBean">
  <property name="dataSource">
  <ref bean="DataSource"></ref>
  </property>
  <property name="hibernateProperties">
  <props>
  <prop key="hibernate.dialect">org.hibernate.dialect.MySQLDialect</prop>
  </props>
  </property>
  <property name="mappingResources">
  <list>
  <value>com/test/Hibernate/User.hbm.xml</value>
  </list>
  </property>
  </bean>
  <bean id="UserDAO" class="com.test.Hibernate.UserDAO">
  <property name="sessionFactory">
  <ref bean="SessionFactory" />
  </property>
  </bean>
  </beans>
 
 
  DAO.java如下:
  package com.test.Hibernate;
 
  import java.util.List;
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.hibernate.LockMode;
  import org.hibernate.Session;
  import org.hibernate.criterion.Example;
  import org.springframework.context.ApplicationContext;
  import org.springframework.orm.hibernate3.support.HibernateDaoSupport;
 
  /**
  * Data access object (DAO) for domain model class User.
  * @see com.test.Hibernate.User
  * @author MyEclipse - Hibernate Tools
  */
  public class UserDAO extends HibernateDaoSupport {
 
  private static final Log log = LogFactory.getLog(UserDAO.class);
 
  protected void initDao() {
  //do nothing
  }
 
  private static String hql = "from User u where u.username=? ";
 
  public boolean isValidUser(String username, String password) {
 
          

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