Spring + Mybatis 组合报错

Spring + Mybatis 结合报错
rt。我在搭建一个struts2+spring+mybatis+mysql的web环境。在搭建好之后，可以使用mybatis访问数据库，检索出数据。但当我使用spring与mybatis结合后，就报错了。

错误发生在我打开session的时候
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public boolean checkUser(String userName, String password) {
SqlSession sqlSession = sqlSessionFactory.openSession();

try {
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
UserExample example = new UserExample();

example.clear();
example.or().andUsernameEqualTo(userName).andPasswordEqualTo(password);
List<User> lst = mapper.selectByExample(example);

return !lst.isEmpty();
} finally {
sqlSession.close();
}
}
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错误信息如下。
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org.apache.ibatis.exceptions.PersistenceException: 
### Error opening session.  Cause: java.lang.NullPointerException
### Cause: java.lang.NullPointerException
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spring的配置文件（applicationContext.xml）
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<?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:aop="http://www.springframework.org/schema/aop"
xmlns:tx="http://www.springframework.org/schema/tx" 
xmlns:jdbc="http://www.springframework.org/schema/jdbc"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="
     http://www.springframework.org/schema/context 
     http://www.springframework.org/schema/context/spring-context-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/jdbc 
     http://www.springframework.org/schema/jdbc/spring-jdbc-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/aop 
     http://www.springframework.org/schema/aop/spring-aop-3.0.xsd">

<!-- 配置要扫描的包 -->      
    <context:component-scan base-package="com.test" use-default-filters="false">
<context:include-filter type="annotation" expression="org.springframework.stereotype.Controller"/>
<context:include-filter type="annotation" expression="org.springframework.stereotype.Service"/>
<context:include-filter type="annotation" expression="org.springframework.stereotype.Repository"/>
</context:component-scan>

<!-- 定义数据源连接 -->
<bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource">
<property name="driverClassName" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://127.0.0.1:3306/test_for_ssi"/>