我使用JPA为我的DAO类编写测试,使用Hibernate作为JPA提供程序,以及Spring 3.2.我无法正确注入实体管理器,尝试访问它时会出现NullPointerException.我的GenericDAO实现如下所示：

@Repository
public class GenericDAOImpl implements GenericDAO {

    @PersistenceContext(unitName="unitname")
    private EntityManager entityManager;

    public EntityManager getEntityManager() {
        return entityManager;
    }


    public void setEntityManager(EntityManager entityManager) {
        this.entityManager = entityManager;
    }

    // NullPointerException when calling this,entityManager is null
    public Query createNamedQuery(String name) {
        return entityManager.createNamedQuery(name);
    }        

    // many other methods....
}
@H_301_8@
测试类看起来像这样：

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = { "/com/main/resources/root-context.xml","/com/main/resources/servlet-context.xml"})
public class TestModel {

    @Before
    public void setUp() throws Exception{
        ...
    }

    @Test
    public void test(){
        ...
    }
}
@H_301_8@
我的root-context.xml如下：

MysqL.jdbc.Driver" />
        factorybean">
        sql" value="true" />
                MysqL5Dialect" />
            @H_301_8@
我已经尝试了几种方法但没有成功,甚至按照其他SO问题的建议添加了PersistenceAnnotationBeanPostProcessor.所有其他的东西似乎工作正常：Hibernate创建数据库表,加载上下文等.我做错了什么？
编辑：堆栈跟踪如下：

java.lang.NullPointerException
    at com.main.model.dao.JPAImpl.GenericDAOImpl.createNamedQuery(GenericDAOImpl.java:119)
    at com.main.model.bo.DescriptorBO.persist(DescriptorBO.java:52)
    at com.main.webmodule.JSONSerializer.deserialize(JSONSerializer.java:149)
    at com.main.tests.TestModel.test(TestModel.java:86)
    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.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:45)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:42)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
    at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:74)
    at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:83)
    at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:72)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:231)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:88)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)
    at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
    at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:71)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:300)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:174)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
@H_301_8@
这是persistence.xml：

Meta-INF/jpql/NamedQueries.xmlMysqL.jdbc.Driver"/>
            MysqL://127.0.0.1:3306/testweb"/>
            MysqL5Dialect"/>

        @H_301_8@