Spring通用Hibernate DAO

Question

I am writing a Generic Hibernate DAO class that all Hibernate DAO classes will inherit from. I am trying to use spring to inject the dependencies for the classes but I am getting an exception.

@Repository
public class HibernateDaoImpl <T>  implements Dao<T>{
    @Autowired
    private SessionFactory sessionFactory;
    @Autowired
    private Class<T> clazz;

     //setter & getter

    public HibernateDaoImpl (Class<T> clazz)
    {
      this.clazz = clazz;
    }
    public Session getCurrentSession ()
    {
        return sessionFactory.getCurrentSession();
    }

    public void save(T t) 
    {
        getCurrentSession().save(t);
    }

    public void update(T t) 
    {
        getCurrentSession().update(t);
    }


    @SuppressWarnings("unchecked")
    public T findById(Object object)
    {
        return (T) getCurrentSession().get(clazz, (Serializable)object);
    }

    @SuppressWarnings("unchecked")
    public List<T> findAll(int page, int maxResult) 
    {
        return getCurrentSession().createQuery(String.format("FROM %s", clazz.getSimpleName())).list();
    }

My derived class

public class SubscriberHibernateDao extends HibernateDaoImpl<Subscriber> implements SubscriberDao {

    public SubscriberHibernateDao ()
    {
        super(Subscriber.class);
    }
}

My spring-xml

<bean id="subscriber" class="com.example.model.Subscriber" autowire="byName">
    <property name="email" value="mdennis10"></property>
</bean>

<bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource">
    <property name="driverClassName" value="com.mysql.jdbc.Driver"/>
    <property name="url" value="jdbc:mysql://localhost/kyro"/>
    <property name="username" value="root"/>
</bean>

<bean id="sessionFactory" class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">
    <property name="dataSource" ref="dataSource"/>
    <property name="packagesToScan" value="com.kyrogaming.model"/>
    <property name="hibernateProperties">
        <props>
            <prop key="hibernate.dialect">org.hibernate.dialect.MySQLDialect</prop>
            <prop key="hibernate.cache.provider_class">org.hibernate.cache.internal.NoCacheProvider</prop>
            <prop key="hibernate.show_sql">true</prop>
        </props>
    </property>
</bean>

<bean id="subcriberDao" class="com.example.dao.SubscriberHibernateDao">
 <property name="clazz" value="com.example.model.Subscriber"></property>
</bean>

When I run this I get the following stack trace:

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'hibernateDaoImpl': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private java.lang.Class com.example.dao.HibernateDaoImpl.clazz; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [java.lang.Class] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:288)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1116)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:519)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:458)
at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:295)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:223)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:292)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:626)
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:932)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:479)
at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:139)
at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:83)
at com.kyrogaming.test.BeanTest.test(BeanTest.java:18)
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:606)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
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)

Caused by: org.springframework.beans.factory.BeanCreationException: Could not autowire field: private java.lang.Class com.example.dao.HibernateDaoImpl.clazz; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [java.lang.Class] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)} at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:514) at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:87) at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:285) ... 36 more Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [java.lang.Class] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)} at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoSuchBeanDefinitionException(DefaultListableBeanFactory.java:986) at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:856) at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:768) at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:486) ... 38 more

How can I fix this.

Answer 1

@Autowired 
private Class<T> clazz;

This line in your code will never work because spring does not know what to Autowire. You can only autowire by type or working class, type preferably.

You will need to wrap this Class in a wrapper object so you can do the Autowire by type then inject that type into the DAO.

Example

@Autowired
private Entity<T> entity;

Answer 2

You are already setting the field clazz via setter-injection (in your spring-xml ):

<property name="clazz" value="com.example.model.Subscriber"></property>

So there's no need for @Autowired on the field clazz . However, you need to add a setter for field clazz , otherwise Spring won't be able to perform Setter-Injection.