错误在DAO类中使用泛型

当

我尽量集中在一个通用类使用我的DAO类常用的方法，如下所示：错误在DAO类中使用泛型

public class Dao<E> { 

    private final E entity; 

    @Autowired 
    SessionFactory sessionFactory; 

    protected Session getCurrentSession(){ 
     return sessionFactory.getCurrentSession(); 
    } 

    public Dao(E entity) { 
     this.entity = entity; 
    } 

    public E getEntity() { 
     return this.entity; 
    } 

    @Transactional 
    public boolean persist(E transientInstance) { 
     try { 
      sessionFactory.getCurrentSession().persist(transientInstance); 
      return true; 
     } catch (RuntimeException re) { 
      return false; 
     } 
    } 

    @Transactional 
    public boolean remove(E transientInstance) { 
     try { 
      sessionFactory.getCurrentSession().delete(transientInstance); 
      return true; 
     } catch (RuntimeException re) { 
      return false; 
     } 
    } 

    @SuppressWarnings("unchecked") 
    @Transactional 
    public E merge(E detachedInstance) { 
     try { 
      E result = (E) sessionFactory.getCurrentSession().merge(detachedInstance); 
      return result; 
     } catch (RuntimeException re) { 
      return null; 
     } 
    } 

    @SuppressWarnings("unchecked") 
    @Transactional 
    public E findById(int id) { 
     try { 
      E instance = (E) sessionFactory.getCurrentSession().get(entity.getClass(), id); 
      return instance; 
     } catch (RuntimeException re) { 
      return null; 
     } 
    } 

    @SuppressWarnings("unchecked") 
    @Transactional 
    public E findByUsername(String username) { 
     try { 
      E instance = (E) sessionFactory.getCurrentSession().createCriteria(entity.getClass(), username).add(Restrictions.like("login", username)).list().get(0); 
      return instance; 
     } catch (RuntimeException re) { 
      return null; 
     } 
    } 

    @SuppressWarnings("unchecked") 
    @Transactional 
    public List<E> findAll() { 
     try { 
      List<E> instance = sessionFactory.getCurrentSession().createCriteria(entity.getClass()).list(); 
      return instance; 
     } catch (RuntimeException re) { 
      return null; 
     } 
    } 

}

吾道类是这样写的：

@Repository 
public class UsuarioHome extends Dao<Usuario> { 

    public UsuarioHome(Usuario entity) { 
     super(entity); 
     // TODO Auto-generated constructor stub 
    } 

}

但是当我尝试运行应用程序我得到这个错误：如果我的做法确实WO

Caused by: org.springframework.beans.factory.BeanCreationException: Could not autowire field: private com.spring.webapp.lojavirtual.acesso.persistence.UsuarioHome com.spring.webapp.lojavirtual.acesso.service.AuthenticationService.accountDao; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'usuarioHome' defined in file [/home/kleber/workspace/.metadata/.plugins/org.eclipse.wst.server.core/tmp0/wtpwebapps/webapp2/WEB-INF/classes/com/spring/webapp/lojavirtual/acesso/persistence/UsuarioHome.class]: Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [com.spring.webapp.lojavirtual.acesso.persistence.UsuarioHome]: No default constructor found; nested exception is java.lang.NoSuchMethodException: com.spring.webapp.lojavirtual.acesso.persistence.UsuarioHome.<init>() 
    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) 
    ... 48 more 
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'usuarioHome' defined in file [/home/kleber/workspace/.metadata/.plugins/org.eclipse.wst.server.core/tmp0/wtpwebapps/webapp2/WEB-INF/classes/com/spring/webapp/lojavirtual/acesso/persistence/UsuarioHome.class]: Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [com.spring.webapp.lojavirtual.acesso.persistence.UsuarioHome]: No default constructor found; nested exception is java.lang.NoSuchMethodException: com.spring.webapp.lojavirtual.acesso.persistence.UsuarioHome.<init>() 
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:1007) 
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:953) 
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:487) 
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:458) 
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:295) 
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:223) 
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:292) 
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194) 
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.findAutowireCandidates(DefaultListableBeanFactory.java:912) 
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:855) 
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:770) 
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:486) 
    ... 50 more 
Caused by: org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [com.spring.webapp.lojavirtual.acesso.persistence.UsuarioHome]: No default constructor found; nested exception is java.lang.NoSuchMethodException: com.spring.webapp.lojavirtual.acesso.persistence.UsuarioHome.<init>() 
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:83) 
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:1000) 
    ... 61 more 
Caused by: java.lang.NoSuchMethodException: com.spring.webapp.lojavirtual.acesso.persistence.UsuarioHome.<init>() 
    at java.lang.Class.getConstructor0(Class.java:2810) 
    at java.lang.Class.getDeclaredConstructor(Class.java:2053) 
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:78) 
    ... 62 more

任何人都可以说，如果这是真的，我在这里错过了什么？

来源

2014-04-14 Kleber Mota

您在UsuarioHome中缺少无参数构造函数。添加一个和spring应该能够实例化它。

@Repository 
public class UsuarioHome extends Dao<Usuario> { 

    public UsuarioHome() { //<--- 
     super(null); 
    } 

    public UsuarioHome(Usuario entity) { 
     super(entity); 
     // TODO Auto-generated constructor stub 
    } 
}

有一两件事，我建议是不是有场 - private final E entity;。这真的没用。

此外，最好从您的DAO中取出交易设置并将它们放入您的服务中。

来源

2014-04-14 23:22:10

错误在DAO类中使用泛型

回答

相关问题