Java Hibernate:复合id服务
我的实体:文章,类别。这是一种n:m关系。 我想获得特定类别引用的文章数量 以下是我的实体:Java Hibernate:复合id服务,java,spring,hibernate,Java,Spring,Hibernate,我的实体:文章,类别。这是一种n:m关系。 我想获得特定类别引用的文章数量 以下是我的实体: @Entity @Table( name = "tbl_articles" ) public class Article implements Serializable { private static final long serialVersionUID = 1L; @Id @Column( nullable = false ) @GeneratedValue( s
@Entity
@Table( name = "tbl_articles" )
public class Article implements Serializable
{
private static final long serialVersionUID = 1L;
@Id
@Column( nullable = false )
@GeneratedValue( strategy = GenerationType.IDENTITY )
private Integer id;
@Column( nullable = false )
private String title;
@Column( nullable = false )
private Date creationDate = new Date();
@Lob
@Type( type = "org.hibernate.type.StringClobType" )
@Column( nullable = false )
private String text;
// Getter + setter
}
@Entity
@Table( name = "tbl_categories" )
public class Category implements Serializable
{
private static final long serialVersionUID = 1L;
@Id
@Column( nullable = false )
@GeneratedValue( strategy = GenerationType.IDENTITY )
private Integer id;
@Column( nullable = false )
private String title;
// Getter + setter
}
@Entity
@Table( name = "tbl_articles_categories" )
@AssociationOverrides({
@AssociationOverride( name = "pk.article", joinColumns = @JoinColumn( name = "article_id" ) ),
@AssociationOverride( name = "pk.category", joinColumns = @JoinColumn( name = "category_id" ) )
})
public class ArticleCategory
{
@EmbeddedId
private ArticleCategoryPK pk = new ArticleCategoryPK();
public ArticleCategoryPK getPk() ...
public void setPk( ArticleCategoryPK pk ) ...
@Transient
public Article getArticle()
{
return pk.getArticle();
}
public void setArticle( Article article )
{
pk.setArticle( article );
}
@Transient
public Category getCategory()
{
return pk.getCategory();
}
public void setCategory( Category category )
{
pk.setCategory( category );
}
}
现在我有了文章和类别的存储库和服务层。
我将只提供文章层来显示结构
public abstract class BaseDAO<E>
{
public abstract List<E> list( int offset, int limit );
public abstract void delete( int id );
public abstract void save( E entity );
public abstract E get( int id );
public abstract List<E> list();
public abstract Integer size();
}
@Repository
public class ArticleDAO extends BaseDAO<Article>
{
@Autowired
private SessionFactory sessionFactory;
@Override
public void delete( int id )
{
Article article = get( id );
if ( article != null )
{
sessionFactory.getCurrentSession().delete( article );
}
}
@Override
public void save( Article article )
{
sessionFactory.getCurrentSession().save( article );
}
@Override
public Article get( int id )
{
return ( Article ) sessionFactory.getCurrentSession().load( Article.class, id );
}
@SuppressWarnings( "unchecked" ) // The type is determined by the HQL query but the interface returns an untyped list
@Override
public List<Article> list()
{
return sessionFactory.getCurrentSession().createQuery( "from Article" ).list();
}
@Override
public Integer size()
{
Number ret = ( Number ) criteria.setProjection( Projections.rowCount() ).uniqueResult();
return ret.intValue();
}
}
public abstract class BaseService<E, D extends BaseDAO<E>>
{
protected D dao;
public BaseService()
{
}
protected D getDao()
{
return dao;
}
@Autowired
protected void setDAO( D dao )
{
this.dao = dao;
}
@Transactional
public void delete( int id )
{
dao.delete( id );
}
@Transactional
public void save( E entity )
{
dao.save( entity );
}
@Transactional
public E get( int id )
{
return dao.get( id );
}
@Transactional
public List<E> list()
{
return dao.list();
}
@Transactional
public Integer size()
{
return dao.size();
}
}
@Service
public class ArticleService extends BaseService<Article, ArticleDAO>
{
public ArticleService()
{
setDAO( dao );
}
}
您的异常与您的问题无关,请休眠,结束与Spring有关的一切。Spring找不到任何类型为
ArticleCategoryDAO
的Springbean。您可能忘了用@Repository
对其进行注释
顺便说一句,您询问是否应该为ArticleCategory
创建DAO,但错误消息显示您已经创建了一个DAO
附带问题:为什么不简单地在文章和类别之间创建一个多个关联呢?
articleCography
实体根本不需要。是的,我忘了用@Repository
注释它。是的,我问我是否应该创建一个,并且已经尝试过显示异常。我需要一个助手表,所以我想我需要实体?!不,您不需要实体。你为什么不阅读文档并搜索很多呢?或者简单地查找javadoc,看看@manytomy
是如何记录的。
No matching bean of type [com.example.model.ArticleCategoryDAO] found for
dependency: expected at least 1 bean which qualifies as autowire candidate for
this dependency. Dependency annotations: {}