休眠限制ManyToMany

Question

我有一个Teacher类，其中包含一个课程列表，现在我不知道如何使用休眠criteria和限制过滤这个列表的课程？

public class Teacher extends BaseEntity implements Serializable { 
    @ManyToMany(targetEntity = Course.class, fetch = FetchType.EAGER) 
    private Set<Course> courses; 
} 

public class TeacherSearchCriteria extends Criteria { 
    private Course course; 
} 

这里是我的服务类，提供了限制逻辑：

EntityManager em = getEntityManager(); 
    CriteriaBuilder builder = em.getCriteriaBuilder(); 
    List<Teacher> result = Collections.EMPTY_LIST; 

    CriteriaQuery<Teacher> criteria = builder.createQuery(Teacher.class); 
    Root<Teacher> from = criteria.from(Teacher.class); 

    if (searchCriteria != null) { 
     List<Predicate> restrictions = new ArrayList<Predicate>(); 

     if (searchCriteria.getCourse() != null) { 
      //Here I don't know how to make the restrictions on Set of 
      //courses 
      restrictions.add(builder.equal(from.get("courses"), 
      searchCriteria.getCourse())); 
     } 
     addRestrictionsToCriteria(restrictions, criteria, builder); 
    } 

Answer 1

您需要为您收集alias。然后，您可以添加对集合中属性的限制。别名的创建告诉hibernate在构造sql时执行到表的连接。

EntityManager em = getEntityManager(); 
CriteriaBuilder builder = em.getCriteriaBuilder(); 
List<Teacher> result = Collections.EMPTY_LIST; 

CriteriaQuery<Teacher> criteria = builder.createQuery(Teacher.class); 
criteria.createAlias("courses", "c") 
     .add(Restrictions.eq("c", searchCriteria.getCourse());