如何正確使用setProjection？

Question

我想在我的UserAccount類只檢索某些列，所以我有下面的代碼：

UserAccount aUser = (UserAccount)currentSession().createCriteria(UserAccount.class) 
         /* .setProjection(Projections.projectionList() 
            .add(Projections.property("id")) 
            .add(Projections.property("username")) 
            .add(Projections.property("email")) 
            .add(Projections.property("displayname"))) */ 
          .add(Restrictions.eq("email", email)) 
          .add(Restrictions.eq("password", password)) 
          .add(Restrictions.eq("enabled", true)) 
          .add(Restrictions.eq("role", Role.CUSTOMER)) 
          .uniqueResult(); 
    System.out.println(aUser); 
    return aUser; 

我得到的回報零。但是，如果我註釋掉setProjections，我將得到所有屬性的用戶。如何在這種情況下正確使用setProjection？

Answer 1

它返回一個Object數組，因此代碼應該是：

Object[] rows = (Object[]) session 
     .createCriteria(UserAccount.class) 
     .setProjection(
       Projections.projectionList() 
         .add(Projections.property("id")) 
         .add(Projections.property("username")) 
         .add(Projections.property("email")) 
         .add(Projections.property("displayname"))) 
     .add(Restrictions.eq("email", email)) 
     .add(Restrictions.eq("password", password)) 
     .add(Restrictions.eq("enabled", true)) 
     .add(Restrictions.eq("role", Role.CUSTOMER)) 
     .uniqueResult(); 

Answer 2

有凸起我們應該用結果變壓器和走樣：

UserAccount aUser = (UserAccount)currentSession() 
    // FROM 
    .createCriteria(UserAccount.class) 
    // WHERE 
    .add(Restrictions.eq("email", email)) 
    .add(Restrictions.eq("password", password)) 
    .add(Restrictions.eq("enabled", true)) 
    .add(Restrictions.eq("role", Role.CUSTOMER)) 
    // SELECT with alias 
    .setProjection(Projections.projectionList() 
     .add(Projections.property("id"),"id")    // alias is a must for 
     .add(Projections.property("username"),"username") // result transformer 
     .add(Projections.property("email"),"email") 
     .add(Projections.property("displayname"),"displayname") 
    ) 
    // here we go - this will convert projection into entity 
    .setResultTransformer(Transformers.aliasToBean(UserAccount.class)) 
    .uniqueResult(); 

檢查：

• Complex Hibernate Projections
• B.9. Projections, aggregation and grouping