複雜的休眠投影

Question

我想問一下，我有可能創建查詢投影和多個級別的標準？ 我有2模型類：

@Entity 
@Table(name = "person") 
public class Person implements Serializable { 
    @Id 
    @GeneratedValue 
    private int personID; 
    private double valueDouble; 
    private int valueInt; 
    private String name; 
    @OneToOne(cascade = {CascadeType.ALL}, orphanRemoval = true) 
    @JoinColumn(name="wifeId") 
    private Wife wife; 
     /* 
     * Setter Getter  
     */ 
} 


@Entity 
@Table(name = "wife") 
public class Wife implements Serializable { 

    @Id 
    @GeneratedValue  
    @Column(name="wifeId") 
    private int id; 
    @Column(name="name") 
    private String name; 
    @Column(name="age") 
    private int age;    
    /* 
    * Setter Getter 
    */  
} 

我的標準API：

ProjectionList projections = Projections.projectionList(); 
projections.add(Projections.property("this.personID"), "personID"); 
projections.add(Projections.property("this.wife"), "wife"); 
projections.add(Projections.property("this.wife.name"), "wife.name"); 

Criteria criteria = null; 
criteria = getHandlerSession().createCriteria(Person.class); 
criteria.createCriteria("wife", "wife", JoinType.LEFT.ordinal()); 
criterion = Restrictions.eq("wife.age", 19); 
criteria.add(criterion); 
criteria.setProjection(projections); 
criteria.setResultTransformer(Transformers.aliasToBean(Person.class)); 
return criteria.list(); 

，我希望，我可以查詢人，與妻子屬性指定的標準，以及指定的返回結果集。 所以我用投影獲得指定的返回結果集

我想personID，名稱（人），姓名（妻子）將返回。我如何使用API​​，我更喜歡使用Hibernate Criteria API。

這一次，我用上面得到我預期的結果代碼，但它會拋出異常與錯誤消息： Exception in thread "main" org.hibernate.QueryException: could not resolve property: wife.name of: maladzan.model.Person， 是否我Restrictions.eq("wife.age", 19);是獲得具有妻子19她的年齡價值的人是否正確？

感謝

Answer 1

AFAIK這是不可能的項目深具aliastobean變壓器不止一個級別。你的選擇是

• 創建一個扁平的數據傳輸對象（DTO）
• 填補由此造成的人員在記錄自己
• 實現自己的使用ResultTransformer（類似於選項2）

選項1個長相像這樣：

Criteria criteria = getHandlerSession().createCriteria(Person.class) 
    .createAlias("wife", "wife", JoinType.LEFT.ordinal()) 
    .add(Restrictions.eq("wife.age", 19)); 
    .setProjection(Projections.projectionList() 
     .add(Projections.property("personID"), "personID") 
     .add(Projections.property("name"), "personName") 
     .add(Projections.property("wife.name"), "wifeName")); 
    .setResultTransformer(Transformers.aliasToBean(PersonWifeDto.class)); 

return criteria.list(); 

Answer 2

我寫了ResultTransformer，就是這麼做的。它的名字是AliasToBeanNestedResultTransformer，查看​​。

Answer 3

謝謝薩米安多尼。我能夠對您的AliasToBeanNestedResultTransformer進行小修改以適應我的情況。我發現的是，嵌套變換器不支持字段處於超類的場景，所以我增強了它，以便在您要投影到的類的類繼承層次結構中查找深達10級的字段：

public Object transformTuple(Object[] tuple, String[] aliases) { 

     ... 


       if (alias.contains(".")) { 
        nestedAliases.add(alias); 

        String[] sp = alias.split("\\."); 
        String fieldName = sp[0]; 
        String aliasName = sp[1]; 

        Class<?> subclass = getDeclaredFieldForClassOrSuperClasses(resultClass, fieldName, 1); 
... 
} 

凡getDeclaredFieldForClassOrSuperClasses（）被定義如下：

private Class<?> getDeclaredFieldForClassOrSuperClasses(Class<?> resultClass, String fieldName, int level) throws NoSuchFieldException{ 
    Class<?> result = null; 
    try { 
     result = resultClass.getDeclaredField(fieldName).getType(); 
    } catch (NoSuchFieldException e) { 
     if (level <= 10){ 
     return getDeclaredFieldForClassOrSuperClasses(
       resultClass.getSuperclass(), fieldName, level++); 
     } else { 
      throw e; 
     } 
    } 
    return result; 
} 

我的休眠投影此嵌套屬性是這樣的：

Projections.projectionList().add(Property.forName("metadata.copyright").as("productMetadata.copyright")); 

和類我伸入這個樣子的：

public class ProductMetadata extends AbstractMetadata { 
... 
} 

public abstract class AbstractMetadata { 
... 
    protected String copyright; 
... 
} 

Answer 4

而不是創造Data Transfer Object (DTO)
在projectionlist修改下面，它會爲你工作。

ProjectionList projections = Projections.projectionList(); 
    projections.add(Projections.property("person.personID"), "personID"); 
    projections.add(Projections.property("person.wife"), "wife"); 
    projections.add(Projections.property("wife.name")); 

    Criteria criteria = null; 
    criteria = getHandlerSession().createCriteria(Person.class,"person").createAlias("person.wife", "wife"); 
    criterion = Restrictions.eq("wife.age", 19); 
    criteria.add(criterion); 
    criteria.setProjection(projections); 
    criteria.setResultTransformer(Transformers.aliasToBean(Person.class)); 
    return criteria.list();