复杂的休眠投影

Question

我想问一下，我有可能创建查询投影和多个级别的标准？ 我有2模型类：

@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 
    */  
} 

我的标准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，我可以查询人，与妻子属性指定的标准，以及指定的返回结果集。 所以我用投影获得指定的返回结果集

我想personID，名称（人），姓名（妻子）将返回。我如何使用API​​，我更喜欢使用Hibernate Criteria API。

这一次，我用上面得到我预期的结果代码，但它会抛出异常与错误消息： 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);是获得具有妻子19她的年龄价值的人是否正确？

感谢

Answer 1

AFAIK这是不可能的项目深具aliastobean变压器不止一个级别。你的选择是

• 创建一个扁平的数据传输对象（DTO）
• 填补由此造成的人员在记录自己
• 实现自己的使用ResultTransformer（类似于选项2）

选项1个长相像这样：

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

我写了ResultTransformer，就是这么做的。它的名字是AliasToBeanNestedResultTransformer，查看​​。

Answer 3

谢谢萨米安多尼。我能够对您的AliasToBeanNestedResultTransformer进行小修改以适应我的情况。我发现的是，嵌套变换器不支持字段处于超类的场景，所以我增强了它，以便在您要投影到的类的类继承层次结构中查找深达10级的字段：

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（）被定义如下：

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属性是这样的：

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

和类我伸入这个样子的：

public class ProductMetadata extends AbstractMetadata { 
... 
} 

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

Answer 4

而不是创造Data Transfer Object (DTO)
在projectionlist修改下面，它会为你工作。

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();