java 复杂的休眠投影
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Complex Hibernate Projections
提问by Fauzi Achmad
I want to ask, it is possible that I create query projections and criterion for more than one level deep? I have 2 model classes:
我想问一下，我有可能为不止一个级别的深度创建查询投影和标准吗？我有 2 个模型类：
@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
*/
}
My Criteria API :
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();
and I hope, I can query Person, with specified criteria for wife property, and specified return resultSet. so i used Projections for getting specified return resultSet
我希望，我可以查询 Person，指定妻子属性的条件，并指定返回结果集。所以我使用 Projections 来获取指定的返回结果集
I want personID, name(Person), name(Wife) will returned. how API i must Use, i more prefer use Hibernate Criteria API.
我想要 personID, name(Person), name(Wife) 将返回。我必须如何使用 API，我更喜欢使用 Hibernate Criteria API。
This time, I used code above for getting my expected result, but it will throw Exception with error message :
Exception in thread "main" org.hibernate.QueryException: could not resolve property: wife.name of: maladzan.model.Person,
and whether my Restrictions.eq("wife.age", 19);is correct for getting person which has wife with 19 as her age value ?
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和我是否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？
Thanks
谢谢
回答by Firo
AFAIK it is not possible to project more than one level deep with aliastobean transformer. Your options are
AFAIK 不可能使用 aliastobean 转换器投射超过一层的深度。你的选择是
- create a flattened Data Transfer Object (DTO)
- fill the resulting Person in memory yourself
- implement your own resulttransformer (similar to option 2)
- 创建扁平化数据传输对象 (DTO)
- 自己在记忆中填充由此产生的 Person
- 实现您自己的 resulttransformer（类似于选项 2）
option 1 looks like this:
选项 1 如下所示：
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();
回答by Sami Andoni
回答by whitestryder
Thanks Sami Andoni. I was able to use your AliasToBeanNestedResultTransformer with a minor modification to suit my situation. What I found was that the nested transformer did not support the scenario where the field is in a super class so I enhanced it to look for fields up to 10 levels deep in the class inheritance hierarchy of the class you're projecting into:
谢谢萨米·安多尼。我能够使用您的 AliasToBeanNestedResultTransformer 并稍作修改以适应我的情况。我发现嵌套转换器不支持字段位于超类中的场景，因此我对其进行了增强，以在您投射到的类的类继承层次结构中查找最多 10 层的字段：
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);
...
}
Where getDeclaredFieldForClassOrSuperClasses() is defined as follows:
其中 getDeclaredFieldForClassOrSuperClasses() 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;
}
My Hibernate projection for this nested property looked like this:
我对此嵌套属性的 Hibernate 投影如下所示：
Projections.projectionList().add( Property.forName("metadata.copyright").as("productMetadata.copyright"));
and the class I am projecting into looks like this:
我正在投射的课程如下所示：
public class ProductMetadata extends AbstractMetadata {
...
}
public abstract class AbstractMetadata {
...
protected String copyright;
...
}
回答by Jubin Patel
Instead of creating Data Transfer Object (DTO)
In projectionlistmake below changes and it will work for you.
而不是创建Data Transfer Object (DTO)
In projectionlistmake 下面的更改，它将为您工作。
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();
