对父级执行createCriteria（）,在该父级中计算子级及其属性

Question

class Parent {
    Long id
    static hasMany = [ children: Child ]
}

class Child {
    Long id
    static belongsTo = [ parent: Parent ]
}

如何选择以下条件：

1. 选择不带子项的所有父项
2. 选择所有父级和子级
3. 选择带有雄性子项的所有父项（因此，当通过作为JSONgroovy类型转换转换为JSON时，只应包括雄性子项）

我不知道如何开始编码1和2，也许与child.size()有关--我真的不知道。虽然我在第3章的想法是：

ArrayList<Parent> PARENTS_WITH_SON = Parent.createCriteria().list {
    children {
        eq("gender", "male")
    }
}

但问题是，当转换为JSON时，它包含了非男性条目。有谁能帮我解决问题吗？使用createCriteria()会很好，但也可以在HQL中使用。

Answer 1

1和2是非常简单的：

1.选择不带子级所有父级

Parent.createCriteria().list {
    sizeEq("children", 0)
}

2.选择所有父级和子级

Parent.createCriteria().list {
    sizeGt("children", 0)
}

Parent.createCriteria().listDistinct {
    children {
        eq("gender", "male")
    }
}

/*
  create a new Grails Criteria that internally will use
  Hibernate's org.hibernate.Criteria.
*/
List<Map<String, Object>> resultList = Parent.createCriteria().list {
    /*
     Set a strategy for handling the query results.
     This determines the "shape" of the query result.

     See org.hibernate.Criteria.setResultTransformer(...)

     CriteriaSpecification.ALIAS_TO_ENTITY_MAP transformer will transform the results into a Map<String, Object>
    */
    resultTransformer(org.hibernate.criterion.CriteriaSpecification.ALIAS_TO_ENTITY_MAP)

    /*
     Join an association using the specified join-type, 
     assigning an alias to the joined association.

     org.hibernate.Criteria.createAlias(...)
    */
    createAlias("children", "child", JoinType.INNER_JOIN);

    projections {
        property("id", "parentId")
        property("child.id", "childId")
        property("child.gender", "gender")
    }

    eq("child.gender", "MALE")
}

[
  {
    "childId": 1,
    "gender": "MALE",
    "parentId": 2
  },
  {
    "childId": 3,
    "gender": "MALE",
    "parentId": 2
  },
  {
    "childId": 4,
    "gender": "MALE",
    "parentId": 3
  },
  {
    "childId": 5,
    "gender": "MALE",
    "parentId": 3
  }
]