我正在尝试创建一个条件,从3个表(关联,更新和细节)中检索一些对象.详细信息参考关联和更新,更新引用了详细信息列表.我的目标是在给定一个关联标识符的情况下,在指定的字段中检索至少具有空值的详细信息的更新列表.在JPQL中很容易做到,但客户端表示这必须用标准编码.
我的JPQL是:
public List<Update> getUpdates(long associateId) {
TypedQuery<Update> query = em.createquery("select distinct u from Update u,Detail dt,Associate a "
+ "where dt.update = u and dt.associate = a and a.associateId = :id and "
+ "dt.ack_date is null",Update.class);
query.setParameter("id",associateId);
return query.getResultList();
}
我尝试了以下,但它只是返回数据库中的所有更新:
public List<Update> getUpdates(long associateId) {
CriteriaBuilder builder = em.getCriteriaBuilder();
CriteriaQuery<Update> query = builder.createquery(Update.class);
Root<Update> fromUpdates = query.from(Update.class);
Root<Associate> fromAssociate = query.from(Associate.class);
Root<Detail> fromDetail = query.from(Detail.class);
Join<Detail,Associate> associateJoin = fromDetail.join("associate");
Join<Detail,Update> updateJoin = fromDetail.join("update");
TypedQuery<Update> typedQuery = em.createquery(query
.select(fromUpdates)
.where(builder.and(
builder.equal(fromAssociate.get("associateId"),associateId),builder.equal(fromDetail.get("associate"),associateJoin),builder.equal(fromDetail.get("update"),updateJoin),builder.isNull(fromDetail.get("ack_date"))
))
.orderBy(builder.asc(fromUpdates.get("updateId")))
.distinct(true)
);
return typedQuery.getResultList();
}
有人可以帮我吗我搜索,但找不到任何与3个实体的例子.
解决方法
每个连接都可以将您从左边的类型参数传给最右边的参数.所以,我的代码(第二行)的细节连接从fromUpdates开始,这是一个Path< Update>,并创建了一些幕后的路径< Detail>.从此,您可以构建其他连接.尝试这个(代码未测试):
Root<Update> fromUpdates = query.from(Update.class);
Join<Update,Detail> details = fromUpdates.join("details");
Join<Detail,Associate> associate = details.join("associate");
List<Predicate> conditions = new ArrayList();
conditions.add(builder.equal(associate.get("associateId"),associateId));
conditions.add(builder.isNull(details.get("ack_date")));
TypedQuery<Update> typedQuery = em.createquery(query
.select(fromUpdates)
.where(conditions.toArray(new Predicate[] {}))
.orderBy(builder.asc(fromUpdates.get("updateId")))
.distinct(true)
);