使用对象 ID 进行 JDO 查询

发布于 2024-10-15 19:02:47 字数 1090 浏览 2 评论 0原文

我有一个 User 对象，它下面有一个 Transaction 对象的集合。

我存储了 User 对象的对象 ID，现在需要一个查询来求和 User 对象下的交易：

    @Persistable
    public class User {
      private String username;
      private Collection<Transaction> transactions
      //...getter/setters...
    }

    @Persistable
    public class Transaction {
      private int txnAmount;
      //...getter/setter...
    }

给定 User 的对象ID，我想要 User.transactions 集合中所有 Transaction.txnAmount 的总和。

我的想法是：

    Query query = pm.newQuery(User.class);
    query.setFilter("JDOHelper.getObjectId(this) == :userIDParam");
    query.setResult("sum(transactions.credits)");
    query.execute(userID);

我已经验证了 userID 确实是一个数据库标识符对象，因为它应该是（我可以使用它通过 ID 来查询用户对象）。但我在 query.execute() 方法中遇到异常：

javax.jdo.JDOException: Invoice of method "JDOHelper.getObjectId" is on null but this is not current support by SODA query

using DB4O as the datastore, DataNucleus 2.2.1作为 JDO 实现

原文

I have a User object which has a collection of Transaction objects under it.

I store the object ID for my User object and now need a query to sum the transactions under the User object:

    @Persistable
    public class User {
      private String username;
      private Collection<Transaction> transactions
      //...getter/setters...
    }

    @Persistable
    public class Transaction {
      private int txnAmount;
      //...getter/setter...
    }

Given the User's object ID, I want a sum of all Transaction.txnAmount's in the User.transactions collection.

My shot at this was:

    Query query = pm.newQuery(User.class);
    query.setFilter("JDOHelper.getObjectId(this) == :userIDParam");
    query.setResult("sum(transactions.credits)");
    query.execute(userID);

I have verified that userID is indeed a Database Identifier object as it should be (I can use it to query the User object by ID using it). But I get an exception in the query.execute() method:

javax.jdo.JDOException: Invocation of method "JDOHelper.getObjectId" is on null but this is not currently supported by SODA queries

Using DB4O as the datastore, DataNucleus 2.2.1 as the JDO implementation

分享到QQ

分享到微博