Question

我希望根据主键选择数据库中的多个项目。

所以，如果我有名字，我想从DB中选择imagename和refName。

我在http://www.objectdb.com/java/jpa/query/jpql/select

找到了一些东西

TypedQuery<Object[]> query = em.createQuery(
      "SELECT c.name, c.capital.name FROM Country AS c", Object[].class);
  List<Object[]> results = query.getResultList();
  for (Object[] result : results) {
      System.out.println("Country: " + result[0] + ", Capital: " + result[1]);
  }

哪个不起作用，而其他人似乎认为代码非常错误，所以我很好奇我将如何做到这一点？

全部谢谢！

Caused by: java.lang.IllegalArgumentException: You have attempted to set a parameter value using a name of i.name that does not exist in the query string SELECT i.name, i.refName, i.imageName FROM Items AS i.
    at org.eclipse.persistence.internal.jpa.QueryImpl.setParameterInternal(QueryImpl.java:928)  at org.eclipse.persistence.internal.jpa.QueryImpl.setParameterInternal(QueryImpl.java:928)
    at org.eclipse.persistence.internal.jpa.EJBQueryImpl.setParameter(EJBQueryImpl.java:593)
    at uploader.AdminControl.fileCreate(AdminControl.java:745)
    at uploader.AdminControl.upload(AdminControl.java:660)
    ... 57 more

...

TypedQuery<Object[]> q = em2.createQuery("SELECT i.name, i.refName, i.imageName FROM Items AS i",Object[].class);
q.setParameter("name", plan.getFace()[i].name);
System.out.println(q);


                            List<Object[]> results = q.getResultList();

                            for (Object[] result : results)
                            {
                            bw.write(result[1].toString());
                            bw.write(result[2].toString());
                            System.out.println("result:" + result[1].toString() + "and" + result[2].toString());
                            }

Answer 1

问题在于这段代码：

q.setParameter("i.name", plan.getFace()[i].name);

看看你的JPQL：

SELECT i.name, i.refName, i.imageName FROM Items AS i

您没有名为i.name的参数。您应该创建一个将接收参数的。像

这样的东西

    SELECT i.name, i.refName, i.imageName FROM Items AS i where i.name = :parameterName

确实传递了价值：

q.setParameter("parameterName", plan.getFace()[i].name);

Answer 2

问题是参数名称

TypedQuery<Object[]> q = em2.createQuery("SELECT i.name, i.refName, i.imageName FROM Items WHERE i.name = :someparam AS i",Object[].class);
q.setParameter("someparam", plan.getFace()[i].name);

如何使用JPA使用多SELECT查询

2 个答案: