无法将getNamedQuery结果转换为表类 [英] Cannot cast getNamedQuery results to table class

问题描述

我一直在寻找并尝试我在Google上搜索过的最近4小时的命名查询结果的教程，但没有找到可行的解决方案。当我运行下面代码的snippit时，我收到一个 java.lang.ClassCastException 错误（见下文）。

我从使用 sessionCriteria （其工作）获取整个记录结果转换为仅使用 getNamedQuery 返回表列的3个结果， 。

$ hr
$ b

原始代码块

  Criteria sessionCriteria = session.createCriteria（RunContainer.class）; 
 
 @SuppressWarnings（unchecked）
 List< RunContainer> runContainer = sessionCriteria.list（）; 
  

命名查询代码块

 查询查询= session.getNamedQuery（RunContainer.GetRunsForCalendar）; 
 
列表结果= query.list（）; （int i = 0; i< results.size（）; i ++）{
 RunContainer result =（RunContainer）results.get（i）; 
 
。 
 System.out.println（result.getNotes（））; 
} 
  

运行容器表类

  @Entity 
 @Table（name =container）
 @NamedQueries（{
 @NamedQuery（name = RunContainer.GetRunsForCalendar，
 query =SELECT id，date，notes FROM RunContainer）
}）
 public class RunContainer {
 
 @Id 
 @GeneratedValue 
 @Column（columnDefinition =INT UNSIGNED）
 private Integer id; 
 
私人日期日期; 
 
 @Column（columnDefinition =TEXT）
私人字符串笔记; 
 
 
  

错误 p>

  java.lang.ClassCastException：
 [Ljava.lang.Object;不能转换为com.scene7.is.qa.jorogumo.tables.RunContainer 
  

---

任何人都可以帮我调试吗？

---

来自已接受答案的工作代码

对于Java而言，我相当新，这是我第一个与工作有关的项目。

如果有人遇到这篇文章，下面的代码就是我从接受的答案中得出的结论。

 查询查询= session.getNamedQuery（RunContainer.GetRunsForCalendar）; 
列表< Object> containerResults = query.list（）; 
列表< RunContainer> runContainers = new ArrayList< RunContainer>（）; 
 
 for（Object result：containerResults）{
 
 Object [] temp =（Object []）result; 
 RunContainer runContainer = new RunContainer（）; 
 
 runContainer.setId（（Integer）temp [0]）; 
 runContainer.setDate（（Date）temp [1]）; 
 runContainer.setNotes（（String）temp [2]）; 
 
 runContainers.add（runContainer）; 
} 
  

解决方案

SELECT子句查询多个列或实体，结果
聚合在getResultList（）返回的java.util.List
中的对象数组（Object []）中。

在这里，您将它转换为导致问题的 RunContainer 。遍历列表和<从数组中获取单个字段。

  List containerResults = query.List（）; 
 
 for（Object [] result：containerResults）
 {
 Integer id =（Integer）result [0]; 
日期日期=（日期）结果[1]; 
 String notes =（String）result [2]; 
} 
  

[注意：提供示例代码而不编译， b
$ b 在实体中的名字，你可以尝试

session.createSQLQuery（SELECT id，date，notes FROM RunContainer）addEntity（RunContainer.class ）;

您可以参阅此处 a>了解更多详情。

I have been looking and trying the tutorials I have googled for casting named query results for the last 4 hours and have not found a workable solution. When I run the snippit of code below I receive a java.lang.ClassCastException error (see below).

I switched from getting the whole record result using sessionCriteria (which worked) to only returning 3 of the table columns using getNamedQuery.

---

Original Code Block

Criteria sessionCriteria = session.createCriteria(RunContainer.class);

@SuppressWarnings ("unchecked")
List<RunContainer> runContainer = sessionCriteria.list();

Named Query Code Block

Query query = session.getNamedQuery("RunContainer.GetRunsForCalendar");

List results = query.list();

for(int i = 0; i < results.size(); i++){
    RunContainer result = (RunContainer)results.get(i);
    System.out.println(result.getNotes());
}

RunContainer Table Class

@Entity
@Table (name = "container")
@NamedQueries ( {
    @NamedQuery (name = "RunContainer.GetRunsForCalendar", 
        query = "SELECT id, date, notes FROM RunContainer")
    })
public class RunContainer {

    @Id
    @GeneratedValue
    @Column (columnDefinition = "INT UNSIGNED")
    private Integer id;

    private Date date;

    @Column(columnDefinition = "TEXT")
    private String notes;

    ...

Error

java.lang.ClassCastException:
[Ljava.lang.Object; cannot be cast to com.scene7.is.qa.jorogumo.tables.RunContainer

---

Can anyone help me debug this? I am fairly new to Java and this is my first work related project.

---

Working Code from Accepted Answer

In case anyone runs into this post, the following code is what I ended up with from accepted answer.

Query query = session.getNamedQuery("RunContainer.GetRunsForCalendar");
List<Object> containerResults = query.list();
List<RunContainer> runContainers = new ArrayList<RunContainer>();

for (Object result : containerResults) {

    Object[] temp = (Object[]) result;
    RunContainer runContainer = new RunContainer();

    runContainer.setId((Integer) temp[0]);
    runContainer.setDate((Date) temp[1]);
    runContainer.setNotes((String) temp[2]);

    runContainers.add(runContainer);
}

解决方案

The SELECT clause queries more than one column or entity, the results are aggregated in an object array (Object[]) in the java.util.List returned by getResultList( ).

Here you're casting it to RunContainer which causes problem. Iterate through the list & fetch individual fields from the array.

List containerResults = query.List(); 

    for(Object[] result : containerResults) 
    {
       Integer id = (Integer) result[0];
       Date date = (Date) result[1];
       String notes = (String) result[2];
    }

[Note : provided sample code without compilation, make changes accordingly]

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Edit: Alternatively, if the selected fields are same as the field names in the entity, you can try

session.createSQLQuery("SELECT id, date, notes FROM RunContainer").addEntity(RunContainer.class);

You can refer here for more details.

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