java.lang.ClassCastException: [Ljava.lang.Object; 不能投射到
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java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to
提问by Michael1
why java.lang.ClassCastException is triggered in my program ?
为什么在我的程序中会触发 java.lang.ClassCastException ？
java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to com.App.Equip]
java.lang.ClassCastException: [Ljava.lang.Object; 不能投射到 com.App.Equip]
The query returns the list of checklists that are answered (found in the CheckLists calsse) and not yet answered by Equip object
查询返回已回答（在 CheckLists calsse 中找到）但尚未由 Equip 对象回答的清单列表
-Here is the code:
- 这是代码：
import org.json.simple.*;
@SuppressWarnings("unchecked")
public JSONObject ListCheckListsNonETRepondu( long idEqp, long idmiss){
Query query = manager.createNativeQuery("SELECT"
+ " checksl.id_check_lists as IdCheckLists,"
+ " checksl.titre_check as NomCheckLists,"
+ " checksl.recommendation as Recommendation, "
+ " resp.id_responsescheck as IdResponse, "
+ " resp.conformite as Conformite, "
+ " resp.date_response as DateResponse, "
+ " resp.missions_id as IdMission "
+ " FROM equipements eq "
+ " LEFT JOIN check_lists checksl"
+ " ON eq.id_equipements= checksl.equipements_id "
+ " LEFT JOIN responses_check_lists resp "
+ " ON checksl.id_check_lists = resp.check_lists_id "
+ " AND resp.missions_id ="+idmiss+""
+ " AND eq.id_equipements ="+idEqp
+ " ORDER BY checksl.id_check_lists"
);
List<Equip> res = query.getResultList();
JSONObject obj = new JSONObject();
for( Equip eq: res) //--The problem is here --
{
for(CheckLists checks : eq.getChecks())
{
obj.put("idCheckLists", checks.getIdCheckLists());
obj.put("NomCheckLists", checks.getTitreCheck());
obj.put("Recommendation", checks.getRecommendation());
for(ResponsesCheckLists resp :checks.getResponsesChecks())
{
obj.put("IdResponse",resp.getIdResponsesCHeck());
obj.put("DateResponse",resp.getDateResponse());
obj.put("Conformite",resp.isConformite());
obj.put("IdMission",resp.getRespmission().getIdMission());
}
}
}
return (JSONObject)obj;
}
-My java classes:
-我的java类：
@Entity
public class CheckLists implements Serializable{
@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
@Column(name="idCheckLists")
private long idCheckLists;
@Column(name="titreCheck")
private String titreCheck;
@Column(name="recommendation")
private String recommendation;
@ManyToOne(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
@JoinColumn(name="equipements_id")
@JsonBackReference
private Equipements equipements;
@OneToMany(mappedBy="CheckLts", cascade=CascadeType.ALL, fetch=FetchType.EAGER)
//@Fetch(value = FetchMode.SUBSELECT)
private Set<ResponsesCheckLists> ResponsesChecks;
..
}
//
@Entity
public class ResponsesCheckLists implements Serializable{
@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
@Column(name="idResponsesCHeck")
private long idResponsesCHeck;
@Column(name="conformite")
private boolean conformite;
@Column(name="dateResponse")
private String dateResponse;
@ManyToOne
@JoinColumn(name="missionsId")
private Missions Respmission;
@ManyToOne
@JoinColumn(name="checkLists_Id")
private CheckLists CheckLts;
....
}
//
@Entity
public class Equip implements Serializable{
@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
@Column(name="idEquipements")
private long idEquipements;
@Column(name="nomEq")
private String nomEq;
@Column(name="dateAjoutEq")
private String dateAjoutEq;
@Column(name="dateModificationEq")
private String dateModificationEq;
@OneToMany(mappedBy="equipements", cascade=CascadeType.ALL, fetch=FetchType.EAGER)
//@Fetch(value = FetchMode.SUBSELECT)
@JsonManagedReference
private Set<CheckLists> checks;
@ManyToOne
@JoinColumn(name="actifs_id")
private Actifs actifsEquipements;
}
I want to format the result of my SQl query in Json format.
Here is what the SQL query returns query.getResultList():
我想以 Json 格式格式化我的 SQl 查询的结果。这是 SQL 查询返回的内容query.getResultList()：
[
[
1,
"2.1 Create Separate Partition ",
"Description.... ",
1,
false,
"25/05/2017",
15
],
[
2,
"2.2 Set nodev option ",
" Description:.... ",
1,
false,
"25/05/2017",
15
]
......
]
could anyone mind giving some advice for me?
谁能介意给我一些建议？
Thanks a lot!!!
非常感谢！！！
回答by cн?dk
Your query is returning a Listof Object[]because you aren't selecting an EquipEntity, but you are only selecting columns in :
您的查询返回 a ListofObject[]因为您没有选择Equip实体，但您只选择了中的列：
Query query = manager.createNativeQuery("SELECT"
+ " checksl.id_check_lists as IdCheckLists,"
+ " checksl.titre_check as NomCheckLists,"
+ " checksl.recommendation as Recommendation, "
+ " resp.id_responsescheck as IdResponse, "
+ " resp.conformite as Conformite, "
+ " resp.date_response as DateResponse, "
+ " resp.missions_id as IdMission "
Hibernate won't convert the ResultSetresults to an Equipentity object, the result will be an array of objects because Hibernate won't determine the types of selected columns.
Hibernate 不会将ResultSet结果转换为Equip实体对象，结果将是objects的数组，因为 Hibernate 不会确定所选列的类型。
You need to loop over this Listelements and transform each Object[]to an Equipobject manually.
您需要遍历这些List元素并手动将每个元素转换Object[]为一个Equip对象。
Edit:
编辑：
This is how you should implement it:
这是你应该如何实现它：
List<Object[]> res = query.getResultList();
List<Equip> list= new ArrayList<Equip>();
JSONObject obj = new JSONObject();
Iterator it = res.iterator();
while(it.hasNext()){
Object[] line = it.next();
Equip eq = new Equip();
eq.setIdEquipement(line[0]);
eq.setTitre(line[1]);
eq.setDescription(line[2]);
//And set all the Equip fields here
//And last thing add it to the list
list.add(eq);
}
回答by Michael1
My problem is solved through the use of the List: using the following code:
我的问题是通过使用 List: 解决的，代码如下：
List<Object[]> res = query.getResultList();
List<Equip> list= new ArrayList<Equip>();
Iterator it = res.iterator();
while(it.hasNext()){
Object[] line = it.next();
Equip eq = new Equip();
eq.setIdEquipement(line[0]);
eq.setTitre(line[1]);
eq.setDescription(line[2]);
list.add(eq);
}
We return afterwards list
之后我们回来 list
回答by Mike Adamenko
query.getResultList()returns List<Object[]>
query.getResultList()回报 List<Object[]>
So you can either use JPA query to return List<Equip>or
因此，您可以使用 JPA 查询返回List<Equip>或
From JPA 2.0
从 JPA 2.0
use mapped entities (as Jure Kolenko said)
使用映射实体（如 Jure Kolenko 所说）
createNativeQuery(sql, Equip.class)
From JPA 2.1
从 JPA 2.1
If you want map your result to POJO class use SqlResultSetMapping
如果要将结果映射到 POJO 类，请使用SqlResultSetMapping
Example:
Query q = em.createNativeQuery( "SELECT o.id AS order_id, " + "o.quantity AS order_quantity, " + "o.item AS order_item, " + "i.name AS item_name, " + "FROM Order o, Item i " + "WHERE (order_quantity > 25) AND (order_item = i.id)", "OrderResults"); @SqlResultSetMapping(name="OrderResults", entities={ @EntityResult(entityClass=com.acme.Order.class, fields={ @FieldResult(name="id", column="order_id"), @FieldResult(name="quantity", column="order_quantity"), @FieldResult(name="item", column="order_item")})}, columns={ @ColumnResult(name="item_name")} )
例子：
Query q = em.createNativeQuery( "SELECT o.id AS order_id, " + "o.quantity AS order_quantity, " + "o.item AS order_item, " + "i.name AS item_name, " + "FROM Order o, Item i " + "WHERE (order_quantity > 25) AND (order_item = i.id)", "OrderResults"); @SqlResultSetMapping(name="OrderResults", entities={ @EntityResult(entityClass=com.acme.Order.class, fields={ @FieldResult(name="id", column="order_id"), @FieldResult(name="quantity", column="order_quantity"), @FieldResult(name="item", column="order_item")})}, columns={ @ColumnResult(name="item_name")} )
@FieldResultis the field from your Entity class
@FieldResult是来自您的实体类的字段
@ColumnResultis the result column from your ResultList that not exist into the your Entity class
@ColumnResult是您的 ResultList 中不存在于您的实体类中的结果列
See complete example here
在此处查看完整示例
