java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to

Question

why java.lang.ClassCastException is triggered in my program ?

java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to 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

-Here is the code:

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:

@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():

[
   [
    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?

Thanks a lot!!!

What is Equip? What is Query? are you using some library? The main problem is, probably, that the list returned by query.getResultList(); has pure Object elements which cannot be cast to Equip, a reference to the classes you are using is necessary to understand the real problem. — bracco23
– bracco23, Commented May 31, 2017 at 12:50
In this line for( Equip eq: res) //--The problem is here -- — Michael1
– Michael1, Commented May 31, 2017 at 12:50
Your query is returning an Object. Use the createNativeQuery(String sqlString, Class resultClass) method with a class parameter, eg createNativeQuery(sql, Equip.class). This might not work if query return column names don't map to the entity class. — Jure Kolenko
– Jure Kolenko, Commented May 31, 2017 at 12:51

cнŝdk · Accepted Answer · 2017-05-31 13:39:02Z

10

Your query is returning a List of Object[] because you aren't selecting an Equip Entity, but you are only selecting columns in :

   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 ResultSet results to an Equip entity object, the result will be an array of objects because Hibernate won't determine the types of selected columns.

You need to loop over this List elements and transform each Object[] to an Equip object manually.

Edit:

This is how you should implement it:

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);
}

edited May 31, 2017 at 13:39

answered May 31, 2017 at 13:03

cнŝdk

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5 Comments

Michael1 Over a year ago

How to get the text in Object [] and display it like this { "idEquipement":"1", "titre":2.1 Create Separate Partition , "description":"Description: ......", }

cнŝdk Over a year ago

You need to lop over this array of objects.

Michael1 Over a year ago

how @chsdk,? I am a beginner in java

cнŝdk Over a year ago

@Michel Check my eDit.

Michael1 Over a year ago

Thanks for your reply @ chsdk , i will test now

Michael1 · Accepted Answer · 2017-05-31 17:51:29Z

2

My problem is solved through the use of the List: using the following code:

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

edited May 31, 2017 at 17:51

answered May 31, 2017 at 17:45

Michael1

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Comments

barbsan · Accepted Answer · 2019-05-22 08:12:54Z

0

query.getResultList() returns List<Object[]>

So you can either use JPA query to return List<Equip> or

From JPA 2.0

use mapped entities (as Jure Kolenko said)

createNativeQuery(sql, Equip.class)

From JPA 2.1

If you want map your result to POJO class use 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")}
)

@FieldResult is the field from your Entity class

@ColumnResult is the result column from your ResultList that not exist into the your Entity class

See complete example here

edited May 22, 2019 at 8:12

barbsan

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answered May 31, 2017 at 13:03

Mike Adamenko

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4 Comments

Michael1 Over a year ago

I did not understand what this line is: @ColumnResult(name="item_name")} @Mike Adamenko

Vikrant Kashyap Over a year ago

@MikeAdamenko isn't it only copy paste from this url -- >> docs.oracle.com/javaee/7/api/javax/persistence/… Need to delete this..

barbsan Over a year ago

@VikrantKashyap this example is rather copied from url link SqlResultSetMapping right above the example

Ajay Takur Over a year ago

complete example here link is broken

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