ClassCastException while retrieving list from database using Hibernate

Question

@Id
@Column(name="Item", unique = true, nullable = false)
@GeneratedValue(strategy=GenerationType.IDENTITY)
private int itemId;

@Column(name="ItemName")
private String itemName;

@Column(name="ItemPrice")
private double itemPrice;

@Column(name="status")
private String status;

@Column(name="image")
private String image;

@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "RestaurantId", nullable = false)
private Restaurant restaurant;

this is my Entity class ,

public List<FoodItem> getFoodItems(Restaurant restaurant) {
    Session session=getSession();
    List<FoodItem> list=null;
    NativeQuery<?> query = session.createNativeQuery("SELECT " + 
            "   \"Item\"," + 
            "   \"ItemName\"," + 
            "   \"ItemPrice\"," + 
            "   \"RestaurantId\"," + 
            "   \"status\"," + 
            "   \"image\" " + 
            "FROM \"SYSTEM\".\"FoodItem\" where \"RestaurantId\"="+restaurant.getRestaurantId());
    list = (List<FoodItem>) query.getResultList();
    return  list;
}

when i run this method, it doesn't return me a List<FoodItem> instead it returns a List<Array> like this,

[
[
    1,
    "Pasta",
    55,
    14,
    "Veg",
    null
],
[
    2,
    "Burger",
    35,
    14,
    "Veg",
    null
]
]

and if i try to set the restaurant object to null in each object in the list,

for(int index=0 ;index< list.size();index++)
        list.get(index).setRestaurant(null);

i got ClassCastException. i need the response in key : value pair as per my entity class can anyone solve this for me. thanks. [update] Solved!

you are trying to fetch the list of an object using native query. I guess removing the native query will work. records which you are getting are in format of tuples — Taufik Pirjade
– Taufik Pirjade, Commented Jan 14, 2019 at 9:04

shakhawat · Accepted Answer · 2019-01-14 09:27:58Z

1

You suppose to get list of object array from the native query. It will not construct type objects out of the box for you. If you want typed list, you need to do JPQL instead of native query.

List<Object[]> listResults = query.getResultList();

Iterate over the list and construct the typed object list -

List<FoodItem> foodItems = new ArrayList();

for (Object[] record : listResults) {

       FoodItem item = new FoodItem();
       // set values from record, do necessary casts as well.

       foodItems.add(item);

  }

edited Jan 14, 2019 at 9:27

answered Jan 14, 2019 at 9:22

shakhawat

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1 Comment

Kiran S Over a year ago

This worked, I'll see about the JPQL methods. thanks.

J-Alex · Accepted Answer · 2019-01-14 09:33:27Z

0

NativeQuery has a bounded type parameter. Use it and pass expected resultClass as a second parameter for a proper generic resolution and you'll get an expected result.

NativeQuery<FoodItem> query = session.createNativeQuery("SELECT " + 
            "   \"Item\"," + 
            "   \"ItemName\"," + 
            "   \"ItemPrice\"," + 
            "   \"RestaurantId\"," + 
            "   \"status\"," + 
            "   \"image\" " + 
            "FROM \"SYSTEM\".\"FoodItem\" where \"RestaurantId\"="+restaurant.getRestaurantId(), 
            FoodItem.class);
List<FoodItem> list = query.getResultList();
return  list;

edited Jan 14, 2019 at 9:33

answered Jan 14, 2019 at 9:27

J-Alex

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1 Comment

Kiran S Over a year ago

Still the same , threw exception [Request processing failed; nested exception is java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to com.xxx.foodorder.entity.FoodItem (loaded by org.apache.catalina.loader.ParallelWebappClassLoader@0x00000001003006e8)] with root cause java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to com.xxx.foodorder.entity.FoodItem (loaded by org.apache.catalina.loader.ParallelWebappClassLoader@0x00000001003006e8)

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