带 getter 但不带 setter 的休眠实体属性：PropertyNotFoundException

Question

I would like to have a entity attribute that hibernate saves to a database, but does not try to set when it reconstructs the object.

I have a class like this;

@Entity
class Quote {
    private int itemCost;
    private int quantity;

    public Quote(int itemCost, int quantity) {
        this.itemCost = itemCost;
        this.quantity = quantity;
    }

    public void setItemCost(int itemCost) {
        this.itemCost = itemCost;
    }

    public void setQuantity(int quantity) {
        this.quantity = quantity;
    }

    public int getItemCost() {
        return this.itemCost;
    }

    public int getQuantity() {
        return this.quantity;
    }

    // This attribute "totalCost" has a getter only, no setter. 
    // It causes a runtime error (see below). 
    public int getTotalCost() {
        return this.itemCost * this.quantity;
    }
}

I would like the following database table;

quotes
itemCost   | quantity    | totalCost
------------------------------------
100        | 7           | 700
10         | 2           | 20
6          | 3           | 18

As you can see, the field "totalCost" can be taken from getTotalCost() , but I do not want to have a setTotalCost() method, in my application it would make no sense.

The reason that I would like a field written to a database that is not set again, is so this value is available to other applications that share the database (namely, the graphical interface).

Obviously, at runtime I currently get this error:

org.hibernate.PropertyNotFoundException: Could not find a setter for property totalCost in class Quote

I could have an empty setter, but this is unclean. In my real code there are about 13 "read only" attributes like this, I don't want 13 blank setters cluttering up my code.

Is there an elegant solution to this?

Answer 1

See Does Hibernate always need a setter when there is a getter? :

On the class use

@Entity(access = AccessType.FIELD) and annotate your attributes.

or

You can use the @Transient annotation to mark the field that it shouldn't be stored in the database. You can even use the @Formula annotation to have Hibernate derive the field for you (it does this by using the formula in the query it sends to the database).