CODEWITHSUNDEEP
javaeclipsejpa
Jucaalpa
Jucaalpa

Reputation: 310

Problem with Eclipse default equals() implementation

I'm having some problems with the equals method generated by Eclipse.

Suppose I have an Entity Bean with the attributes entityId and name, but I just selected for the equals generation the entityId attribute. So, the code generated by eclipse is the following:

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Entity other = (Entity) obj;
        if (entityId == null) {
            if (other.entityId != null)
                return false;
        } else if (!entityId.equals(other.entityId))
            return false;
        return true;
    }

The problem is that when comparing two different instances of the class Entity that have null as the entityId, the equals method returns true.

For me, this equals implementation is not correct (at least when using it with JPA), because two entities without an entityId are just object that are going (probably) to be persisted as new objects in a database. If I add these two objects to a Set (one to many relationship, for example), after the two insertions the Set is going to have just one element (Sets don't allow duplicates).

So, the question is why Eclipse generates the equals method like this? Do you think is better to implement the equals method with the following code?

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Entity other = (Entity) obj;
        if (entityId == null) {
            if (other.entityId != null)
                return false;
            else 
                return true;
        } else if (!entityId.equals(other.entityId))
            return false;
        return true;
    }

Upvotes: 0

Views: 163

Answers (1)

talex
talex

Reputation: 20455

Eclipse simply doesn't know about how you will use your class.

Usually if fields have equal values objects considered equal

class Human {
    String name;
    String petName;
}

Human("Bob", null) is equal to Human("Bob", null).

You case is somewhat special, so you have to made adjustment by yourself.

Upvotes: 2

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