When using JPA you should implement equals() and hashCode() if you
- Intend to put instances of persistent classes in a Set.
- Intend to use reattachment of detached instances.
For JDK 7 and above, you can use the new java.util.Objects class to generate the equals and hash code values.
import java.util.Objects;
public class Fruit {
private Long id;
private String name;
private int weight;
@Override
public boolean equals(Object obj) {
if (obj == this) {
return true;
}
if (!(obj instanceof Fruit)) {
return false;
}
Fruit fruit = (Fruit) obj;
return Objects.equals(id, fruit.id) && Objects.equals(name, fruit.name) && Objects.equals(weight, fruit.weight);
}
@Override
public int hashCode() {
return Objects.hash(id, name, weight);
}
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getWeight() {
return weight;
}
public void setWeight(int weight) {
this.weight = weight;
}
}
Test code
Fruit fruit1 = new Fruit();
fruit1.setId(78L);
fruit1.setName("apple");
fruit1.setWeight(35);
Fruit fruit2 = new Fruit();
fruit2.setId(78L);
fruit2.setName("apple");
fruit2.setWeight(35);
assertTrue(fruit1.equals(fruit2));
assertFalse("Not same instance", fruit1 == fruit2);
assertThat(fruit1, is(equalTo(fruit2)));
