Why should anybody put annotations on the getters or setters when using JPA to map the classes?

Question

Subject says it all... I see no advantage of people declaring annotations on the getters and/or setters so far. For me this only has the disadvantage of spreading the annotations over the class, which can make the class more unreadable.

Putting the annotations on the fields clearly reduces the amount of code to post when needing help. This is just a tiny advantage though. But putting annotations on methods would serve no purpose to me.

Answer 1

Putting annotations on methods forces JPA to access properties via methods. It makes sense when internal state of your object differs from the database schema:

@Entity
public class Employee {
    private String firstName;
    private String lastName;

    @Column(name = "EMP_NAME") // Due to legacy database schema
    public String getName() {
        return fisrtName + " " + lastName;
    }

    public void setName(String name) {
        ...
    }

    ... Getters and setters for firstName and lastName with @Transient ...
}

In JPA 2.0 you can specify access type at fine-grained level with @Access:

@Entity @Access(AccessType.FIELD)
public class Employee {
    @Access(AccessType.PROPERTY) @Column(name = "EMP_NAME")
    public String getName() { ... }
    ... other properties have field access ...
}