JPA - FindByExample

Question

Does anyone have a good example for how to do a findByExample in JPA that will work within a generic DAO via reflection for any entity type? I know I can do it via my prov

Answer 1

you can use this https://github.com/xiaod0510/jpa-findbyexample

if your entity is Contact:

@Entity
public class Contact {
    @Id
    @GeneratedValue
    private Long id;
    @Column
    private String name;
    @Column
    private Date birthday;
    //Getter and Setter
}
public interface ContactRepository
        extends
        JpaSpecificationExecutor {
}

just create your own Example like this:

public class ContactExample extends BaseExample {
    public final Attr id = new Attr("id");
    public final Attr name = new Attr("name");
    public final Attr birthday = new Attr("birthday");
    //default builder  
    public static ContactExample where() {
        ContactExample example = new ContactExample();
        example.operatorType = OperatorType.and;
        return example;
    }
}

and now you can query by example :

 ContactRepository.findOne(ContactExample
                    .where()//default is and
                    .id.eq(1l)
);

the example implements the interface "Specification",more information on that github