java - Repository Inheritance -

i create repository performs basic crud operations.

since have different kind of photos (companyphoto, carphoto, ..), prefer make jpa repository generic, ejb service well.

here classes:

    @entity     @inheritance     @discriminatorcolumn(name = "descriminator")     @table(name = "photos")     public abstract class photo {         public photo() {         }          public photo(string filename) {             this.filename = filename;     //      this.file = file;         }          @id         @generatedvalue(strategy = generationtype.table, generator = "photos_seq")         @tablegenerator(name = "photos_seq", table = "sequence", pkcolumnname = "seq_name", pkcolumnvalue = "photos_seq", valuecolumnname = "seq_count", allocationsize = 50)         @column(nullable = false)         private long id;          @column(length = 255)         @size(min = 0, max = 255, message = "{photo.description.size}")         protected string description;          @column(nullable = false, length = 255)         @notnull(message = "{photo.filename.notnull}")         @size(min = 1, max = 255, message = "{photo.filename.size}")         protected string filename;          // ...  @entity @discriminatorvalue("c") public class carphoto extends photo {      public carphoto() {      }      public carphoto(string filename) {         super.filename = filename;     }      @manytoone(cascade = { cascadetype.detach })     @joincolumn(name = "carid", nullable = false)     @notnull     private car car;         // ...  @entity @discriminatorvalue("p") public class personphoto extends photo {      public personphoto() {      }      public personphoto(string filename) {         super.filename = filename;     }      @manytoone(cascade = { cascadetype.detach })     @joincolumn(name = "personid", nullable = false)     @notnull     private person person;         // ...  @stateless @localbean public class photorepository<e> {          // in class create, remove, update , basic find       //operations..       @persistencecontext     private entitymanager em;      public photorepository() {     }      photorepository(entitymanager em) {         this.em = em;     }      @override     public e create(e photo) {         em.persist(photo);         return photo;     }      @override     public e modify(e photo)     {         class<e> photoclass;                 // question: how going call getid() method object of type e  class?         em.find(photoclass, photo.getid()); // not work.. =(         e mergedphoto = em.merge(photo);         return mergedphoto;     }         // ... 

i hope understand want perform. generic repository different kind of classes inherit same baseclass. can give me best practices examples? =)

best regards

change generics definition e has type extends photo. able access methods of photo class on variables of type e

@stateless @localbean public class photorepository<e extends photo> { 

you can use following method retrieve actual class.

public class getentityclass() {   parameterizedtype parameterizedtype =     (parameterizedtype) getclass().getgenericsuperclass();  return (class) parameterizedtype.getactualtypearguments()[0]; } 

ir using spring should take @ spring-data-jpa - provides such generic repositories implementation.