java - JPA: Find by Interface instead of Implementation -

i want use find method interface, instead of using implementation.

that said here code:

public goods findgoods(long goodsid) {     return this.jpaapi.withtransaction(()->{         goods goods = null;         try{             entitymanager em = this.jpaapi.em();             query query = em.createquery("select g goods g id=:id", goods.class);             query.setparameter("id", goodsid);             goods = (goods) query.getsingleresult();         }catch (exception e) {             // todo: handle exception             e.printstacktrace();         }         return goods;     }); } 

my entity:

@entity(name = "goods") @table(name = "goods") @inheritance(strategy = inheritancetype.single_table) public class goodsimp implements goods,  serializable { .. } 

my interface:

@jsontypeinfo(include = jsontypeinfo.as.property, property = "type",  use = id.name, defaultimpl = goodsimp.class, visible = true) @jsonsubtypes({ @type(value = productimp.class, name = "product"),                 @type(value = serviceimp.class, name = "service") }) @implementedby(goodsimp.class) public interface goods { .. } 

error:

java.lang.illegalargumentexception: unable locate persister: interfaces.goods @ org.hibernate.internal.sessionimpl.find(sessionimpl.java:3422) @ org.hibernate.internal.sessionimpl.find(sessionimpl.java:3365) @ repository.jpagoodsrepository.lambda$deletegoods$2(jpagoodsrepository.java:58) @ play.db.jpa.defaultjpaapi.lambda$withtransaction$3(defaultjpaapi.java:197)

my doubt why have issue, if when use query statement works fine interface.

this works:

 @override     public collection<goods> getallgoods() {         return this.jpaapi.withtransaction(() -> {             collection<goods> goods = null;             try {                 entitymanager em = this.jpaapi.em();                 query query = em.createquery("select g goods g", goods.class);                 goods = query.getresultlist();             } catch (exception e) {                 // todo: handle exception                 e.printstacktrace();             }             return goods;         });      } 

the entitymanager method createquery used declared as:

<t> typedquery<t> createquery(string qlstring, class<t> resultclass) 

the only reason class<t> resultclass parameter infer type of t, write:

list<goods> listofgoods = em.createquery("select g goods g id=:id", goods.class).getresultlist(); 

without getting compiler warnings. resultclass parameter certainly not telling entitymanager entity type querying for. done select g goods g part of query, , incidentally, goods alias entity goodsimpl (you annotate goodsimpl entity @entity(name = "bads") , select b bads b work).

now, if understand correctly, you're asking why call em.find(entityclass, primarykey) fails when goods.class used entityclass. can find answer in javadoc entitymanager, in find said throw:

illegalargumentexception - if first argument not denote entity type

an entity type is, unsuprisingly, class annotated @entity.

if you're asking why way implemented, answer pretty simple. interface can implemented several classes. suppose had multiple entity classes implementing goods, each own table , own id. there no reason ids not overlap across these different entities. how jpa supposed know of these entities you're hoping get?