[Javalist] Generics kerdes

[János Háber]

Es most mar tudjuk, miert nem megyek el tanarnak :D

2012/5/9 János Háber <janos.haber at javaportal.hu>:
> bar a kod kicsit kusza, mivel gondolom valami html szuro kivette a <>
> kozti reszt. De logikus hogy nem fog menni.
>
> D tipust varsz vissza ami kiterjeszti DAOB<P>,t theat abbolszarmazik,
> viszont pelda nyosiraskor "csak" DAOB<P>-t csinalsz (ami "kevesebb"
> mint D)
>
> Tehat minden D -> DAOB<P> de nem minden DAOB<P> D
> :DDD
>
> Ezert nem tudsz DAOB<P>-t returnolni ott ahol D-t varsz.
>
>
>
> On Wed, May 9, 2012 at 10:56 AM, zamek <zamek at vili.pmmf.hu> wrote:
>> hello,
>>
>> Kicsit beletekeredtem a generics-be :(
>>
>> Csinaltam egy kivonatot, hogy egyben latsszon a problema.
>>
>> Van egy POJO hierarchia, amit egy Dao hierarchia tud feldolgozni. Ehhez
>> szeretnek egy factory hierarchiat is csinalni. Minden ok, kiveve a
>> DAOBFactory-t, aminel a fordito hibat dob.
>>
>> Van valakinek otlete, hogy lehet megoldani ezt?
>>
>>
>> itt a kod:
>>
>> import java.util.Map;
>>
>> public class Q {
>>
>>    interface POJO { int asd();    }
>>
>>    abstract class AbstractPOJO implements POJO { }
>>
>>    class POJOA extends AbstractPOJO {
>>        @Override public int asd() { return 1; }
>>        public int pojoAValue() { return 1; }
>>    }
>>
>>    class POJOB extends AbstractPOJO {
>>            @Override public int asd() { return 2; }
>>            public int pojoBValue() { return 2; }
>>    }
>>
>>    class POJOC extends POJOB {
>>        @Override public int asd() {    return 3; }
>>        public int pojoCValue() { return 3; }
>>    }
>>
>>    interface DAO<P extends POJO> {
>>        P getPojo();
>>        void setPojo(P pojo);
>>        void update();
>>    }
>>
>>    abstract class AbstractDAO<P extends POJO> implements DAO<P> {
>>        P pojo;
>>        @Override public P getPojo() { return this.pojo;    }
>>        @Override public void setPojo(P pojo) {    this.pojo = pojo; }
>>    }
>>
>>    class DAOA<P extends POJOA> extends AbstractDAO<P> {
>>
>>        @Override
>>        public void update() {
>>            System.out.println(String.format("in daoa pojoa value is %d",
>> this.getPojo().pojoAValue())); //$NON-NLS-1$
>>        }
>>
>>    }
>>
>>    class DAOB<P extends POJOB> extends AbstractDAO<P> {
>>        @Override
>>        public void update() {
>>            System.out.println(String.format("in daob pojob value is %d",
>> this.getPojo().pojoBValue())); //$NON-NLS-1$
>>        }
>>    }
>>
>>    class DAOC<P extends POJOC> extends DAOB<P> {
>>        @Override
>>        public void update() {
>>            System.out.println(String.format("in daoa pojoc value is %d",
>> this.getPojo().pojoCValue())); //$NON-NLS-1$
>>        }
>>    }
>>
>>    abstract class AbstractFactory<T> {
>>        T target;
>>        abstract T createTarget(Node n);
>>        T getTarget() { return this.target; }
>>        void processParam(Node n) {    }
>>    }
>>
>>    abstract class AbstractDaoFactory<D extends AbstractDAO<P>, P extends
>> POJO> extends AbstractFactory<D> {    }
>>
>>    class DAOAFactory extends AbstractDaoFactory<DAOA<POJOA>, POJOA> {
>>        @Override DAOA<POJOA> createTarget(Node n) { return new DAOA<>(); }
>>    }
>>
>>    class DAOBFactory<D extends DAOB<P>, P extends POJOB> extends
>> AbstractDaoFactory<D, P> {
>>
>>        @Override D createTarget(Node n) { return return new DAOB<>(); } //
>> Type mismatch: cannot convert from Q.DAOB<Q.POJOB> to D
>>    }
>> -------------------------------------------------------------------------------------------------^
>>
>>    class DAOCFactory extends DAOBFactory<DAOC<POJOC>, POJOC> {
>>        @Override  DAOC<POJOC> createTarget(Node n) {    return new DAOC<>();
>> }
>>    }
>>
>>    class Store {
>>        private Map<String, DAO<? extends POJO>> store;
>>
>>        public Store() {
>>            DAOA<POJOA> daoa = new DAOA<>();
>>            this.store.put("", daoa); //$NON-NLS-1$
>>        }
>>    }
>> }
>>
>> --
>>  thx,
>> ----------------------------------
>> Zoltan Zidarics programmer
>> PTE-PMMFK H-7621 Pecs, Boszorkany u. 2. Hungary
>> E-Mail: zamek at vili.pmmf.hu
>> ----------------------------------
>>
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