[英]Java - Generalize different classes, similar methods (without changing the subclasses?)
不確定這是否可行,但我有一個案例,其中兩個接口具有相同的方法。 這些是給定的接口,所以我不能改變它們。
給定接口
interface SomeGivenService {
boolean authenticate(String username, String password);
Object someSpecialMethod(Object param);
}
interface AnotherGivenService {
boolean authenticate(String username, String password);
String aGreatMethod();
String sayHello();
}
為了使用這個服務,我創建了一個類,並在此服務拋出錯誤的情況下進行了一些處理。
class SomeGivenServiceConsumer {
SomeGivenService a;
public SomeGivenServiceConsumer(SomeGivenService a) {
this.a = a;
}
public authenticate(MyUserPassBean bean) {
try {
a.authenticate(bean.username, bean.password);
} catch (Exception e) {
throw new MyException();
}
...
}
}
class AnotherGivenServiceConsumer {
AnotherGivenService a;
public AnotherGivenServiceConsumer(AnotherGivenService a) {
this.a = a;
}
public authenticate(MyUserPassBean bean) {
try {
a.authenticate(bean.username, bean.password);
} catch (Exception e) {
throw new MyException();
}
...
}
}
我的消費者可以避免這種代碼重復嗎? 我可能會有很多,並希望避免這些重復的代碼。 我最初想過更改我的使用者以接收實現此身份驗證的接口,但由於我無法更改給定的接口,因此不確定這是否可行。
是否可以擁有“具有方法的通用接口?” 或使用一些設計模式? 有任何想法嗎? 我在嘗試什么:
class AnotherGivenServiceConsumer {
AnotherGivenService a;
GivenServiceAuthenticable b;
public AnotherGivenServiceConsumer(AnotherGivenService a,
GivenServiceAuthenticable b) {
this.a = a;
this.b = b;
}
public authenticate(MyUserPassBean bean) throws MyException {
return b.authenticate(bean.username, bean.password);
}
}
interface GivenServiceAuthenticable<T> {
boolean authenticate(T givenService, MyUserPassBean bean);
}
class GivenServiceAuthenticableImpl<T> implements GivenServiceAuthenticable<T> {
boolean authenticate(T givenService, MyUserPassBean bean) {
try {
//this won't compile as it's a generic class..
t.authenticate(bean.username, bean.password);
} catch (Exception e) {
throw new MyException();
}
...
}
}
其他問題是如果我無法更改它以實現我的新對象如何實例化此對象?
您可以使用模板模式在基類中實現通用功能,同時將單個變化行委托給子類:
abstract class ConsumerBase {
public void authenticate(MyUserPassBean bean) {
try {
authenticate(bean.username, bean.password);
} catch (Exception e) {
throw new MyException();
}
//...
}
protected abstract boolean authenticate(String username, String password);
}
class SomeGivenServiceConsumer extends ConsumerBase {
SomeGivenService a;
public SomeGivenServiceConsumer(SomeGivenService a) {
this.a = a;
}
@Override
protected boolean authenticate(String username, String password) {
return a.authenticate(username, password);
}
}
class AnotherGivenServiceConsumer extends ConsumerBase {
AnotherGivenService a;
public AnotherGivenServiceConsumer(AnotherGivenService a) {
this.a = a;
}
@Override
protected boolean authenticate(String username, String password) {
return a.authenticate(username, password);
}
}
你需要做的是使用繼承。 然后處理超類中的錯誤即
class SomeGivenServiceConsumer {
SomeGivenService a;
AnotherGivenService b;
public SomeGivenServiceConsumer(SomeGivenService a) {
this.a = a;
try{
authenticate(MyUserPassBean);
}catch (Exception e) {
System.out.println("Thrown exception has been caught : "+e.getMessage());
}
}
public authenticate(MyUserPassBean bean) throws MyException {
//your implementation here
}
}
class AnotherGivenServiceConsumer extends SomeGivenServiceConsumer{
public AnotherGivenServiceConsumer(AnotherGivenService b) {
super(someGivenService);//construct superclass
authenticate(MyUserPassBean);//call subclass authenticate method
}
@override
public authenticate(MyUserPassBean bean) throws MyException {
super.authenticate(MyUserPassBean);//call superclass method
//your implementation here
}
}
然后你構造子類:
public static void main(String[] args) {
new AnotherGivenServiceConsumer(AnotherGivenService);
}
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