我正在嘗試對不同的服務實現進行通用處理，但我經常收到“由于原始類型而導致未檢查的調用”錯誤。我嘗試了幾種實現，但不太明白這里的問題是什么。我有以下模型：public abstract class Fruit { public List<String> vitamins; public String originCountry; // getters and setters omitted}具體實現如下：public class Kiwi extends Fruit {}public class Pineapple extends Fruit {}我有以下界面：public interface FruitCheckService<T extends Fruit> { List<String> compareVitaminsFromDifferentCountries(T firstFruit, T secondFruit); Class<T> getImplementation();}對于上面給出的 2 個模型的實現：@Servicepublic class KiwiCheckServiceImpl implements FruitCheckService<Kiwi> { @Override public List<String> compareVitaminsFromDifferentCountries(Kiwi firstFruit, Kiwi secondFruit) { // some implementation return new ArrayList<>(); } @Override public Class<Kiwi> getImplementation() { return Kiwi.class; }}還有菠蘿：@Servicepublic class PineappleCheckServiceImpl implements FruitCheckService<Pineapple> { @Override public List<String> compareVitaminsFromDifferentCountries(Pineapple firstFruit, Pineapple secondFruit) { // some implementation return new ArrayList<>(); } @Override public Class<Pineapple> getImplementation() { return Pineapple.class; }}我有以下類正在使用不同的 bean 進行操作：@Servicepublic class FruitServices { private Map<Class, FruitCheckService> beansMap; @Autowired public FruitServices(List<FruitCheckService> fruitCheckServices) { beansMap = new HashMap<>(); fruitCheckServices .forEach( fruitCheckService -> { Class implementation = fruitCheckService.getImplementation(); beansMap.put(implementation, fruitCheckService); } ); } public FruitCheckService getFruitCheckService(Class clazz) { return beansMap.get(clazz); }}
1 回答
POPMUISE
TA貢獻1765條經驗 獲得超5個贊
問題是您Class在服務定義中使用原始類型。要解決此問題，您可以使用有界通配符類型 ?，如下所示：
class FruitServices {
private Map<Class<? extends Fruit>, FruitCheckService<? extends Fruit>> beansMap;
public FruitServices(List<FruitCheckService<? extends Fruit>> fruitCheckServices) {
beansMap = new HashMap<>();
fruitCheckServices
.forEach(
fruitCheckService -> {
Class<? extends Fruit> implementation = fruitCheckService.getImplementation();
beansMap.put(implementation, fruitCheckService);
}
);
}
public FruitCheckService<? extends Fruit> getFruitCheckService(Class<? extends Fruit> clazz) {
return beansMap.get(clazz);
}
}
對于課堂來說，BusinessService事情會變得更加棘手。首先，有必要制定compareVitamins一個通用方法來確保兩個水果屬于同一類型。但即使那樣，我也不相信你可以避免 unchecked cast from the result，getFruitCheckService因為，由于FruitServices必須處理不同類型水果的服務，你不能為 的返回值提供精確的類型參數getFruitCheckService。
class BusinessService {
private FruitServices fruitServices;
public <T extends Fruit> void compareVitamins(T one, T two) {
@SuppressWarnings("unchecked")
FruitCheckService<T> fruitCheckService =
(FruitCheckService<T>) fruitServices.getFruitCheckService(one.getClass());
List<String> result = fruitCheckService.compareVitaminsFromDifferentCountries(one, two);
}
}
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