java - Java 中的泛型无效

Question

我有一个返回void的函数

public interface IProductService {
   void delete(String id);
}

通用方法

public interface IRequestHandler<C , R> {
    R handler(C c);
    Class<C> commandType();
}

通用接口(interface)的实现

 @Singleton
    public record DeleteProductCommandHandler(IProductService iProductService)
            implements IRequestHandler<DeleteProductCommand, Void> {


        @Override
        public Void handler(DeleteProductCommand deleteProductCommand) {
            return iProductService.delete(deleteProductCommand.id);
        }

        @Override
        public Class<DeleteProductCommand> commandType() {
            return DeleteProductCommand.class;
        }
    }

如何在 IRequestHandler<DeleteProductCommand, Void> 中使用 void这样我就可以从 iProductService.delete(deleteProductCommand.id); 映射 void

Answer 1

选项 1:

只返回null:

@Override
public Void handler(DeleteProductCommand deleteProductCommand) {
    iProductService.delete(deleteProductCommand.id);
    return null;
}

选项 2:

更新 IProductService::delete 方法以返回有意义的内容，例如像 Collection::remove 这样的 boolean 值:

public interface IProductService {
   boolean delete(String id);
}

@Singleton
public record DeleteProductCommandHandler(IProductService iProductService)
            implements IRequestHandler<DeleteProductCommand, Boolean> {

    @Override
    public Boolean handler(DeleteProductCommand deleteProductCommand) {
        return iProductService.delete(deleteProductCommand.id);
    }

    @Override
    public Class<DeleteProductCommand> commandType() {
        return DeleteProductCommand.class;
    }
}