我做了我的真实代码的简化示例,它没有编译:

public class Example {

    public static void main(String[] args) {
        Callback<BalanceResponse> balanceRequestCaller = new Callback<BalanceResponse>() {
            @Override
            public void onResponse(BalanceResponse response) {}

            @Override
            public void onFailure(String error, int code) {}

            @Override
            public void onFailure(Throwable t) {}
        };

        BalanceRequest breq = new BalanceRequest();

        Interceptor interceptor = new Interceptor(balanceRequestCaller);

        breq.startRequest((Callback<BaseResponse>) interceptor); //compile-time error!!!
    }


    public static class Interceptor implements Callback<BaseResponse> {

        public Interceptor(Callback<? extends BaseResponse> originalCaller) {
            this.originalCaller = originalCaller;
        }

        private Callback<? extends BaseResponse> originalCaller;

        @Override
        public void onResponse(BaseResponse response) {
            //do some interception stuff

            if (response instanceof BalanceResponse) {
                ((Callback<BalanceResponse>) originalCaller).onResponse((BalanceResponse) response);
            } else if (response instanceof SubscriptionResponse) {
                ((Callback<SubscriptionResponse>) originalCaller).onResponse((SubscriptionResponse) response);
            }
        }

        @Override
        public void onFailure(String error, int code) {}

        @Override
        public void onFailure(Throwable t) {}
    }

    public interface Request<T extends BaseResponse> {
        void startRequest(Callback<T> callback);
    }

    public static class BalanceRequest implements Request<BalanceResponse> {
        @Override
        public void startRequest(Callback<BalanceResponse> callback) {}
    }

    public static class SubscriptionRequest implements Request<SubscriptionResponse> {
        @Override
        public void startRequest(Callback<SubscriptionResponse> callback) {}
    }

    public static class BaseResponse {
        public String status;
    }

    public static class BalanceResponse extends BaseResponse {

    }

    public static class SubscriptionResponse extends BaseResponse {

    }

    public interface Callback<T> {
        void onResponse(T response);
        void onFailure(String error, int code);
        void onFailure(Throwable t);
    }
}

我正在尝试做的是制作一个Interceptor来拦截回调,对响应进行一些处理,然后将其传递给原始回调。

我想制作一个通用的Interceptor,它可以拦截任何是Callback<? extends BaseResponse>的回调。

顺便说一句,我从NetBeans得到的编译时错误是
incompatible types: Callback<BaseResponse> cannot be converted to Callback<BalanceResponse>

给我建议,我该如何进行这项工作?

最佳答案

您应该在类Interceptor上定义一个类型参数,以防止编译错误并避免在onResponse方法中进行显式转换,这通常是设计问题的证明。

您的Interceptor类具有类型参数:

public static class Interceptor<T extends BaseResponse> implements Callback<T> {

    public Interceptor(Callback<T> originalCaller) {
        this.originalCaller = originalCaller;
    }

    private Callback<T> originalCaller;

    @Override
    public void onResponse(T response) {
        originalCaller.onResponse(response);
    }

    ...
}

然后,您将其实例化并将其用作下一个:
Interceptor<BalanceResponse> interceptor = new Interceptor<>(balanceRequestCaller);
breq.startRequest(interceptor);

10-06 10:25
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