okhttp 客户端何时缓存服务器响应？

Question

我在 java 中使用 okhttp 客户端 3.5.0 来缓存响应，服务器响应具有以下缓存控制标头：

缓存控制：私有，max-age=0，必须重新验证

首先我尝试进行实际的网络调用以获取服务器响应，然后在第二个请求中我想获取缓存的响应。

这是我的java代码：

HttpUrl.Builder httpUrlBuilder = HttpUrl.parse(serverUrl).newBuilder();

HttpUrl httpUrl = httpUrlBuilder.build();

Request request = new Request.Builder()
    .url(httpUrl)
    .cacheControl(new CacheControl.Builder().maxAge(1, TimeUnit.DAYS).build())
    .build();

Call call = okHttpClient.newCall(request);
call.enqueue(new Callback() {
    @Override
    public void onFailure(Call call, IOException e) {

    }

    @Override
    public void onResponse(Call call, final Response response) throws IOException {

        System.out.println("***************Response 1**************");

        System.out.println("isSucess:"+response.isSuccessful());

        Response text = response.cacheResponse();

        System.out.println("Cached Response:" + text);

        Response networkResponse = response.networkResponse();

        System.out.println("Network Response ::" +networkResponse);

    }
});

Thread.sleep(5000);


Request request2 = new Request.Builder()
    .cacheControl(new CacheControl.Builder().onlyIfCached().build())
    .url(httpUrlBuilder.build())
    .build();


call = okHttpClient.newCall(request2);
call.enqueue(new Callback() {
    @Override
    public void onFailure(Call call, IOException e) {

    }

    @Override
    public void onResponse(Call call, final Response response) throws IOException {
        System.out.println("***********Response 2************");

        System.out.println("isSucess:" +response.isSuccessful());

        final Response text = response.cacheResponse();

        System.out.println("Cached Response:" + text);

        Response networkResponse = response.networkResponse();

        System.out.println("Network Response:" +networkResponse);

    }
});

下面是第二个请求输出：（部分输出）

***********响应 2************

成功：假

缓存响应：null

网络响应：null

我是否遗漏了什么？

Answer 1

除非您阅读并关闭响应正文，否则 OkHttp 不会缓存响应。这就是触发这些字节被下载和保存的原因。

try {
  if (response.cacheResponse() == null) {
    body.source().skip(Long.MAX_VALUE); // Exhaust response body.
  }
} finally {
  body.close();
}