Question

服务器发送给我json对象，expiration和ETAg ..我想Voley在缓存中保存这个对象，并在下一个请求中使用该对象请求到服务器，包括标题中的ETag。如果响应将是304 Not Modified，那么它应该使用缓存资源，如果它是200 OK，它应该使用来自服务器的新资源。

Volley根本不发送请求（如果缓存未过期），或者它已过期，它会发送带有If-None-Match + etag字符串的新请求..并且服务器始终响应200

Answer 1

如果检测到缓存条目尚未过期，Volley将不会向服务器发出请求。以下是一些代码摘录来证明它：

// If it is completely expired, just send it to the network.
if (entry.isExpired()) {
    request.addMarker("cache-hit-expired");
    request.setCacheEntry(entry);
    mNetworkQueue.put(request);
    continue;
}

和

if (!entry.refreshNeeded()) {
    // Completely unexpired cache hit. Just deliver the response.
    mDelivery.postResponse(request, response);
} else {
    // Soft-expired cache hit. We can deliver the cached response,
    // but we need to also send the request to the network for
    // refreshing.
    request.addMarker("cache-hit-refresh-needed");
    request.setCacheEntry(entry);

    // Mark the response as intermediate.
    response.intermediate = true;

    // Post the intermediate response back to the user and have
    // the delivery then forward the request along to the network.
    mDelivery.postResponse(request, response, new Runnable() {
        @Override
        public void run() {
            try {
                mNetworkQueue.put(request);
            } catch (InterruptedException e) {
                // Not much we can do about this.
            }
        }
    });
}

您可能希望通过在max-age或Cache-Control标头设置Expires来控制服务器上的资源过期，以便在客户端调整缓存。

volley - json缓存无法正常工作

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