据返回的缓存时间来缓存响应,可以通过使用OkHttp的CacheControl
和ResponseCacheInterceptor
来实现。以下是一个示例代码:
// 创建缓存目录和缓存对象
File cacheDirectory = new File(context.getCacheDir(), "http-cache");
int cacheSize = 10 * 1024 * 1024; // 10 MiB
Cache cache = new Cache(cacheDirectory, cacheSize);// 创建OkHttpClient实例,并添加自定义的ResponseCacheInterceptor
OkHttpClient client = new OkHttpClient.Builder().cache(cache).addNetworkInterceptor(new ResponseCacheInterceptor()).build();class ResponseCacheInterceptor implements Interceptor {@Overridepublic Response intercept(Chain chain) throws IOException {Request request = chain.request();Response originalResponse = chain.proceed(request);if (originalResponse.isSuccessful()) {// 获取服务器返回的缓存相关信息String cacheControl = originalResponse.header("Cache-Control");String expires = originalResponse.header("Expires");// 根据缓存相关信息判断是否需要缓存boolean shouldCache = shouldCacheResponse(cacheControl, expires);if (shouldCache) {// 设置缓存的有效期为服务器返回的缓存时间CacheControl cacheControlHeader = new CacheControl.Builder().maxAge(getMaxAge(cacheControl)).build();// 构建新的响应并返回Response cachedResponse = originalResponse.newBuilder().header("Cache-Control", cacheControlHeader.toString()).build();return cachedResponse;}}return originalResponse;}
}// 判断是否应该缓存响应的方法
private boolean shouldCacheResponse(String cacheControl, String expires) {if (cacheControl == null && expires == null) {return false;}// 判断缓存控制头中是否包含no-store、no-cache指令if (cacheControl != null && (cacheControl.contains("no-store") || cacheControl.contains("no-cache"))) {return false;}// 判断过期时间是否已过期if (expires != null) {try {Date expirationDate = HttpDate.parse(expires);Date currentDate = new Date();if (expirationDate != null && expirationDate.before(currentDate)) {return false;}} catch (ParseException e) {e.printStackTrace();}}return true;
}// 获取缓存的最大有效时间
private int getMaxAge(String cacheControl) {if (cacheControl != null) {CacheControl cc = CacheControl.parse(cacheControl);return cc.maxAgeSeconds();}return -1;
}
在上述示例中,我们创建了一个自定义的ResponseCacheInterceptor
拦截器,并将其添加到OkHttpClient
中。该拦截器会在每次网络请求返回响应后进行处理。
在拦截器中,我们从服务器的响应中获取Cache-Control
和Expires
头部信息,并使用shouldCacheResponse()
方法判断是否需要缓存响应。如果需要缓存,我们根据服务器返回的缓存时间构建新的响应,并设置对应的Cache-Control
头部,然后返回新的响应。