- HttpUrlConnection / HttpClient / OkHttp 都是Android 网络通信的类库。
- HttpClient是Apache基金会下的开源网络库，功能强大，API众多。正是因为API极多，很难兼容情况下升级维护，因此Android团队在提升优化httpClient方面的工作态度不积极。
- HttpUrlConnection是一款轻量级Http客户端，提供的API比较简单，容易使用和扩展。
- OkHttp功能更强大，不仅具有高效的请求效率，并且提供了很多开箱即用的网络疑难杂症的解决方案。
- Android 5.1 即API 22 弃用 HttpClient ; Android 6.0 即API 23 移除Apache HTTP Client ； 并推荐使用HttpUrlConnection。
- 从Android 4.4起，HttpUrlConnection内部实现使用OkHttp
HttpUrlConnection通信流程：
HttpUrlConnection对象的获取方式：
- 通过URL构造获得
->URL url = new URL(String uri);
transient URLStreamHandler handler;
public URL(){
......
static URLStreamHandler getURLStreamHandler(String protocol) {
......
} else if (protocol.equals("http")) {
handler = (URLStreamHandler)Class.
forName("com.android.okhttp.HttpHandler").newInstance();
} else if (protocol.equals("https")) {
handler = (URLStreamHandler)Class.
forName("com.android.okhttp.HttpsHandler").newInstance();
}
......
}
-> HttpURLConnection con = (HttpURLConnection) url.openConnection();
->public URLConnection openConnection() throws java.io.IOException {
return handler.openConnection(this);
}
-> @Override protected URLConnection openConnection(URL url) throws IOException {
return newOkUrlFactory(null /* proxy */).open(url);
}
-> public HttpURLConnection open(URL url) {
return open(url, client.getProxy());
}
HttpURLConnection open(URL url, Proxy proxy) {
String protocol = url.getProtocol();
OkHttpClient copy = client.copyWithDefaults();
copy.setProxy(proxy);
if (protocol.equals("http")) return new HttpURLConnectionImpl(url, copy);
if (protocol.equals("https")) return new HttpsURLConnectionImpl(url, copy);
throw new IllegalArgumentException("Unexpected protocol: " + protocol);
}
- 通过NetWork对象获取
why "com.android.okhttp" not "com.squareup.okhttp"?
jarjar.txt-https://android.googlesource.com/platform/external/okhttp/+/master/jarjar-rules.txt
rule com.squareup.** com.android.@1
rule okio.** com.android.okhttp.okio.@1
HttpHandler的openConnection()实现：
Android 6.0 newOkUrlFactory(null /* proxy */).open(url);
newOkHttpClient(null /* proxy */).open(url); //Android 不知道什么版本
OKUrlFactory :
HttpURLConnectionImpl: