Okhttp攔截器Interceptor學習和使用

OkHttpClient client = new OkHttpClient();

String run(String url) throws IOException {
Request request = new Request.Builder()
.url(url)
.build();

Response response = client.newCall(request).execute();
return response.body().string();
}

public class OkHttpClient implements Cloneable, Call.Factory, Socket/">WebSocket.Factory {
/***部分程式碼省略***/
/**
* Prepares the {@code request} to be executed at some point in the future.
*/
@Override 
public Call newCall(Request request) {
return new RealCall(this, request, false /* for web socket */);
}
}

final class RealCall implements Call {
final RetryAndFollowUpInterceptor retryAndFollowUpInterceptor;
RealCall(OkHttpClient client, Request originalRequest, boolean forWebSocket) {
final EventListener.Factory eventListenerFactory = client.eventListenerFactory();
this.client = client;
this.originalRequest = originalRequest;
this.forWebSocket = forWebSocket;
this.retryAndFollowUpInterceptor = new RetryAndFollowUpInterceptor(client, forWebSocket);
// TODO(jwilson): this is unsafe publication and not threadsafe.
this.eventListener = eventListenerFactory.create(this);
}
@Override 
public Response execute() throws IOException {
synchronized (this) {
if (executed) throw new IllegalStateException("Already Executed");
executed = true;
}
captureCallStackTrace();
try {
//進行網路請求
client.dispatcher().executed(this);
//經過一層層網路攔截器之後，獲取網路請求的返回值
Response result = getResponseWithInterceptorChain();
if (result == null) throw new IOException("Canceled");
return result;
} finally {
client.dispatcher().finished(this);
}
}
Response getResponseWithInterceptorChain() throws IOException {
// Build a full stack of interceptors.
List<Interceptor> interceptors = new ArrayList<>();
//Application攔截器
interceptors.addAll(client.interceptors());
//重定向和失敗後重新請求攔截器
interceptors.add(retryAndFollowUpInterceptor);
//網橋攔截器，顧名思義client和Server之前的橋樑
interceptors.add(new BridgeInterceptor(client.cookieJar()));
//快取處理攔截器
interceptors.add(new CacheInterceptor(client.internalCache()));
//Socket層的握手鍊接
interceptors.add(new ConnectInterceptor(client));
if (!forWebSocket) {
//網路爛攔截器
interceptors.addAll(client.networkInterceptors());
}
//client和Server之前的讀寫操作
interceptors.add(new CallServerInterceptor(forWebSocket));
//責任鏈開始執行
Interceptor.Chain chain = new RealInterceptorChain(
interceptors, null, null, null, 0, originalRequest);
return chain.proceed(originalRequest);
}
}

public interface Interceptor {
//攔截處理
Response intercept(Chain chain) throws IOException;
interface Chain {
//獲取請求的request
Request request();
//處理request獲取response
Response proceed(Request request) throws IOException;

/**
* Returns the connection the request will be executed on. This is only available in the chains
* of network interceptors; for application interceptors this is always null.
*/
@Nullable Connection connection();
}
}

HttpUrl httpurl = request.url();
//獲取request中的原始url地址
String requestUrl = httpurl.url().toString();
/**
 * 獲取url中的引數
 * @param httpUrl
 * @return
 */
private Map<String, String> getHttpUrlParams(HttpUrl httpUrl) {
Set<String> paramsSet = httpUrl.queryParameterNames();
Map<String, String> paramMap = new HashMap<>();
if (paramsSet != null && paramsSet.size() > 0) {
for (String s: paramsSet) {
paramMap.put(s, httpUrl.queryParameter(s));
}
}
return paramMap;
}
//一般POST請求引數都是放在RequestBody中,使用時需要判斷RequestBody是否為子類FormBody的例項
RequestBody requestBody = request.body();
/**
 * 獲取請求form中的引數
 * @param formBody
 * @return
 */
private Map<String, String> getHttpUrlParams(FormBody formBody) {
Map<String, String> paramMap = new HashMap<>();
if (formBody != null) {
for (int i = 0; i < formBody.size(); i++) {
paramMap.put(formBody.name(i), formBody.value(i));
}
}
return paramMap;
}
//構造新的POST表單
FormBody.Builder formBuilder = new FormBody.Builder();
for (String key: map.keySet()) {
formBuilder.add(key, map.get(key));
}
//構造新的HttpUrl，動態修改請求url地址
HttpUrl httpUrl = HttpUrl.parse(requestUrlTrue);
//構造新的request請求
request = request.newBuilder()
.method(POST, formBuilder.build())
.url(httpUrl)
.build();
//獲取相應體對應的請求體，請求和返回一一對應
Request request = response.request()
//獲取請求的相應體
ResponseBody responseBody = response.body();
//獲取返回值型別
MediaType mediaType = responseBody.contentType();
//獲取相應體重的資料流，只能獲取一次，在獲取之後資料流會關閉，再次獲取會有異常丟擲
byte[] responseBytes = responseBytes = responseBody.bytes();
//利用修改後的返回值，構造新的相應體
response = response.newBuilder()
.body(ResponseBody.create(mediaType, responseBytes))
.build();