前言
回顧：
Okhttp的基本用法
Okhttp3源碼解析(1)-OkHttpClient分析
Okhttp3源碼解析(2)-Request分析
Okhttp3源碼解析(3)-Call分析(整體流程)
Okhttp3源碼解析(4)-攔截器與設計模式
Okhttp3源碼解析(5)-攔截器RetryAndFollowUpInterceptor
今天講一下BridgeInterceptor，我們先看一下源碼對此類的解釋：
/**
* Bridges from application code to network code. First it builds a network request from a user
* request. Then it proceeds to call the network. Finally it builds a user response from the network
* response.
*/
意思就是從應用程序代碼到網絡代碼的橋樑
- 它從用戶請求構建成網絡請求
- 然後進行網絡請求
- 將返回的響應數據轉用戶可用的response
下面貼出BridgeInterceptor 代碼：
public final class BridgeInterceptor implements Interceptor {
private final CookieJar cookieJar;
public BridgeInterceptor(CookieJar cookieJar) {
this.cookieJar = cookieJar;
}
@Override public Response intercept(Chain chain) throws IOException {
Request userRequest = chain.request();
Request.Builder requestBuilder = userRequest.newBuilder();
RequestBody body = userRequest.body();
if (body != null) {
MediaType contentType = body.contentType();
if (contentType != null) {
requestBuilder.header("Content-Type", contentType.toString());
}
long contentLength = body.contentLength();
if (contentLength != -1) {
requestBuilder.header("Content-Length", Long.toString(contentLength));
requestBuilder.removeHeader("Transfer-Encoding");
} else {
requestBuilder.header("Transfer-Encoding", "chunked");
requestBuilder.removeHeader("Content-Length");
}
}
if (userRequest.header("Host") == null) {
requestBuilder.header("Host", hostHeader(userRequest.url(), false));
}
if (userRequest.header("Connection") == null) {
requestBuilder.header("Connection", "Keep-Alive");
}
// If we add an "Accept-Encoding: gzip" header field we're responsible for also decompressing
// the transfer stream.
boolean transparentGzip = false;
if (userRequest.header("Accept-Encoding") == null && userRequest.header("Range") == null) {
transparentGzip = true;
requestBuilder.header("Accept-Encoding", "gzip");
}
List<Cookie> cookies = cookieJar.loadForRequest(userRequest.url());
if (!cookies.isEmpty()) {
requestBuilder.header("Cookie", cookieHeader(cookies));
}
if (userRequest.header("User-Agent") == null) {
requestBuilder.header("User-Agent", Version.userAgent());
}
Response networkResponse = chain.proceed(requestBuilder.build());
HttpHeaders.receiveHeaders(cookieJar, userRequest.url(), networkResponse.headers());
Response.Builder responseBuilder = networkResponse.newBuilder()
.request(userRequest);
if (transparentGzip
&& "gzip".equalsIgnoreCase(networkResponse.header("Content-Encoding"))
&& HttpHeaders.hasBody(networkResponse)) {
GzipSource responseBody = new GzipSource(networkResponse.body().source());
Headers strippedHeaders = networkResponse.headers().newBuilder()
.removeAll("Content-Encoding")
.removeAll("Content-Length")
.build();
responseBuilder.headers(strippedHeaders);
String contentType = networkResponse.header("Content-Type");
responseBuilder.body(new RealResponseBody(contentType, -1L, Okio.buffer(responseBody)));
}
return responseBuilder.build();
}
/** Returns a 'Cookie' HTTP request header with all cookies, like {@code a=b; c=d}. */
private String cookieHeader(List<Cookie> cookies) {
StringBuilder cookieHeader = new StringBuilder();
for (int i = 0, size = cookies.size(); i < size; i++) {
if (i > 0) {
cookieHeader.append("; ");
}
Cookie cookie = cookies.get(i);
cookieHeader.append(cookie.name()).append('=').append(cookie.value());
}
return cookieHeader.toString();
}
}
BridgeInterceptor初始化方法中也實例了cookieJar，cookieJar代碼如下：
public interface CookieJar {
/** A cookie jar that never accepts any cookies. */
CookieJar NO_COOKIES = new CookieJar() {
@Override public void saveFromResponse(HttpUrl url, List<Cookie> cookies) {
}
@Override public List<Cookie> loadForRequest(HttpUrl url) {
return Collections.emptyList();
}
};
/**
* Saves {@code cookies} from an HTTP response to this store according to this jar's policy.
*
* <p>Note that this method may be called a second time for a single HTTP response if the response
* includes a trailer. For this obscure HTTP feature, {@code cookies} contains only the trailer's
* cookies.
*/
void saveFromResponse(HttpUrl url, List<Cookie> cookies);
/**
* Load cookies from the jar for an HTTP request to {@code url}. This method returns a possibly
* empty list of cookies for the network request.
*
* <p>Simple implementations will return the accepted cookies that have not yet expired and that
* {@linkplain Cookie#matches match} {@code url}.
*/
List<Cookie> loadForRequest(HttpUrl url);
}
發現cookieJar就是個接口，裏面有兩個方法：
- saveFromResponse 自定義去存儲
cookie - loadForRequest 獲取指定URL的
cookie
我們在請求時需要配置一些東西，例如header等等，例如下圖：
這就很好理解了吧？我們繼續看BridgeInterceptor源碼：
所以BridgeInterceptor 第一步就是給rquest設置header等配置，這塊主要強調的是：
List<Cookie> cookies = cookieJar.loadForRequest(userRequest.url());
if (!cookies.isEmpty()) {
requestBuilder.header("Cookie", cookieHeader(cookies));
}
我們可以調用loadForRequest獲取我們自定義的cookie ，設置到header中。
設置之後，進行網絡請求：
Response networkResponse = chain.proceed(requestBuilder.build());
很熟悉了，這裏就不講了。
最後就是將返回的networkResponse 轉用戶可用的response ，這裏需要注意的是：
1.接收header信息，存儲cookie：
HttpHeaders.receiveHeaders(cookieJar, userRequest.url(), networkResponse.headers());
public static void receiveHeaders(CookieJar cookieJar, HttpUrl url, Headers headers) {
if (cookieJar == CookieJar.NO_COOKIES) return;
List<Cookie> cookies = Cookie.parseAll(url, headers);
if (cookies.isEmpty()) return;
cookieJar.saveFromResponse(url, cookies);
}
gzip解壓
如果服務器返回的networkResponse 是壓縮過的，需要GzipSource解壓，讀取response
if (transparentGzip
&& "gzip".equalsIgnoreCase(networkResponse.header("Content-Encoding"))
&& HttpHeaders.hasBody(networkResponse)) {
GzipSource responseBody = new GzipSource(networkResponse.body().source());
Headers strippedHeaders = networkResponse.headers().newBuilder()
.removeAll("Content-Encoding")
.removeAll("Content-Length")
.build();
responseBuilder.headers(strippedHeaders);
String contentType = networkResponse.header("Content-Type");
responseBuilder.body(new RealResponseBody(contentType, -1L, Okio.buffer(responseBody)));
}
這節就說到這，希望對大家有所幫助…
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