前言
今天讲一下BridgeInterceptor，我们先看一下源码对此类的解释：
/**
* 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.
*/
意思就是从应用程序代码到网络代码的桥梁
- 它从用户请求构建成网络请求
- 然后进行网络请求
- 将返回的响应数据转用户可用的response
下面贴出BridgeInterceptor 代码：
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初始化方法中也实例了cookieJar，cookieJar代码如下：
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);
}
发现cookieJar就是个接口，里面有两个方法：
- saveFromResponse 自定义去存储
cookie - loadForRequest 获取指定URL的
cookie
我们在请求时需要配置一些东西，例如header等等，例如下图：
这就很好理解了吧？我们继续看BridgeInterceptor源码：
所以BridgeInterceptor 第一步就是给rquest设置header等配置，这块主要强调的是：
List<Cookie> cookies = cookieJar.loadForRequest(userRequest.url());
if (!cookies.isEmpty()) {
requestBuilder.header("Cookie", cookieHeader(cookies));
}
我们可以调用loadForRequest获取我们自定义的cookie ，设置到header中。
设置之后，进行网络请求：
Response networkResponse = chain.proceed(requestBuilder.build());
很熟悉了，这里就不讲了。
最后就是将返回的networkResponse 转用户可用的response ，这里需要注意的是：
1.接收header信息，存储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解压
如果服务器返回的networkResponse 是压缩过的，需要GzipSource解压，读取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)));
}
这节就说到这，希望对大家有所帮助.....
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