RetryAndFollowUpInterceptor
重试重定向拦截器
@Override public Response intercept(Chain chain) throws IOException {
Request request = chain.request();
RealInterceptorChain realChain = (RealInterceptorChain) chain;
Transmitter transmitter = realChain.transmitter();
int followUpCount = 0;
Response priorResponse = null;
//无限循环去重试，直到不符合条件，跳出循环或抛出异常
while (true) {
transmitter.prepareToConnect(request);
//如果已经取消就抛出异常，循环中断，链就断了
if (transmitter.isCanceled()) {
throw new IOException("Canceled");
}
Response response;
boolean success = false;
try {
//先proceed 责任链一直到拿到响应回来
response = realChain.proceed(request, transmitter, null);
success = true;
} catch (RouteException e) {
// The attempt to connect via a route failed. The request will not have been sent.
//如果是路由异常判断可否恢复，如果不可以恢复抛出异常
if (!recover(e.getLastConnectException(), transmitter, false, request)) {
throw e.getFirstConnectException();
}
//如果路由异常就跳过这一次
continue;
} catch (IOException e) {
//如果是IO异常判断是否连接关闭，并尝试恢复，如果无法恢复就抛出异常
// An attempt to communicate with a server failed. The request may have been sent.
boolean requestSendStarted = !(e instanceof ConnectionShutdownException);
if (!recover(e, transmitter, requestSendStarted, request)) throw e;
continue;
} finally {
// The network call threw an exception. Release any resources.
//如果没有成功，释放资源
if (!success) {
transmitter.exchangeDoneDueToException();
}
}
// Attach the prior response if it exists. Such responses never have a body.
//将之前的响应附加到这次上，但是不能有body
if (priorResponse != null) {
response = response.newBuilder()
.priorResponse(priorResponse.newBuilder()
.body(null)
.build())
.build();
}
Exchange exchange = Internal.instance.exchange(response);
Route route = exchange != null ? exchange.connection().route() : null;
//返回重试重定向的request
Request followUp = followUpRequest(response, route);
//如果不需要的话返回null，直接返回response
if (followUp == null) {
if (exchange != null && exchange.isDuplex()) {
transmitter.timeoutEarlyExit();
}
return response;
}
//到这里是需要重试重定向的
//只希望调用一次的就是直接返回
RequestBody followUpBody = followUp.body();
if (followUpBody != null && followUpBody.isOneShot()) {
return response;
}
//把之前的通道关闭
closeQuietly(response.body());
if (transmitter.hasExchange()) {
exchange.detachWithViolence();
}
//如果重试的次数没有超过最大值
if (++followUpCount > MAX_FOLLOW_UPS) {
throw new ProtocolException("Too many follow-up requests: " + followUpCount);
}
request = followUp;
priorResponse = response;
}
}
//可否恢复
//1.是否允许重试
//2.是否允许多次请求
//3.是否可恢复
//4.是否有更多的路由选择
private boolean recover(IOException e, Transmitter transmitter,
boolean requestSendStarted, Request userRequest) {
// The application layer has forbidden retries.
if (!client.retryOnConnectionFailure()) return false;//我们设置了不允许重试返回false
// We can't send the request body again.
if (requestSendStarted && requestIsOneShot(e, userRequest)) return false;//不允许多次请求
// This exception is fatal.
if (!isRecoverable(e, requestSendStarted)) return false;//是否可恢复
// No more routes to attempt.
if (!transmitter.canRetry()) return false;//没有更多路由选择
// For failure recovery, use the same route selector with a new connection.
return true;
}
//是否可恢复
//1.如果是协议不支持则无法恢复
//2.如果SocketTimeoutException，并且请求没开始，不可恢复
//3.如果是证书错误不可恢复
//4.证书绑定错误不可恢复
private boolean isRecoverable(IOException e, boolean requestSendStarted) {
// If there was a protocol problem, don't recover.
if (e instanceof ProtocolException) {//协议不支持恢复不了
return false;
}
// If there was an interruption don't recover, but if there was a timeout connecting to a route
// we should try the next route (if there is one).
if (e instanceof InterruptedIOException) {
return e instanceof SocketTimeoutException && !requestSendStarted;//如果超时尝试尝试下一个路由
}
// Look for known client-side or negotiation errors that are unlikely to be fixed by trying
// again with a different route.
if (e instanceof SSLHandshakeException) { //Https证书认证问题不用恢复了
// If the problem was a CertificateException from the X509TrustManager,
// do not retry.
if (e.getCause() instanceof CertificateException) {
return false;
}
}
if (e instanceof SSLPeerUnverifiedException) {//证书绑定的认证问题不用恢复了
// e.g. a certificate pinning error.
return false;
}
// An example of one we might want to retry with a different route is a problem connecting to a
// proxy and would manifest as a standard IOException. Unless it is one we know we should not
// retry, we return true and try a new route.
return true;
}
可否重试重定向
private Request followUpRequest(Response userResponse, @Nullable Route route) throws IOException {
if (userResponse == null) throw new IllegalStateException();
int responseCode = userResponse.code();
final String method = userResponse.request().method();
//处理特殊状态码 302 307 401 407等
switch (responseCode) {
case HTTP_PROXY_AUTH://407需要代理授权
Proxy selectedProxy = route != null
? route.proxy()
: client.proxy();
if (selectedProxy.type() != Proxy.Type.HTTP) {
throw new ProtocolException("Received HTTP_PROXY_AUTH (407) code while not using proxy");
}
return client.proxyAuthenticator().authenticate(route, userResponse);
case HTTP_UNAUTHORIZED://401未授权
return client.authenticator().authenticate(route, userResponse);
case HTTP_PERM_REDIRECT:
case HTTP_TEMP_REDIRECT://307 重定向
// "If the 307 or 308 status code is received in response to a request other than GET
// or HEAD, the user agent MUST NOT automatically redirect the request"
//get 和 head之外的请求方法不能重定向
if (!method.equals("GET") && !method.equals("HEAD")) {
return null;
}
// fall-through
case HTTP_MULT_CHOICE:
case HTTP_MOVED_PERM:
case HTTP_MOVED_TEMP:
case HTTP_SEE_OTHER:
// Does the client allow redirects?
if (!client.followRedirects()) return null;//我们设置了不允许重定向
String location = userResponse.header("Location");//重定向到哪里
if (location == null) return null;//null直接返回不可以重定向
HttpUrl url = userResponse.request().url().resolve(location);
// Don't follow redirects to unsupported protocols.
if (url == null) return null;
// If configured, don't follow redirects between SSL and non-SSL.
boolean sameScheme = url.scheme().equals(userResponse.request().url().scheme());
if (!sameScheme && !client.followSslRedirects()) return null;
// Most redirects don't include a request body.
Request.Builder requestBuilder = userResponse.request().newBuilder();
if (HttpMethod.permitsRequestBody(method)) {
final boolean maintainBody = HttpMethod.redirectsWithBody(method);
if (HttpMethod.redirectsToGet(method)) {
requestBuilder.method("GET", null);
} else {
RequestBody requestBody = maintainBody ? userResponse.request().body() : null;
requestBuilder.method(method, requestBody);
}
if (!maintainBody) {
requestBuilder.removeHeader("Transfer-Encoding");
requestBuilder.removeHeader("Content-Length");
requestBuilder.removeHeader("Content-Type");
}
}
// When redirecting across hosts, drop all authentication headers. This
// is potentially annoying to the application layer since they have no
// way to retain them.
if (!sameConnection(userResponse.request().url(), url)) {
requestBuilder.removeHeader("Authorization");
}
return requestBuilder.url(url).build();
case HTTP_CLIENT_TIMEOUT:
// 408's are rare in practice, but some servers like HAProxy use this response code. The
// spec says that we may repeat the request without modifications. Modern browsers also
// repeat the request (even non-idempotent ones.)
if (!client.retryOnConnectionFailure()) {
// The application layer has directed us not to retry the request.
return null;
}
RequestBody requestBody = userResponse.request().body();
if (requestBody != null && requestBody.isOneShot()) {
return null;
}
if (userResponse.priorResponse() != null
&& userResponse.priorResponse().code() == HTTP_CLIENT_TIMEOUT) {
// We attempted to retry and got another timeout. Give up.
return null;
}
if (retryAfter(userResponse, 0) > 0) {
return null;
}
return userResponse.request();
case HTTP_UNAVAILABLE:
if (userResponse.priorResponse() != null
&& userResponse.priorResponse().code() == HTTP_UNAVAILABLE) {
// We attempted to retry and got another timeout. Give up.
return null;
}
if (retryAfter(userResponse, Integer.MAX_VALUE) == 0) {
// specifically received an instruction to retry without delay
return userResponse.request();
}
return null;
default:
return null;
}
}