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OkHttp源码解析(二)

news 2025/10/15 10:17:59

五大拦截器

一、重定向与重试拦截器

catch (IOException e) {// todo 请求发出去了，但是和服务器通信失败了。(socket 流正在读/写数据时断开连接)// HTTP/2 才会抛出 ConnectionShutdownException，所以对于 HTTP/1，requestSendStarted 一定是 trueboolean requestSendStarted = !(e instanceof ConnectionShutdownException);if (!recover(e, streamAllocation, requestSendStarted, request)) {throw e;}releaseConnection = false;continue;
}

两个异常都是根据 recover 方法判断是否能够进行重试，如果返回 true ，则表示允许重试。

private boolean recover(IOException e,StreamAllocation streamAllocation,boolean requestSendStarted,Request userRequest) {streamAllocation.streamFailed(e);// todo 1. 如果在 OkHttpClient 配置中关闭了重试（默认允许），则失败后不再重试if (!client.retryOnConnectionFailure()) return false;// todo 2. 如果是 RouteException 不用看这个条件；// 如果是 IOException，且请求体不可重复，则不能重试if (requestSendStarted && userRequest.body() instanceof UnrepeatableRequestBody) {return false;}// todo 3. 判断异常是否属于可重试的异常if (!isRecoverable(e, requestSendStarted)) return false;// todo 4. 是否还有可用的路由路径if (!streamAllocation.hasMoreRoutes()) return false;// 失败恢复时，使用相同的路由选择器并建立新连接return true;
}

1、协议异常，如果是那么直接判定不能重试;（你的请求或者服务器的响应本身就存在问题，没有按照http协议来定义数据，再重试也没用）

2、超时异常，可能由于网络波动造成了Socket连接的超时，可以使用不同路线重试。

3、SSL证书异常/SSL验证失败异常，前者是证书验证失败，后者可能就是压根就没证书，或者证书数据不正确，那还怎么重试？

经过了异常的判定之后，如果仍然允许进行重试，就会再检查当前有没有可用路由路线来进行连接。简单来说，比如 DNS 对域名解析后可能会返回多个 IP，在一个IP失败后，尝试另一个IP进行重试。

private Request followUpRequest(Response userResponse) throws IOException {if (userResponse == null) throw new IllegalStateException();Connection connection = streamAllocation.connection();Route route = connection != null ? connection.route() : null;int responseCode = userResponse.code();final String method = userResponse.request().method();switch (responseCode) {// 407 代理认证case HTTP_PROXY_AUTH: {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);}// 401 服务器认证case HTTP_UNAUTHORIZED:return client.authenticator().authenticate(route, userResponse);// 308/307 保持方法case HTTP_PERM_REDIRECT:case HTTP_TEMP_REDIRECT: {if (!method.equals("GET") && !method.equals("HEAD")) return null;// fall-through 到重定向处理}// 300/301/302/303 各类重定向case HTTP_MULT_CHOICE:case HTTP_MOVED_PERM:case HTTP_MOVED_TEMP:case HTTP_SEE_OTHER: {if (!client.followRedirects()) return null;String location = userResponse.header("Location");if (location == null) return null;HttpUrl url = userResponse.request().url().resolve(location);if (url == null) return null;// 跨 Scheme 的重定向是否允许boolean sameScheme = url.scheme().equals(userResponse.request().url().scheme());if (!sameScheme && !client.followSslRedirects()) return null;Request.Builder requestBuilder = userResponse.request().newBuilder();// 是否保留请求体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");}}// 跨主机时移除认证头if (!sameConnection(userResponse, url)) {requestBuilder.removeHeader("Authorization");}return requestBuilder.url(url).build();}// 408 客户端超时case HTTP_CLIENT_TIMEOUT: {if (!client.retryOnConnectionFailure()) return null;if (userResponse.request().body() instanceof UnrepeatableRequestBody) return null;// 如果前一个响应也是 408，则不再重试if (userResponse.priorResponse() != null&& userResponse.priorResponse().code() == HTTP_CLIENT_TIMEOUT) {return null;}// Respect Retry-Afterif (retryAfter(userResponse, 0) > 0) return null;return userResponse.request();}// 503 服务不可用case HTTP_UNAVAILABLE: {if (userResponse.priorResponse() != null&& userResponse.priorResponse().code() == HTTP_UNAVAILABLE) {return null;}if (retryAfter(userResponse, Integer.MAX_VALUE) == 0) {return userResponse.request();}return null;}default:return null;}
}private boolean sameConnection(Response response, HttpUrl url) {HttpUrl priorUrl = response.request().url();return priorUrl.host().equals(url.host())&& priorUrl.port() == url.port()&& priorUrl.scheme().equals(url.scheme());
}private int retryAfter(Response response, int defaultDelaySeconds) {String header = response.header("Retry-After");if (header == null) return defaultDelaySeconds;// 仅支持秒的简单实现；非法值按很大值处理表示不应立刻重试try {return Integer.parseInt(header.trim());} catch (NumberFormatException ignore) {return Integer.MAX_VALUE;}
}