Interceptor 拦截器
一、概述
OkHttp 版本： 3.14.7
在 OkHttp(一) — OkHttp 调用流程分析 中，我们介绍了一个请求的调用流程。请求最后是在
RealCall.getResponseWithInterceptorChain()方法中执行的。
拦截器中 intercept() 方法的执行逻辑主要分为三部分：
- 在发起请求前对 request 进行处理。
- 调用下一个拦截器，获取 response。
- 对 Response 进行处理，并返回给上一个拦截器。
本篇文章我们来具体分析这几个拦截器的作用：
| 序号 | 拦截器 | 作用 |
|---|---|---|
| 1 | interceptors | 用户自定义拦截器，可以实现日志打印 |
| 2 | RetryAndFollowUpInterceptor | 负责失败重连以及重定向 |
| 3 | BridgeInterceptor | 负责请求和响应的转换 |
| 4 | CacheInterceptor | 负责处理缓存 |
| 5 | ConnectInterceptor | 负责与服务器构建连接 |
| 6 | networkInterceptors | 用户自定义网络拦截器，可以实现日志打印 |
| 7 | CallServerInterceptor | 负责数据传输 |
二、RetryAndFollowUpInterceptor
RetryAndFollowUpInterceptor 负责失败重连以及重定向。
//RetryAndFollowUpInterceptor.class
//最大重试次数：
private static final int MAX_FOLLOW_UPS = 20;
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;
while (true) {
// 这个执行连接前的准备工作。
transmitter.prepareToConnect(request);
if (transmitter.isCanceled()) {
throw new IOException("Canceled");
}
Response response;
boolean success = false;
try {
//执行下一个拦截器，即BridgeInterceptor
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.
//检测路由异常是否能重新连接
if (!recover(e.getLastConnectException(), transmitter, false, request)) {
throw e.getFirstConnectException();
}
continue; //重新进行while循环，进行网络请求
} catch (IOException e) {
// An attempt to communicate with a server failed. The request may have been sent.
boolean requestSendStarted = !(e instanceof ConnectionShutdownException);
//检测该IO异常是否能重新连接
if (!recover(e, transmitter, requestSendStarted, request))
throw e;
continue; //重新进行while循环，进行网络请求
} finally {
// The network call threw an exception. Release any resources.
if (!success) {// 由于上面抛出了异常，所以要释放相关资源。
transmitter.exchangeDoneDueToException();
}
}
// Attach the prior response if it exists. Such responses never have a 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;
// 通过响应码判断当前的请求是否需要重定向，否则直接返回。
Request followUp = followUpRequest(response, route);
if (followUp == null) {
if (exchange != null && exchange.isDuplex()) {
transmitter.timeoutEarlyExit();
}
return response; //正常的情况下，这里就返回的响应报文response
}
RequestBody followUpBody = followUp.body();
if (followUpBody != null && followUpBody.isOneShot()) {
return response;
}
closeQuietly(response.body());
if (transmitter.hasExchange()) {
exchange.detachWithViolence();
}
if (++followUpCount > MAX_FOLLOW_UPS) { //重试次数不能大于限定的次数
throw new ProtocolException("Too many follow-up requests: " + followUpCount);
}
request = followUp;
priorResponse = response;
}
}
三、BridgeInterceptor
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.
BridgeInterceptor 是一个将用户态请求构建成真正网络请求，同时将网络返回数据构建成用户响应数据的桥梁。
这部分可以参考：OkHttp 官方文档 - Rewriting Requests部分
涉及到的几个请求头字段：
| 序号 | 请求头名称 | 含义 |
|---|---|---|
| 1 | Content-Type |
请求的与实体对应的MIME信息 |
| 2 | Content-Length |
请求的内容长度 |
| 3 | Transfer-Encoding |
文件传输编码 (如：chunked) |
| 4 | Host |
指定请求的服务器的域名和端口号 |
| 5 | Connection |
表示是否需要持久连接 (如：Keep-Alive) |
| 6 | Accept-Encoding |
接收者支持的类型 (如：gzip) |
| 7 | Cookie |
HTTP请求发送时，会把保存在该请求域名下的所有cookie值一起发送给web服务器 |
| 8 | User-Agent |
User-Agent的内容包含发出请求的用户信息 |
//BridgeInterceptor.class
public Response intercept(Chain chain) throws IOException {
Request userRequest = chain.request();
// 将用户态的请求构建称网络请求
Request.Builder requestBuilder = userRequest.newBuilder();
// 1.下面就是将请求头需要的参数添加到请求头
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"); //支持分片传输
//由于支持分片传输，所以请求体的长度content-length没有意义，可以移除。
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; //1.1开启压缩
requestBuilder.header("Accept-Encoding", "gzip"); //这里默认时支持gzip压缩的
}
//1.2 加载cookie
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());
}
// 2.这里实际上是调用下一个 Interceptor(即CacheInterceptor) 获取Response
Response networkResponse = chain.proceed(requestBuilder.build());
// 3.如果cookieJar不为空，则将响应报文的请求头保存到cookie中。
HttpHeaders.receiveHeaders(cookieJar, userRequest.url(), networkResponse.headers());
// 根据之前的响应报文新构建一个Response
Response.Builder responseBuilder = networkResponse.newBuilder()
.request(userRequest);
// 4.如果上面开启了数据压缩，这里要解压。
if (transparentGzip
&& "gzip".equalsIgnoreCase(networkResponse.header("Content-Encoding"))
&& HttpHeaders.hasBody(networkResponse)) {
// 返回的Response报文，body数据是压缩过的，所以需要使用Gzip解压缩。
GzipSource responseBody = new GzipSource(networkResponse.body().source());
// 同时移除响应头部的Content-Encoding，Content-Length
Headers strippedHeaders = networkResponse.headers().newBuilder()
.removeAll("Content-Encoding")
.removeAll("Content-Length")
.build();
responseBuilder.headers(strippedHeaders);
String contentType = networkResponse.header("Content-Type");
// 将解压后的body重新放入Response中。
responseBuilder.body(new RealResponseBody(contentType, -1L, Okio.buffer(responseBody)));
}
// 5.返回Response
return responseBuilder.build();
}
小结：
- 在发送请求阶段，BridgeInterceptor 补充了网络请求需要的请求头(header)信息：
Content-Type、Content-Length、Transfer-Encoding、Host、Connection、Accept-Encoding、User-Agent。1.1
Accept-Encoding是否开启gzip压缩。
1.2 加载 Cookie。 - 创建真正的 request 并传递给后续的 interceptor(CacheInterceptor) 来处理，并等待获取响应。
- 获取到响应后，先保存Cookie。
- 如果服务器返回的响应content是以gzip压缩过的，则会先进行解压缩，并移除响应报文header的
Content-Encoding和Content-Length，构造新的响应返回。 - 返回response。
四、CacheInterceptor
CacheInterceptor 类是专门处理缓存的，缓存相关的类有：
CacheCacheStrategyDiskLruCacheCacheInterceptorCacheControl
此处我们暂时先分析涉及的缓存拦截器(CacheInterceptor)。
//CacheInterceptor.class
public Response intercept(Chain chain) throws IOException {
//1.如果存在缓存，则从缓存中取出，有可能为null
Response cacheCandidate = cache != null
? cache.get(chain.request())
: null;
long now = System.currentTimeMillis();
// 2.获取缓存策略对象
CacheStrategy strategy = new CacheStrategy.Factory(now, chain.request(), cacheCandidate).get();
// 策略中的网络请求
Request networkRequest = strategy.networkRequest;
// 策略中的缓存响应
Response cacheResponse = strategy.cacheResponse;
if (cache != null) {
cache.trackResponse(strategy);
}
if (cacheCandidate != null && cacheResponse == null) {
closeQuietly(cacheCandidate.body()); // The cache candidate wasn't applicable. Close it.
}
// If we're forbidden from using the network and the cache is insufficient, fail.
// 3.禁止使用网络(根据缓存策略)，且缓存又无效，直接返回异常(504)的响应报文。
if (networkRequest == null && cacheResponse == null) {
return new Response.Builder()
.request(chain.request())
.protocol(Protocol.HTTP_1_1)
.code(504)
.message("Unsatisfiable Request (only-if-cached)")
.body(Util.EMPTY_RESPONSE)
.sentRequestAtMillis(-1L)
.receivedResponseAtMillis(System.currentTimeMillis())
.build();
}
// If we don't need the network, we're done.
// 4.上面判断了缓存跟网络请求都为null的场景，因此这里网络请求为空时，缓存一定存在且缓存有效，所以直接返回缓存数据。
if (networkRequest == null) {
// 直接返回缓存(走缓存策略，其实到这一步就结束了，然后返回到上一级拦截器BridgeInterceptor)
return cacheResponse.newBuilder()
.cacheResponse(stripBody(cacheResponse))
.build();
}
Response networkResponse = null;
try {
// 5.执行到这里，说明缓存没有命中，需要执行网络请求。
networkResponse = chain.proceed(networkRequest);
} finally {
// If we're crashing on I/O or otherwise, don't leak the cache body.
if (networkResponse == null && cacheCandidate != null) {
closeQuietly(cacheCandidate.body());
}
}
// If we have a cache response too, then we're doing a conditional get.
// 执行到这里说明 networkRequest 跟 cacheResponse 都不为null。
if (cacheResponse != null) {
// 6. HTTP_NOT_MODIFIED=304 说明内容无变化，还是从缓存获取数据，并将网络报文返回的请求头更新到缓存的请求头中。
if (networkResponse.code() == HTTP_NOT_MODIFIED) {
Response response = cacheResponse.newBuilder()
.headers(combine(cacheResponse.headers(), networkResponse.headers()))
.sentRequestAtMillis(networkResponse.sentRequestAtMillis())
.receivedResponseAtMillis(networkResponse.receivedResponseAtMillis())
.cacheResponse(stripBody(cacheResponse))
.networkResponse(stripBody(networkResponse))
.build();
networkResponse.body().close();
// Update the cache after combining headers but before stripping the
// Content-Encoding header (as performed by initContentStream()).
cache.trackConditionalCacheHit();
// 更新缓存
cache.update(cacheResponse, response);
return response;
} else {//走到这里，说明服务端数据有变化。
closeQuietly(cacheResponse.body());
}
}
//7.使用网络响应
Response response = networkResponse.newBuilder()
.cacheResponse(stripBody(cacheResponse))
.networkResponse(stripBody(networkResponse))
.build();
if (cache != null) {
//8.缓存到本地
if (HttpHeaders.hasBody(response) && CacheStrategy.isCacheable(response, networkRequest)) {
// Offer this request to the cache.
// 注意：Cache.put()操作只支持Get操作。
CacheRequest cacheRequest = cache.put(response);
return cacheWritingResponse(cacheRequest, response);
}
if (HttpMethod.invalidatesCache(networkRequest.method())) {
try {
cache.remove(networkRequest);
} catch (IOException ignored) {
// The cache cannot be written.
}
}
}
return response;
}
小结：
CacheInterceptor 的操作流程如下：
- 如果配置缓存，则从缓存中取一次，缓存不一定存在。
- 根据获取到的缓存跟当前的请求来创建一个缓存策略。
- 如果当前请求禁止使用网络（根据缓存策略），且缓存无效，直接返回异常(504)的响应报文。
- 如果缓存有效，则直接从缓存中获取数据。
- 如果缓存无效，且网络请求有效，则执行下一个拦截器(ConnectInterceptor)的操作。
- 缓存有效的条件下，执行步骤5获取响应报文，如果响应
code=HTTP_NOT_MODIFIED，说明服务端数据无改变，则直接使用本地缓存数据。 - 如果响应报文
code !=HTTP_NOT_MODIFIED，说明服务端数据有改变，直接使用网络返回的报文。 - 更新本地的缓存。
注意：
- 目前 CacheInterceptor 缓存只支持
Get请求 (可以查看Cache.put()源码)。
五、ConnectInterceptor
ConnectInterceptor 的主要作用是负责与服务器构建连接。
// ConnectInterceptor.class
public Response intercept(Chain chain) throws IOException {
RealInterceptorChain realChain = (RealInterceptorChain) chain;
Request request = realChain.request();
Transmitter transmitter = realChain.transmitter();
// We need the network to satisfy this request. Possibly for validating a conditional GET.
boolean doExtensiveHealthChecks = !request.method().equals("GET");
// 这一步很重要，构建一个Exchange对象，该对象传输单个HTTP请求和响应对。
Exchange exchange = transmitter.newExchange(chain, doExtensiveHealthChecks);
return realChain.proceed(request, transmitter, exchange);
}
下面看以下 transmitter.newExchange() 方法具体做了什么？
Transmitter
- 通过 ExchangeFinder 查找到一个处理网络请求编解码的类ExchangeCodec；
- 将 ExchangeCodec 传递给 Exchange 对象统一管理。
// Transmitter.class
Exchange newExchange(Interceptor.Chain chain, boolean doExtensiveHealthChecks) {
// ...代码省略...
// 通过ExchangeFinder构建一个ExchangeCodec，ExchangeCodec是一个网络请求编解码的类
ExchangeCodec codec = exchangeFinder.find(client, chain, doExtensiveHealthChecks);
// 将ExchangeCodec委托给Exchange统一管理。
Exchange result = new Exchange(this, call, eventListener, exchangeFinder, codec);
synchronized (connectionPool) {
this.exchange = result;
this.exchangeRequestDone = false;
this.exchangeResponseDone = false;
return result;
}
}
ExchangeFinder
//ExchangeFinder.class
public ExchangeCodec find(OkHttpClient client, Interceptor.Chain chain, boolean doExtensiveHealthChecks) {
int connectTimeout = chain.connectTimeoutMillis();
int readTimeout = chain.readTimeoutMillis();
int writeTimeout = chain.writeTimeoutMillis();
int pingIntervalMillis = client.pingIntervalMillis();
boolean connectionRetryEnabled = client.retryOnConnectionFailure();
try {
// 查找一个可以使用的连接通道。
RealConnection resultConnection = findHealthyConnection(connectTimeout, readTimeout,
writeTimeout, pingIntervalMillis, connectionRetryEnabled, doExtensiveHealthChecks);
// 通过RealConnection构造一个ExchangeCodec对象，处理请求和响应报文。
return resultConnection.newCodec(client, chain);
} catch (RouteException e) {
trackFailure();
throw e;
} catch (IOException e) {
trackFailure();
throw new RouteException(e);
}
}
/**
* Finds a connection and returns it if it is healthy. If it is unhealthy the process is repeated
* until a healthy connection is found.
*/
private RealConnection findHealthyConnection(int connectTimeout, int readTimeout,
int writeTimeout, int pingIntervalMillis, boolean connectionRetryEnabled,
boolean doExtensiveHealthChecks) throws IOException {
while (true) { //一直查找，直到找到可用的Connection。
// 从ConnectionPool中查找一个连接(RealConnection)
RealConnection candidate = findConnection(connectTimeout, readTimeout, writeTimeout,
pingIntervalMillis, connectionRetryEnabled);
// 下面的条件校验，是为了判断上一步获取的连接是否正常可用，如果不可用，就继续查找查找。
// If this is a brand new connection, we can skip the extensive health checks.
synchronized (connectionPool) {
if (candidate.successCount == 0 && !candidate.isMultiplexed()) {
return candidate;
}
}
// Do a (potentially slow) check to confirm that the pooled connection is still good. If it
// isn't, take it out of the pool and start again.
if (!candidate.isHealthy(doExtensiveHealthChecks)) {
candidate.noNewExchanges();
continue;
}
return candidate;
}
}
private RealConnection findConnection(int connectTimeout, int readTimeout, int writeTimeout,
int pingIntervalMillis, boolean connectionRetryEnabled) throws IOException {
boolean foundPooledConnection = false;
RealConnection result = null;
Route selectedRoute = null;
RealConnection releasedConnection;
Socket toClose;
synchronized (connectionPool) {
if (transmitter.isCanceled()) throw new IOException("Canceled");
hasStreamFailure = false; // This is a fresh attempt.
// Attempt to use an already-allocated connection. We need to be careful here because our
// already-allocated connection may have been restricted from creating new exchanges.
releasedConnection = transmitter.connection;
toClose = transmitter.connection != null && transmitter.connection.noNewExchanges
? transmitter.releaseConnectionNoEvents()
: null;
if (transmitter.connection != null) {
// We had an already-allocated connection and it's good.
result = transmitter.connection;
releasedConnection = null;
}
if (result == null) {
// Attempt to get a connection from the pool.
// 查找可以复用的连接
if (connectionPool.transmitterAcquirePooledConnection(address, transmitter, null, false)) {
foundPooledConnection = true;
result = transmitter.connection; //这里表示找到了可以复用的连接
} else if (nextRouteToTry != null) {
selectedRoute = nextRouteToTry;
nextRouteToTry = null;
} else if (retryCurrentRoute()) {
selectedRoute = transmitter.connection.route();
}
}
}
closeQuietly(toClose);
if (releasedConnection != null) {
eventListener.connectionReleased(call, releasedConnection);
}
if (foundPooledConnection) {
eventListener.connectionAcquired(call, result);
}
if (result != null) {
// If we found an already-allocated or pooled connection, we're done.
//如果有已知连接且可用，则直接返回
return result;
}
// If we need a route selection, make one. This is a blocking operation.
boolean newRouteSelection = false;
if (selectedRoute == null && (routeSelection == null || !routeSelection.hasNext())) {
newRouteSelection = true;
// 切换路由选择器
routeSelection = routeSelector.next();
}
List<Route> routes = null;
synchronized (connectionPool) {
if (transmitter.isCanceled()) throw new IOException("Canceled");
//在新的路由选择器里尝试获取连接。
if (newRouteSelection) {
// Now that we have a set of IP addresses, make another attempt at getting a connection from
// the pool. This could match due to connection coalescing.
routes = routeSelection.getAll();
// 这里跟上面获取的方法一样，获取到连接就返赋值给result
if (connectionPool.transmitterAcquirePooledConnection(address, transmitter, routes, false)) {
foundPooledConnection = true;
result = transmitter.connection;
}
}
//如果上一步该是没有获取到，则切换下一个路由选择器，并重新创建一个RealConnection。
if (!foundPooledConnection) {
if (selectedRoute == null) {
selectedRoute = routeSelection.next();
}
// Create a connection and assign it to this allocation immediately. This makes it possible
// for an asynchronous cancel() to interrupt the handshake we're about to do.
// 如果上面的条件都不满足，则创建一个RealConnection
result = new RealConnection(connectionPool, selectedRoute);
connectingConnection = result;
}
}
// If we found a pooled connection on the 2nd time around, we're done.
if (foundPooledConnection) {
eventListener.connectionAcquired(call, result);
return result;
}
// Do TCP + TLS handshakes. This is a blocking operation.
// 开始TCP的三次握手
result.connect(connectTimeout, readTimeout, writeTimeout, pingIntervalMillis,
connectionRetryEnabled, call, eventListener);
//计入数据库
connectionPool.routeDatabase.connected(result.route());
Socket socket = null;
synchronized (connectionPool) {
connectingConnection = null;
// Last attempt at connection coalescing, which only occurs if we attempted multiple
// concurrent connections to the same host.
if (connectionPool.transmitterAcquirePooledConnection(address, transmitter, routes, true)) {
// We lost the race! Close the connection we created and return the pooled connection.
result.noNewExchanges = true;
socket = result.socket();
result = transmitter.connection;
// It's possible for us to obtain a coalesced connection that is immediately unhealthy. In
// that case we will retry the route we just successfully connected with.
nextRouteToTry = selectedRoute;
} else {
//加入连接池
connectionPool.put(result);
transmitter.acquireConnectionNoEvents(result);
}
}
closeQuietly(socket);
eventListener.connectionAcquired(call, result);
return result; //返回可用的连接
}
六、CallServerInterceptor
在 ConnectInterceptor 中已经成功连接到服务器，所以 CallServerInterceptor 的主要目的就是发送请求和回写响应报文。
public Response intercept(Chain chain) throws IOException {
RealInterceptorChain realChain = (RealInterceptorChain) chain;
// 数据交换器
Exchange exchange = realChain.exchange();
Request request = realChain.request();
long sentRequestMillis = System.currentTimeMillis();
//1.写入请求头
exchange.writeRequestHeaders(request);
boolean responseHeadersStarted = false;
Response.Builder responseBuilder = null;
if (HttpMethod.permitsRequestBody(request.method()) && request.body() != null) {
// If there's a "Expect: 100-continue" header on the request, wait for a "HTTP/1.1 100
// Continue" response before transmitting the request body. If we don't get that, return
// what we did get (such as a 4xx response) without ever transmitting the request body.
if ("100-continue".equalsIgnoreCase(request.header("Expect"))) {
exchange.flushRequest();
responseHeadersStarted = true;
exchange.responseHeadersStart();
responseBuilder = exchange.readResponseHeaders(true);
}
//2.写入请求体
if (responseBuilder == null) {
if (request.body().isDuplex()) {
// Prepare a duplex body so that the application can send a request body later.
exchange.flushRequest();
BufferedSink bufferedRequestBody = Okio.buffer(exchange.createRequestBody(request, true));
request.body().writeTo(bufferedRequestBody); //将请求体写入服务器
} else {
// Write the request body if the "Expect: 100-continue" expectation was met.
BufferedSink bufferedRequestBody = Okio.buffer(exchange.createRequestBody(request, false));
request.body().writeTo(bufferedRequestBody);
bufferedRequestBody.close();
}
} else {
exchange.noRequestBody();
if (!exchange.connection().isMultiplexed()) {
// If the "Expect: 100-continue" expectation wasn't met, prevent the HTTP/1 connection
// from being reused. Otherwise we're still obligated to transmit the request body to
// leave the connection in a consistent state.
exchange.noNewExchangesOnConnection();
}
}
} else {
exchange.noRequestBody();
}
// 这里完成了请求的写入
if (request.body() == null || !request.body().isDuplex()) {
exchange.finishRequest();
}
if (!responseHeadersStarted) {
exchange.responseHeadersStart();
}
//3.读取报文的响应头
if (responseBuilder == null) {
responseBuilder = exchange.readResponseHeaders(false);
}
// 这里构建响应报文的Response对象，此时只有响应头，还没有响应体。
Response response = responseBuilder
.request(request)
.handshake(exchange.connection().handshake())
.sentRequestAtMillis(sentRequestMillis) //发送请求的时间
.receivedResponseAtMillis(System.currentTimeMillis()) //接收到响应的时间
.build();
int code = response.code();
if (code == 100) {
// server sent a 100-continue even though we did not request one.
// try again to read the actual response
response = exchange.readResponseHeaders(false)
.request(request)
.handshake(exchange.connection().handshake())
.sentRequestAtMillis(sentRequestMillis)
.receivedResponseAtMillis(System.currentTimeMillis())
.build();
code = response.code();
}
exchange.responseHeadersEnd(response);
if (forWebSocket && code == 101) {
// Connection is upgrading, but we need to ensure interceptors see a non-null response body.
response = response.newBuilder()
.body(Util.EMPTY_RESPONSE)
.build();
} else {
//读取报文响应体
response = response.newBuilder()
.body(exchange.openResponseBody(response)) //真正读取响应体
.build();
}
if ("close".equalsIgnoreCase(response.request().header("Connection"))
|| "close".equalsIgnoreCase(response.header("Connection"))) {
exchange.noNewExchangesOnConnection();
}
if ((code == 204 || code == 205) && response.body().contentLength() > 0) {
throw new ProtocolException(
"HTTP " + code + " had non-zero Content-Length: " + response.body().contentLength());
}
//返回响应报文
return response;
}
小结： CallServerInterceptor 主要完成了4个操作：
- 写入请求头
- 写入请求体
- 读取响应头
- 读取响应体
