知其然知其所以然,我們不做只會調(diào)用 API 的碼農(nóng),不要重復(fù)制造輪子不代表我們不應(yīng)該了解輪子的構(gòu)造!
Talk is cheap, show me the code
1. GET 請求使用
- 異步 GET 請求
private OkHttpClient client = new OkHttpClient();
public void get(String url, Map<String, Object> params, Callback responseCallback) {
HttpUrl.Builder httpBuider = HttpUrl.parse(url).newBuilder();
if (params != null) {
for (Map.Entry<String, Object> param : params.entrySet()) {
httpBuider.addQueryParameter(param.getKey(), param.getValue().toString());
}
}
Request request = new Request.Builder().url(httpBuider.build()).build();
client.newCall(request).enqueue(responseCallback);
}
// 調(diào)用簡單的異步get請求
findViewById(R.id.btn_get).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String url = "http://192.168.6.21:9090/get";
HashMap<String, Object> map = new HashMap<>();
map.put("name", "xiaocai");
map.put("age", 25 );
get(url, map, new Callback() {
@Override
public void onFailure(Call call, IOException e) {
}
@Override
public void onResponse(Call call, Response response) throws IOException {
String data = response.body().string();
Log.d("xiaocai", "response:" + data);
}
});
}
});
springboot中簡單的處理:
@GetMapping("/get")
public String testGet(@RequestParam(value = "name") String name,
@RequestParam(value = "age", required = false) int age) {
String data = "name:" + name + " age:" + age;
return JsonHelper.success(data);
}
輸出:
xiaocai: response:{"msg":"成功","code":0,"data":"name:xiaocai age:25","status":"0"}
- 同步GET請求:
OkHttpClient client = new OkHttpClient();
String run(String url) throws IOException {
Request request = new Request.Builder()
.url(url)
.build();
Response response = client.newCall(request).execute();
return response.body().string();
2. POST 請求使用
- 異步 POST 請求
findViewById(R.id.btn_post).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
connectEnqueue();
}
});
private void connectEnqueue() {
RequestBody formBody = new FormBody.Builder()
.add("name", "xiaocai")
.add("email", "xiaocai@163.com")
.build();
Request request = new Request.Builder().url(url)
.post(formBody)
.build();
client.newCall(request).enqueue(new Callback() {
@Override
public void onFailure(Call call, IOException e) {
e.printStackTrace();
}
@Override
public void onResponse(Call call, Response response) throws IOException {
String data = response.body().string();
Log.d("xiaocai", "response:" + data);
}
});
}
輸出:
{"msg":"成功","code":0,"data":"name:xiaocai email:xiaocai@163.com","status":"0"}
- 同步 POST 請求
private void connectExecute() {
new Thread(new Runnable() {
@Override
public void run() {
try {
String response = connectExecute(url);
Log.d("xiaocai", "response:" + response);
} catch (IOException e) {
e.printStackTrace();
}
}
}).start();
}
private String connectExecute(String url) throws IOException {
Request request = new Request.Builder().url(url).build();
Response response = client.newCall(request).execute();
if (response.isSuccessful()) {
return response.body().string();
} else {
throw new IOException("Unexpected code " + response);
}
}
同步請求為「execute」,異步為「enqueue」.可以先簡單看下這兩個單詞的意思:
- execute : vt. 實行榛瓮；執(zhí)行；處死
- enqueue : n. 排隊袱巨；入隊删咱；隊列
從意思我們大概可以猜出它們的執(zhí)行方式了
- execute : 是個及物動詞,為「執(zhí)行」之意,顧名思義就是直接執(zhí)行(同步).
- enqueue : 是名詞「入隊」,所以對加入到一個隊列中,排隊等候執(zhí)行(異步).
3. 發(fā)起請求跟蹤
首先從
client.newCall(request).enqueue(responseCallback);
看里面具體執(zhí)行.該方法返回 Call 對象,是個接口.而具體實現(xiàn)在 RealCall 中,具體實行的邏輯:
@Override public void enqueue(Callback responseCallback) {
synchronized (this) {
if (executed) throw new IllegalStateException("Already Executed");
executed = true;
}
captureCallStackTrace();
client.dispatcher().enqueue(new AsyncCall(responseCallback));
}
在這里直接傳遞給 Dispatcher 進(jìn)行分發(fā):
synchronized void enqueue(AsyncCall call) {
if (runningAsyncCalls.size() < maxRequests && runningCallsForHost(call) < maxRequestsPerHost) {
runningAsyncCalls.add(call);
executorService().execute(call);
} else {
readyAsyncCalls.add(call);
}
}
加入到異步請求集合中:
/** Running asynchronous calls. Includes canceled calls that haven't finished yet. */
private final Deque<AsyncCall> runningAsyncCalls = new ArrayDeque<>();
使用線程池管理線程,不限容量:
public synchronized ExecutorService executorService() {
if (executorService == null) {
executorService = new ThreadPoolExecutor(0, Integer.MAX_VALUE, 60, TimeUnit.SECONDS,
new SynchronousQueue<Runnable>(), Util.threadFactory("OkHttp Dispatcher", false));
}
return executorService;
}
返回來 client.newCall(request).enqueue(responseCallback); 看 AsyncCall 這個對象:
// NamedRunnable里面事項了runnable接口
final class AsyncCall extends NamedRunnable {
private final Callback responseCallback;
AsyncCall(Callback responseCallback) {
super("OkHttp %s", redactedUrl());
this.responseCallback = responseCallback;
}
String host() {
return originalRequest.url().host();
}
Request request() {
return originalRequest;
}
RealCall get() {
return RealCall.this;
}
@Override protected void execute() {
boolean signalledCallback = false;
try {
Response response = getResponseWithInterceptorChain();// 真正發(fā)起請求
// 處理響應(yīng)
if (retryAndFollowUpInterceptor.isCanceled()) {
signalledCallback = true;
responseCallback.onFailure(RealCall.this, new IOException("Canceled"));
} else {
signalledCallback = true;
responseCallback.onResponse(RealCall.this, response);
}
} catch (IOException e) {
if (signalledCallback) {
// Do not signal the callback twice!
Platform.get().log(INFO, "Callback failure for " + toLoggableString(), e);
} else {
responseCallback.onFailure(RealCall.this, e);
}
} finally {
client.dispatcher().finished(this);
}
}
}
這里最重要的是 getResponseWithInterceptorChain 方法了
Response getResponseWithInterceptorChain() throws IOException {
// Build a full stack of interceptors.
List<Interceptor> interceptors = new ArrayList<>();
interceptors.addAll(client.interceptors()); // 用戶自定義的攔截器
interceptors.add(retryAndFollowUpInterceptor); // 重試攔截器
interceptors.add(new BridgeInterceptor(client.cookieJar())); // 鏈接橋攔截器
interceptors.add(new CacheInterceptor(client.internalCache())); // 緩存攔截器
interceptors.add(new ConnectInterceptor(client)); // 鏈接攔截器
if (!forWebSocket) {
interceptors.addAll(client.networkInterceptors()); // 用戶自定義網(wǎng)絡(luò)攔截器
}
interceptors.add(new CallServerInterceptor(forWebSocket)); // 發(fā)起請求和獲得響應(yīng)的攔截器
Interceptor.Chain chain = new RealInterceptorChain(
interceptors, null, null, null, 0, originalRequest);
return chain.proceed(originalRequest);
}
添加攔截器 interceptor,從字面上不能正確的理解,其實攔截器里面才是正在做網(wǎng)絡(luò)操作的!這幾個攔截器都比較重要,接下來逐個分析.
到此我們差不多看到了一個簡單的流程,還有很多的細(xì)節(jié)慢慢進(jìn)行分析.
4. 總攔截器 RealInterceptorChain (分發(fā)攔截器)
在上面的源碼,只是添加到攔截器集合中,但真正調(diào)用攔截的是在 RealInterceptorChain 中.在這個攔截器中進(jìn)行遍歷所有攔截器,有意思的是遍歷的方式不是直接調(diào)用 for 或者一般的遞歸方法,而是取出當(dāng)前的攔截器,將角標(biāo)增1后重新構(gòu)建 RealInterceptorChain .
這里我們看到了另一種遞歸方式.
/**
* 調(diào)用所有攔截器的攔截器,okhttpclient會將所有的攔截器傳進(jìn)來,內(nèi)部遍歷所有進(jìn)行請求
*/
public final class RealInterceptorChain implements Interceptor.Chain {
private final List<Interceptor> interceptors;
private final StreamAllocation streamAllocation;
private final HttpCodec httpCodec;
private final RealConnection connection;
private final int index;
private final Request request;
private int calls;
public RealInterceptorChain(List<Interceptor> interceptors, StreamAllocation streamAllocation,
HttpCodec httpCodec, RealConnection connection, int index, Request request) {
this.interceptors = interceptors;
this.connection = connection;
this.streamAllocation = streamAllocation;
this.httpCodec = httpCodec;
this.index = index;
this.request = request;
}
@Override public Connection connection() {
return connection;
}
public StreamAllocation streamAllocation() {
return streamAllocation;
}
public HttpCodec httpStream() {
return httpCodec;
}
@Override public Request request() {
return request;
}
@Override public Response proceed(Request request) throws IOException {
return proceed(request, streamAllocation, httpCodec, connection);
}
public Response proceed(Request request, StreamAllocation streamAllocation, HttpCodec httpCodec,
RealConnection connection) throws IOException {
// 檢查角標(biāo)是否越界
if (index >= interceptors.size()) throw new AssertionError();
calls++;
// If we already have a stream, confirm that the incoming request will use it.
if (this.httpCodec != null && !this.connection.supportsUrl(request.url())) {
throw new IllegalStateException("network interceptor " + interceptors.get(index - 1)
+ " must retain the same host and port");
}
// If we already have a stream, confirm that this is the only call to chain.proceed().
if (this.httpCodec != null && calls > 1) {
throw new IllegalStateException("network interceptor " + interceptors.get(index - 1)
+ " must call proceed() exactly once");
}
// 重新構(gòu)建一個RealInterceptorChain,將下標(biāo)增加
okhttp3.internal.http.RealInterceptorChain next = new okhttp3.internal.http.RealInterceptorChain(
interceptors, streamAllocation, httpCodec, connection, index + 1, request);
Interceptor interceptor = interceptors.get(index); // 取出當(dāng)前角標(biāo)的攔截器
Response response = interceptor.intercept(next); // 執(zhí)行攔截
// Confirm that the next interceptor made its required call to chain.proceed().
if (httpCodec != null && index + 1 < interceptors.size() && next.calls != 1) {
throw new IllegalStateException("network interceptor " + interceptor
+ " must call proceed() exactly once");
}
if (response == null) {
throw new NullPointerException("interceptor " + interceptor + " returned null");
}
return response;
}
}
5. 用戶自定義攔截器
我們可以自己添加一些攔截器進(jìn)行統(tǒng)一攔截處理,比如統(tǒng)一添加 token 或者 phone 等,也就是所謂的「AOP」.
自定義攔截器:
/**
* 統(tǒng)一追加Header 參數(shù)
*/
public class AppendHeaderParamInterceptor implements Interceptor {
@Override
public Response intercept(Chain chain) throws IOException {
Request request = chain.request();
Headers.Builder builder = request.
headers().
newBuilder();
//統(tǒng)一追加header參數(shù)
Headers newHeader = builder
.add("token", getToken())
.build();
Request newRequest = request.newBuilder()
.headers(newHeader)
.build();
return chain.proceed(newRequest);
}
}
可以添加多個攔截器,操作也很簡單:
OkHttpClient.Builder builder = new OkHttpClient.Builder();
builder.addInterceptor(new AppendHeaderParamInterceptor());
6. 失敗重連攔截器
重試那些失敗或重定向的請求
/**
* 重試那些失敗或重定向的請求
*/
public final class RetryAndFollowUpInterceptor implements Interceptor {
/**
* 重定向或授權(quán)執(zhí)行最大允許次數(shù)
*/
private static final int MAX_FOLLOW_UPS = 20;
private final OkHttpClient client;
private final boolean forWebSocket;
private StreamAllocation streamAllocation;
private Object callStackTrace;
private volatile boolean canceled;
public RetryAndFollowUpInterceptor(OkHttpClient client, boolean forWebSocket) {
this.client = client;
this.forWebSocket = forWebSocket;
}
/**
* 立即取消網(wǎng)絡(luò)請求(若此處持有該請求的話)
*/
public void cancel() {
canceled = true;
StreamAllocation streamAllocation = this.streamAllocation;
if (streamAllocation != null) streamAllocation.cancel();
}
public boolean isCanceled() {
return canceled;
}
public void setCallStackTrace(Object callStackTrace) {
this.callStackTrace = callStackTrace;
}
public StreamAllocation streamAllocation() {
return streamAllocation;
}
@Override public Response intercept(Chain chain) throws IOException {
Request request = chain.request();
streamAllocation = new StreamAllocation(
client.connectionPool(), createAddress(request.url()), callStackTrace);
int followUpCount = 0;
Response priorResponse = null;
while (true) {
if (canceled) { // 已取消
streamAllocation.release();
throw new IOException("Canceled");
}
Response response = null;
boolean releaseConnection = true;
try {
// 執(zhí)行請求
response = ((RealInterceptorChain) chain).proceed(request, streamAllocation, null, null);
releaseConnection = false;
} catch (RouteException e) {
// route 通道連接失敗,請求將不會發(fā)出
if (!recover(e.getLastConnectException(), false, request)) {
throw e.getLastConnectException();
}
releaseConnection = false;
continue;
} catch (IOException e) {
// 連接不到服務(wù)器
boolean requestSendStarted = !(e instanceof ConnectionShutdownException);
if (!recover(e, requestSendStarted, request)) throw e;
releaseConnection = false;
continue;
} finally {
// 釋放資源
if (releaseConnection) {
streamAllocation.streamFailed(null);
streamAllocation.release();
}
}
// 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();
}
Request followUp = followUpRequest(response);
if (followUp == null) {
if (!forWebSocket) {
streamAllocation.release();
}
return response;
}
closeQuietly(response.body());
// 超過了最大請求次數(shù)
if (++followUpCount > MAX_FOLLOW_UPS) {
streamAllocation.release();
throw new ProtocolException("Too many follow-up requests: " + followUpCount);
}
// 讀不到的body
if (followUp.body() instanceof UnrepeatableRequestBody) {
streamAllocation.release();
throw new HttpRetryException("Cannot retry streamed HTTP body", response.code());
}
if (!sameConnection(response, followUp.url())) {
streamAllocation.release();
streamAllocation = new StreamAllocation(
client.connectionPool(), createAddress(followUp.url()), callStackTrace);
} else if (streamAllocation.codec() != null) {
throw new IllegalStateException("Closing the body of " + response
+ " didn't close its backing stream. Bad interceptor?");
}
request = followUp;
priorResponse = response;
}
}
// 相當(dāng)于構(gòu)建一個完整的請求信息
private Address createAddress(HttpUrl url) {
SSLSocketFactory sslSocketFactory = null;
HostnameVerifier hostnameVerifier = null;
CertificatePinner certificatePinner = null;
if (url.isHttps()) { // https的配置
sslSocketFactory = client.sslSocketFactory();
hostnameVerifier = client.hostnameVerifier();
certificatePinner = client.certificatePinner();
}
return new Address(url.host(), url.port(), client.dns(), client.socketFactory(),
sslSocketFactory, hostnameVerifier, certificatePinner, client.proxyAuthenticator(),
client.proxy(), client.protocols(), client.connectionSpecs(), client.proxySelector());
}
/**
* true則為可重連,不可重連為false
*/
private boolean recover(IOException e, boolean requestSendStarted, Request userRequest) {
streamAllocation.streamFailed(e);
// application 層拒絕重連
if (!client.retryOnConnectionFailure()) return false;
// 不能重復(fù)發(fā)送請求
if (requestSendStarted && userRequest.body() instanceof UnrepeatableRequestBody) return false;
// 發(fā)生了致命錯誤不能重連
if (!isRecoverable(e, requestSendStarted)) return false;
// route不足
if (!streamAllocation.hasMoreRoutes()) return false;
return true;
}
// 判斷是否可恢復(fù)
private boolean isRecoverable(IOException e, boolean requestSendStarted) {
if (e instanceof ProtocolException) {
return false;
}
if (e instanceof InterruptedIOException) {
return e instanceof SocketTimeoutException && !requestSendStarted;
}
if (e instanceof SSLHandshakeException) {
// If the problem was a CertificateException from the X509TrustManager,
// do not retry.
if (e.getCause() instanceof CertificateException) {
return false;
}
}
if (e instanceof SSLPeerUnverifiedException) {
// e.g. a certificate pinning error.
return false;
}
return true;
}
/**
* 縷清HTTP請求以返回響應(yīng). This will
* either add authentication headers, follow redirects or handle a client request timeout. If a
* follow-up is either unnecessary or not applicable, this returns null.
*/
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) {
case HTTP_PROXY_AUTH: // 設(shè)置代理
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:
return client.authenticator().authenticate(route, userResponse);
case HTTP_PERM_REDIRECT:
case HTTP_TEMP_REDIRECT: // 重定向
if (!method.equals("GET") && !method.equals("HEAD")) {
return null;
}
case HTTP_MULT_CHOICE:
case HTTP_MOVED_PERM:
case HTTP_MOVED_TEMP:
case HTTP_SEE_OTHER:
// 判斷是否允許重定向?
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;
if (!sameScheme && !client.followSslRedirects()) return null;
// 大多數(shù)重定向都不包含請求體,所以會從新構(gòu)建請求體
Request.Builder requestBuilder = userResponse.request().newBuilder();
if (HttpMethod.permitsRequestBody(method)) {
final boolean maintainBody = HttpMethod.redirectsWithBody(method);
if (HttpMethod.redirectsToGet(method)) { // GET 請求不包含請求體
requestBuilder.method("GET", null);
} else {
// 構(gòu)建請求體(將之前的請求體添加到新的請求中)
RequestBody requestBody = maintainBody ? userResponse.request().body() : null;
requestBuilder.method(method, requestBody);
}
if (!maintainBody) { // 若沒有請求體,則一出一些請求頭
requestBuilder.removeHeader("Transfer-Encoding");
requestBuilder.removeHeader("Content-Length");
requestBuilder.removeHeader("Content-Type");
}
}
//移除authentication請求頭
if (!sameConnection(userResponse, url)) {
requestBuilder.removeHeader("Authorization");
}
return requestBuilder.url(url).build();
case HTTP_CLIENT_TIMEOUT:
// 請求超時
if (userResponse.request().body() instanceof UnrepeatableRequestBody) {
return null;
}
return userResponse.request();
default:
return null;
}
}
// 判斷是否與HttpUrl為同一個請求
private boolean sameConnection(Response response, HttpUrl followUp) {
HttpUrl url = response.request().url();
return url.host().equals(followUp.host())
&& url.port() == followUp.port()
&& url.scheme().equals(followUp.scheme());
}
}
7. BridgeInterceptor
構(gòu)建一個更友好的請求頭/請求體 (更完整的請求頭/體)
/**
* 構(gòu)建一個更友好的請求頭/請求體 (更完整的請求頭/體)
*/
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) { // 構(gòu)建請求體
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");
}
// 判斷是否支持 gzip 傳輸,并構(gòu)建 gzip 請求頭
boolean transparentGzip = false;
if (userRequest.header("Accept-Encoding") == null && userRequest.header("Range") == null) {
transparentGzip = true;
requestBuilder.header("Accept-Encoding", "gzip");
}
// 投建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()); // 版本為:okhttp/3.8.1
}
Response networkResponse = chain.proceed(requestBuilder.build());
HttpHeaders.receiveHeaders(cookieJar, userRequest.url(), networkResponse.headers());
Response.Builder responseBuilder = networkResponse.newBuilder()
.request(userRequest);
// 判斷是否為 gzip 傳輸
if (transparentGzip
&& "gzip".equalsIgnoreCase(networkResponse.header("Content-Encoding"))
&& HttpHeaders.hasBody(networkResponse)) {
// 構(gòu)建 gzip 響應(yīng)體
GzipSource responseBody = new GzipSource(networkResponse.body().source());
Headers strippedHeaders = networkResponse.headers().newBuilder()
.removeAll("Content-Encoding")
.removeAll("Content-Length")
.build();
responseBuilder.headers(strippedHeaders);
responseBuilder.body(new RealResponseBody(strippedHeaders, Okio.buffer(responseBody)));
}
return responseBuilder.build();
}
/** 構(gòu)建 cookie 頭 */
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();
}
}
主要的職責(zé)：
- 負(fù)責(zé)將用戶構(gòu)建的一個 Request 請求轉(zhuǎn)化為能夠進(jìn)行網(wǎng)絡(luò)訪問的請求掩幢。
- 將這個符合網(wǎng)絡(luò)請求的 request 進(jìn)行網(wǎng)絡(luò)請求免绿。
8. CacheInterceptor
CacheInterceptor 會根據(jù)是否有網(wǎng)絡(luò)和緩存策略提供緩存,網(wǎng)絡(luò)響應(yīng)后將響應(yīng)
/**
* 根據(jù)請求拿到緩存和將響應(yīng)寫到緩存中.
*/
public final class CacheInterceptor implements Interceptor {
final InternalCache cache;
public CacheInterceptor(InternalCache cache) {
this.cache = cache;
}
@Override
public Response intercept(Chain chain) throws IOException {
// 得到 request 對應(yīng)緩存中的 response
Response cacheCandidate = cache != null
? cache.get(chain.request())
: null;
long now = System.currentTimeMillis();
CacheStrategy strategy = new CacheStrategy.Factory(now, chain.request(), cacheCandidate).get();
Request networkRequest = strategy.networkRequest;
Response cacheResponse = strategy.cacheResponse;
if (cache != null) {
cache.trackResponse(strategy);
}
// 不適用 關(guān)閉
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.
// 禁止使用網(wǎng)絡(luò)并且沒有緩存 返回504
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();
}
// 禁止使用網(wǎng)絡(luò) 就沒有必要進(jìn)行下去了,直接使用緩存
if (networkRequest == null) {
return cacheResponse.newBuilder()
.cacheResponse(stripBody(cacheResponse))
.build();
}
Response networkResponse = null;
try {
// 交給下一個攔截器郭脂，返回 networkResponse
networkResponse = chain.proceed(networkRequest);
} finally {
// 關(guān)閉資源
if (networkResponse == null && cacheCandidate != null) {
closeQuietly(cacheCandidate.body());
}
}
// 同時存在緩存和網(wǎng)絡(luò)響應(yīng)的情況 ==> 整合后返回響應(yīng)
if (cacheResponse != null) {
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();
// 合并請求頭后更新緩存
cache.trackConditionalCacheHit();
cache.update(cacheResponse, response);
return response;
} else {
closeQuietly(cacheResponse.body());
}
}
// 能執(zhí)行到此處說明緩存不可用,要使用網(wǎng)絡(luò)響應(yīng)
Response response = networkResponse.newBuilder()
.cacheResponse(stripBody(cacheResponse))
.networkResponse(stripBody(networkResponse))
.build();
if (cache != null) {
if (HttpHeaders.hasBody(response) && CacheStrategy.isCacheable(response, networkRequest)) {
// 添加到緩存中
CacheRequest cacheRequest = cache.put(response);
return cacheWritingResponse(cacheRequest, response);
}
// 不適用緩存
if (HttpMethod.invalidatesCache(networkRequest.method())) {
try {
cache.remove(networkRequest);
} catch (IOException ignored) {
// The cache cannot be written.
}
}
}
return response;
}
private static Response stripBody(Response response) {
return response != null && response.body() != null
? response.newBuilder().body(null).build()
: response;
}
}
9 ConnectInterceptor
向目標(biāo)服務(wù)器開啟鏈接 和 開啟下一個攔截器
/** 向目標(biāo)服務(wù)器開啟鏈接 和 開啟下一個攔截器 */
public final class ConnectInterceptor implements Interceptor {
public final OkHttpClient client;
public ConnectInterceptor(OkHttpClient client) {
this.client = client;
}
@Override public Response intercept(Chain chain) throws IOException {
RealInterceptorChain realChain = (RealInterceptorChain) chain;
Request request = realChain.request();
StreamAllocation streamAllocation = realChain.streamAllocation();
// We need the network to satisfy this request. Possibly for validating a conditional GET.
boolean doExtensiveHealthChecks = !request.method().equals("GET");
HttpCodec httpCodec = streamAllocation.newStream(client, doExtensiveHealthChecks);
RealConnection connection = streamAllocation.connection();
return realChain.proceed(request, streamAllocation, httpCodec, connection);
}
}
10 .CallServerInterceptor
CallServerInterceptor 是最后一個攔截器,內(nèi)部主要是通過 HttpCodec 構(gòu)建一個響應(yīng)體.
/** 這是鏈中的最后一個攔截器.向服務(wù)器發(fā)起請求. */
public final class CallServerInterceptor implements Interceptor {
private final boolean forWebSocket;
public CallServerInterceptor(boolean forWebSocket) {
this.forWebSocket = forWebSocket;
}
@Override public Response intercept(Chain chain) throws IOException {
RealInterceptorChain realChain = (RealInterceptorChain) chain;
HttpCodec httpCodec = realChain.httpStream();
StreamAllocation streamAllocation = realChain.streamAllocation();
RealConnection connection = (RealConnection) realChain.connection();
Request request = realChain.request();
long sentRequestMillis = System.currentTimeMillis();
httpCodec.writeRequestHeaders(request);
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"))) {
httpCodec.flushRequest();
responseBuilder = httpCodec.readResponseHeaders(true);
}
if (responseBuilder == null) {
// Write the request body if the "Expect: 100-continue" expectation was met.
Sink requestBodyOut = httpCodec.createRequestBody(request, request.body().contentLength());
BufferedSink bufferedRequestBody = Okio.buffer(requestBodyOut);
request.body().writeTo(bufferedRequestBody); // 寫到請求體中
bufferedRequestBody.close();
} else if (!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.
streamAllocation.noNewStreams();
}
}
httpCodec.finishRequest(); // 結(jié)束請求階段并將管道中的數(shù)據(jù) Flush
// 獲取響應(yīng)
if (responseBuilder == null) {
responseBuilder = httpCodec.readResponseHeaders(false);
}
// 構(gòu)建響應(yīng) (此處還未構(gòu)建響應(yīng)體)
Response response = responseBuilder
.request(request)
.handshake(streamAllocation.connection().handshake())
.sentRequestAtMillis(sentRequestMillis)
.receivedResponseAtMillis(System.currentTimeMillis())
.build();
int code = response.code();
if (forWebSocket && code == 101) {
// 鏈接還在更新中,確保攔截器不會得到 空 的響應(yīng)體
// Connection is upgrading, but we need to ensure interceptors see a non-null response body.
response = response.newBuilder()
.body(Util.EMPTY_RESPONSE)
.build();
} else {
// 構(gòu)建響應(yīng)體
response = response.newBuilder()
.body(httpCodec.openResponseBody(response))
.build();
}
if ("close".equalsIgnoreCase(response.request().header("Connection"))
|| "close".equalsIgnoreCase(response.header("Connection"))) {
streamAllocation.noNewStreams();
}
if ((code == 204 || code == 205) && response.body().contentLength() > 0) {
throw new ProtocolException(
"HTTP " + code + " had non-zero Content-Length: " + response.body().contentLength());
}
return response;
}
}
再來看下總的一張流程圖就會清晰了:
okhttp源碼分析.png
到這里我們只是從發(fā)起請求到獲得響應(yīng)的過程,還有很多細(xì)節(jié)的地方需要我們慢慢學(xué)習(xí).
