connect方法分析

2,connect方法

HttpURLConnectionImpl的connect方法如下,

public final void connect() throws IOException {
initHttpEngine();
boolean success;
do {
success = execute(false);
} while (!success);
}

首先调用initHttpEngine方法构造HttpEngine对象,然后调用execute方法进行连接,

2.1 构造HttpEngine对象

HttpURLConnectionImpl的initHttpEngine方法如下,

httpEngine = newHttpEngine(method, null, null, null);

在newHttpEngine方法的最后会构造HttpEngine对象,

return new HttpEngine(engineClient, request, bufferRequestBody, true, false, connection, null,
requestBody, priorResponse);

2.2 execute连接

调用流程图如下,



HttpURLConnectionImpl的execute方法主要逻辑如下,

try {
httpEngine.sendRequest();

调用HttpEngine对象的sendRequest发送请求,在该方法中会进行连接,

if (connection == null) {
connect();
}

如果Connection对象connection为空,就调用connect方法进行连接, connect方法主要逻辑如下,

1,首先调用createAddress创建Address对象,

address = createAddress(client, networkRequest);

2,然后调用nextConnection方法创建Connection对象并进行连接,

connection = nextConnection();

nextConnection方法如下,

Connection connection = createNextConnection();
Internal.instance.connectAndSetOwner(client, connection, this, networkRequest);

首先调用createNextConnection方法构造Connection对象,然后调用Internal的connectAndSetOwner方法进行连接。

Internal是一个abstract类,定义如下,

public abstract class Internal {

有一个static变量instance,

public static Internal instance;

现在问题是哪个类继承了Internal并且实现了对应的方法呢?

在源码下面全局搜索,居然没有类继承Internal!  后来才发现,是在OkHttpClient中内部匿名实现的。

并且OkHttpClient是在HttpHandler的createHttpOkUrlFactory方法中构造的,

OkHttpClient client = new OkHttpClient();

Internal在OkHttpClient是一个static的代码块,

Internal.instance = new Internal() {
@Override public Transport newTransport(
Connection connection, HttpEngine httpEngine) throws IOException {
return connection.newTransport(httpEngine);
}
•••

其connectAndSetOwner方法如下,

@Override public void connectAndSetOwner(OkHttpClient client, Connection connection,
HttpEngine owner, Request request) throws RouteException {
connection.connectAndSetOwner(client, owner, request);
}

Connection的connectAndSetOwner逻辑如下,

if (!isConnected()) {
List<ConnectionSpec> connectionSpecs = route.address.getConnectionSpecs();
connect(client.getConnectTimeout(), client.getReadTimeout(), client.getWriteTimeout(),
request, connectionSpecs, client.getRetryOnConnectionFailure());
if (isSpdy()) {
client.getConnectionPool().share(this);
}
client.routeDatabase().connected(getRoute());
}

如果还未连接,则调用connect方法进行连接。

2.3 socket连接

Connection的connect调用流程图如下,



Connection的connect的主要逻辑如下,

1,构造SocketConnector对象,

SocketConnector socketConnector = new SocketConnector(this, pool);

2,构造SocketConnector的内部类ConnectedSocket对象,

if (route.address.getSslSocketFactory() != null) {
// https:// communication
connectedSocket = socketConnector.connectTls(connectTimeout, readTimeout, writeTimeout,
request, route, connectionSpecs, connectionRetryEnabled);
} else {
// http:// communication.
if (!connectionSpecs.contains(ConnectionSpec.CLEARTEXT)) {
throw new RouteException(
new UnknownServiceException(
"CLEARTEXT communication not supported: " + connectionSpecs));
}
connectedSocket = socketConnector.connectCleartext(connectTimeout, readTimeout, route);
}

如果是https网址请求,就调用SocketConnector的connectTls方法创建ConnectedSocket对象,

否则就调用connectCleartext方法创建ConnectedSocket对象。

3,最后为Connection的变量赋值,

socket = connectedSocket.socket;
handshake = connectedSocket.handshake;
protocol = connectedSocket.alpnProtocol == null
? Protocol.HTTP_1_1 : connectedSocket.alpnProtocol;

SocketConnector的connectCleartext方法如下,

public ConnectedSocket connectCleartext(int connectTimeout, int readTimeout, Route route)
throws RouteException {
Socket socket = connectRawSocket(readTimeout, connectTimeout, route);
return new ConnectedSocket(route, socket);
}

首先调用connectRawSocket方法获取Socket对象,然后利用Socket对象构造并返回ConnectedSocket对象。

connectRawSocket方法的逻辑如下,

Platform platform = Platform.get();
try {
Proxy proxy = route.getProxy();
Address address = route.getAddress();
Socket socket;
if (proxy.type() == Proxy.Type.DIRECT || proxy.type() == Proxy.Type.HTTP) {
socket = address.getSocketFactory().createSocket();
} else {
socket = new Socket(proxy);
}
socket.setSoTimeout(soTimeout);
platform.connectSocket(socket, route.getSocketAddress(), connectTimeout);

return socket;
} catch (IOException e) {
throw new RouteException(e);
}

首先获取Socket对象,然后调用Platform的connectSocket方法。

Platform这个类还是有点内涵,先来分析一下。

Platform的get方法如下,

public static Platform get() {
return PLATFORM;
}

PLATFORM是Platform对象,并且是调用findPlatform方法获取

private static final Platform PLATFORM = findPlatform();

findPlatform方法根据android 系统进行构造Platform对象,

1,如果是android 2.3以上版本,就构造Android对象,

•••
return new Android(setUseSessionTickets, setHostname, trafficStatsTagSocket,
trafficStatsUntagSocket, getAlpnSelectedProtocol, setAlpnProtocols);

当然Android是Platform的子类,并且是Platform的内部类。

2,否则就构造Platform对象,

return new Platform();

Android对象的connectSocket方法如下,

try {
socket.connect(address, connectTimeout);
} catch (SecurityException se) {
// Before android 4.3, socket.connect could throw a SecurityException
// if opening a socket resulted in an EACCES error.
IOException ioException = new IOException("Exception in connect");
ioException.initCause(se);
throw ioException;
}

其实就是调用socket的connect方法进行连接,如果连接出错则抛出异常。

论述了这么多,本质就是构造Socket对象,并调用Socket对象的connect方法进行连接。