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本文主要研究一下httpclient的connect

HttpClientConnectionOperator

org/apache/http/conn/HttpClientConnectionOperator.java

public interface HttpClientConnectionOperator {void connect(ManagedHttpClientConnection conn,HttpHost host,InetSocketAddress localAddress,int connectTimeout,SocketConfig socketConfig,HttpContext context) throws IOException;void upgrade(ManagedHttpClientConnection conn,HttpHost host,HttpContext context) throws IOException;}

HttpClientConnectionOperator定义了connect及upgrade方法，它有一个默认的实现类为DefaultHttpClientConnectionOperator

DefaultHttpClientConnectionOperator

org/apache/http/impl/conn/DefaultHttpClientConnectionOperator.java

public class DefaultHttpClientConnectionOperator implements HttpClientConnectionOperator {static final String SOCKET_FACTORY_REGISTRY = "http.socket-factory-registry";private final Log log = LogFactory.getLog(getClass());private final Lookup<ConnectionSocketFactory> socketFactoryRegistry;private final SchemePortResolver schemePortResolver;private final DnsResolver dnsResolver;public DefaultHttpClientConnectionOperator(final Lookup<ConnectionSocketFactory> socketFactoryRegistry,final SchemePortResolver schemePortResolver,final DnsResolver dnsResolver) {super();Args.notNull(socketFactoryRegistry, "Socket factory registry");this.socketFactoryRegistry = socketFactoryRegistry;this.schemePortResolver = schemePortResolver != null ? schemePortResolver :DefaultSchemePortResolver.INSTANCE;this.dnsResolver = dnsResolver != null ? dnsResolver :SystemDefaultDnsResolver.INSTANCE;}//......public void connect(final ManagedHttpClientConnection conn,final HttpHost host,final InetSocketAddress localAddress,final int connectTimeout,final SocketConfig socketConfig,final HttpContext context) throws IOException {final Lookup<ConnectionSocketFactory> registry = getSocketFactoryRegistry(context);final ConnectionSocketFactory sf = registry.lookup(host.getSchemeName());if (sf == null) {throw new UnsupportedSchemeException(host.getSchemeName() +" protocol is not supported");}final InetAddress[] addresses = host.getAddress() != null ?new InetAddress[] { host.getAddress() } : this.dnsResolver.resolve(host.getHostName());final int port = this.schemePortResolver.resolve(host);for (int i = 0; i < addresses.length; i++) {final InetAddress address = addresses[i];final boolean last = i == addresses.length - 1;Socket sock = sf.createSocket(context);sock.setSoTimeout(socketConfig.getSoTimeout());sock.setReuseAddress(socketConfig.isSoReuseAddress());sock.setTcpNoDelay(socketConfig.isTcpNoDelay());sock.setKeepAlive(socketConfig.isSoKeepAlive());if (socketConfig.getRcvBufSize() > 0) {sock.setReceiveBufferSize(socketConfig.getRcvBufSize());}if (socketConfig.getSndBufSize() > 0) {sock.setSendBufferSize(socketConfig.getSndBufSize());}final int linger = socketConfig.getSoLinger();if (linger >= 0) {sock.setSoLinger(true, linger);}conn.bind(sock);final InetSocketAddress remoteAddress = new InetSocketAddress(address, port);if (this.log.isDebugEnabled()) {this.log.debug("Connecting to " + remoteAddress);}try {sock = sf.connectSocket(connectTimeout, sock, host, remoteAddress, localAddress, context);conn.bind(sock);if (this.log.isDebugEnabled()) {this.log.debug("Connection established " + conn);}return;} catch (final SocketTimeoutException ex) {if (last) {throw new ConnectTimeoutException(ex, host, addresses);}} catch (final ConnectException ex) {if (last) {final String msg = ex.getMessage();throw "Connection timed out".equals(msg)? new ConnectTimeoutException(ex, host, addresses): new HttpHostConnectException(ex, host, addresses);}} catch (final NoRouteToHostException ex) {if (last) {throw ex;}}if (this.log.isDebugEnabled()) {this.log.debug("Connect to " + remoteAddress + " timed out. " +"Connection will be retried using another IP address");}}}
}    

DefaultHttpClientConnectionOperator的connect先通过getSocketFactoryRegistry获取Lookup<ConnectionSocketFactory>，再通过它获取ConnectionSocketFactory，之后通过dnsResolver解析地址，再通过schemePortResolver解析port，然后通过ConnectionSocketFactory创建socket，并根据socketConfig设置socket的参数，最后执行connectSocket，并绑定到conn

connectSocket

org/apache/http/conn/socket/PlainConnectionSocketFactory.java

public class PlainConnectionSocketFactory implements ConnectionSocketFactory {public static final PlainConnectionSocketFactory INSTANCE = new PlainConnectionSocketFactory();public static PlainConnectionSocketFactory getSocketFactory() {return INSTANCE;}public PlainConnectionSocketFactory() {super();}@Overridepublic Socket createSocket(final HttpContext context) throws IOException {return new Socket();}@Overridepublic Socket connectSocket(final int connectTimeout,final Socket socket,final HttpHost host,final InetSocketAddress remoteAddress,final InetSocketAddress localAddress,final HttpContext context) throws IOException {final Socket sock = socket != null ? socket : createSocket(context);if (localAddress != null) {sock.bind(localAddress);}try {sock.connect(remoteAddress, connectTimeout);} catch (final IOException ex) {try {sock.close();} catch (final IOException ignore) {}throw ex;}return sock;}}

PlainConnectionSocketFactory的createSocket直接new一个socket，其connectSocket方法则执行sock.connect

socketConfig

resolveSocketConfig

org/apache/http/impl/conn/PoolingHttpClientConnectionManager.java

    private SocketConfig resolveSocketConfig(final HttpHost host) {SocketConfig socketConfig = this.configData.getSocketConfig(host);if (socketConfig == null) {socketConfig = this.configData.getDefaultSocketConfig();}if (socketConfig == null) {socketConfig = SocketConfig.DEFAULT;}return socketConfig;}

PoolingHttpClientConnectionManager的resolveSocketConfig先是从configData根据指定host获取socketConfig，若为null则再从configData获取默认的socketConfig，若为null则返回默认的socketConfig

setSocketConfig

org/apache/http/impl/conn/PoolingHttpClientConnectionManager.java

    public void setDefaultSocketConfig(final SocketConfig defaultSocketConfig) {this.configData.setDefaultSocketConfig(defaultSocketConfig);}public void setSocketConfig(final HttpHost host, final SocketConfig socketConfig) {this.configData.setSocketConfig(host, socketConfig);}

PoolingHttpClientConnectionManager提供了setDefaultSocketConfig、setSocketConfig方法

SocketConfig.DEFAULT

org/apache/http/config/SocketConfig.java

public class SocketConfig implements Cloneable {public static final SocketConfig DEFAULT = new Builder().build();//......public static class Builder {private int soTimeout;private boolean soReuseAddress;private int soLinger;private boolean soKeepAlive;private boolean tcpNoDelay;private int sndBufSize;private int rcvBufSize;private int backlogSize;Builder() {this.soLinger = -1;this.tcpNoDelay = true;}//......}
}        

默认的socketConfig，除了tcpNoDelay为true，其他的都为false，然后soLinger为-1

小结

HttpClientConnectionOperator定义了connect及upgrade方法，它有一个默认的实现类为DefaultHttpClientConnectionOperator；DefaultHttpClientConnectionOperator的connect先通过getSocketFactoryRegistry获取Lookup<ConnectionSocketFactory>，再通过它获取ConnectionSocketFactory，之后通过dnsResolver解析地址，再通过schemePortResolver解析port，然后通过ConnectionSocketFactory创建socket，并根据socketConfig设置socket的参数，最后执行connectSocket，并绑定到conn；默认的socketConfig，除了tcpNoDelay为true，其他的都为false，然后soLinger为-1。