目录
- 序
- DnsResolver
- InMemoryDnsResolver
- SystemDefaultDnsResolver
- DefaultHttpClientConnectionOperator
- 小结
序
本文主要研究一下HttpClient的DnsResolver
DnsResolver
org/apache/http/conn/DnsResolver.Java
/** * Users may implement this interface to override the normal DNS lookup offered * by the OS. * * @since 4.2 */ public interface DnsResolver { /** * Returns the IP address for the specified host name, or null if the given * host is not recognized or the associated IP address cannot be used to * build an InetAddress instance. * * @see InetAddress * * @param host * The host name to be resolved by this resolver. * @return The IP address associated to the given host name, or null if the * host name is not known by the implementation class. */ InetAddress[] resolve(String host) throws UnknownHostException; }
DnsResolver定义了resolve方法,可用于替换OS提供的DNS lookup
InMemoryDnsResolver
org/apache/http/impl/conn/InMemoryDnsResolver.java
/** * In-memory {@link DnsResolver} implementation. * * @since 4.2 */ public class InMemoryDnsResolver implements DnsResolver { /** Logger associated to this class. */ private final Log log = LogFactory.getLog(InMemoryDnsResolver.class); /** * In-memory collection that will hold the associations between a host name * and an array of InetAddress instances. */ private final Map<String, InetAddress[]> dnsMap; /** * Builds a DNS resolver that will resolve the host names against a * collection held in-memory. */ public InMemoryDnsResolver() { dnsMap = new ConcurrentHashMap<String, InetAddress[]>(); } /** * Associates the given array of IP addresses to the given host in this DNS overrider. * The IP addresses are assumed to be already resolved. * * @parwww.devze.comam host * The host name to be associated with the given IP. * @param ips * array of IP addresses to be resolved by this DNS overrider to the given * host name. */ public void add(final String host, final InetAddress... ips) { Args.notNull(host, "Host name"); Args.notNull(ips, "Array of IP addresses"); dnsMap.put(host, ips); } /** * {@inheritDoc} */ @Override public InetAddress[] resolve(final String host) throws UnknownHostException { final InetAddress[] resolvedAddresses = dnsMap.get(host); if (log.isInfoEnabled()) { log.info("Resolving " + host + " to " + Arrays.deepToString(resolvedAddresses)); } if(resolvedAddresses == null){ throw new UnknownHostException(host + " cannot be resolved"); } return resolvedAddresses; } }
InMemoryDnsResolver实现了DnsResolver接口,它用一个ConcurrentHashMap来存放dns信息,提供add方法往map添编程客栈加host及对应的ip地址,然后其resolve就是从这个map来读取对应的ip地址信息
SystemDefaultDnsResolver
org/apache/http/impl/conn/SystemDefaultDnsResolver.java
/** * DNS resolver that uses the default OS implementation for resolving host names. * * @since 4.2 */ public class SystemDefaultDnsResolver implements DnsResolver { public static final SystemDefaultDnsResolver INSTANCE = new SystemDefaultDnsResolver(); @Override public InetAddress[] resolve(final String host) throws UnknownHostException { return InetAddress.getAllByName(host); } }
SystemDefaultDnsResolver实现了DnsResolver,它用的就是jdk提供的InetAddress.getAllByName,默认是走的OS的DNS,可以通过sun.net.spi.nameservice.provider.<n>去自定义
DefaultHttpClientConnectionOperator
org/apache/http/impl/conn/DefaultHttpClientConnectionOperator.java
@Contract(threading = ThreadingBehavior.IMMUTABLE_CONDITIONAL) 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; } @Override 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(www.devze.com"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; } php } if (this.log.isDebugEnabled()) { this.log.debug("Connect to " + remoteAddress + " timed out. " + "Connection will be retried using another IP address"); } } } //...... }
DefaultHttpClientConnectionOperator的connect方法会通过dnsResolver.resolve解析host
小结
HttpClient提供了DnsResolver接口,可以用于自定义DNS解析,是除了使用sun.net.spi.nameservice.provider.<编程客栈n>
去自定义JDK全局dns解析外的另外一种方案。
以上就是HttpClient的DnsResolver自定义DNS解析另一种选择深入研究的详细内容,更多关于HttpClient DnsResolver解析DNS的资料请关注编程客栈(www.devze.com)其它相关文章!
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