HTTPCLIENT-1123: Support for pluggable DNS resolvers (default resolver).

Contributed by Alin Vasile <alinachegalati at yahoo dot com>



git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpclient/trunk@1165863 13f79535-47bb-0310-9956-ffa450edef68

httpclient/src/main/java/org/apache/http/impl/conn/DefaultClientConnectionOperator.java

@@ -105,7 +105,7 @@ public DefaultClientConnectionOperator(final SchemeRegistry schemes) {
             throw new IllegalArgumentException("Scheme registry amy not be null");
         }
         this.schemeRegistry = schemes;
-        this.dnsResolver = null;
+        this.dnsResolver = new SystemDefaultDnsResolver();
     }
 
     /**
@@ -120,7 +120,11 @@ public DefaultClientConnectionOperator(final SchemeRegistry schemes) {
     public DefaultClientConnectionOperator(final SchemeRegistry schemes,final DnsResolver dnsResolver) {
         if (schemes == null) {
             throw new IllegalArgumentException(
-                     "Scheme registry amy not be null");
+                     "Scheme registry may not be null");
+        }
+
+        if(dnsResolver == null){
+            throw new IllegalArgumentException("DNS resolver may not be null");
         }
 
         this.schemeRegistry = schemes;
@@ -256,24 +260,19 @@ protected void prepareSocket(
 
     /**
      * Resolves the given host name to an array of corresponding IP addresses, based on the
-     * configured name service on the system.
-     *
-     * If a custom DNS resolver is provided, the given host will be searched in
-     * it first. If the host is not configured, the default OS DNS-lookup
-     * mechanism is used.
+     * configured name service on the provided DNS resolver. If one wasn't provided, the system
+     * configuration is used.
      *
      * @param host host name to resolve
      * @return array of IP addresses
      * @exception  UnknownHostException  if no IP address for the host could be determined.
      *
+     * @see {@link DnsResolver}
+     * @see {@link SystemDefaultDnsResolver}
      * @since 4.1
      */
     protected InetAddress[] resolveHostname(final String host) throws UnknownHostException {
-        if (dnsResolver != null) {
             return dnsResolver.resolve(host);
-        } else {
-            return InetAddress.getAllByName(host);
-        }
     }
 
 }

httpclient/src/main/java/org/apache/http/impl/conn/PoolingClientConnectionManager.java

@@ -101,7 +101,7 @@ public PoolingClientConnectionManager(
             throw new IllegalArgumentException("Scheme registry may not be null");
         }
         this.schemeRegistry = schemeRegistry;
-        this.dnsResolver = null;
+        this.dnsResolver = new SystemDefaultDnsResolver();
         this.operator = createConnectionOperator(schemeRegistry);
         this.pool = new HttpConnPool(this.log, 2, 20, timeToLive, tunit);
     }
@@ -114,7 +114,7 @@ public PoolingClientConnectionManager(final SchemeRegistry schemeRegistry,
             throw new IllegalArgumentException("Scheme registry may not be null");
         }
         this.schemeRegistry = schemeRegistry;
-        this.dnsResolver = dnsResolver;
+        this.dnsResolver  = new SystemDefaultDnsResolver();
         this.operator = createConnectionOperator(schemeRegistry);
         this.pool = new HttpConnPool(this.log, 2, 20, timeToLive, tunit);
     }

httpclient/src/main/java/org/apache/http/impl/conn/SystemDefaultDnsResolver.java

@@ -0,0 +1,47 @@
+/*
+ * ====================================================================
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ * ====================================================================
+ *
+ * This software consists of voluntary contributions made by many
+ * individuals on behalf of the Apache Software Foundation.  For more
+ * information on the Apache Software Foundation, please see
+ * <http://www.apache.org/>.
+ *
+ */
+package org.apache.http.impl.conn;
+
+import java.net.InetAddress;
+import java.net.UnknownHostException;
+
+import org.apache.http.conn.DnsResolver;
+
+/**
+ * DNS resolver that uses the default OS implementation for resolving host names.
+ *
+ */
+public class SystemDefaultDnsResolver implements DnsResolver {
+
+    /**
+     * {@inheritDoc}
+     */
+    public InetAddress[] resolve(String host) throws UnknownHostException {
+        return InetAddress.getAllByName(host);
+    }
+
+}

httpclient/src/test/java/org/apache/http/impl/conn/TestDefaultClientConnectOperator.java

@@ -65,6 +65,13 @@ public void testDnsResolverUnknownHost() throws Exception {
         operator.resolveHostname("unknown.example.com");
     }
 
+    @Test
+    public void testDefaultLocalHost() throws Exception {
+        DefaultClientConnectionOperator operator = new DefaultClientConnectionOperator(
+                SchemeRegistryFactory.createDefault());
+        operator.resolveHostname("localhost");
+    }
+
     private InetAddress[] translateIp(String ip) throws UnknownHostException {
         String[] ipParts = ip.split("\\.");