Index: test/src/org/apache/jmeter/protocol/http/sampler/HTTPSamplerFactoryTest.java
===================================================================
--- test/src/org/apache/jmeter/protocol/http/sampler/HTTPSamplerFactoryTest.java	(revision 0)
+++ test/src/org/apache/jmeter/protocol/http/sampler/HTTPSamplerFactoryTest.java	(revision 0)
@@ -0,0 +1,15 @@
+package org.apache.jmeter.protocol.http.sampler;
+
+import junit.framework.TestCase;
+
+public class HTTPSamplerFactoryTest extends TestCase {
+
+	public void testGetImplementation() throws Exception {
+
+		HTTPAbstractImpl implementation = HTTPSamplerFactory.getImplementation(
+				StubHTTPSamplerBase.class.getName(),
+				HTTPSamplerFactory.newInstance());
+
+		assertEquals(StubHTTPSamplerBase.class.getName(), implementation.getClass().getName());
+	}
+}
Index: src/protocol/http/org/apache/jmeter/protocol/http/sampler/HTTPSamplerFactory.java
===================================================================
--- src/protocol/http/org/apache/jmeter/protocol/http/sampler/HTTPSamplerFactory.java	(revision 1696806)
+++ src/protocol/http/org/apache/jmeter/protocol/http/sampler/HTTPSamplerFactory.java	(working copy)
@@ -65,7 +65,7 @@
      *
      * @param alias HTTP_SAMPLER or HTTP_SAMPLER_APACHE or IMPL_HTTP_CLIENT3_1 or IMPL_HTTP_CLIENT4
      * @return the appropriate sampler
-     * @throws UnsupportedOperationException if alias is not recognised
+     * @throws UnsupportedOperationException if alias is not recognized
      */
     public static HTTPSamplerBase newInstance(String alias) {
         if (alias ==null || alias.length() == 0) {
@@ -101,8 +101,14 @@
         } else if (IMPL_HTTP_CLIENT4.equals(impl)) {
             return new HTTPHC4Impl(base);
         } else {
-            throw new IllegalArgumentException("Unknown implementation type: '"+impl+"'");
+        	try {
+        		Class<?> implClass = Class.forName(impl);
+        		return  (HTTPAbstractImpl)implClass.getConstructor(HTTPSamplerBase.class).newInstance(base);
+        	} catch(Exception e) {
+        		e.printStackTrace();
+            }
         }
+		throw new IllegalArgumentException("Unknown implementation type: '"+impl+"'");
     }
 
 }
Index: test/src/org/apache/jmeter/protocol/http/sampler/StubHTTPSamplerBase.java
===================================================================
--- test/src/org/apache/jmeter/protocol/http/sampler/StubHTTPSamplerBase.java	(revision 0)
+++ test/src/org/apache/jmeter/protocol/http/sampler/StubHTTPSamplerBase.java	(revision 0)
@@ -0,0 +1,22 @@
+package org.apache.jmeter.protocol.http.sampler;
+
+import java.net.URL;
+
+public class StubHTTPSamplerBase extends HTTPAbstractImpl {
+
+	public StubHTTPSamplerBase(HTTPSamplerBase testElement) {
+		super(testElement);
+	}
+
+	@Override
+	public boolean interrupt() {
+		return false;
+	}
+
+	@Override
+	protected HTTPSampleResult sample(URL url, String method,
+			boolean areFollowingRedirect, int frameDepth) {
+		return null;
+	}
+	
+}
\ No newline at end of file