Configure the TFS SDK native folder's location automatically.

This avoids having to add the com.microsoft.tfs.jni.native.base-directory property in the container's configuration file.
Added an integration test to verify the functionality.

src/main/java/hudson/plugins/tfs/model/Server.java

@@ -4,9 +4,13 @@
 import hudson.plugins.tfs.commands.ServerConfigurationProvider;
 import hudson.plugins.tfs.util.MaskedArgumentListBuilder;
 
+import java.io.File;
 import java.io.IOException;
 import java.io.Reader;
 import java.net.URI;
+import java.net.URL;
+import java.security.CodeSource;
+import java.security.ProtectionDomain;
 import java.util.HashMap;
 import java.util.Map;
 
@@ -19,6 +23,7 @@
 
 public class Server implements ServerConfigurationProvider {
 
+    private static final String nativeFolderPropertyName = "com.microsoft.tfs.jni.native.base-directory";
     private final String url;
     private final String userName;
     private final String userPassword;
@@ -45,6 +50,7 @@ else if (username != null && password != null) {
         }
 
         if (credentials != null) {
+            ensureNativeLibrariesConfigured();
             // TODO: TFSTeamProjectCollection implements Closeable
             // and should be disposed as soon as no longer needed.
             this.tpc = new TFSTeamProjectCollection(uri, credentials);
@@ -54,6 +60,22 @@ else if (username != null && password != null) {
         }
     }
 
+    static synchronized void ensureNativeLibrariesConfigured() {
+        final String nativeFolder = System.getProperty(nativeFolderPropertyName);
+        if (nativeFolder == null) {
+            final Class<TFSTeamProjectCollection> metaclass = TFSTeamProjectCollection.class;
+            final ProtectionDomain protectionDomain = metaclass.getProtectionDomain();
+            final CodeSource codeSource = protectionDomain.getCodeSource();
+            // TODO: codeSource could be null; what should we do, then?
+            final URL location = codeSource.getLocation();
+            final String stringPathToJar = location.getFile();
+            final File pathToJar = new File(stringPathToJar);
+            final File pathToLibFolder = pathToJar.getParentFile();
+            final File pathToNativeFolder = new File(pathToLibFolder, "native");
+            System.setProperty(nativeFolderPropertyName, pathToNativeFolder.toString()); 
+        }
+    }
+
     Server(String url) {
         this(null, url, null, null);
     }

src/test/java/hudson/plugins/tfs/model/ServerIntegrationTest.java

@@ -0,0 +1,25 @@
+package hudson.plugins.tfs.model;
+
+import org.jvnet.hudson.test.JenkinsRule;
+import org.junit.Rule;
+import org.junit.Test;
+
+import com.microsoft.tfs.core.TFSTeamProjectCollection;
+import com.microsoft.tfs.core.exceptions.TECoreException;
+
+public class ServerIntegrationTest {
+
+    @Rule public JenkinsRule j = new JenkinsRule();
+
+    @Test(expected = TECoreException.class)
+    /**
+     * It's OK for this test to throw a TECoreException for "unknown host";
+     * it means we were able to load the native libraries,
+     * otherwise an @link UnsatisfiedLinkError would have been thrown earlier.
+     */
+    public void canFindTfsSdkNativeLibraries() {
+        final Server server = new Server(null, "http://tfs.invalid:8080/tfs", "username", "password");
+        final TFSTeamProjectCollection tpc = server.getTeamProjectCollection();
+        tpc.getVersionControlClient();
+    }
+}