DPML Notify

[niclas AT hedhman.org]

Author: niclas AT hedhman.org
Date: Sun Mar 27 13:31:45 2005
New Revision: 2157

Added:
   
development/main/transit/core/handler/src/main/net/dpml/transit/link/ArtifactLinkManager.java
   (contents, props changed)
   
development/main/transit/core/handler/src/main/net/dpml/transit/link/FileLinkManager.java
   (contents, props changed)
   
development/main/transit/core/handler/src/main/net/dpml/transit/link/Handler.java
   (contents, props changed)
   
development/main/transit/core/handler/src/main/net/dpml/transit/link/Link.java
   (contents, props changed)
   
development/main/transit/core/handler/src/main/net/dpml/transit/link/LinkManager.java
   (contents, props changed)
   
development/main/transit/core/handler/src/main/net/dpml/transit/link/LinkURLConnection.java
   (contents, props changed)
   
development/main/transit/core/handler/src/test/net/dpml/transit/test/LinkTestCase.java
   (contents, props changed)
Modified:
   
development/main/transit/core/handler/src/main/net/dpml/transit/SecuredTransitContext.java
   
development/main/transit/core/handler/src/main/net/dpml/transit/Transit.java
   
development/main/transit/core/handler/src/main/net/dpml/transit/artifact/ArtifactURLConnection.java
   
development/main/transit/core/handler/src/main/net/dpml/transit/util/MimeTypeHandler.java
   
development/main/transit/core/handler/src/main/net/dpml/transit/util/StreamUtils.java
   
development/main/transit/core/handler/src/test/net/dpml/transit/test/MimeHandlerTestCase.java
   
development/main/transit/core/handler/src/test/net/dpml/transit/test/OfflineTestCase.java
Log:
Added a link: handler, which is similar to symlinks.

Modified: 
development/main/transit/core/handler/src/main/net/dpml/transit/SecuredTransitContext.java
==============================================================================
--- 
development/main/transit/core/handler/src/main/net/dpml/transit/SecuredTransitContext.java
  (original)
+++ 
development/main/transit/core/handler/src/main/net/dpml/transit/SecuredTransitContext.java
  Sun Mar 27 13:31:45 2005
@@ -1,5 +1,5 @@
 /*
- * Copyright 2004 Niclas Hedhman
+ * Copyright 2004-2005 Niclas Hedhman
  *
  * Licensed  under the  Apache License,  Version 2.0  (the "License");
  * you may not use  this file  except in  compliance with the License.
@@ -23,6 +23,8 @@
 import net.dpml.transit.cache.CacheHandler;
 import net.dpml.transit.cache.RemoteCacheHandler;
 import net.dpml.transit.host.ResourceManager;
+import net.dpml.transit.link.FileLinkManager;
+import net.dpml.transit.link.LinkManager;
 import net.dpml.transit.monitors.SystemMonitor;
 import net.dpml.transit.network.DelegatingAuthenticator;
 import net.dpml.transit.network.RequestIdentifier;
@@ -143,6 +145,11 @@
     private CacheHandler m_cacheHandler;
 
    /**
+    * The LinkManager instance.
+    */
+    private LinkManager m_linkManager;
+
+   /**
     * The authoritive anchor url.
     */
     private URL m_authorativeHost;
@@ -182,32 +189,6 @@
         }
     }
 
-    /** Set the Transit instance into Server mode.
-     * @param serverMode true to operate Transit in Server mode.
-     * @exception TransitException if not possible to make this Transit into 
a server.
-     */
-    public void setServer( boolean serverMode )
-        throws TransitException
-    {
-        m_server = serverMode;
-        if( m_server ^ serverMode )  // Is there a change?
-        {
-            if( m_server )
-            {
-                bindServer();
-            }
-            else
-            {
-                unbindServer();
-            }
-        }
-    }
-
-    public boolean isServer()
-    {
-        return m_server;
-    }
-
    /**
     * Creation of the transit context.  If the transit context has already
     * been established the method returns the singeton context otherwise a 
new context
@@ -288,6 +269,32 @@
         }
     }
 
+    /** Set the Transit instance into Server mode.
+     * @param serverMode true to operate Transit in Server mode.
+     * @exception TransitException if not possible to make this Transit into 
a server.
+     */
+    public void setServer( boolean serverMode )
+        throws TransitException
+    {
+        m_server = serverMode;
+        if( m_server ^ serverMode )  // Is there a change?
+        {
+            if( m_server )
+            {
+                bindServer();
+            }
+            else
+            {
+                unbindServer();
+            }
+        }
+    }
+
+    public boolean isServer()
+    {
+        return m_server;
+    }
+
    /**
     * Create the resource manager that will be responsible for the 
establishment
     * of the transit cache handler. The class implementating the resource 
manager
@@ -351,6 +358,11 @@
     {
         m_authorativeHost = null;
         m_cacheHandler = handler;
+
+        // Niclas; Hardcoding the LinkManager for now. When/If pluggable
+        //         LinkManagers becomes a reality, we'll worry about how
+        //         to install them.
+        m_linkManager = new FileLinkManager();
     }
 
     /**
@@ -363,8 +375,7 @@
     private SecuredTransitContext( URL authorative, CacheHandler handler, 
Properties props )
         throws TransitException
     {
-        m_authorativeHost = authorative;
-        m_cacheHandler = handler;
+        this( handler );
         try
         {
             setupAuthenticator( props );
@@ -400,6 +411,11 @@
         return m_cacheHandler;
     }
 
+    public LinkManager getLinkManager()
+    {
+        return m_linkManager;
+    }
+
     /**
      * Return the authorative host URL.
      * @return the authorative host url

Modified: 
development/main/transit/core/handler/src/main/net/dpml/transit/Transit.java
==============================================================================
--- 
development/main/transit/core/handler/src/main/net/dpml/transit/Transit.java  
      (original)
+++ 
development/main/transit/core/handler/src/main/net/dpml/transit/Transit.java  
      Sun Mar 27 13:31:45 2005
@@ -1,6 +1,6 @@
 /*
  * Copyright 2004 Stephen McConnell.
- * Copyright 2004 Niclas Hedhman.
+ * Copyright 2004-2005 Niclas Hedhman.
  *
  * Licensed  under the  Apache License,  Version 2.0  (the "License");
  * you may not use  this file  except in  compliance with the License.

Modified: 
development/main/transit/core/handler/src/main/net/dpml/transit/artifact/ArtifactURLConnection.java
==============================================================================
--- 
development/main/transit/core/handler/src/main/net/dpml/transit/artifact/ArtifactURLConnection.java
 (original)
+++ 
development/main/transit/core/handler/src/main/net/dpml/transit/artifact/ArtifactURLConnection.java
 Sun Mar 27 13:31:45 2005
@@ -175,7 +175,7 @@
         }
         catch( UnknownServiceException use )
         {
-            boolean ignore = true;
+            // Ignore
         }
 
         //

Added: 
development/main/transit/core/handler/src/main/net/dpml/transit/link/ArtifactLinkManager.java
==============================================================================
--- (empty file)
+++ 
development/main/transit/core/handler/src/main/net/dpml/transit/link/ArtifactLinkManager.java
       Sun Mar 27 13:31:45 2005
@@ -0,0 +1,92 @@
+/*
+ * Copyright 2005 Niclas Hedhman
+ * Licensed  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.
+ */
+
+package net.dpml.transit.link;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.InputStream;
+import java.io.IOException;
+import java.io.OutputStream;
+
+import java.net.URI;
+import java.net.URL;
+
+import java.util.Properties;
+
+import net.dpml.transit.SecuredTransitContext;
+import net.dpml.transit.Transit;
+
+import net.dpml.transit.util.StreamUtils;
+
+/** The LinkManager is responsible for storing the mapping between a Link
+ *  instance and a URI.
+ * <p>
+ *  Applications should never call the methods for the LinkManager directly,
+ *  and it is likely that the LinkManager remains outside the reachability of
+ *  applications.
+ * </p>
+ * <p>
+ *  This LinkManager stores all the link: to URI mappings in artifact:link:
+ *  cache objects.
+ * </p>
+ */
+public class ArtifactLinkManager
+    implements LinkManager
+{
+
+    public ArtifactLinkManager()
+    {
+    }
+
+    /** Sets the URI for the provided Link.
+     * The LinkManager is required to persist this information between
+     * JVM restarts and should be persisted on a scope larger than a
+     * single JVM, typically a host or a local area network. LinkManagers
+     * are encouraged to establish other virtual scopes independent of
+     * network topologies.
+     * @exception IOException if the mapping could not be updated.
+     */
+    public void setTargetURI( URI linkUri, URI targetUri )
+        throws IOException
+    {
+        String artifact = "artifact:" + linkUri.toString();
+        URL store = new URL( artifact );
+        OutputStream out = store.openConnection().getOutputStream();
+        byte[] array = targetUri.toString().getBytes( "ISO8859-1" );
+        ByteArrayInputStream in = new ByteArrayInputStream( array );
+        StreamUtils.copyStream( in, out, true );
+    }
+
+    /** Returns the URI that the provided link: URI instance is pointing to.
+     * @exception IOException if the mapping could not be retrieved, due to
+     *            a IOException.
+     * @return target URI that the link points to, or null if it could not
+     *         be found.
+     */
+    public URI getTargetURI( URI linkUri )
+        throws IOException
+    {
+        String artifact = "artifact:" + linkUri.toString();
+        URL store = new URL( artifact );
+        ByteArrayOutputStream out = new ByteArrayOutputStream();
+        InputStream in = store.openConnection().getInputStream();
+        StreamUtils.copyStream( in, out, true );
+        String target = out.toString( "ISO8859-1" );
+        return URI.create( target );
+    }
+}

Added: 
development/main/transit/core/handler/src/main/net/dpml/transit/link/FileLinkManager.java
==============================================================================
--- (empty file)
+++ 
development/main/transit/core/handler/src/main/net/dpml/transit/link/FileLinkManager.java
   Sun Mar 27 13:31:45 2005
@@ -0,0 +1,179 @@
+/*
+ * Copyright 2005 Niclas Hedhman
+ * Licensed  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.
+ */
+
+package net.dpml.transit.link;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.io.IOException;
+
+import java.net.URI;
+
+import java.util.Properties;
+
+import net.dpml.transit.SecuredTransitContext;
+import net.dpml.transit.Transit;
+
+/** The LinkManager is responsible for storing the mapping between a Link
+ *  instance and a URI.
+ * <p>
+ *  Applications should never call the methods for the LinkManager directly,
+ *  and it is likely that the LinkManager remains outside the reachability of
+ *  applications.
+ * </p>
+ * <p>
+ *  This LinkManager stores all the link: to URI mappings in text files,
+ *  which are stored in $DPML_PREFS/transit/links.
+ * </p>
+ * <p>
+ *  The SchemeSpecificPart of the link: URI, i.e. the value between the colon
+ *  (:) and the hash (#) in "link:something#3.1", will be used as the 
filename.
+ *  That file is in the standard java.util.Properties format and
+ *  the key is the string representation of the link URI and the value is the
+ *  string representation of the target URI.
+ * </p>
+ */
+public class FileLinkManager
+    implements LinkManager
+{
+    private File m_linksDir;
+
+    public FileLinkManager()
+    {
+        m_linksDir = new File( Transit.DPML_PREFS, "transit/links" );
+        m_linksDir.mkdirs();
+
+    }
+
+    /** Sets the URI for the provided Link.
+     * The LinkManager is required to persist this information between
+     * JVM restarts and should be persisted on a scope larger than a
+     * single JVM, typically a host or a local area network. LinkManagers
+     * are encouraged to establish other virtual scopes independent of
+     * network topologies.
+     * @exception IOException if the mapping could not be updated.
+     */
+    public void setTargetURI( URI linkUri, URI targetUri )
+        throws IOException
+    {
+        File linkFile = getLinkFile( linkUri );
+        lockWrite( linkFile );
+        try
+        {
+            setTargetURI( linkFile, linkUri, targetUri );
+        } finally
+        {
+            unlock( linkFile );
+        }
+    }
+
+    /** Returns the URI that the provided link: URI instance is pointing to.
+     * @exception IOException if the mapping could not be retrieved, due to
+     *            a IOException.
+     * @return target URI that the link points to, or null if it could not
+     *         be found.
+     */
+    public URI getTargetURI( URI linkUri )
+        throws IOException
+    {
+        File linkFile = getLinkFile( linkUri );
+        lockRead( linkFile );
+        try
+        {
+            return getTargetURI( linkFile, linkUri );
+        } finally
+        {
+            unlock( linkFile );
+        }
+    }
+
+    private File getLinkFile( URI linkUri )
+    {
+        String filename = linkUri.getSchemeSpecificPart();
+        File f = new File( m_linksDir, filename );
+        return f;
+    }
+
+    private void setTargetURI( File linkFile, URI linkUri, URI targetUri )
+        throws IOException
+    {
+        Properties props = new Properties();
+        if( linkFile.exists() )
+        {
+            FileInputStream in = new FileInputStream( linkFile );
+            try
+            {
+                props.load( in );
+            } finally
+            {
+                in.close();
+            }
+        }
+        String link = linkUri.toString();
+        String target = targetUri.toString();
+        props.put( link, target );
+        File parent = linkFile.getParentFile();
+        parent.mkdirs();
+        FileOutputStream out = new FileOutputStream( linkFile );
+        try
+        {
+            props.store( out, "Links for " + linkUri.getSchemeSpecificPart() 
);
+        } finally
+        {
+            out.close();
+        }
+    }
+
+    private URI getTargetURI( File linkFile, URI linkUri )
+        throws IOException
+    {
+        if( linkFile.exists() == false )
+            return null;
+
+        FileInputStream in = new FileInputStream( linkFile );
+        Properties props = new Properties();
+        try
+        {
+            props.load( in );
+        } finally
+        {
+            in.close();
+        }
+        in.close();
+        String link = linkUri.toString();
+        String target = props.getProperty( link );
+        if( target == null )
+            return null;
+        return URI.create( target );
+    }
+
+    private void lockWrite( File file )
+    {
+        // TODO
+    }
+
+    private void lockRead( File file )
+    {
+        // TODO
+    }
+
+    private void unlock( File file )
+    {
+        // TODO
+    }
+}

Added: 
development/main/transit/core/handler/src/main/net/dpml/transit/link/Handler.java
==============================================================================
--- (empty file)
+++ 
development/main/transit/core/handler/src/main/net/dpml/transit/link/Handler.java
   Sun Mar 27 13:31:45 2005
@@ -0,0 +1,60 @@
+/*
+ * Copyright 2005 Niclas Hedhman
+ * Licensed  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.
+ */
+
+package net.dpml.transit.link;
+
+import java.io.IOException;
+
+import java.net.URL;
+import java.net.URLConnection;
+import java.net.URLStreamHandler;
+
+/** link: URL protocol handler.
+ * <p>
+ *   The <strong>link:</strong> protocol is similar to the symlink concept
+ *   in Linux/Unix, where something that looks like a file points to another
+ *   file. In this case, the link URL points to another URL. The resolution
+ *   of the link translation is picked up from managed Transit server(s)
+ * </p>
+ */
+public class Handler extends URLStreamHandler
+{
+   /**
+    * Creation of a new transit link: protocol handler.
+    * @exception TransitException if a transit system error occurs
+    */
+    public Handler()
+    {
+    }
+
+    // 
------------------------------------------------------------------------
+    // implementation
+    // 
------------------------------------------------------------------------
+
+    /**
+     * Opens a connection to the specified URL.
+     *
+     * @param url A URL to open a connection to.
+     * @return The established connection.
+     * @throws IOException If a connection failure occurs.
+     */
+    protected URLConnection openConnection( final URL url )
+        throws IOException
+    {
+        return new LinkURLConnection( url );
+    }
+}

Added: 
development/main/transit/core/handler/src/main/net/dpml/transit/link/Link.java
==============================================================================
--- (empty file)
+++ 
development/main/transit/core/handler/src/main/net/dpml/transit/link/Link.java
      Sun Mar 27 13:31:45 2005
@@ -0,0 +1,83 @@
+/*
+ * Copyright 2005 Niclas Hedhman
+ * Licensed  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.
+ */
+
+package net.dpml.transit.link;
+
+import java.io.IOException;
+
+import java.net.URI;
+
+/** The Link class represents the content of the link: URL and not the 
content
+ *  of the target that the link: points to.
+ *  It is not intended that the applications instantiates this class 
directly,
+ *  but obtains it as a object from the <code>URL.getContent()</code> method.
+ *  Example;
+ *  <pre><code>
+ *      URL url = new URL( "link:some/opague/pointer" );
+ *      Class[] type = new Class[] { Link.class };
+ *
+ *      // Get the Link object from the URL
+ *      Link link = (Link) url.getContent( type );
+ *
+ *      // Get the URI that this link is pointing to at the moment
+ *      URI uri = link.getURI();
+ *
+ *      // Change the link to point somewhere else.
+ *      URI newUri = new URI( "artifact:jar:abc/def/hoopla#3.1.2" );
+ *      link.setURI( newUri );
+ *  </code></pre>
+ */
+public class Link
+{
+    private LinkManager m_manager;
+    private URI m_uri;
+
+    /** Constructor for the Link.
+     */
+    public Link( URI linkURI, LinkManager manager )
+    {
+        m_manager = manager;
+        m_uri = linkURI;
+    }
+
+    public URI getLinkURI()
+    {
+        return m_uri;
+    }
+
+    /** Return the URI that is currently bound to the Link.
+     * @return the current URI the link: is pointing to.
+     */
+    public URI getTargetURI( URI defaultUri )
+        throws IOException
+    {
+        URI uri = m_manager.getTargetURI( m_uri );
+        if( uri == null )
+            return defaultUri;
+        return uri;
+    }
+
+    /** Sets (and permanently remembers) the Link to point to a new URI.
+     * @param uri the URI that this link: should be pointing to.
+     */
+    public void setTargetURI( URI uri )
+        throws IOException
+    {
+        m_manager.setTargetURI( m_uri, uri );
+    }
+}
+

Added: 
development/main/transit/core/handler/src/main/net/dpml/transit/link/LinkManager.java
==============================================================================
--- (empty file)
+++ 
development/main/transit/core/handler/src/main/net/dpml/transit/link/LinkManager.java
       Sun Mar 27 13:31:45 2005
@@ -0,0 +1,47 @@
+/*
+ * Copyright 2005 Niclas Hedhman
+ * Licensed  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.
+ */
+
+package net.dpml.transit.link;
+
+import java.io.IOException;
+
+import java.net.URI;
+
+/** The LinkManager is responsible for storing the mapping between a Link
+ *  instance and a URI.
+ *  Applications should never call the methods for the LinkManager directly,
+ *  and it is likely that the LinkManager remains outside the reachability of
+ *  applications.
+ */
+public interface LinkManager
+{
+    /** Sets the URI for the provided link URI.
+     * The LinkManager is required to persist this information between
+     * JVM restarts and should be persisted on a scope larger than a
+     * single JVM, typically a host or a local area network. LinkManagers
+     * are encouraged to establish other virtual scopes independent of
+     * network topologies.
+     */
+    void setTargetURI( URI link, URI target )
+        throws IOException;
+
+    /** Returns the URI that the provided link URI is pointing to.
+     */
+    URI getTargetURI( URI link )
+        throws IOException;
+
+}

Added: 
development/main/transit/core/handler/src/main/net/dpml/transit/link/LinkURLConnection.java
==============================================================================
--- (empty file)
+++ 
development/main/transit/core/handler/src/main/net/dpml/transit/link/LinkURLConnection.java
 Sun Mar 27 13:31:45 2005
@@ -0,0 +1,166 @@
+/*
+ * Copyright 2005 Niclas Hedhman
+ * Licensed  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.
+ */
+
+package net.dpml.transit.link;
+
+import java.io.InputStream;
+import java.io.IOException;
+import java.io.OutputStream;
+
+import java.net.UnknownServiceException;
+import java.net.URI;
+import java.net.URL;
+import java.net.URLConnection;
+
+import net.dpml.transit.Transit;
+import net.dpml.transit.SecuredTransitContext;
+import net.dpml.transit.util.MimeTypeHandler;
+
+/**
+ * link: URL protocol connection processor.
+ */
+public class LinkURLConnection extends URLConnection
+{
+    private boolean m_connected;
+    private URL     m_targetURL;
+
+    /**
+     * Creation of a new handler.
+     * @param url the url to establish a connection with
+     * @param context the transit context
+     * @exception NullPointerException if the url argument is null
+     * @exception IOException if the url argument is not a valid,
+     *            i.e. the path must contain a group and an artifactId
+     *            separated by a slash.
+     */
+    LinkURLConnection( URL url )
+        throws NullPointerException, IOException
+    {
+        super( url );
+        m_connected = false;
+    }
+
+   /**
+    * Establish a connection.
+    *
+    * @exception IOException is an error occurs while attempting to establish
+    *  the connection.
+    */
+    public void connect()
+        throws IOException
+    {
+        if( m_connected )
+            return;
+        m_connected = true;
+        LinkManager linkManager = 
SecuredTransitContext.create().getLinkManager();
+        URI linkUri = URI.create( url.toExternalForm() );
+        URI targetUri = linkManager.getTargetURI( linkUri );
+        if( targetUri != null )
+            m_targetURL = new URL( targetUri.toString() );
+        else
+            m_targetURL = null;
+    }
+
+   /**
+    * Return an input stream to the resource.
+    * @return the input stream
+    * @exception IOException is an error occurs
+    */
+    public InputStream getInputStream()
+        throws IOException
+    {
+        connect();
+        if( m_targetURL == null )
+            return null;
+        URLConnection conn = m_targetURL.openConnection();
+        InputStream in = conn.getInputStream();
+        return in;
+    }
+
+   /**
+    * Return an output stream to the resource.
+    * @return the output stream
+    * @exception IOException if any I/O problems occur.
+    */
+    public OutputStream getOutputStream()
+        throws IOException
+    {
+        connect();
+        if( m_targetURL == null )
+            return null;
+        URLConnection conn = m_targetURL.openConnection();
+        OutputStream out = conn.getOutputStream();
+        return out;
+    }
+
+   /**
+    * Reutrn the mimetype of the content.
+    * @return the content mimetype
+    */
+    public String getContentType()
+    {
+        return MimeTypeHandler.getMimeType( "link" );
+    }
+
+   /**
+    * Return the content for this Link.
+    * @param classes a sequence of classes against which the
+    *   implementation will attempt to establish a known match
+    * @return the content object (possibly null)
+    * @exception IOException is an error occurs
+    */
+    public Object getContent( Class[] classes )
+        throws IOException
+    {
+        try
+        {
+            Object content = super.getContent( classes );
+            if( content != null )
+            {
+                return content;
+            }
+        }
+        catch( UnknownServiceException use )
+        {
+            // Ignore
+        }
+
+        //
+        // attempt to resolve this locally
+        //
+
+        for( int i=0; i < classes.length; i++ )
+        {
+            Class c = classes[i];
+            if( c.equals( Link.class ) )
+            {
+                LinkManager linkManager = 
SecuredTransitContext.getInstance().getLinkManager();
+                String extUri = getURL().toString();
+                URI uri = URI.create( extUri );
+                Link link = new Link( uri, linkManager );
+                return link;
+            }
+            if( c.equals( URI.class ) )
+            {
+                String extUri = getURL().toString();
+                URI uri = URI.create( extUri );
+                return uri;
+            }
+        }
+        return null;
+    }
+}

Modified: 
development/main/transit/core/handler/src/main/net/dpml/transit/util/MimeTypeHandler.java
==============================================================================
--- 
development/main/transit/core/handler/src/main/net/dpml/transit/util/MimeTypeHandler.java
   (original)
+++ 
development/main/transit/core/handler/src/main/net/dpml/transit/util/MimeTypeHandler.java
   Sun Mar 27 13:31:45 2005
@@ -1,5 +1,5 @@
 /*
- * Copyright 2004 Niclas Hedhman.
+ * Copyright 2004-2005 Niclas Hedhman.
  *
  * Licensed  under the  Apache License,  Version 2.0  (the "License");
  * you may not use  this file  except in  compliance with the License.
@@ -45,6 +45,7 @@
         MIME_TYPES.put( "png", "image/png" );
         MIME_TYPES.put( "gif", "image/gif" );
         MIME_TYPES.put( "jpg", "image/jpg" );
+        MIME_TYPES.put( "link", "application/x-dpml-link" );
     }
 
    /**

Modified: 
development/main/transit/core/handler/src/main/net/dpml/transit/util/StreamUtils.java
==============================================================================
--- 
development/main/transit/core/handler/src/main/net/dpml/transit/util/StreamUtils.java
       (original)
+++ 
development/main/transit/core/handler/src/main/net/dpml/transit/util/StreamUtils.java
       Sun Mar 27 13:31:45 2005
@@ -124,4 +124,22 @@
             }
         }
     }
+
+    static public boolean compareStreams( InputStream in1, InputStream in2 )
+        throws IOException
+    {
+        boolean result = true;
+        do
+        {
+            int v1 = in1.read();
+            int v2 = in2.read();
+            if( v1 != v2 )
+            {
+                return false;
+            }
+            if( v1 == -1 )
+                break;
+        } while( true );
+        return result;
+    }
 }

Added: 
development/main/transit/core/handler/src/test/net/dpml/transit/test/LinkTestCase.java
==============================================================================
--- (empty file)
+++ 
development/main/transit/core/handler/src/test/net/dpml/transit/test/LinkTestCase.java
      Sun Mar 27 13:31:45 2005
@@ -0,0 +1,135 @@
+/*
+ * Copyright 2005 Niclas Hedhman
+ *
+ * Licensed  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.
+ */
+
+package net.dpml.transit.test;
+
+import java.io.File;
+import java.io.InputStream;
+import java.io.OutputStream;
+
+import java.net.URI;
+import java.net.URL;
+
+import junit.framework.TestCase;
+
+import net.dpml.transit.artifact.ArtifactNotFoundException;
+import net.dpml.transit.link.Link;
+import net.dpml.transit.util.StreamUtils;
+
+/**
+ *
+ * @author <a href="http://www.dpml.net/";>The Digital Product Meta 
Library</a>
+ * @version $Id$
+ */
+public class LinkTestCase extends TestCase
+{
+    protected void setUp() throws Exception
+    {
+        System.setProperty( "java.protocol.handler.pkgs", "net.dpml.transit" 
);
+        System.setProperty( "dpml.transit.secured.disable", "true" );
+        System.setProperty( "dpml.transit.authority.file", 
"target/test/test.authority" );
+        String test = System.getProperty( "project.dir" );
+        File old = new File( test, "target/test/cache" );
+        old.delete();
+    }
+
+    /**
+     * Constructor
+     * @param name the test name
+     */
+    public LinkTestCase( String name )
+    {
+        super( name );
+    }
+
+    public void testDefaultValue()
+        throws Exception
+    {
+        URL url = new URL( "link:transit/test/aaa/bbb" );
+        Class[] args = new Class[] { Link.class };
+        Link link = (Link) url.getContent( args );
+        URI defUri = URI.create( "artifact:bla:abc/def#142" );
+        URI uri = link.getTargetURI( defUri );
+        assertEquals( "default", defUri, uri );
+    }
+
+    public void testContentUri()
+        throws Exception
+    {
+        URI orig = URI.create( "link:transit/test/aaa/bbb" );
+        URL url = orig.toURL();
+        Class[] args = new Class[] { URI.class };
+        URI found = (URI) url.getContent( args );
+        assertEquals( "default", orig, found );
+    }
+
+    public void testSetValue()
+        throws Exception
+    {
+        URL url = new URL( "link:transit/test/aaa/ccc" );
+        Class[] args = new Class[] { Link.class };
+        Link link = (Link) url.getContent( args );
+        URI newUri = URI.create( "artifact:testfile:dpml/test/abc#1.0.1" );
+        link.setTargetURI( newUri );
+
+        url = new URL( "link:transit/test/aaa/ccc" );
+        link = (Link) url.getContent( args );
+        URI defUri = URI.create( "artifact:bla:ccc/ddd#222" );
+        URI uri = link.getTargetURI( defUri );
+
+        assertEquals( "setting", newUri, uri );
+    }
+
+    public void testGetValue()
+        throws Exception
+    {
+        URL url = new URL( "link:transit/test/aaa/ccc" );
+        Class[] args = new Class[] { Link.class };
+        Link link = (Link) url.getContent( args );
+        URI newUri = URI.create( "artifact:testfile:dpml/test/abc#1.0.1" );
+        link.setTargetURI( newUri );
+
+        url = new URL( "link:transit/test/aaa/ccc" );
+        URL original = newUri.toURL();
+        InputStream in1 = url.openConnection().getInputStream();
+        InputStream in2 = original.openConnection().getInputStream();
+        assertTrue( "different content", StreamUtils.compareStreams( in1, 
in2 ) );
+    }
+
+    public void testIllegalArtifact()
+        throws Exception
+    {
+        URL url = new URL( "link:transit/test/errors/aaa" );
+        Class[] args = new Class[] { Link.class };
+        URI newUri = URI.create( "artifact:abc:aaa/bbb/def" );
+
+        url = new URL( "link:transit/test/errors/aaa" );
+        try
+        {
+            Link link = (Link) url.getContent( args );
+            link.setTargetURI( newUri );
+
+            link = (Link) url.getContent( args );
+            fail( "No ArtifactNotFoundException" );
+        } catch( ArtifactNotFoundException e )
+        {
+            // should throw an exception if we try to read a against a
+            // non existent artifact.
+        }
+    }
+}

Modified: 
development/main/transit/core/handler/src/test/net/dpml/transit/test/MimeHandlerTestCase.java
==============================================================================
--- 
development/main/transit/core/handler/src/test/net/dpml/transit/test/MimeHandlerTestCase.java
       (original)
+++ 
development/main/transit/core/handler/src/test/net/dpml/transit/test/MimeHandlerTestCase.java
       Sun Mar 27 13:31:45 2005
@@ -35,7 +35,8 @@
         { "pdf", "application/pdf" },
         { "png", "image/png" },
         { "jpg", "image/jpg" },
-        { "gif", "image/gif" }
+        { "gif", "image/gif" },
+        { "link", "application/x-dpml-link" }
     };
 
     static public Test suite()

Modified: 
development/main/transit/core/handler/src/test/net/dpml/transit/test/OfflineTestCase.java
==============================================================================
--- 
development/main/transit/core/handler/src/test/net/dpml/transit/test/OfflineTestCase.java
   (original)
+++ 
development/main/transit/core/handler/src/test/net/dpml/transit/test/OfflineTestCase.java
   Sun Mar 27 13:31:45 2005
@@ -44,6 +44,9 @@
         System.setProperty( "java.protocol.handler.pkgs", "net.dpml.transit" 
);
         System.setProperty( "dpml.transit.secured.disable", "true" );
         System.setProperty( "dpml.transit.authority.file", 
"target/test/test.authority" );
+        String test = System.getProperty( "project.dir" );
+        File old = new File( test, "target/test/cache/" );
+        delete( old );
     }
 
     public void testDownloadNoVersion()
@@ -117,10 +120,6 @@
     public void testWriteNewArtifact()
         throws Exception
     {
-        String test = System.getProperty( "project.dir" );
-        File old = new File( test, 
"target/test/cache/dpml/test/txts/sample.txt" );
-        System.out.println( old.getAbsolutePath() );
-        old.delete();
         URL url = new URL( "artifact:txt:dpml/test/sample" );
         OutputStream out = url.openConnection().getOutputStream();
         for( int i = 65 ; i < 91 ; i++ )
@@ -166,6 +165,19 @@
             stream.close();
         }
     }
+
+    private void delete( File dir )
+    {
+        File[] entries = dir.listFiles();
+        for( int i = 0; i < entries.length; i++ )
+        {
+            File f = entries[ i ];
+            if( f.isDirectory() )
+                delete( f );
+            f.delete();
+        }
+    }
+
 /* TODO: not used
     private void print( URL url )
     {