[JBVFS-157]; add lazy input stream.

src/main/java/org/jboss/vfs/VFSInputSource.java

@@ -22,9 +22,10 @@
 package org.jboss.vfs;
 
 import java.io.InputStream;
-import java.io.IOException;
-import java.io.Reader;
 import java.io.InputStreamReader;
+import java.io.Reader;
+
+import org.jboss.vfs.util.LazyInputStream;
 
 import org.xml.sax.InputSource;
 
@@ -54,11 +55,7 @@ public String getSystemId() {
 
     @Override
     public InputStream getByteStream() {
-        try {
-            return file.openStream();
-        } catch (IOException e) {
-            throw new RuntimeException(e);
-        }
+        return new LazyInputStream(file); 
     }
 
     @Override

src/main/java/org/jboss/vfs/util/LazyInputStream.java

@@ -0,0 +1,130 @@
+/*
+ * JBoss, Home of Professional Open Source.
+ * Copyright 2010, Red Hat Middleware LLC, and individual contributors
+ * as indicated by the @author tags. See the copyright.txt file in the
+ * distribution for a full listing of individual contributors.
+ *
+ * This is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation; either version 2.1 of
+ * the License, or (at your option) any later version.
+ *
+ * This software is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this software; if not, write to the Free
+ * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
+ * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
+ */
+
+package org.jboss.vfs.util;
+
+import java.io.IOException;
+import java.io.InputStream;
+
+import org.jboss.vfs.VirtualFile;
+
+/**
+ * Lazy input stream.
+ *
+ * Delaying opening stream from underlying virtual file as long as possible.
+ * Won't be opened if not used at all.
+ *
+ * @author <a href="mailto:ales.justin@jboss.org">Ales Justin</a>
+ */
+public class LazyInputStream extends InputStream
+{
+   private VirtualFile file;
+   private InputStream stream;
+
+   public LazyInputStream(VirtualFile file)
+   {
+      if (file == null)
+         throw new IllegalArgumentException("Null file");
+      this.file = file;
+   }
+
+   /**
+    * Open stream.
+    *
+    * @return file's stream
+    * @throws IOException for any IO error
+    */
+   protected synchronized InputStream openStream() throws IOException
+   {
+      if (stream == null)
+         stream = file.openStream();
+      return stream;
+   }
+
+   @Override
+   public int read() throws IOException
+   {
+      return openStream().read();
+   }
+
+   @Override
+   public int read(byte[] b) throws IOException
+   {
+      return openStream().read(b);
+   }
+
+   @Override
+   public int read(byte[] b, int off, int len) throws IOException
+   {
+      return openStream().read(b, off, len);
+   }
+
+   @Override
+   public long skip(long n) throws IOException
+   {
+      return openStream().skip(n);
+   }
+
+   @Override
+   public int available() throws IOException
+   {
+      return openStream().available();
+   }
+
+   @Override
+   public void close() throws IOException
+   {
+      openStream().close();
+   }
+
+   @Override
+   public void mark(int readlimit)
+   {
+      try
+      {
+         openStream().mark(readlimit);
+      }
+      catch (IOException e)
+      {
+         throw new RuntimeException(e);
+      }
+   }
+
+   @Override
+   public void reset() throws IOException
+   {
+      openStream().reset();
+   }
+
+   @Override
+   public boolean markSupported()
+   {
+      try
+      {
+         return openStream().markSupported();
+      }
+      catch (IOException e)
+      {
+         throw new RuntimeException(e);
+      }
+   }
+}