Create our own ClasspathResourceLoader that does not suffer from the annoying

URLConnection jar resource caching problem. Wired up a simple test case for
same.


git-svn-id: https://samskivert.googlecode.com/svn/trunk@2606 6335cc39-0255-0410-8fd6-9bcaacd3b74c

src/java/com/samskivert/velocity/ClasspathResourceLoader.java

@@ -0,0 +1,94 @@
+//
+// $Id$
+//
+// samskivert library - useful routines for java programs
+// Copyright (C) 2001-2008 Michael Bayne
+// 
+// This library 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 library 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 library; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+
+package com.samskivert.velocity;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.URL;
+import java.net.URLConnection;
+
+import com.samskivert.util.StringUtil;
+
+import org.apache.commons.collections.ExtendedProperties;
+import org.apache.velocity.exception.ResourceNotFoundException;
+import org.apache.velocity.runtime.resource.Resource;
+import org.apache.velocity.runtime.resource.loader.ResourceLoader;
+
+/**
+ * Loads Velocity templates from the classpath. Works around the problem that templates loaded from
+ * a .jar file are cached for the lifetime of the VM even if a totally new class loader loads a new
+ * copy of that jar file from the same path.
+ */
+public class ClasspathResourceLoader extends ResourceLoader
+{
+    @Override // from ResourceLoader
+    public void init (ExtendedProperties config)
+    {
+    }
+
+    @Override // from ResourceLoader
+    public InputStream getResourceStream (String name) 
+        throws ResourceNotFoundException
+    {
+        if (StringUtil.isBlank(name)) {
+            throw new ResourceNotFoundException ("No template name provided");
+        }
+        ClassLoader loader = Thread.currentThread().getContextClassLoader();
+        try {
+            if (loader != null) {
+                return getResourceStream(loader, name);
+            }
+        } catch (IOException ioe) {
+            // fall through and try the system classloader
+        }
+        try {
+            return getResourceStream(getClass().getClassLoader(), name);
+        } catch (IOException ioe) {
+            throw new ResourceNotFoundException("Unable to find template: " + name);
+        }
+    }
+
+    @Override // from ResourceLoader
+    public boolean isSourceModified (Resource resource)
+    {
+        return false;
+    }
+
+    @Override // from ResourceLoader
+    public long getLastModified (Resource resource)
+    {
+        return 0;
+    }
+
+    protected InputStream getResourceStream (ClassLoader loader, String name)
+        throws IOException
+    {
+        URL rsrc = loader.getResource(name);
+        URLConnection uconn = rsrc.openConnection();
+        // we have to disable caching otherwise once a resource is loaded from a jar file we will
+        // never get a new version of that resource even if the jar file is replaced on disk and a
+        // totally separate classloader is created to read it because Java caches jar resources
+        // globally in the VM based on filename only
+        uconn.setUseCaches(false);
+        return uconn.getInputStream();
+    }
+}
+

src/java/com/samskivert/velocity/VelocityTestCase.java

@@ -33,7 +33,6 @@ import org.apache.velocity.VelocityContext;
 import org.apache.velocity.app.VelocityEngine;
 import org.apache.velocity.runtime.RuntimeServices;
 import org.apache.velocity.runtime.log.LogChute;
-import org.apache.velocity.runtime.resource.loader.ClasspathResourceLoader;
 
 import com.samskivert.servlet.MessageManager;
 

src/java/com/samskivert/velocity/VelocityUtil.java

@@ -23,7 +23,6 @@ package com.samskivert.velocity;
 import org.apache.velocity.app.VelocityEngine;
 import org.apache.velocity.runtime.RuntimeServices;
 import org.apache.velocity.runtime.log.LogChute;
-import org.apache.velocity.runtime.resource.loader.ClasspathResourceLoader;
 
 import static com.samskivert.Log.log;
 

src/java/com/samskivert/velocity/tests/VelocityTest.java

@@ -0,0 +1,51 @@
+//
+// $Id$
+//
+// samskivert library - useful routines for java programs
+// Copyright (C) 2001-2008 Michael Bayne
+// 
+// This library 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 library 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 library; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+
+package com.samskivert.velocity.tests;
+
+import java.io.StringWriter;
+
+import org.apache.velocity.VelocityContext;
+import org.apache.velocity.app.VelocityEngine;
+
+import org.junit.*;
+import static org.junit.Assert.*;
+
+import com.samskivert.velocity.VelocityUtil;
+
+/**
+ * Tests some Velocity stuff.
+ */
+public class VelocityTest
+{
+    @Test
+    public void testClasspathLoader ()
+        throws Exception
+    {
+        VelocityContext ctx = new VelocityContext();
+        ctx.put("foo", "bar");
+
+        StringWriter writer = new StringWriter();
+        VelocityEngine engine = VelocityUtil.createEngine();
+        engine.mergeTemplate("com/samskivert/velocity/tests/test.tmpl", "UTF-8", ctx, writer);
+
+        assertTrue(writer.toString().trim().equals("Hello bar."));
+    }
+}

src/java/com/samskivert/velocity/tests/test.tmpl

@@ -0,0 +1 @@
+Hello ${foo}.