[VELOCITY-585] Update URL Resource Loader to Implement Timeout

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 1.5
• Fix Version/s: 1.6
• Component/s: Engine
• Assignee: Unassigned
• Reporter: Tim White
• Created: 30/Jan/08 17:22
• Updated: 21/Aug/08 00:34
• Resolved: 21/Aug/08 00:34

Description

Since sometimes URLs can be down, or take forever to load, it's important to be able to implement a timeout for them, to avoid threads hanging forever.

I've hacked the URLResourceLoader, as below, to implement this timeout. I think it would be wise to add a config param to adjust the timeout for the final version.

package com.qwest.velocity.runtime.resource.loader;

/*

• Licensed to the Apache Software Foundation (ASF) under one
• or more contributor license agreements. See the NOTICE file
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• regarding copyright ownership. The ASF licenses this file
• to you 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
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• 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
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  */

import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;
import java.util.HashMap;

import org.apache.commons.collections.ExtendedProperties;
import org.apache.commons.lang.StringUtils;
import org.apache.velocity.exception.ResourceNotFoundException;
import org.apache.velocity.runtime.resource.Resource;
import org.apache.velocity.runtime.resource.loader.ResourceLoader;

/**

• This is a simple URL-based loader.
• @author <a href="mailto:[e-mail]">Geir Magnusson Jr.</a>
• @author <a href="mailto:[e-mail]">Nathan Bubna</a>
• @version $Id: URLResourceLoader.java 191743 2005-06-21 23:22:20Z dlr $
  */
  public class PortalURLResourceLoader extends ResourceLoader {
  private String[] roots = null;

protected HashMap templateRoots = null;

/**

• @see org.apache.velocity.runtime.resource.loader.ResourceLoader#init(org.apache.commons.collections.ExtendedProperties)
  */
  public void init(ExtendedProperties configuration) {
  rsvc.getLog().debug("URLResourceLoader : initialization starting.");

roots = configuration.getStringArray("root");

for (int i = 0; i < roots.length; i++)

{ rsvc.getLog().info("URLResourceLoader : adding root '" + roots[i] + "'"); }

// init the template paths map
templateRoots = new HashMap();

rsvc.getLog().debug("URLResourceLoader : initialization complete.");
}

/**

• Get an InputStream so that the Runtime can build a template with it.
• @param name
• name of template to fetch bytestream of
• @return InputStream containing the template
• @throws ResourceNotFoundException
• if template not found in the file template path.
  */
  public synchronized InputStream getResourceStream(String name) throws ResourceNotFoundException {
  if (StringUtils.isEmpty(name)) { throw new ResourceNotFoundException("URLResourceLoader : No template name provided"); }

InputStream inputStream = null;
Exception exception = null;
for (int i = 0; i < roots.length; i++) {
try {
URL u = new URL(roots[i] + name);
URLConnection conn = u.openConnection();
conn.setConnectTimeout(10000);
conn.setReadTimeout(10000);
inputStream = conn.getInputStream();

if (inputStream != null) {
if (rsvc.getLog().isDebugEnabled())

{ rsvc.getLog().debug("URLResourceLoader: Found '" + name + "' at '" + roots[i] + "'"); }

// save this root for later re-use
templateRoots.put(name, roots[i]);
break;
}
} catch (Exception e) {
rsvc.getLog().error("URLResourceLoader: Exception when looking for '" + name + "' at '" + roots[i] + "'");
rsvc.getLog().error(e);

// only save the first one for later throwing
if (exception == null)

{ exception = e; }

}
}

// if we never found the template
if (inputStream == null) {
String msg;
if (exception == null)

{ msg = "URLResourceLoader : Resource '" + name + "' not found."; }

else

{ msg = exception.getMessage(); }

// convert to a general Velocity ResourceNotFoundException
throw new ResourceNotFoundException(msg);
}

return inputStream;
}

/**

• Checks to see if a resource has been deleted, moved or modified.
• @param resource
• Resource The resource to check for modification
• @return boolean True if the resource has been modified, moved, or unreachable
  */
  public boolean isSourceModified(Resource resource)
  Unknown macro: { long fileLastModified = getLastModified(resource); // if the file is unreachable or otherwise changed if (fileLastModified == 0 || fileLastModified != resource.getLastModified()) { return true; } return false; }

/**

• Checks to see when a resource was last modified
• @param resource
• Resource the resource to check
• @return long The time when the resource was last modified or 0 if the file can't be reached
  */
  public long getLastModified(Resource resource) {
  // get the previously used root
  String name = resource.getName();
  String root = (String) templateRoots.get(name);

try

{ // get a connection to the URL URL u = new URL(root + name); URLConnection conn = u.openConnection(); conn.setConnectTimeout(10000); conn.setReadTimeout(10000); return conn.getLastModified(); }

catch (IOException ioe)

{ // the file is not reachable at its previous address rsvc.getLog().error("URLResourceLoader: '" + name + "' is no longer reachable at '" + root + "'"); rsvc.getLog().error(ioe); return 0; }

}

}