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VelocityEngine.java

package edu.virtualschool.jwaa.xml;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.StringWriter;

import org.apache.log4j.Logger;
import org.apache.velocity.VelocityContext;
import org.apache.velocity.app.Velocity;
import org.apache.velocity.exception.MethodInvocationException;
import org.apache.velocity.exception.ParseErrorException;
import org.apache.velocity.exception.ResourceNotFoundException;
import org.apache.velocity.runtime.RuntimeServices;
import org.apache.velocity.runtime.log.LogSystem;
import org.jdom.Element;

import edu.virtualschool.jwaa.Fault;
public class VelocityEngine 
  extends org.apache.velocity.app.VelocityEngine
{
  final static Logger logger = Logger.getLogger(VelocityEngine.class.getName());

  VelocityEngine(ApplicationElement app, Element element) throws Fault
  {
    if (element == null)
      throw new ValidationFault("application requires a macros element");
    String name = element.getAttributeValue("path");
    if (name == null)
      throw new ValidationFault("macros element requires a path attribute");
    boolean enableDebug = isTrue(element.getAttributeValue("debug"));
    File file = new File(app.fileMonitor.file.getParent(), name);
    logger.debug("Loading velocity macros from "+file);
    VelocityLogger velocityLogger = new VelocityLogger();
    try
    {
      /* Specify file plus classpath resource loaders */
      setProperty("resource.loader", "file,class");

      /* File Resource Loader */
      setProperty("file.resource.loader.path",
        file.getParent());
      setProperty("file.resource.loader.description",
        "File Loader");
      setProperty("file.resource.loader.cache",
        enableDebug?"false":"true");
      setProperty("file.resource.loader.modificationCheckInterval",
        enableDebug?"0":"2");

      /* Classpath Resource Loader */
      setProperty("class.resource.loader.description",
        "Classpath Resource Loader");
      setProperty("class.resource.loader.class", 
        "org.apache.velocity.runtime.resource.loader.ClasspathResourceLoader");

      /* Velocimacros */
      setProperty("velocimacro.library", 
        file.getName());
      setProperty("velocimacro.library.autoreload",
        enableDebug?"true":"false");

      /* Logging */
      setProperty("runtime.log.logsystem",
        velocityLogger);
      setProperty("runtime.log.logsystem.log4j.category",
        logger.getName());
      setProperty("runtime.log.logsystem.class",
        velocityLogger.getClass().getName());
    /*
      setProperty("velocimacro.permissions.allow.inline", "true");
      setProperty("velocimacro.permissions.allow.inline.local.scope", "false");
      setProperty("resource.manager.logwhenfound", "false");
      setProperty("velocimacro.context.localscope", "false");
      setProperty("runtime.log.invalid.references", "true");
    */
      init();
    }
    catch (FileNotFoundException e)
    {
      throw new FileNotFoundFault(file + " not found");
    }
    catch (Exception e)
    {
      throw new Fault("Exception initializing Velocity engine", e);
    }
  }
  String evaluate(String text, VelocityContext context)
  throws Fault
  {
    StringWriter writer = new StringWriter();
    try
    {
      evaluate(context, writer, "", text);
    }
    catch (ResourceNotFoundException e)
    {
      throw new Fault("couldn't find resource: "+e.getMessage(), e);
    }
    catch (ParseErrorException e)
    {
      throw new Fault("velocity syntax error\n"+ e.getMessage()+
        "\n<pre>\n"+
        XMLUtil.escape(text)+
        "\n</pre>");
    }
    catch (MethodInvocationException e)
    {
      throw new Fault("Fault in the java code called by velocity\n\t"+  e.getMessage(), e);
    }
    catch (IOException e)
    {
      throw new Fault("IO fault in code called by velocity\n\t"+e.getMessage());
    }
    catch (Throwable e)
    {
      throw new Fault("Throwable in velocity", e);
    }
    return writer.toString();
  }
  public static class VelocityLogger implements LogSystem
  {
    public VelocityLogger()
    {
      try
      {
        Velocity.setProperty(Velocity.RUNTIME_LOG_LOGSYSTEM, this );
        Velocity.init();
      }
      catch (Exception e)
      {
      }
    }
    public void init( RuntimeServices rsvc )
    {
    }
    public void logVelocityMessage(int level, String message)
    {
      logger.debug(level+": "+message);
    }
  }
  static boolean isTrue(String s)
  {
    if (s == null)
      return false;
    return (s.equals("true") || s.equals("yes"));
  }
}