velocityhelper.java

webwork source

package webwork.view.velocity;

import java.util.Properties;
import java.util.Enumeration;
import java.util.Iterator;
import java.io.Writer;

import javax.servlet.ServletContext;
import javax.servlet.ServletResponse;
import javax.servlet.ServletRequest;

import org.apache.velocity.app.Velocity;
import org.apache.velocity.context.Context;
import org.apache.velocity.VelocityContext;
import org.apache.velocity.Template;
import org.apache.velocity.runtime.RuntimeSingleton;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import webwork.config.Configuration;
import webwork.util.ServletValueStack;

/**
 * @author Hani Suleiman ([e-mail])
 *         Date: Nov 15
 * @author 2003
 *         Time: 11:21:14 AM
 */
public class VelocityHelper
{
  private static final Log log = LogFactory.getLog(VelocityHelper.class);

  /**
   * The HTTP request object context key.
   */
  public static final String REQUEST = "req";

  /**
   * The HTTP response object context key.
   */
  public static final String RESPONSE = "res";

  static final String WEBWORK_UTIL = "webwork";
  private static boolean initialized = false;
  public static final String VELO_CONTEXT = "__webwork__velocity__context";

  /**
   *   Hook up Velocity with the WebWork configuration.
   */
  public static synchronized void initVelocity(ServletContext context) throws Exception
  {
    // WebWork configuration provides main config
    final Properties conf = new Properties()
    {
      public Object get(Object key)
      {
        return Configuration.get(key.toString());
      }

      public String getProperty(String key)
      {
        return Configuration.getString(key.toString());
      }

      public Enumeration keys()
      {
        final Iterator list = Configuration.list();
        return new Enumeration()
        {
          public Object nextElement()
          {
            return list.next();
          }

          public boolean hasMoreElements()
          {
            return list.hasNext();
          }
        };
      }
    };

    // Set dynamic properties here
    // The properties not set here are taken from the WebWork configuration
    Properties p = new Properties(conf)
    {
      public Enumeration keys()
      {
        return conf.keys();
      }
    };

    /*
    *  first, normalize our velocity log file to be in the
    *  webapp
    */

    String log = p.getProperty(Velocity.RUNTIME_LOG);

    if(log != null)
    {
      log = context.getRealPath(log);

      if(log != null)
      {
        p.setProperty(Velocity.RUNTIME_LOG, log);
      }
    }


    /*
    *  If there is a file loader resource path, treat it the
    *  same way, but only if it doesn't start with /. In that case
    *  we use it as-is to allow the templates to be taken from some
    *  repository (!very useful during development!).
    */
    String path = p.getProperty(Velocity.FILE_RESOURCE_LOADER_PATH);

    if(path != null && (path.equals("/") || !path.startsWith("/")))
    {
      path = context.getRealPath(path);
      if(path != null)
      {
        p.setProperty(Velocity.FILE_RESOURCE_LOADER_PATH, path);
      }
    }

    Velocity.setApplicationAttribute(ServletContext.class.getName(), context); 
    Velocity.init(p);
    initialized = true;
  }

  public static void merge(Context context, String templateName, Writer writer)
  {
    try
    {
      Template t = RuntimeSingleton.getTemplate(templateName);
      t.merge(context, writer);
      //java.io.PrintWriter out = new java.io.PrintWriter(System.out);
      //t.merge(context, out);
      //out.close();
    }
    catch(Exception e)
    {
      log.error(e.getMessage(), e);
    }
  }

  public static Context getContext(ServletContext context, ServletRequest request, ServletResponse response)
  {
    if(!initialized)
    {
      try
      {
        initVelocity(context);
      }
      catch(Exception e)
      {
        log.error(e.getMessage(), e);
        return null;
      }
    }
    WebWorkVelocityContext ctx = (WebWorkVelocityContext)request.getAttribute(VELO_CONTEXT);
    if(ctx==null)
    {
      ctx = new WebWorkVelocityContext(ServletValueStack.getStack(request));
      ctx.put(REQUEST, request);
      ctx.put(RESPONSE, response);
      ctx.put(WEBWORK_UTIL, new WebWorkUtil(ctx));
      request.setAttribute(VELO_CONTEXT, ctx);
    }
    return ctx;
  }

  /**
   * WebWork specific Velocity context implementation.
   */
  static class WebWorkVelocityContext extends VelocityContext
  {
    ServletValueStack stack;

    WebWorkVelocityContext(ServletValueStack aStack)
    {
      stack = aStack;
    }

    public boolean internalContainsKey(java.lang.Object key)
    {
      boolean contains = super.internalContainsKey(key);
      return contains ? true : stack.test(key.toString());
    }

    public Object internalGet(String key)
    {
      return super.internalContainsKey(key) ? super.internalGet(key) : stack.findValue(key);
    }
  }
}