Metacat

	<group>

		<index>5</index>

		<name>Handler Plugin Configuration</name>

		<description>Register Handler Plugin extensions</description>

	</group>

	<!-- handler plugin -->

	<config>

		<key>plugin.handlers</key>

		<label>Plugin class name[s]</label>

		<group>5</group>

		<index>1</index>

		<description>Comma-separated list of fully-qualified class names that implement MetacatHandlerPlugin interface</description>

		<helpFile>properties.html#plugin.handlers</helpFile>

	</config>

######## Plugin section              #######################################

plugin.handlers=

import edu.ucsb.nceas.metacat.plugin.MetacatHandlerPlugin;

import edu.ucsb.nceas.metacat.plugin.MetacatHandlerPluginManager;

				//try the plugin handler if it has an entry for handling this action

				MetacatHandlerPlugin handlerPlugin = MetacatHandlerPluginManager.getInstance().getHandler(action);

				if (handlerPlugin != null) {

					handlerPlugin.handleAction(action, params, request, response, userName, groupNames, sessionId);

				} 

				else {

					PrintWriter out = response.getWriter();

					out.println("<?xml version=\"1.0\"?>");

					out.println("<error>");

					out.println("Error: action: " + action + " not registered.  Please report this error.");

					out.println("</error>");

					out.close();

				}

package edu.ucsb.nceas.metacat.plugin;

import java.util.ArrayList;

import java.util.List;

import java.util.Map;

import java.util.Map.Entry;

import org.apache.commons.logging.Log;

import org.apache.commons.logging.LogFactory;

import edu.ucsb.nceas.metacat.properties.PropertyService;

import edu.ucsb.nceas.metacat.shared.ServiceException;

import edu.ucsb.nceas.utilities.PropertyNotFoundException;

public class MetacatHandlerPluginManager {

	private static MetacatHandlerPluginManager instance = null;

	private static Log log = LogFactory.getLog(MetacatHandlerPluginManager.class);

	private List<MetacatHandlerPlugin> handlers= new ArrayList<MetacatHandlerPlugin>();

	private MetacatHandlerPluginManager() {

		String[] configuredHandlers = null;

		try {

			String handlersString = PropertyService.getProperty("plugin.handlers");

			if (handlersString != null && handlersString.length() > 0) {

				configuredHandlers = handlersString.split(",");

				for (String className: configuredHandlers) {

					MetacatHandlerPlugin handlerInstance = null;

					try {

						Class<?> handlerClass = Class.forName(className);

						handlerInstance = (MetacatHandlerPlugin) handlerClass.newInstance();

					} catch (Exception e) {

						log.error("Problem initializing MetacatHandlerPlugin: " + className, e);

						continue;

					}

					handlers.add(handlerInstance);

				}

			}

		} catch (PropertyNotFoundException e) {

			log.warn("Could not find any MetacatPluginHandlers", e);

			return;

		}

	}

	public static MetacatHandlerPluginManager getInstance() throws ServiceException {

		if (instance == null) {

			try {

				instance = new MetacatHandlerPluginManager();

			} catch (Exception e) {

				throw new ServiceException(e.getMessage());

			}

		}

		return instance;

	}

	public void addHandler(MetacatHandlerPlugin plugin) {

	}

	public MetacatHandlerPlugin getHandler(String action) {

		for (MetacatHandlerPlugin plugin: handlers) {

			if (plugin.handlesAction(action)) {

				return plugin;

			}

		}

		return null;

	}

}

package edu.ucsb.nceas.metacat.plugin;

import java.util.Hashtable;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import edu.ucsb.nceas.metacat.shared.HandlerException;

public interface MetacatHandlerPlugin {

	public boolean handlesAction(String action);

	public boolean handleAction(

			String action, 

			Hashtable<String, String[]> params,

            HttpServletRequest request, 

            HttpServletResponse response,

            String username, 

            String[] groups,

            String sessionId) throws HandlerException;

}