ModuleServlet.java

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 * Copyright (c) 2008, 2009 Bug Labs, Inc.
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *    - Redistributions of source code must retain the above copyright notice,
 *      this list of conditions and the following disclaimer.
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 *      used to endorse or promote products derived from this software without
 *      specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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package com.buglabs.bug.ws.module;

import java.io.IOException;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.osgi.framework.BundleContext;
import org.osgi.framework.ServiceEvent;
import org.osgi.framework.ServiceListener;
import org.osgi.service.log.LogService;

import com.buglabs.bug.dragonfly.module.IModuleControl;
import com.buglabs.bug.dragonfly.module.IModuleProperty;
import com.buglabs.bug.dragonfly.module.MutableModuleProperty;
import com.buglabs.bug.ws.Activator;
import com.buglabs.util.osgi.BUGBundleConstants;
import com.buglabs.util.xml.XmlNode;

/**
 * A servlet to expose BUG module data to web clients.
 *
 */
public class ModuleServlet extends HttpServlet implements ServiceListener {

	private static final long serialVersionUID = -6977609397049223637L;

	private IModuleControl[] modules;

	private BundleContext context;

	/**
	 * Construct a ModuleServlet with no existing modules.
	 */
	public ModuleServlet() {
		context = Activator.getContext();
		//Initialize the array that tracks modules.
		this.modules = new IModuleControl[BUGBundleConstants.BUG_TOTAL_BMI_SLOTS];
		for (int i = 0; i < modules.length; ++i)
			modules[i] = null;
	}
	
	/**
	 * Construct a ModuleServlet with pre-existing modules.
	 * 
	 * @param mcontrols IModuleControl[]
	 */
	public ModuleServlet(IModuleControl[] mcontrols) {
		context = Activator.getContext();
		this.modules = mcontrols;
	}

	/* (non-Javadoc)
	 * @see javax.servlet.http.HttpServlet#doPost(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)
	 */
	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		String path = req.getPathInfo();
		// Must have a module in the path.
		if (path == null) {
			resp.sendError(BUGBundleConstants.WS_HTTP_ERROR_INVALID_MODULE, "Error: invalid module.");
			return;
		}

		int index = Integer.parseInt(path.substring(1).trim().toUpperCase());
		IModuleControl mc = modules[index];
		// Must be a valid module
		if (mc == null) {
			resp.sendError(BUGBundleConstants.WS_HTTP_ERROR_UNKNOWN_MODULE, "Error: unknown module " + path);
			return;
		}

		// Iterate thru post variables and set them on
		for (Enumeration names = req.getParameterNames(); names.hasMoreElements();) {
			String paramName = (String) names.nextElement();
			String paramValue = req.getParameter(paramName);

			// TODO: Make sure all properties are valid before setting them.
			if (!containsProperty(mc.getModuleProperties(), paramName)) {
				resp.sendError(BUGBundleConstants.WS_HTTP_ERROR_INVALID_PROPERTY, "Error: invalid property " + paramName);
				return;
			}

			if (!mc.setModuleProperty(new MutableModuleProperty(paramName, paramValue))) {
				resp.sendError(BUGBundleConstants.WS_HTTP_ERROR_CANT_SET_PROPERTY, "Error: unable to set property " + paramName);
			}
		}
	}

	/* (non-Javadoc)
	 * @see javax.servlet.http.HttpServlet#doGet(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)
	 */
	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		String path = req.getPathInfo();
		String response = null;

		resp.setContentType("text/xml");

		if (path == null) {
			response = getModules();
		} else {
			try {
				int index = Integer.parseInt(path.substring(1).trim());

				if (index < 0 || index > 3) {
					resp.setContentType("text/plain");
					response = "Error: expected BMI slot index (0 - 3)";
				}

				IModuleControl mc = modules[index];

				if (mc != null) {
					response = getModuleXML(mc);
				} else {
					resp.setContentType("text/plain");
					response = "Error: no module.";
				}
			} catch (NumberFormatException e) {
				resp.setContentType("text/plain");
				response = "Error: expected BMI slot index (0 - 3)";
			}
		}

		resp.getWriter().print(response);
	}

	/**
	 * @param mc IModuleControl
	 * @return module XML
	 */
	private String getModuleXML(IModuleControl mc) {
		XmlNode root = new XmlNode("module");
		root.setAttribute("name", mc.getModuleName());

		for (Iterator i = mc.getModuleProperties().iterator(); i.hasNext();) {
			IModuleProperty prop = (IModuleProperty) i.next();
			XmlNode propNode = new XmlNode("property");
			propNode.setAttribute("name", prop.getName());
			if (prop.getValue() != null) {
				propNode.setAttribute("value", prop.getValue().toString());
			} else {
				propNode.setAttribute("value", "null");
			}
			propNode.setAttribute("type", prop.getType());

			propNode.setAttribute("mutable", Boolean.toString(prop.isMutable()));

			root.addChild(propNode);
		}

		return root.toString();
	}

	/**
	 * @return XML as string of modules
	 */
	private String getModules() {
		XmlNode root = new XmlNode("modules");

		for (int i = 0; i < modules.length; ++i) {
			if (modules[i] != null) {
				String moduleName = modules[i].getModuleName();
				XmlNode mod = new XmlNode("module");
				mod.setAttribute("name", moduleName);
				mod.setAttribute("index", "" + modules[i].getSlotId());
				root.addChild(mod);
			}
		}

		return root.toString();
	}

	// TODO rewrite property storage from List to map to reduce tc of search.
	private boolean containsProperty(List properties, String name) {
		for (Iterator i = properties.iterator(); i.hasNext();) {
			IModuleProperty p = (IModuleProperty) i.next();

			if (p.getName().toUpperCase().equals(name.toUpperCase())) {
				return true;
			}
		}

		return false;
	}

	@Override
	public void serviceChanged(ServiceEvent event) {
		//Here we get notified when IModuleControls are added and removed from OSGi service registry.  
		//We want to keep our state up-to-date with the modules array.
		IModuleControl imc = (IModuleControl) context.getService(event.getServiceReference());
		
		if (event.getType() == ServiceEvent.REGISTERED) {
			if (modules[imc.getSlotId()] != null)
				Activator.getLog().log(LogService.LOG_WARNING
						, "A new IModuleControl registration is overwriting a pre-existing module.");
			
			modules[imc.getSlotId()] = imc;
		} else if (event.getType() == ServiceEvent.UNREGISTERING) {
			modules[imc.getSlotId()] = null;
		}
	}
}