source: main/trunk/greenstone3/src/java/org/greenstone/gsdl3/LibraryServlet.java@ 29057

package org.greenstone.gsdl3;

import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.Serializable;
import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Hashtable;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpSessionBindingEvent;
import javax.servlet.http.HttpSessionBindingListener;

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import org.apache.commons.lang3.StringUtils;
import org.apache.log4j.Logger;
import org.greenstone.gsdl3.action.PageAction;
import org.greenstone.gsdl3.comms.Communicator;
import org.greenstone.gsdl3.comms.SOAPCommunicator;
import org.greenstone.gsdl3.core.DefaultReceptionist;
import org.greenstone.gsdl3.core.MessageRouter;
import org.greenstone.gsdl3.core.Receptionist;
import org.greenstone.gsdl3.service.Authentication;
import org.greenstone.gsdl3.util.GSConstants;
import org.greenstone.gsdl3.util.GSParams;
import org.greenstone.gsdl3.util.GSXML;
import org.greenstone.gsdl3.util.UserContext;
import org.greenstone.gsdl3.util.XMLConverter;
import org.greenstone.util.GlobalProperties;
import org.json.JSONObject;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;

/**
 * a servlet to serve the greenstone library - we are using servlets instead of
 * cgi the init method is called only once - the first time the servlet classes
 * are loaded. Each time a request comes in to the servlet, the session() method
 * is called in a new thread (calls doGet/doPut etc) takes the a=p&p=home type
 * args and builds a simple request to send to its receptionist, which returns a
 * result in html, cos output=html is set in the request
 * 
 * 18/Jul/07 xiao modify to make the cached parameters collection-specific. Most
 * of the work is done in doGet(), except adding an inner class
 * UserSessionCache.
 * 
 * @see Receptionist
 */
public class LibraryServlet extends BaseGreenstoneServlet
{
    /** the receptionist to send messages to */
    protected Receptionist recept = null;

    /**
     * the default language - is specified by setting a servlet param, otherwise
     * DEFAULT_LANG is used
     */
    protected String default_lang = null;

  /** We record the library name for later */
  protected String library_name = null;
    /** Whether or not client-side XSLT support should be exposed */
    protected boolean supports_client_xslt = false;

    /**
     * The default default - used if a default lang is not specified in the
     * servlet params
     */
    protected final String DEFAULT_LANG = "en";

    /**
     * the cgi stuff - the Receptionist can add new args to this
     * 
     * its used by the servlet to determine what args to save
     */
    protected GSParams params = null;

    /**
     * user id - new one per session. This doesn't work if session state is
     * saved between restarts - this requires this value to be saved too.
     */
    protected int next_user_id = 0;

    /**
     * a hash that contains all the active session IDs mapped to the cached
     * items It is updated whenever the whole site or a particular collection is
     * reconfigured using the command a=s&sa=c or a=s&sa=c&c=xxx It is in the
     * form: sid -> (UserSessionCache object)
     */
    protected Hashtable<String, UserSessionCache> session_ids_table = new Hashtable<String, UserSessionCache>();

    /**
     * the maximum interval that the cached info remains in session_ids_table
     * (in seconds) This is set in web.xml
     */
    protected int session_expiration = 1800;

    static Logger logger = Logger.getLogger(org.greenstone.gsdl3.LibraryServlet.class.getName());

    /** initialise the servlet */
    public void init(ServletConfig config) throws ServletException
    {
        // always call super.init;
        super.init(config);
        // disable preferences - does this work anyway??
        //System.setProperty("java.util.prefs.PreferencesFactory", "org.greenstone.gsdl3.util.DisabledPreferencesFactory");

        library_name = config.getInitParameter(GSConstants.LIBRARY_NAME);
        String interface_name = config.getInitParameter(GSConstants.INTERFACE_NAME);

        String allowXslt = (String) config.getInitParameter(GSConstants.ALLOW_CLIENT_SIDE_XSLT);
        supports_client_xslt = allowXslt != null && allowXslt.equals("true");

        this.default_lang = config.getInitParameter(GSConstants.DEFAULT_LANG);
        String sess_expire = config.getInitParameter(GSXML.SESSION_EXPIRATION);

        if (sess_expire != null && !sess_expire.equals(""))
        {
            this.session_expiration = Integer.parseInt(sess_expire);
        }

        if (library_name == null || interface_name == null)
        {
            // must have this
            System.err.println("initialisation parameters not all set!");
            System.err.println(" you must have libraryname and interfacename");
            System.exit(1);
        }

        String site_name = config.getInitParameter(GSConstants.SITE_NAME);
        String remote_site_name = null;
        String remote_site_type = null;
        String remote_site_address = null;

        if (site_name == null)
        {
            // no site, try for communicator
            remote_site_name = config.getInitParameter("remote_site_name");
            remote_site_type = config.getInitParameter("remote_site_type");
            remote_site_address = config.getInitParameter("remote_site_address");
            if (remote_site_name == null || remote_site_type == null || remote_site_address == null)
            {
                System.err.println("initialisation paramters not all set!");
                System.err.println("if site_name is not set, then you must have remote_site_name, remote_site_type and remote_site_address set");
                System.exit(1);
            }
        }

        if (this.default_lang == null)
        {
            // choose english
            this.default_lang = DEFAULT_LANG;
        }

        HashMap<String, Object> config_params = new HashMap<String, Object>();

        config_params.put(GSConstants.LIBRARY_NAME, library_name);
        config_params.put(GSConstants.INTERFACE_NAME, interface_name);
        config_params.put(GSConstants.ALLOW_CLIENT_SIDE_XSLT, supports_client_xslt);

        if (site_name != null)
        {
            config_params.put(GSConstants.SITE_NAME, site_name);
        }
        //this.converter = new XMLConverter();
        //this.doc = XMLConverter.newDOM();

        // the receptionist -the servlet will talk to this
        String recept_name = (String) config.getInitParameter("receptionist_class");
        if (recept_name == null)
        {
            this.recept = new DefaultReceptionist();
        }
        else
        {
            try
            {
                this.recept = (Receptionist) Class.forName("org.greenstone.gsdl3.core." + recept_name).newInstance();
            }
            catch (Exception e)
            { // cant use this new one, so use normal one
                System.err.println("LibraryServlet configure exception when trying to use a new Receptionist " + recept_name + ": " + e.getMessage());
                e.printStackTrace();
                this.recept = new DefaultReceptionist();
            }
        }
        this.recept.setConfigParams(config_params);

        // the receptionist uses a MessageRouter or Communicator to send its requests to. We either create a MessageRouter here for the designated site (if site_name set), or we create a Communicator for a remote site. The is given to teh Receptionist, and the servlet never talks to it again.directly.
        if (site_name != null)
        {
            String mr_name = (String) config.getInitParameter("messagerouter_class");
            MessageRouter message_router = null;
            if (mr_name == null)
            { // just use the normal MR
                message_router = new MessageRouter();
            }
            else
            { // try the specified one
                try
                {
                    message_router = (MessageRouter) Class.forName("org.greenstone.gsdl3.core." + mr_name).newInstance();
                }
                catch (Exception e)
                { // cant use this new one, so use normal one
                    System.err.println("LibraryServlet configure exception when trying to use a new MessageRouter " + mr_name + ": " + e.getMessage());
                    e.printStackTrace();
                    message_router = new MessageRouter();
                }
            }

            message_router.setSiteName(site_name);
            message_router.setLibraryName(library_name);
            message_router.configure();
            this.recept.setMessageRouter(message_router);
        }
        else
        {
            // talking to a remote site, create a communicator
            Communicator communicator = null;
            // we need to create the XML to configure the communicator
            Document doc = XMLConverter.newDOM();
            Element site_elem = doc.createElement(GSXML.SITE_ELEM);
            site_elem.setAttribute(GSXML.TYPE_ATT, remote_site_type);
            site_elem.setAttribute(GSXML.NAME_ATT, remote_site_name);
            site_elem.setAttribute(GSXML.ADDRESS_ATT, remote_site_address);

            if (remote_site_type.equals(GSXML.COMM_TYPE_SOAP_JAVA))
            {
                communicator = new SOAPCommunicator();
            }
            else
            {
                System.err.println("LibraryServlet.init Error: invalid Communicator type: " + remote_site_type);
                System.exit(1);
            }

            if (!communicator.configure(site_elem))
            {
                System.err.println("LibraryServlet.init Error: Couldn't configure communicator");
                System.exit(1);
            }
            this.recept.setMessageRouter(communicator);
        }

        // the params arg thingy

        String params_name = (String) config.getInitParameter("params_class");
        if (params_name == null)
        {
            this.params = new GSParams();
        }
        else
        {
            try
            {
                this.params = (GSParams) Class.forName("org.greenstone.gsdl3.util." + params_name).newInstance();
            }
            catch (Exception e)
            {
                System.err.println("LibraryServlet configure exception when trying to use a new params thing " + params_name + ": " + e.getMessage());
                e.printStackTrace();
                this.params = new GSParams();
            }
        }
        // pass it to the receptionist
        this.recept.setParams(this.params);
        this.recept.configure();

        //Allow the message router and the document to be accessed from anywhere in this servlet context
        this.getServletContext().setAttribute("GSRouter", this.recept.getMessageRouter());
        //this.getServletContext().setAttribute("GSDocument", this.doc);
    }

    private void logUsageInfo(HttpServletRequest request)
    {
        String usageInfo = "";

        //session-info: get params stored in the session
        HttpSession session = request.getSession(true);
        Enumeration attributeNames = session.getAttributeNames();
        while (attributeNames.hasMoreElements())
        {
            String name = (String) attributeNames.nextElement();
            usageInfo += name + "=" + session.getAttribute(name) + " ";
        }

        //logged info = general-info + session-info
        usageInfo = request.getServletPath() + " " + //serlvet
        "[" + request.getQueryString() + "]" + " " + //the query string
        "[" + usageInfo.trim() + "]" + " " + // params stored in a session
        request.getRemoteAddr() + " " + //remote address
        request.getRequestedSessionId() + " " + //session id
        request.getHeader("user-agent") + " "; //the remote brower info

        logger.info(usageInfo);

    }

    public class UserSessionCache implements HttpSessionBindingListener
    {
        String session_id = "";

        /**
         * a hash that maps the session ID to a hashtable that maps the
         * coll_name to its parameters coll_name -> Hashtable (param_name ->
         * param_value)
         */
        protected Hashtable<String, Hashtable<String, String>> coll_name_params_table = null;

        public UserSessionCache(String id, Hashtable<String, Hashtable<String, String>> table)
        {
            session_id = id;
            coll_name_params_table = (table == null) ? new Hashtable() : table;
        }

        protected void cleanupCache(String coll_name)
        {
            if (coll_name_params_table.containsKey(coll_name))
            {
                coll_name_params_table.remove(coll_name);
            }
        }

        protected Hashtable<String, Hashtable<String, String>> getParamsTable()
        {
            return coll_name_params_table;
        }

        public void valueBound(HttpSessionBindingEvent event)
        {
            // Do nothing
        }

        public void valueUnbound(HttpSessionBindingEvent event)
        {
            if (session_ids_table.containsKey(session_id))
            {
                session_ids_table.remove(session_id);
            }
        }

        public int tableSize()
        {
            return (coll_name_params_table == null) ? 0 : coll_name_params_table.size();
        }
    }

    public void destroy()
    {
        recept.cleanUp();
    }

    public void doGetOrPost(HttpServletRequest request, HttpServletResponse response, Map<String, String[]> queryMap) throws ServletException, IOException
    {
        logUsageInfo(request);

        if (queryMap != null)
        {
            Iterator<String> queryIter = queryMap.keySet().iterator();
            boolean redirect = false;
            String href = null;
            String rl = null;
            String el = null;

            while (queryIter.hasNext())
            {
                String q = queryIter.next();
                if (q.equals(GSParams.EXTERNAL_LINK_TYPE))
                {
                    el = queryMap.get(q)[0];
                }
                else if (q.equals(GSParams.HREF))
                {
                    href = queryMap.get(q)[0];
                    href = StringUtils.replace(href, "%2f", "/");
                    href = StringUtils.replace(href, "%7e", "~");
                    href = StringUtils.replace(href, "%3f", "?");
                    href = StringUtils.replace(href, "%3A", "\\:");
                }
                else if (q.equals(GSParams.RELATIVE_LINK))
                {
                    rl = queryMap.get(q)[0];
                }
            }

            //if query_string contains "el=direct", an href is specified, and its not a relative link, then the web page will be redirected to the external URl, otherwise a greenstone page with an external URL will be displayed
            //"rl=0" this is an external link
            //"rl=1" this is an internal link
            if ((href != null) && (rl.equals("0")))
            {// This is an external link, 

                if (el.equals("framed"))
                {
                    //TODO **** how best to change to a=p&sa=html&c=collection&url=href
                    // response.setContentType("text/xml");
                    //response.sendRedirect("http://localhost:8383/greenstone3/gs3library?a=p&sa=html&c=external&url="+href);
                }
                else
                {
                    // el = '' or direct
                    //the web page is re-directed to the external URL (&el=&rl=0&href="http://...")
                    response.setContentType("text/xml");
                    response.sendRedirect(href);
                }
            }
        }

        // Nested Diagnostic Configurator to identify the client for
        HttpSession session = request.getSession(true);
        session.setMaxInactiveInterval(session_expiration);
        String uid = (String) session.getAttribute(GSXML.USER_ID_ATT);
        if (uid == null)
        {
            uid = "" + getNextUserId();
            session.setAttribute(GSXML.USER_ID_ATT, uid);
        }

        request.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();

        String lang = getFirstParam(GSParams.LANGUAGE, queryMap);
        if (lang == null || lang.equals(""))
        {
            // try the session cached lang
            lang = (String) session.getAttribute(GSParams.LANGUAGE);
            if (lang == null || lang.equals(""))
            {
                // still not set, use the default
                lang = this.default_lang;
            }
        }
        UserContext userContext = new UserContext();
        userContext.setLanguage(lang);
        userContext.setUserID(uid);

        if (request.getAuthType() != null)
        {
            //Get the username
            userContext.setUsername(request.getUserPrincipal().getName());

            //Get the groups for the user
            Document msg_doc = XMLConverter.newDOM();
            Element acquireGroupMessage = msg_doc.createElement(GSXML.MESSAGE_ELEM);
            Element acquireGroupRequest = GSXML.createBasicRequest(msg_doc, GSXML.REQUEST_TYPE_PROCESS, "GetUserInformation", userContext);
            acquireGroupMessage.appendChild(acquireGroupRequest);

            Element paramList = msg_doc.createElement(GSXML.PARAM_ELEM + GSXML.LIST_MODIFIER);
            acquireGroupRequest.appendChild(paramList);
            paramList.appendChild(GSXML.createParameter(msg_doc, GSXML.USERNAME_ATT, request.getUserPrincipal().getName()));

            Element aquireGroupsResponseMessage = (Element) this.recept.process(acquireGroupMessage);
            Element aquireGroupsResponse = (Element) GSXML.getChildByTagName(aquireGroupsResponseMessage, GSXML.RESPONSE_ELEM);
            Element param_list = (Element) GSXML.getChildByTagName(aquireGroupsResponse, GSXML.PARAM_ELEM + GSXML.LIST_MODIFIER);

            if (param_list != null)
            {
                HashMap<String, Serializable> params = GSXML.extractParams(param_list, false);
                String groups = (String) params.get("groups");
                userContext.setGroups(groups.split(","));
            }
        }

        // set the lang in the session
        session.setAttribute(GSParams.LANGUAGE, lang);

        String output = getFirstParam(GSParams.OUTPUT, queryMap);
        if (output == null || output.equals(""))
        {
            output = "html"; // uses html by default
        }

        // If server output, force a switch to traditional interface
        //output = (output.equals("server")) ? "html" : output;

        // Force change the output mode if client-side XSLT is supported - server vs. client
        // BUT only if the library allows client-side transforms    
        if (supports_client_xslt)
        {
            // MUST be done before the xml_message is built
            Cookie[] cookies = request.getCookies();
            Cookie xsltCookie = null;

            // The client has cookies enabled and a value set - use it!
            if (cookies != null)
            {
                for (Cookie c : cookies)
                {
                    if (c.getName().equals("supportsXSLT"))
                    {
                        xsltCookie = c;
                        break;
                    }
                }
                output = (xsltCookie != null && xsltCookie.getValue().equals("true") && output.equals("html")) ? "xsltclient" : output;
            }
        }

        // the request to the receptionist
        Document msg_doc = XMLConverter.newDOM();
        Element xml_message = msg_doc.createElement(GSXML.MESSAGE_ELEM);
        Element xml_request = GSXML.createBasicRequest(msg_doc, GSXML.REQUEST_TYPE_PAGE, "", userContext);
        xml_request.setAttribute(GSXML.OUTPUT_ATT, output);

        xml_message.appendChild(xml_request);

        String action = getFirstParam(GSParams.ACTION, queryMap);
        String subaction = getFirstParam(GSParams.SUBACTION, queryMap);
        String collection = getFirstParam(GSParams.COLLECTION, queryMap);
        String document = getFirstParam(GSParams.DOCUMENT, queryMap);
        String service = getFirstParam(GSParams.SERVICE, queryMap);

        // We clean up the cache session_ids_table if system
        // commands are issued (and also don't need to do caching for this request)
        boolean should_cache = true;
        if (action != null && action.equals(GSParams.SYSTEM_ACTION))
        {
            should_cache = false;

            // we may want to remove all collection cache info, or just a specific collection
            boolean clean_all = true;
            String clean_collection = null;
            // system commands are to activate/deactivate stuff
            // collection param is in the sc parameter.
            // don't like the fact that it is hard coded here
            String coll = getFirstParam(GSParams.SYSTEM_CLUSTER, queryMap);
            if (coll != null && !coll.equals(""))
            {
                clean_all = false;
                clean_collection = coll;
            }
            else
            {
                // check other system types
                if (subaction.equals("a") || subaction.equals("d"))
                {
                    String module_name = getFirstParam("sn", queryMap);
                    if (module_name != null && !module_name.equals(""))
                    {
                        clean_all = false;
                        clean_collection = module_name;
                    }
                }
            }
            if (clean_all)
            {
                session_ids_table = new Hashtable<String, UserSessionCache>();
                session.removeAttribute(GSXML.USER_SESSION_CACHE_ATT);
            }
            else
            {
                // just clean up info for clean_collection
                ArrayList<UserSessionCache> cache_list = new ArrayList<UserSessionCache>(session_ids_table.values());
                for (int i = 0; i < cache_list.size(); i++)
                {
                    UserSessionCache cache = cache_list.get(i);
                    cache.cleanupCache(clean_collection);
                }

            }
        }

        // cache_key is the collection name, or service name
        String cache_key = collection;
        if (cache_key == null || cache_key.equals(""))
        {
            cache_key = service;
        }

        // logger.info("should_cache= " + should_cache);

        //clear the collection-specific cache in the session, since we have no way to know whether this session is 
        //about the same collection as the last session or not.
        Enumeration attributeNames = session.getAttributeNames();
        while (attributeNames.hasMoreElements())
        {
            String name = (String) attributeNames.nextElement();
            if (!name.equals(GSXML.USER_SESSION_CACHE_ATT) && !name.equals(GSParams.LANGUAGE) && !name.equals(GSXML.USER_ID_ATT))
            {
                session.removeAttribute(name);
            }
        }

        UserSessionCache session_cache = null;
        Hashtable<String, Hashtable<String, String>> param_table = null;
        Hashtable<String, String> table = null;
        String sid = session.getId();
        if (should_cache == true && cache_key != null && !cache_key.equals(""))
        {
            if (session_ids_table.containsKey(sid))
            {
                session_cache = session_ids_table.get(sid);
                param_table = session_cache.getParamsTable();
                logger.info("collections in table: " + tableToString(param_table));
                if (param_table.containsKey(cache_key))
                {
                    //logger.info("existing table: " + collection);
                    table = param_table.get(cache_key);
                }
                else
                {
                    table = new Hashtable<String, String>();
                    param_table.put(cache_key, table);
                    //logger.info("new table: " + collection);
                }
            }
            else
            {
                param_table = new Hashtable<String, Hashtable<String, String>>();
                table = new Hashtable<String, String>();
                param_table.put(cache_key, table);
                session_cache = new UserSessionCache(sid, param_table);
                session_ids_table.put(sid, session_cache);
                session.setAttribute(GSXML.USER_SESSION_CACHE_ATT, session_cache);
                //logger.info("new session id");
            }
        }

        if (action == null || action.equals(""))
        {
            // should we do all the following stuff if using default page?
            // display the home page  - the default page
            xml_request.setAttribute(GSXML.ACTION_ATT, "p");
            xml_request.setAttribute(GSXML.SUBACTION_ATT, PageAction.HOME_PAGE);
        }
        else
        {
            xml_request.setAttribute(GSXML.ACTION_ATT, action);
            if (subaction != null)
            {
                xml_request.setAttribute(GSXML.SUBACTION_ATT, subaction);
            }

            //  create the param list for the greenstone request - includes
            // the params from the current request and any others from the saved session
            Element xml_param_list = msg_doc.createElement(GSXML.PARAM_ELEM + GSXML.LIST_MODIFIER);
            xml_request.appendChild(xml_param_list);

            for (String name : queryMap.keySet())
            {
                if (!name.equals(GSParams.ACTION) && !name.equals(GSParams.SUBACTION) && !name.equals(GSParams.LANGUAGE) && !name.equals(GSParams.OUTPUT))
                {// we have already dealt with these

                    String value = "";
                    String[] values = queryMap.get(name);
                    value = values[0];
                    if (values.length > 1)
                    {
                        for (int i = 1; i < values.length; i++)
                        {
                            value += "," + values[i];
                        }
                    }
                    // either add it to the param list straight away, or save it to the session and add it later
                    if (this.params.shouldSave(name) && table != null)
                    {
                        table.put(name, value);
                    }
                    else
                    {
                        Element param = msg_doc.createElement(GSXML.PARAM_ELEM);
                        param.setAttribute(GSXML.NAME_ATT, name);
                        param.setAttribute(GSXML.VALUE_ATT, GSXML.xmlSafe(value));
                        xml_param_list.appendChild(param);
                    }
                }
            }
            //put everything in the table into the session
            // do we need to do this? why not just put from table into param list
            if (table != null)
            {
                Enumeration<String> keys = table.keys();
                while (keys.hasMoreElements())
                {
                    String name = keys.nextElement();
                    session.setAttribute(name, table.get(name));
                }
            }

            // put in all the params from the session cache
            Enumeration params = session.getAttributeNames();
            while (params.hasMoreElements())
            {
                String name = (String) params.nextElement();

                if (!name.equals(GSXML.USER_SESSION_CACHE_ATT) && !name.equals(GSParams.LANGUAGE) && !name.equals(GSXML.USER_ID_ATT))
                {

                    // lang and uid are stored but we dont want it in the param list cos its already in the request
                    Element param = msg_doc.createElement(GSXML.PARAM_ELEM);
                    param.setAttribute(GSXML.NAME_ATT, name);
                    String value = GSXML.xmlSafe((String) session.getAttribute(name));

                    // ugly hack to undo : escaping
                    value = StringUtils.replace(value, "%3A", "\\:");
                    param.setAttribute(GSXML.VALUE_ATT, value);
                    xml_param_list.appendChild(param);
                }
            }
        }

        if (output.equals("json"))
        {
            response.setContentType("application/json");
        }
        else if (!output.equals("html") && !output.equals("server") && !output.equals("xsltclient"))
        {
            response.setContentType("text/xml"); // for now use text
        }

        //Add custom HTTP headers if requested
        String httpHeadersParam = getFirstParam(GSParams.HTTP_HEADER_FIELDS, queryMap);
        if (httpHeadersParam != null && httpHeadersParam.length() > 0)
        {
            Gson gson = new Gson();
            Type type = new TypeToken<List<Map<String, String>>>()
            {
            }.getType();
            List<Map<String, String>> httpHeaders = gson.fromJson(httpHeadersParam, type);
            if (httpHeaders != null && httpHeaders.size() > 0)
            {

                for (int j = 0; j < httpHeaders.size(); j++)
                {
                    Map nameValueMap = httpHeaders.get(j);
                    String name = (String) nameValueMap.get("name");
                    String value = (String) nameValueMap.get("value");

                    if (name != null && value != null)
                    {
                        response.setHeader(name, value);
                    }
                }
            }
        }

        String requestedURL = request.getRequestURL().toString();
        String baseURL = "";
        if (requestedURL.indexOf(library_name) != -1)
        {
            baseURL = requestedURL.substring(0, requestedURL.indexOf(library_name));
            xml_request.setAttribute("baseURL", baseURL);
        }
        String fullURL;
        if (request.getQueryString() != null)
        {
            fullURL = requestedURL + "?" + request.getQueryString();
        }
        else
        {
            fullURL = requestedURL;
        }

        xml_request.setAttribute("remoteAddress", request.getRemoteAddr());
        xml_request.setAttribute("fullURL", fullURL.replace("&", "&amp;"));

        if (!runSecurityChecks(request, xml_request, userContext, out, baseURL, collection, document, queryMap))
        {
            return;
        }

        Node xml_result = this.recept.process(xml_message);
        encodeURLs(xml_result, response);

        String xml_string = XMLConverter.getPrettyString(xml_result);

        if (output.equals("json"))
        {
            try
            {
                JSONObject json_obj = org.json.XML.toJSONObject(xml_string);

                out.println(json_obj.toString());
            }
            catch (Exception e)
            {
                e.printStackTrace();
                out.println("Error: failed to convert output XML to JSON format");
            }
        }
        else
        {
            out.println(xml_string);
        }

        displaySize(session_ids_table);
    }

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
    {
        doGetOrPost(request, response, request.getParameterMap());
    } //end of doGet(HttpServletRequest, HttpServletResponse)

    private boolean runSecurityChecks(HttpServletRequest request, Element xml_request, UserContext userContext, PrintWriter out, String baseURL, String collection, String document, Map<String, String[]> queryMap) throws ServletException
    {
        //Check if we need to login or logout
        String username = getFirstParam("username", queryMap);
        String password = getFirstParam("password", queryMap);
        String logout = getFirstParam("logout", queryMap);

        if (logout != null)
        {
            request.logout();
        }

        if (username != null && password != null)
        {
            //We are changing to another user, so log out first
            if (request.getAuthType() != null)
            {
                request.logout();
            }

            //This try/catch block catches when the login request fails (e.g. The user enters an incorrect password).
            try
            {
                //Try a global login first
                password = Authentication.hashPassword(password);
                request.login(username, password);
            }
            catch (Exception ex)
            {
                try
                {
                    //If the global login fails then try a site-level login
                    String siteName = (String) this.recept.getConfigParams().get(GSConstants.SITE_NAME);
                    request.login(siteName + "-" + username, password);
                }
                catch (Exception exc)
                {
                    //The user entered in either the wrong username or the wrong password
                  Document loginPageDoc = XMLConverter.newDOM();
                    Element loginPageMessage = loginPageDoc.createElement(GSXML.MESSAGE_ELEM);
                    Element loginPageRequest = GSXML.createBasicRequest(loginPageDoc, GSXML.REQUEST_TYPE_PAGE, "", userContext);
                    loginPageRequest.setAttribute(GSXML.ACTION_ATT, "p");
                    loginPageRequest.setAttribute(GSXML.SUBACTION_ATT, "login");
                    loginPageRequest.setAttribute(GSXML.OUTPUT_ATT, "html");
                    loginPageRequest.setAttribute(GSXML.BASE_URL, baseURL);
                    loginPageMessage.appendChild(loginPageRequest);

                    Element paramList = loginPageDoc.createElement(GSXML.PARAM_ELEM + GSXML.LIST_MODIFIER);
                    loginPageRequest.appendChild(paramList);

                    Element messageParam = loginPageDoc.createElement(GSXML.PARAM_ELEM);
                    messageParam.setAttribute(GSXML.NAME_ATT, "loginMessage");
                    messageParam.setAttribute(GSXML.VALUE_ATT, "Either your username or password was incorrect, please try again.");
                    paramList.appendChild(messageParam);

                    Element urlParam = loginPageDoc.createElement(GSXML.PARAM_ELEM);
                    urlParam.setAttribute(GSXML.NAME_ATT, "redirectURL");
                    String queryString = "";
                    if (request.getQueryString() != null)
                    {
                        queryString = "?" + request.getQueryString().replace("&", "&amp;");
                    }
                    urlParam.setAttribute(GSXML.VALUE_ATT, library_name + queryString);
                    paramList.appendChild(urlParam);

                    Node loginPageResponse = this.recept.process(loginPageMessage);
                    out.println(XMLConverter.getPrettyString(loginPageResponse));

                    return false;
                }
            }
        }

        //If a user is logged in
        if (request.getAuthType() != null)
        {
          Element userInformation = xml_request.getOwnerDocument().createElement(GSXML.USER_INFORMATION_ELEM);
            userInformation.setAttribute(GSXML.USERNAME_ATT, request.getUserPrincipal().getName());

            Document msg_doc = XMLConverter.newDOM();
            Element userInfoMessage = msg_doc.createElement(GSXML.MESSAGE_ELEM);
            Element userInfoRequest = GSXML.createBasicRequest(msg_doc, GSXML.REQUEST_TYPE_SECURITY, "GetUserInformation", userContext);
            userInfoMessage.appendChild(userInfoRequest);

            Element paramList = msg_doc.createElement(GSXML.PARAM_ELEM + GSXML.LIST_MODIFIER);
            userInfoRequest.appendChild(paramList);

            Element param = msg_doc.createElement(GSXML.PARAM_ELEM);
            param.setAttribute(GSXML.NAME_ATT, GSXML.USERNAME_ATT);
            param.setAttribute(GSXML.VALUE_ATT, request.getUserPrincipal().getName());
            paramList.appendChild(param);

            Element userInformationResponse = (Element) GSXML.getChildByTagName(this.recept.process(userInfoMessage), GSXML.RESPONSE_ELEM);
            Element responseParamList = (Element) GSXML.getChildByTagName(userInformationResponse, GSXML.PARAM_ELEM + GSXML.LIST_MODIFIER);
            if (responseParamList == null)
            {
                logger.error("Can't get the groups for user " + request.getUserPrincipal().getName());
            }
            else
            {
                HashMap<String, Serializable> responseParams = GSXML.extractParams(responseParamList, true);
                String groups = (String) responseParams.get(GSXML.GROUPS_ATT);
                String editEnabled = (String) responseParams.get("editEnabled");

                userInformation.setAttribute(GSXML.GROUPS_ATT, groups);
                userInformation.setAttribute("editEnabled", (editEnabled != null) ? editEnabled : "false");
                xml_request.appendChild(userInformation);
            }
        }

        //If we are in a collection-related page then make sure this user is allowed to access it
        if (collection != null && !collection.equals(""))
        {
            //Get the security info for this collection
          Document msg_doc = XMLConverter.newDOM();
            Element securityMessage = msg_doc.createElement(GSXML.MESSAGE_ELEM);
            Element securityRequest = GSXML.createBasicRequest(msg_doc, GSXML.REQUEST_TYPE_SECURITY, collection, userContext);
            securityMessage.appendChild(securityRequest);
            if (document != null && !document.equals(""))
            {
                securityRequest.setAttribute(GSXML.NODE_OID, document);
            }

            Element securityResponse = (Element) GSXML.getChildByTagName(this.recept.process(securityMessage), GSXML.RESPONSE_ELEM);
            if (securityResponse == null)
            {
                return false;
            }

            ArrayList<String> groups = GSXML.getGroupsFromSecurityResponse(securityResponse);

            //If guests are not allowed to access this page then check to see if the user is in a group that is allowed to access the page
            if (!groups.contains(""))
            {
                boolean found = false;
                for (String group : groups)
                {
                    if (request.isUserInRole(group))
                    {
                        found = true;
                        break;
                    }
                }

                //The current user is not allowed to access the page so produce a login page
                if (!found)
                {
                  Document loginPageDoc = XMLConverter.newDOM();
                    Element loginPageMessage = loginPageDoc.createElement(GSXML.MESSAGE_ELEM);
                    Element loginPageRequest = GSXML.createBasicRequest(loginPageDoc, GSXML.REQUEST_TYPE_PAGE, "", userContext);
                    loginPageRequest.setAttribute(GSXML.ACTION_ATT, "p");
                    loginPageRequest.setAttribute(GSXML.SUBACTION_ATT, "login");
                    loginPageRequest.setAttribute(GSXML.OUTPUT_ATT, "html");
                    loginPageRequest.setAttribute(GSXML.BASE_URL, baseURL);
                    loginPageMessage.appendChild(loginPageRequest);

                    Element paramList = loginPageDoc.createElement(GSXML.PARAM_ELEM + GSXML.LIST_MODIFIER);
                    loginPageRequest.appendChild(paramList);

                    Element messageParam = loginPageDoc.createElement(GSXML.PARAM_ELEM);
                    messageParam.setAttribute(GSXML.NAME_ATT, "loginMessage");
                    if (request.getAuthType() == null)
                    {
                        messageParam.setAttribute(GSXML.VALUE_ATT, "Please log in to view this page");
                    }
                    else
                    {
                        messageParam.setAttribute(GSXML.VALUE_ATT, "You are not in the correct group to view this page, would you like to log in as a different user?");
                    }
                    paramList.appendChild(messageParam);

                    Element urlParam = loginPageDoc.createElement(GSXML.PARAM_ELEM);
                    urlParam.setAttribute(GSXML.NAME_ATT, "redirectURL");
                    if (request.getQueryString() != null && request.getQueryString().length() > 0)
                    {
                        urlParam.setAttribute(GSXML.VALUE_ATT, request.getRequestURL() + "?" + request.getQueryString().replace("&", "&amp;"));
                    }
                    else
                    {
                        urlParam.setAttribute(GSXML.VALUE_ATT, request.getRequestURL().toString());
                    }
                    paramList.appendChild(urlParam);

                    Node loginPageResponse = this.recept.process(loginPageMessage);
                    out.println(XMLConverter.getPrettyString(loginPageResponse));

                    return false;
                }
            }
        }
        return true;
    }

    //a debugging method
    private void displaySize(Hashtable<String, UserSessionCache> table)
    {
        if (table == null)
        {
            logger.info("cached table is null");
            return;
        }
        if (table.size() == 0)
        {
            logger.info("cached table size is zero");
            return;
        }
        int num_cached_coll = 0;
        ArrayList<UserSessionCache> cache_list = new ArrayList<UserSessionCache>(table.values());
        for (int i = 0; i < cache_list.size(); i++)
        {
            num_cached_coll += cache_list.get(i).tableSize();
        }
        logger.info("Number of sessions : total number of cached collection info = " + table.size() + " : " + num_cached_coll);
    }

    /** merely a debugging method! */
    private String tableToString(Hashtable<String, Hashtable<String, String>> table)
    {
        String str = "";
        Enumeration<String> keys = table.keys();
        while (keys.hasMoreElements())
        {
            String name = keys.nextElement();
            str += name + ", ";
        }
        return str;
    }

    /**
     * this goes through each URL and adds in a session id if needed-- its
     * needed if the browser doesn't accept cookies also escapes things if
     * needed
     */
    protected void encodeURLs(Node dataNode, HttpServletResponse response)
    {
        if (dataNode == null)
        {
            return;
        }

        Element data = null;

        short nodeType = dataNode.getNodeType();
        if (nodeType == Node.DOCUMENT_NODE)
        {
            Document docNode = (Document) dataNode;
            data = docNode.getDocumentElement();
        }
        else
        {
            data = (Element) dataNode;
        }

        if (data != null)
        {

            // get all the <a> elements
            NodeList hrefs = data.getElementsByTagName("a");
            // Instead of calculating each iteration...
            int hrefscount = hrefs.getLength();

            for (int i = 0; hrefs != null && i < hrefscount; i++)
            {
                Element a = (Element) hrefs.item(i);
                // ugly hack to get rid of : in the args - interferes with session handling
                String href = a.getAttribute("href");
                if (!href.equals(""))
                {
                    if (href.indexOf("?") != -1)
                    {
                        String[] parts = StringUtils.split(href, "\\?", -1);
                        if (parts.length == 1)
                        {
                            parts[0] = StringUtils.replace(parts[0], ":", "%3A");
                            href = "?" + parts[0];
                        }
                        else
                        {
                            parts[1] = StringUtils.replace(parts[1], ":", "%3A");
                            href = parts[0] + "?" + parts[1];
                        }

                    }
                    a.setAttribute("href", response.encodeURL(href));
                }
            }

            // now find any submit bits - get all the <form> elements
            NodeList forms = data.getElementsByTagName("form");
            int formscount = forms.getLength();
            for (int i = 0; forms != null && i < formscount; i++)
            {
                Element form = (Element) forms.item(i);
                form.setAttribute("action", response.encodeURL(form.getAttribute("action")));
            }
            // are these the only cases where URLs occur??
            // we should only do this for greenstone urls?
        }

    }

    protected String getFirstParam(String name, Map<String, String[]> map)
    {
        String[] val = map.get(name);
        if (val == null || val.length == 0)
        {
            return null;
        }

        return val[0];
    }

    synchronized protected int getNextUserId()
    {
        next_user_id++;
        return next_user_id;
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
    {
        //Check if we need to process a file upload
        if (ServletFileUpload.isMultipartContent(request))
        {
            DiskFileItemFactory fileItemFactory = new DiskFileItemFactory();

            int sizeLimit = System.getProperties().containsKey("servlet.upload.filesize.limit") ? Integer.parseInt(System.getProperty("servlet.upload.filesize.limit")) : 100 * 1024 * 1024;

            File tempDir = new File(GlobalProperties.getGSDL3Home() + File.separator + "tmp");
            if (!tempDir.exists())
            {
                tempDir.mkdirs();
            }

            //We want all files to be stored on disk (hence the 0)
            fileItemFactory.setSizeThreshold(0);
            fileItemFactory.setRepository(tempDir);

            ServletFileUpload uploadHandler = new ServletFileUpload(fileItemFactory);
            uploadHandler.setFileSizeMax(sizeLimit);

            HashMap<String, String[]> queryMap = new HashMap<String, String[]>();
            try
            {
                List items = uploadHandler.parseRequest(request);
                Iterator iter = items.iterator();
                while (iter.hasNext())
                {
                    FileItem current = (FileItem) iter.next();
                    if (current.isFormField())
                    {
                        queryMap.put(current.getFieldName(), new String[] { current.getString() });
                    }
                    else if (current.getName() != null && !current.getName().equals(""))
                    {
                        File file = new File(tempDir, current.getName());
                        current.write(file);

                        queryMap.put("md___ex.Filesize", new String[] { "" + file.length() });
                        queryMap.put("md___ex.Filename", new String[] { "" + current.getName() });
                    }
                }
            }
            catch (Exception e)
            {
                e.printStackTrace();
            }

            doGetOrPost(request, response, queryMap);
        }
        else
        {
            doGetOrPost(request, response, request.getParameterMap());
        }
    }
}