source: main/trunk/greenstone3/src/java/org/greenstone/gsdl3/OAIServer.java@ 26458

/*
 *    OAIServer.java
 *    Copyright (C) 2002 New Zealand Digital Library, http://www.nzdl.org
 *
 *    This program is free software; you can redistribute it and/or modify
 *    it under the terms of the GNU General Public License as published by
 *    the Free Software Foundation; either version 2 of the License, or
 *    (at your option) any later version.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with this program; if not, write to the Free Software
 *    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
package org.greenstone.gsdl3;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Map;

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

import org.apache.log4j.Logger;
import org.greenstone.gsdl3.comms.Communicator;
import org.greenstone.gsdl3.comms.SOAPCommunicator;
import org.greenstone.gsdl3.core.MessageRouter;
import org.greenstone.gsdl3.core.OAIReceptionist;
import org.greenstone.gsdl3.util.GSConstants;
import org.greenstone.gsdl3.util.GSParams;
import org.greenstone.gsdl3.util.GSXML;
import org.greenstone.gsdl3.util.OAIXML;
import org.greenstone.gsdl3.util.XMLConverter;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;

/** a servlet to serve the OAI metadata harvesting - 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 verb= type args and builds a simple request to send to
 * the oai receptionist, which returns a result in xml, conforming to the OAI-PMH
 * protocol.
 * @see Receptionist
 */
/**
 * OAI server configuration instructions *
 * 
 */
public class OAIServer extends BaseGreenstoneServlet
{

    /** the receptionist to send messages to */
    protected OAIReceptionist recept = null;
    /**
     * the default language - is specified by setting a servlet param, otherwise
     * DEFAULT_LANG is used
     */
    protected String default_lang = null;
    /**
     * The default default - used if a default lang is not specified in the
     * servlet params
     */
    protected final String DEFAULT_LANG = "en";

    /**
     * a converter class to parse XML and create Docs This is only used for
     * generating internal requests passed to MessageRouter. The response
     * message is generated by parsing an existing xml skeleton file
     * (web/WEB-INF/oaixml/oaiversion2.xml, for example).
     */
    protected XMLConverter converter = null;
    /**
     * container Document to create XML Nodes (but only request to the oai
     * receptionist, not response (which is created in OAIXML.java) created by
     * converter class
     */
    protected Document doc = null;

    /** A HashSet which contains all the legal verbs. */
    protected HashSet<String> verb_set = null;
    /**
     * A HashSet which contains all the legal oai keys in the key/value argument
     * pair.
     */
    protected HashSet<String> param_set = null;
    /**
     * The name of the site with which we will finally be dealing, whether it is
     * a local site or a remote site through a communicator.
     */
    protected String site = "";

    // do we output the stylesheet processing instruction?
    protected boolean use_oai_stylesheet = true;
    protected String oai_stylesheet = "interfaces/oai/oai2.xsl";

    // there is no getQueryString() method in the HttpServletRequest returned from doPost, 
    // since that is actually of type apache RequestFacade, and doesn't define such a method
    protected String queryString = null;

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

    /**
     * initialise the servlet
     */
    public void init(ServletConfig config) throws ServletException
    {
        // always call super.init, i.e., HttpServlet.;
        super.init(config);
        this.default_lang = config.getInitParameter(GSConstants.DEFAULT_LANG);

        initVerbs();
        initParams();

        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 local site, try for communicator (remote site)
            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;
        }

        // the receptionist -the servlet will talk to this
        this.recept = new OAIReceptionist();

        // 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)
        {
            //this site_name could consist of comma separated more than one site name.
            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("OAIServlet configure exception when trying to use a new MessageRouter " + mr_name + ": " + e.getMessage());
                    e.printStackTrace();
                    message_router = new MessageRouter();
                }
            }

            message_router.setSiteName(site_name);
            // lots of work is done in this step; see MessageRouter.java
            message_router.configure();
            this.recept.setSiteName(site_name);
            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
            Element site_elem = this.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("OAIServlet.init Error: invalid Communicator type: " + remote_site_type);
                System.exit(1);
            }

            if (!communicator.configure(site_elem))
            {
                System.err.println("OAIServlet.init Error: Couldn't configure communicator");
                System.exit(1);
            }
            this.recept.setSiteName(remote_site_name);
            this.recept.setMessageRouter(communicator);
        }
        // used for composing internal xml requests, but not xml responses.
        // the converter may be used to get pretty xml, though.    
        this.converter = new XMLConverter();
        this.doc = this.converter.newDOM();

        // Read in OAIConfig.xml (residing web/WEB-INF/classes/) and 
        //use it to configure the receptionist. The init() is also called in which
        //the resumption token file is read in and all expired tokens cleared.
        Element oai_config = OAIXML.getOAIConfigXML();
        if (oai_config == null)
        {
            logger.error("Fail to parse oai config file OAIConfig.xml.");
            return;
        }
        // pass it to the receptionist
        this.recept.configure(oai_config);

        // also, we have something we want to get from here - useOAIStylesheet
        this.configure(oai_config);
    }//end of init()

    private void configure(Element oai_config)
    {
        Element use_stylesheet_elem = (Element) GSXML.getChildByTagName(oai_config, OAIXML.USE_STYLESHEET);
        if (use_stylesheet_elem != null)
        {
            String value = GSXML.getNodeText(use_stylesheet_elem);
            if (value.equals("no"))
            {
                this.use_oai_stylesheet = false;
            }
        }
        if (this.use_oai_stylesheet)
        {
            // now see if there is a custom stylesheet specified
            Element stylesheet_elem = (Element) GSXML.getChildByTagName(oai_config, OAIXML.STYLESHEET);
            if (stylesheet_elem != null)
            {
                String value = GSXML.getNodeText(stylesheet_elem);
                if (!value.equals(""))
                {
                    oai_stylesheet = value;
                }
            }

        }
    }

    private void initVerbs()
    {
        verb_set = new HashSet<String>();
        verb_set.add(OAIXML.GET_RECORD);
        verb_set.add(OAIXML.LIST_RECORDS);
        verb_set.add(OAIXML.LIST_IDENTIFIERS);
        verb_set.add(OAIXML.LIST_SETS);
        verb_set.add(OAIXML.LIST_METADATA_FORMATS);
        verb_set.add(OAIXML.IDENTIFY);
    }

    private void initParams()
    {
        param_set = new HashSet<String>();
        param_set.add(OAIXML.METADATA_PREFIX);
        param_set.add(OAIXML.FROM);
        param_set.add(OAIXML.UNTIL);
        param_set.add(OAIXML.SET);
        param_set.add(OAIXML.RESUMPTION_TOKEN);
        param_set.add(OAIXML.IDENTIFIER);
    }

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

        String query = (queryString == null) ? request.getQueryString() : queryString;

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

        logger.info(usageInfo);
    }

    /**
     * return true if the url is in the form of baseURL?verb=...,
     */
    private boolean validate(String query, String verb)
    {
        //Here in OAIServer, only the verbs are validated. All the validation for individual verb
        // is taken in their doXXX() methods.
        if (query == null || !query.startsWith(OAIXML.VERB + "="))
        {
            return false;
        }
        if (!verb_set.contains(verb))
        {
            return false;
        }
        return true;
    }

    private String getVerb(String query)
    {
        if (query == null)
            return "";
        int verb_start_index = query.indexOf("=") + 1;// first occurence of '='
        int verb_end_index = query.indexOf("&");
        if (verb_end_index == -1)
        {
            return query.substring(verb_start_index);
        }
        return query.substring(verb_start_index, verb_end_index);
    }

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
    {
        logUsageInfo(request);
        //out.println("url="+request.getRequestURL());// /oaiserver    
        //out.println("query="+request.getQueryString());// is /greenstone3

        // oai always requires the content type be text/xml
        request.setCharacterEncoding("UTF-8");
        response.setContentType("text/xml;charset=UTF-8");
        PrintWriter out = response.getWriter();

        //
        String lang = request.getParameter(GSParams.LANGUAGE);
        if (lang == null || lang.equals(""))
        {
            // use the default
            lang = this.default_lang;
        }
        //we don't get the baseURL from the http request because what we get might be different from the one known publicly due to local network redirection.
        //For example, puka.cs.waikato.ac.nz vs www.greenstone.org
        //String base_url = request.getRequestURL().toString();
        // if called by doPost (if this was originally a POST request), var queryString would have been set
        String query = (queryString == null) ? request.getQueryString() : queryString;
        queryString = null; // reset member variable, else no doGet will work as long as the server remains running

        String[] pairs = (query == null) ? null : query.split("&");//split into key/value pairs
        String verb = getVerb(query);
        Element xml_response = OAIXML.createBasicResponse(verb, pairs);
        Element verb_elem = null;

        if (validate(query, verb) == false)
        {
            if (verb_set.contains(verb) == false)
            {
                logger.error(OAIXML.BAD_VERB + ": " + query);
                verb_elem = OAIXML.createErrorElement(OAIXML.BAD_VERB, OAIXML.ILLEGAL_OAI_VERB);
            }
            else
            {
                //must be something else other than bad verbs caused an error, so bad argument
                logger.error(OAIXML.BAD_ARGUMENT + ": " + query);
                verb_elem = OAIXML.createErrorElement(OAIXML.BAD_ARGUMENT, "");
            }
            xml_response.appendChild(verb_elem);

            out.println("<?xml version='1.0' encoding='UTF-8' ?>");
            if (this.use_oai_stylesheet)
            {
                out.println("<?xml-stylesheet type='text/xsl' href='" + this.oai_stylesheet + "' ?>\n");
            }
            out.println(this.converter.getPrettyString(xml_response));
            return;
        }//end of if(validate

        // The query is valid, we can now
        // compose the request message to the receptionist
        Element xml_message = this.doc.createElement(GSXML.MESSAGE_ELEM);
        Element xml_request = this.doc.createElement(GSXML.REQUEST_ELEM);
        // The type attribute is set to be 'oaiService' from OAIServer to OAIReceptionist.
        //xml_request.setAttribute(GSXML.TYPE_ATT, OAIXML.OAI_SERVICE);
        xml_request.setAttribute(GSXML.LANG_ATT, lang);
        xml_request.setAttribute(GSXML.TO_ATT, verb);
        addParams(xml_request, pairs);

        //xml_request.setAttribute(GSXML.OUTPUT_ATT, output);????
        xml_message.appendChild(xml_request);

        Node xml_result = this.recept.process(xml_message);
        if (xml_result == null)
        {
            logger.info("xml_result is null");
            verb_elem = OAIXML.createErrorElement("Internal error", "");
            xml_response.appendChild(verb_elem);
        }
        else
        {

            /**
             * All response elements are in the form (with a corresponding verb
             * name): <message> <response> <verb> ... <resumptionToken> .. this
             * is optional! </resumptionToken> </verb> </response> </message>
             */
            Node res = GSXML.getChildByTagName(xml_result, OAIXML.RESPONSE);
            if (res == null)
            {
                logger.info("response element in xml_result is null");
                verb_elem = OAIXML.createErrorElement("Internal error", "");
            }
            else
            {
                verb_elem = GSXML.getFirstElementChild(res);
            }

            if (OAIXML.oai_version.equals(OAIXML.OAI_VERSION2) || verb_elem.getTagName().equals(OAIXML.ERROR))
            {
                xml_response.appendChild(xml_response.getOwnerDocument().importNode(verb_elem, true));
            }
            else
            {
                GSXML.copyAllChildren(xml_response, verb_elem);
            }
        }
        out.println("<?xml version='1.0' encoding='UTF-8' ?>");
        if (this.use_oai_stylesheet)
        {
            out.println("<?xml-stylesheet type='text/xsl' href='" + this.oai_stylesheet + "' ?>\n");
        }
        out.println(this.converter.getPrettyString(xml_response));
        return;
    }

    /** append parameter elements to the request sent to the receptionist */
    public void addParams(Element request, String[] pairs)
    {
        // no params apart from the verb
        if (pairs == null || pairs.length < 2)
            return;

        /**
         * the request xml is composed in the form: <request> <param name=.../>
         * <param name=.../> </request> (No paramList element in between).
         */
        for (int i = 1; i < pairs.length; i++)
        {
            //the first pair in pairs is the verb=xxx
            int index = pairs[i].indexOf("=");
            if (index != -1)
            { //just a double check
                Element param = this.doc.createElement(OAIXML.PARAM);
                param.setAttribute(OAIXML.NAME, pairs[i].substring(0, index));
                param.setAttribute(OAIXML.VALUE, OAIXML.oaiDecode(pairs[i].substring(index + 1)));
                request.appendChild(param);
            }
        }
    }

    // For OAI version 2.0, validation tests indicated that POST needs to be supported. Some
    // modification was required in order to ensure that the request is passed intact to doGet()
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
    {

        // the post method returns a wrapper of type RequestFacade by apache and there
        // is no getQueryString() method defined for it. Therefore, need to work this out
        // manually before calling doGet(request, response) so that doGet can work as before.

        queryString = "";
        Iterator parameter_entries = request.getParameterMap().entrySet().iterator();
        while (parameter_entries.hasNext())
        {
            Map.Entry param_entry = (Map.Entry) parameter_entries.next();
            String[] paramVals = (String[]) param_entry.getValue();
            if (paramVals != null)
            {
                if (paramVals.length > 0)
                {
                    logger.error("POST request received: " + param_entry.getKey() + " - " + paramVals[0]);
                    queryString = queryString + "&" + param_entry.getKey() + "=" + paramVals[0];
                }
            }
        }
        if (queryString.length() > 0)
        {
            queryString = queryString.substring(1);
            //queryString = OAIXML.oaiEncode(queryString);
        }
        if (queryString.equals(""))
        {
            queryString = null;
        }
        doGet(request, response);
    }
}