root/main/trunk/greenstone3/resources/java/QBRSOAPServer.java.in @ 26123

Revision 26123, 36.3 KB (checked in by ak19, 8 years ago)

Diego discovered that the QBRSOAPServer no longer got deployed. 1. The resources/java/QBRSOAPServer.java.in class failed to compile on attempting to deploy the web service owing to the GSXML.createBasicRequest() method's signature having been changed to take a UserContext? parameter in place of lang and uid. 2. Updated UserContext? class with an additional constructor that now takes both lang and uid. This gets called by resources/java/QBRSOAPServer.java.in whenever it needs to pass in a UserContext? object to GSXML.createBasicRequest().

Line 
1/**
2 *#########################################################################
3 * QBRSOAPServer.java.in: a template for a SOAPServer providing
4 * basic Query, Browse, Retrieve web services for Greenstone 3.
5 * Part of the Greenstone digital library suite from the New Zealand
6 * Digital Library Project at the University of Waikato, New Zealand.
7 * <BR><BR>
8 * Copyright (C) 2008 New Zealand Digital Library Project
9 * <BR><BR>
10 * This program is free software; you can redistribute it and/or modify
11 * it under the terms of the GNU General Public License as published by
12 * the Free Software Foundation; either version 2 of the License, or
13 * (at your option) any later version.
14 * <BR><BR>
15 * This program is distributed in the hope that it will be useful,
16 * but WITHOUT ANY WARRANTY; without even the implied warranty of
17 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
18 * GNU General Public License for more details.
19 * <BR><BR>
20 * @author ak19
21 * based on Katherine Don's SOAPServer@sitename@ template file.
22 *########################################################################
23 */
24
25package org.greenstone.gsdl3;
26
27import java.io.File;
28import java.io.InputStream;
29
30import java.util.Properties;
31import java.util.Enumeration;
32import java.util.Map;
33import java.util.Map.Entry;
34import java.util.HashMap;
35import java.util.Set;
36import java.util.Iterator;
37
38import org.w3c.dom.Document;
39import org.w3c.dom.Element;
40import org.w3c.dom.NodeList;
41import org.w3c.dom.Node;
42
43import org.greenstone.util.GlobalProperties;
44import org.greenstone.gsdl3.core.MessageRouter;
45import org.greenstone.gsdl3.util.GSFile;
46import org.greenstone.gsdl3.util.GSXML;
47import org.greenstone.gsdl3.util.UserContext;
48import org.greenstone.gsdl3.util.XMLConverter;
49
50import org.apache.log4j.Logger; // Import log4j classes
51
52/*
53 * Add to $GSDLHOME/web/WEB-INF/server-config.wsdd:
54 * <service name="GS3WebServices" provider="java:RPC">
55 * <parameter name="allowedMethods" value="*"/>
56 * <parameter name="className" value="org.greenstone.gs3services.GS3WebServices"/>
57 * </service>
58*/
59
60/** Class that provides the basic Query, Browse and Retrieve (QBR) web service
61 * operations for Greenstone 3.
62 * It contains a MessageRouter that carries out all the tasks by calling the
63 * appropriate Greenstone functionality for each request message passed to it,
64 * and returning a response message.
65 * 
66 * All response messages are returned from the MessageRouter to clients invoking   
67 * the web services. All return values are strings that represent XML messages.
68 *
69 * Method help() reads from the file QBRWebServicesHelp.properties to list the web
70 * service operations available. Method helpWithMethod(String methodName)
71 * reads from the same file to display a description of the requested operation.
72 * (These method descriptions are mostly the same as those in the Javadoc
73 * comments.)
74 *
75 * NOTE: The folder containing this web service class' properties helpFile
76 * should be on the classpath. (QBRWebServicesHelp.properties)
77 * @author ak19
78*/
79public class QBRSOAPServer@sitename@ {
80    /** site_name the MessageRouter works with, here set to "localsite" */
81    protected String site_name = "@sitename@";
82
83    /** Message Router object to pass requests messages to and which
84     * will process them.*/
85    protected MessageRouter mr = null;
86   
87    /** Container Document to create XML Nodes */
88    protected Document doc=null;
89    /** A converter class to parse XML and create Docs */
90    protected XMLConverter converter=null;
91
92    /** The Logger for this class */
93    private static Logger LOG = Logger.getLogger(QBRSOAPServer@sitename@.class);
94   
95    /** Error message loading helpFile. Remains at "" if everything is fine */
96    protected static String helpErrormessage = "";
97    /** Properties map with mappings from methodname to help
98     * description string. */
99    protected static Properties properties;
100    /** The help properties file describing the web service operations */
101    protected static String helpFile = "QBRWebServicesHelp.properties";
102   
103    // static code block to initialise the help Properties from the helpFile
104    static {
105        properties = new Properties();
106        // load the properties file from a location with respect to the
107        // the Web Service .class file
108        InputStream input = null;
109        try {   
110            // load the properties file from a location with respect to the
111            // the Web Service .class file
112            input
113            = QBRSOAPServer@sitename@.class.getClassLoader().getResourceAsStream(
114                    helpFile);
115            if(input == null) {
116                helpErrormessage = "Cannot find file " + helpFile + " to load.";
117                LOG.warn(helpErrormessage);
118            } else {
119                properties.load(input);
120                input.close();
121            }
122        } catch(Exception e) {
123            helpErrormessage = "Exception loading properties from help file "
124                + helpFile + "\n" + e.getMessage();
125            LOG.warn("Exception loading properties from help file "
126                + helpFile + "\n" + e.getMessage());
127        }
128    }
129   
130   
131    /* Describe subset options for the various Greenstone3 modules */
132    protected static final String mrSubsetOptions = // messageRouter
133        "collectionList serviceClusterList serviceList siteList";
134    protected static final String csSubsetOptions = // collections and serviceClusters
135        "metadataList serviceList displayItemList";
136    protected static final String serviceSubsetOptions = // services
137        "paramList displayItemList";
138    protected static final String structureOptions =
139        "entire ancestors parent siblings children descendants"; // note the spelling
140    protected static final String structureInfoOptions =
141        "numSiblings siblingPosition numChildren";
142   
143       
144    /** Constructor that initializes the web services' MessageRouter object
145     * Reads from GlobalProperties to get gsdl3_home and set the sitename. */
146    public QBRSOAPServer@sitename@() {
147        String gsdl3_home = GlobalProperties.getGSDL3Home();
148        if (gsdl3_home == null || gsdl3_home.equals("")) {
149            LOG.error(
150                "Couldn't access GSDL3Home from GlobalProperties.getGSDL3HOME,"
151                + "can't initialize the SOAP Server.");
152            return;
153        }
154       
155        String site_home = GSFile.siteHome(gsdl3_home, this.site_name);
156       
157        File site_file = new File(site_home);
158        if (!site_file.isDirectory()) {
159            LOG.error("The site directory "+site_file.getPath()
160                +" doesn't exist. Can't initialize the SOAP Server.");
161            return;
162        }
163        this.converter = new XMLConverter();
164        this.doc = this.converter.newDOM();
165       
166        mr = new MessageRouter();
167        mr.setSiteName(this.site_name);
168        mr.configure();
169    }
170   
171    /* (1) DESCRIBE MESSAGES, manual pages 35-41 */
172    /** Sends a describe message to the MessageRouter.
173     * @param lang is the language of the display content in the response.
174     * @param subsetOption are the requested list of items to return in the
175     * response. For the Message Router this can be collectionList,
176     * serviceClusterList, serviceList, siteList
177     * @see <a href="http://wiki.greenstone.org/wiki/index.php/Greenstone3">The Greenstone 3 Developer's Manual - pages 35-41</a>
178    */
179    public String describe(String lang, String subsetOption)
180    {
181        return describe("", lang, subsetOption, mrSubsetOptions);
182    }
183   
184    /** For sending Describe messages to ServiceClusters.
185     * @param serviceCluster is the name of the Service Cluster that this describe
186     * request is sent to.
187     * @param lang is the language of the display content in the response
188     * @param subsetOption is the requested list of items to return in the response
189     * For Service Clusters this can be metadataList, serviceList, displayItemList.
190     * @see <a href="http://wiki.greenstone.org/wiki/index.php/Greenstone3">The Greenstone 3 Developer's Manual - pages 35-41</a>
191     */
192    public String describeServiceCluster(
193            String serviceCluster, String lang, String subsetOption)
194    {
195        return describe(serviceCluster, lang, subsetOption, csSubsetOptions);
196    }
197   
198    /** For sending Describe messages to Collections.
199     * @param collection is the name of the Collection that this describe request
200     * is sent to.
201     * @param lang is the language of the display content in the response
202     * @param subsetOption is the requested list of items to return in the response
203     * For Collections this can be metadataList, serviceList and displayItemList.
204     * @see <a href="http://wiki.greenstone.org/wiki/index.php/Greenstone3">The Greenstone 3 Developer's Manual - pages 35-41</a>
205     */
206    public String describeCollection(
207            String collection, String lang, String subsetOption)
208    {
209        return describe(collection, lang, subsetOption, csSubsetOptions);
210    }
211   
212    /**
213     * For sending a describe message to a Collection's Service.
214     * @see <a href="http://wiki.greenstone.org/wiki/index.php/Greenstone3">The Greenstone 3 Developer's Manual - pages 35-41</a>
215     * @param collection is the name of the Collection whose service
216     * this describe request is sent to.
217     * @param service is the name of the Service (of that collection) to
218     * which this describe request is sent.
219     * @param lang is the language of the display content in the response
220     * @param subsetOption is the requested list of items to return in the response
221     * For Services this can be paramList, displayItemList */
222    public String describeCollectionService(String collection, String service,
223            String lang, String subsetOption)
224    {
225        return describe(collection + "/" + service,
226                lang, subsetOption, serviceSubsetOptions);
227    }
228   
229    /**
230     * For sending a describe message to a Service hosted by the Message Router
231     * (no collection).
232     * @see <a href="http://wiki.greenstone.org/wiki/index.php/Greenstone3">The Greenstone 3 Developer's Manual - pages 35-41</a>
233     * @param service is the name of the MessageRouter's Service to which this
234     * describe request is sent.
235     * @param lang is the language of the display content in the response
236     * @param subsetOption is the requested list of items to return in the response
237     * For Services this can be paramList, displayItemList
238    */
239    public String describeService(
240            String service, String lang, String subsetOption)
241    {
242        return describe(service, lang, subsetOption, serviceSubsetOptions);
243    }
244   
245    /** For sending a describe message.
246     * If public, this method would give full access: a describe message that
247     * lets the user specify all the details of who the receiver is, and what
248     * details are requested.
249     * @param to - the Greenstone module (MessageRouter, Collection,
250     * ServiceCluster or (Collection-)Service to send this describe message to.
251     * (The module asked to describe itself.)
252     * @param lang - the language of the display content in the response.
253     * @param subsetOption - the set of elements of the describe response that
254     * are requested. These vary depending on the GS3 module asked to describe
255     * itself.
256     * @param validSubsetOptions - the list of subsetOptions that are allowed
257     * for the module this describe message is sent to. Parameter subsetOption
258     * has to be among the list of validSubsetOptions.
259     * @see <a href="http://wiki.greenstone.org/wiki/index.php/Greenstone3">The Greenstone 3 Developer's Manual - pages 35-41</a>
260    */
261    protected String describe(String to, String lang,
262            String subsetOption, String validSubsetOptions)
263    {
264        // Create message element: <message></message>
265        Element message = this.doc.createElement(GSXML.MESSAGE_ELEM);
266        // <message><request lang="en" to="" type="describe" uid="" /></message>
267        Element request = GSXML.createBasicRequest(
268                this.doc, GSXML.REQUEST_TYPE_DESCRIBE, to, new UserContext(lang, ""));
269       
270        // Check if only a subset of this Module Interface's data is asked
271        // to be described
272        if(!subsetOption.equals("")) {
273            // Now deal with the value for subset param:
274            // only deal with valid params for subset of to-ModuleInterface
275            if(validSubsetOptions.indexOf(subsetOption) == -1)
276                return error("Invalid List to be described. Choose one of:\n"
277                    + validSubsetOptions);
278           
279            // else, append <paramList>
280            // <param name="subset" value="subsetOption" /></paramList>
281            Element paramList = this.doc.createElement(
282                    GSXML.PARAM_ELEM+GSXML.LIST_MODIFIER);
283            // append <param name="subset" value=paramValue />
284            // createParam(Document, name, value);
285            // Name needs to be "subset", but this can be either GSXML.SUBSET_PARAM
286            // or GSXML.SYSTEM_SUBSET_ATT. It's the first one probably.
287            paramList.appendChild(GSXML.createParameter(
288                            this.doc, GSXML.SUBSET_PARAM, subsetOption));
289            request.appendChild(paramList);
290        }
291        message.appendChild(request);
292       
293        // Send it off to the Message Router and return the response
294        return this.processInternal(message);
295    }
296
297    /* (2) Process-type message, QUERY-TYPE SERVICES - p.45 */
298    /** For executing a (process-type message) query-type service.
299     * @see <a href="http://wiki.greenstone.org/wiki/index.php/Greenstone3">The Greenstone 3 Developer's Manual - page 45</a>
300     * @param collection is the name of the Collection whose query service this 
301     * query-process request is sent to. If "", then the Message Router is assumed.
302     * @param service is the name of the Query Service (of that collection) to 
303     * which  this request is sent.
304     * @param lang is the language of the display content in the response
305     * @param nameToValsMap is a Map of the (fieldname, value) pairs for the
306     * parameters of the query. The field names should be those recognised by
307     * Greenstone 3. That is, the names must exist for the (Collection-)Service Query that this
308     * message is sent To (as given in 'to' argument).
309     * For names of Greenstone-accepted arguments,
310     * @see <a href="http://wiki.greenstone.org/wiki/index.php/Actions_and_Arguments">Greenstone wiki - Actions and Arguments</a>
311    */
312    public String query(String collection, String service,
313            String lang, Map nameToValsMap)
314    {   
315        // <paramList></paramList>
316        Element paramList = this.doc.createElement(
317                GSXML.PARAM_ELEM+GSXML.LIST_MODIFIER);
318        // <param>s: creating parameters of (name, value) pairs
319        Set entrySet = nameToValsMap.entrySet();
320        Iterator i = entrySet.iterator();
321        while(i.hasNext()) {
322            Entry entry = (Entry)i.next();
323            String name = (String)entry.getKey();
324            String value = (String)entry.getValue();
325            paramList.appendChild(GSXML.createParameter(
326                    this.doc, name, value));
327        }
328
329        Element message = this.doc.createElement(GSXML.MESSAGE_ELEM);
330        Element request = GSXML.createBasicRequest(
331                this.doc, GSXML.REQUEST_TYPE_PROCESS,
332                collection+"/"+service, new UserContext(lang, ""));
333       
334        request.appendChild(paramList);
335        message.appendChild(request);
336       
337        // Send it off to the Message Router and return the response
338        return this.processInternal(message);   
339    }
340
341        /**
342     * This method is used to perform the most basic query:
343     * it assumes defaults for all other parameters and provides only
344     * the query string. It is built on top of a TextQuery.
345     * @param collection is the Greenstone collection to be searched
346     * @param lang is the preferred language of the display content in
347     * the response to be returned.
348     * @param query is the string to be sought in the Greenstone collection
349     * @return a Greenstone 3 XML response message for the query specifying
350     * the search results.
351     */
352    public String basicQuery(String collection, String lang, String query) {
353        // The basicQuery is built on top of the TextQuery service
354        final String queryService = "TextQuery";
355       
356        // (1) describe request on the TextQuery
357        String queryDescription = describeCollectionService(
358                collection, queryService, "en", "paramList"); // just get paramList
359        //System.out.println(queryDescription);
360       
361        Document doc = this.converter.getDOM(queryDescription);
362        NodeList nl = doc.getElementsByTagName(
363                GSXML.PARAM_ELEM+GSXML.LIST_MODIFIER);
364       
365        Element paramList = null;
366        if(nl.getLength() <= 0) { // no paramList in textQuery description means
367                // no query field either: that means we can't continue
368            return this.error("BasicQuery is not available for this collection"
369                + " as it provides no TextQuery service.");
370        } //else
371       
372        paramList = (Element)nl.item(0);
373        nl = paramList.getElementsByTagName(GSXML.PARAM_ELEM);
374        if(nl.getLength() <= 0) { // no params, means no query field, so return
375            return this.error("BasicQuery is not available for this collection.");
376        }
377       
378        // (2) get the defaults for each parameter and use that to set
379        // the defaults
380        Map params = new HashMap(nl.getLength()); // field name to value map
381        for(int i = 0; i < nl.getLength(); i++) {
382            Element param = (Element)nl.item(i);
383            String paramName = param.getAttribute(GSXML.NAME_ATT);
384            String def = param.getAttribute(GSXML.DEFAULT_ATT);
385            if(def.equals("")) {
386                // if there's no default, the field must want the query String
387                params.put(paramName, query);
388            } else { // there is a default, use the default for this param
389                params.put(paramName, def);
390            }
391        }
392       
393        // (3) Perform the query using defaults and return the response
394        return this.query(collection, queryService, lang, params);
395    }
396
397       
398    /* (3) RETRIEVE PROCESS METHODS - Manual, pp.47-49 */
399    /** DocumentContentRetrieve request sent to a collection's
400     * DocumentContentRetrieve service (see manual, p.48)
401     * @see <a href="http://wiki.greenstone.org/wiki/index.php/Greenstone3">The Greenstone 3 Developer's Manual - page 48</a>
402     * @param collection is the name of the Collection whose
403     * DocumentContentRetrieve is requested
404     * @param lang is the language of the display content in the response
405     * @param docNodeIDs is the list of documentNodeIDs for which the
406     * content ought to be retrieved. */
407    public String retrieveDocumentContent(
408            String collection, String lang, String[] docNodeIDs)
409    {
410        // creating <documentNodeList></documentNodeList>
411        Element docNodeList = this.doc.createElement(
412                GSXML.DOC_NODE_ELEM+GSXML.LIST_MODIFIER);
413       
414        // creating subelements: <documentNode nodeID="..." />
415        for(int i = 0; i < docNodeIDs.length; i++) {
416            Element docNode = this.doc.createElement(GSXML.DOC_NODE_ELEM);
417            docNode.setAttribute(GSXML.NODE_ID_ATT, docNodeIDs[i]);
418            docNodeList.appendChild(docNode);
419        }
420
421        Element message = doc.createElement(GSXML.MESSAGE_ELEM);
422        Element request = GSXML.createBasicRequest(
423                doc, GSXML.REQUEST_TYPE_PROCESS,
424                collection+"/DocumentContentRetrieve", new UserContext(lang, ""));
425       
426        // create an empty <paramlist /> element (as example in manual)
427        Element paramlist = doc.createElement(
428                GSXML.PARAM_ELEM+GSXML.LIST_MODIFIER);
429       
430        request.appendChild(paramlist);
431        request.appendChild(docNodeList);
432        message.appendChild(request);
433
434        // Send it off to the Message Router and return the response
435        return this.processInternal(message);
436    }
437   
438    /** DocumentStructureRetrieve request sent to a collection's
439     * DocumentStructureRetrieve service (manual pp.48, 49) to retrieve
440     * the entire document structure.
441     * @see <a href="http://wiki.greenstone.org/wiki/index.php/Greenstone3">The Greenstone 3 Developer's Manual - pages 48, 49</a>
442     * @param collection is the name of the Collection whose
443     * DocumentStructureRetrieve is requested
444     * @param lang is the language of the display content in the response
445     * @param docNodeIDs is the list of documentNodeIDs for which the
446     * entire structure ought to be retrieved. */
447    public String retrieveEntireDocumentStructure(String collection,
448            String lang, String[] docNodeIDs)
449    {
450        return retrieveDocumentStructure(collection, lang, docNodeIDs,
451                new String[] { "entire" }, null);
452    }
453   
454    /** DocumentStructureRetrieve request sent to a collection's
455     * DocumentStructureRetrieve service (manual pp.48, 49) to retrieve
456     * the specified part of the document's structure.
457     * @see <a href="http://wiki.greenstone.org/wiki/index.php/Greenstone3">The Greenstone 3 Developer's Manual - pages 48, 49</a>
458     * @param collection is the name of the Collection whose
459     * DocumentStructureRetrieve is requested
460     * @param lang is the language of the display content in the response
461     * @param docNodeIDs is the list of documentNodeIDs for which the
462     * structure ought to be retrieved.
463     * @param structure specifies what structure information needs to
464     * be retrieved. The values can be one or more of ancestors, parent,
465     * siblings, children, descendants (<b>note spelling</b>), entire.
466     * @param info - for specifying extra information to be retrieved.
467     * Possible values for info parameters are numSiblings, siblingPosition,
468     * numChildren */
469    public String retrieveDocumentStructure(String collection, String lang,
470            String[] docNodeIDs, String[] structure, String[] info)
471    {
472        // creating subelements: <documentNode nodeID="..." />
473        Element docNodeList = this.doc.createElement(
474                GSXML.DOC_NODE_ELEM+GSXML.LIST_MODIFIER);
475        for(int i = 0; i < docNodeIDs.length; i++) {
476            Element docNode = this.doc.createElement(GSXML.DOC_NODE_ELEM);
477            docNode.setAttribute(GSXML.NODE_ID_ATT, docNodeIDs[i]);
478            docNodeList.appendChild(docNode);
479        }
480       
481        Element message = doc.createElement(GSXML.MESSAGE_ELEM);
482        Element request = GSXML.createBasicRequest(
483                doc, GSXML.REQUEST_TYPE_PROCESS,
484                collection+"/DocumentStructureRetrieve", new UserContext(lang, ""));
485       
486        // Create the <paramlist></paramlist> element of param elements,
487        // if any; and only if values are legal (that is, if they occur in 
488        // static Strings structureOptions and structureInfoOptions):
489        // <param name="structure" value = "structure[i]">
490        // <param name="info" value = "info[i]">
491        Element paramList = doc.createElement(
492                GSXML.PARAM_ELEM+GSXML.LIST_MODIFIER);
493       
494        if(structure != null) {
495            for(int i = 0; i < structure.length; i++) {
496                if(structureOptions.indexOf(structure[i]) != -1) {
497                    paramList.appendChild(GSXML.createParameter(
498                            this.doc, "structure", structure[i]));                 
499                }
500            }
501        }
502        if(info != null) {
503            for(int i = 0; i < info.length; i++) {
504                if(structureInfoOptions.indexOf(info[i]) != -1) {
505                    paramList.appendChild(GSXML.createParameter(
506                            this.doc, "info", info[i]));
507                }
508            }
509        }
510       
511        // paramList is allowed to be empty and may indeed be empty:
512        request.appendChild(paramList);
513        request.appendChild(docNodeList);
514        message.appendChild(request);
515       
516        // Send it off to the Message Router and return the response
517        return this.processInternal(message);
518    }
519   
520    /* Retrieve for Doc Metadata: explained in the manual on page 47 */
521    /** DocumentMetadataRetrieve request sent to a collection's
522     * DocumentMetadataRetrieve service to retrieve all of a document's metadata.
523     * @see <a href="http://wiki.greenstone.org/wiki/index.php/Greenstone3">The Greenstone 3 Developer's Manual - page 47</a>
524     * @param collection is the name of the Collection whose
525     * DocumentMetadataRetrieve is requested
526     * @param lang is the language of the display content in the response
527     * @param docNodeIDs is the list of documentNodeIDs for which the
528     * structure ought to be retrieved.
529    */
530    public String retrieveAllDocumentMetadata(String collection, String lang,
531            String[] docNodeIDs)
532    {
533        // See bottom of manual p.44 for the fact that "all" is used
534        // as the metaName value when retrieving all metadata for a doc
535        return retrieveDocumentMetadata(collection, lang, docNodeIDs,
536                new String[]{ "all" });
537    }
538   
539    /** DocumentMetadataRetrieve service to retrieve some specific
540     * metadata values of a document. (Manual on page 47.)
541     * @see <a href="http://wiki.greenstone.org/wiki/index.php/Greenstone3">The Greenstone 3 Developer's Manual - page 47</a>
542     * @param collection is the name of the Collection whose
543     * DocumentContentRetrieve is requested
544     * @param lang is the language of the display content in the response
545     * @param docNodeIDs is the list of documentNodeIDs for which the
546     * structure ought to be retrieved.
547     * @param metaNames is a list of metadata names which are requested 
548     * to be fetched for the specified documents */
549    public String retrieveDocumentMetadata(String collection, String lang,
550            String[] docNodeIDs, String[] metaNames)
551    {
552        return metadataRetrieve(collection+"/DocumentMetadataRetrieve",
553                lang, docNodeIDs, metaNames, GSXML.DOC_NODE_ELEM);
554    }
555
556    /** Retrieve all classification Metadata for browsing (sent to the
557     * ClassifierBrowseMetadataRetrieve service).
558     * @see <a href="http://wiki.greenstone.org/wiki/index.php/Greenstone3">The Greenstone 3 Developer's Manual - pages 47, 48</a>
559     * @param collection is the name of the Collection whose
560     * ClassifierBrowseMetadataRetrieve service is called
561     * @param categoryName - name of the browsing category, usually
562     * ClassifierBrowse. (If left as "", then it defaults to ClassifierBrowse)
563     * @param lang is the language of the display content in the response
564     * @param nodeIDs is the list of document or classifier NodeIDs
565     * for which the metadata ought to be retrieved.*/
566    public String retrieveAllBrowseMetadata(String collection,
567            String categoryName, String lang, String[] nodeIDs)
568    {
569        if(categoryName.equals(""))
570            categoryName = "ClassifierBrowse";
571        // See bottom of manual p.47 for the fact that "all" is used as
572        // the metaName value when retrieving all metadata for a classifier
573        return metadataRetrieve(collection+"/"+categoryName+"MetadataRetrieve",
574                lang, nodeIDs, new String[]{ "all" }, GSXML.CLASS_NODE_ELEM);
575    }
576   
577    /** ClassifierBrowseMetadataRetrieve service to retrieve some specific
578     * metadata values of a document.
579     * @see <a href="http://wiki.greenstone.org/wiki/index.php/Greenstone3">The Greenstone 3 Developer's Manual - pages 47, 48</a>
580     * @param collection is the name of the Collection whose
581     * ClassifierBrowseMetadataRetrieve service is called
582     * @param categoryName - name of the browsing category, usually
583     * ClassifierBrowse. (If left as "", then it defaults to ClassifierBrowse)
584     * @param lang is the language of the display content in the response
585     * @param nodeIDs is the list of document or classifier NodeIDs
586     * for which the metadata ought to be retrieved.
587     * @param metaNames is a list of metadata names which are requested 
588     * to be fetched for the specified documents or classifiers */
589    public String retrieveBrowseMetadata(String collection, String categoryName, 
590            String lang, String[] nodeIDs, String[] metaNames)
591    {
592        if(categoryName.equals(""))
593            categoryName = "ClassifierBrowse";
594        return metadataRetrieve(collection+"/"+categoryName+"MetadataRetrieve",
595                lang, nodeIDs, metaNames, GSXML.CLASS_NODE_ELEM);
596    }
597   
598    /** Performs a metadata retrieve for documents and (browse) classification
599     * hierarchies. Sends a Document- or ClassifierBrowse- MetadataRetrieve message
600     * to the Document- or ClassifierBrowse- MetadataRetrieve service.
601     * @param to - the Document- or ClassifierBrowse- MetadataRetrieve service to
602     * send this metadata retrieve message to.
603     * @param lang - the language of the display content in the response
604     * @param nodeIDs - the list of (document or classifier) nodeIDs for which
605     * to retrieve the metadata for
606     * @param metaNames - a list specifiying the names of the metadata items
607     * to be retrieved for each nodeID. E.g. "Title", but a list is allowed.
608     * @param NODE_ELEM - either of GSXML's names for the &lt;documentNode&gt; or
609     * &lt;classifierNode&gt; elements.
610    */
611    protected String metadataRetrieve(String to, String lang,
612            String[] nodeIDs, String[] metaNames, final String NODE_ELEM)
613    {
614        // create the <paramlist></paramlist> element of param elements: 
615        // <param name="metadata" value = "metaName[i]">
616        Element metadataParamList = this.doc.createElement(
617                GSXML.PARAM_ELEM+GSXML.LIST_MODIFIER);
618        for(int i = 0; i < metaNames.length; i++) {
619            metadataParamList.appendChild(GSXML.createParameter(
620                    this.doc, GSXML.METADATA_ELEM, metaNames[i]));
621        }
622       
623        // creating subelements: <documentNode nodeID="..." />
624        // or <classifierNode nodeID="..." />
625        Element nodeList = this.doc.createElement(
626                NODE_ELEM+GSXML.LIST_MODIFIER);
627        for(int i = 0; i < nodeIDs.length; i++) {
628            Element docNode = this.doc.createElement(NODE_ELEM);
629            docNode.setAttribute(GSXML.NODE_ID_ATT, nodeIDs[i]);
630            nodeList.appendChild(docNode);
631        }
632       
633        Element message = doc.createElement(GSXML.MESSAGE_ELEM);
634        Element request = GSXML.createBasicRequest(doc,
635                GSXML.REQUEST_TYPE_PROCESS, to, new UserContext(lang, ""));
636       
637        request.appendChild(metadataParamList);
638        request.appendChild(nodeList);
639        message.appendChild(request);
640       
641        // Send it off to the Message Router and return the response
642        return this.processInternal(message);
643    }
644   
645    /* (4) Classifier BROWSE PROCESS METHODS - p.46 */
646    /** To send a browse request for all the descendants of a classifier node.
647     * Useful for getting the entire structure of a top-level &lt;classificationNode&gt;
648     * @see <a href="http://wiki.greenstone.org/wiki/index.php/Greenstone3">The Greenstone 3 Developer's Manual - page 46</a>
649     * @param collection is the name of the Collection whose browse Classifier
650     * Browse Service is called
651     * @param browseService is the name of the (Classifier) Browse Service (of
652     * the given collection) to which this request message is sent.
653     * @param lang is the language of the display content in the response
654     * @param classifierNodeIDs is an array of classifierNodeIDs for which the
655     * structures ought to be retrieved.
656    */
657    public String browseDescendants(String collection, String browseService,
658            String lang, String[] classifierNodeIDs)
659    {
660        // We are at the top level, we want all the descendants:
661        // <param name="structure" value = "descendants">
662        // <classifierNodeList><classifier nodeID="CLx" /></classifierNodeList>
663        return browse(collection, browseService, lang,   
664                classifierNodeIDs,
665                new String[] {"descendants"}, new String[] {""}); // note the spelling
666    }
667   
668    /** To send a browse request for specific parts of a classifier node
669     * (children, ancestors, descendants). Useful for getting specific parts
670     * of the structure of a top-level &lt;classificationNode&gt;.
671     * @see <a href="http://wiki.greenstone.org/wiki/index.php/Greenstone3">The Greenstone 3 Developer's Manual - page 46</a>
672     * @param collection is the name of the Collection whose browse Classifier
673     * Browse Service is called
674     * @param browseService is the name of the (Classifier) Browse Service (of
675     * the given collection) to which this request message is sent.
676     * @param lang is the language of the display content in the response
677     * @param classifierNodeIDs is the list of classifierNodeIDs for which the
678     * structure ought to be retrieved.
679     * @param structureParams the list of parameters indicating what structure
680     * information is requested. Accepted values are ancestors, parent, siblings,
681     * children, descendants.
682     * @param infoParams - structural info is requested. Can be numSiblings,
683     * siblingPosition, numChildren
684    */
685    public String browse(String collection, String browseService, String lang,
686            String[] classifierNodeIDs, String[] structureParams, String[] infoParams)
687    {
688        if(browseService.equals(""))
689            browseService = "ClassifierBrowse";
690       
691        // Create message element: <message></message>
692        Element message = this.doc.createElement(GSXML.MESSAGE_ELEM);
693        // <message><request lang="en" to="" type="process" uid="" /></message>
694        Element request = GSXML.createBasicRequest(this.doc,
695            GSXML.REQUEST_TYPE_PROCESS, collection+"/"+browseService, new UserContext(lang, ""));
696       
697        // <param name="structure" value = "structureParams[i]">
698        Element paramList = this.doc.createElement(
699                GSXML.PARAM_ELEM+GSXML.LIST_MODIFIER);
700        for(int i = 0; i < structureParams.length; i++) {
701            // check it is a valid structure parameter
702            if(structureOptions.indexOf(structureParams[i]) != -1) {
703                paramList.appendChild(GSXML.createParameter(
704                        this.doc, "structure", structureParams[i]));
705            }
706        }
707
708        if(infoParams != null && !infoParams[0].equals("")) {
709            for(int i = 0; i < infoParams.length; i++) {
710            if(structureInfoOptions.indexOf(infoParams[i]) != -1) {
711                paramList.appendChild(GSXML.createParameter(
712                        this.doc, "info", infoParams[i]));
713            }
714            }
715        }
716       
717        // <classifierNodeList><classifier nodeID="CLx" />
718        //      <classifier nodeID="CLy" /></classifierNodeList>
719        // where CLx and CLy are given in the parameter classifierNodeIDs
720        Element classifierNodeList = this.doc.createElement(
721                GSXML.CLASS_NODE_ELEM+GSXML.LIST_MODIFIER);
722        for(int i = 0; i < classifierNodeIDs.length; i++) {
723            Element classifier = this.doc.createElement(GSXML.CLASS_NODE_ELEM);
724            classifier.setAttribute(GSXML.NODE_ID_ATT, classifierNodeIDs[i]);
725            classifierNodeList.appendChild(classifier);
726        }
727       
728        // now finish constructing the request message:
729        request.appendChild(paramList);
730        request.appendChild(classifierNodeList);
731        message.appendChild(request);
732       
733        // Send it off to the Message Router and return the response
734        return this.processInternal(message);
735    }
736   
737    /** Called by most other methods in order to send the constructed message
738     * to the Greenstone's MessageRouter, intercept the response and return it.
739     * @param message is the XML message Element to send to GS3's MessageRouter.
740     * @return the XML response in String format. */
741    protected String processInternal(Element message) {
742            if(LOG.isDebugEnabled()) { // or LOG.isEnabledFor(Level.DEBUG).
743                                   // Testing for this improves efficiency
744            LOG.debug(this.converter.getPrettyString(message));
745        }
746       
747        // Let the messagerouter process the request message and get the response
748        Element response = XMLConverter.nodeToElement(mr.process(message));
749              // won't be null except when Node returned is not an element
750              // otherwise, MR always returns some response
751
752        // Return it as a String formatted for display
753        String responseMsg = this.converter.getPrettyString(response);
754                          // this.converter.getString(response);
755
756        // In order to avoid "Content is not allowed in prolog" exception on the
757        // web services' client end (problem encountered in GS mailing list), need
758        // to make sure no characters (incl spaces) preceed the  XML sent back
759        // from here. It may also require the <?xml?> tag at the very start.
760        if(responseMsg.charAt(0) == ' ') {
761            responseMsg = responseMsg.trim();
762        }
763       
764        return "<?xml version=\"1.0\" encoding=\"UTF-8\"?>"+responseMsg;
765    }
766   
767    /** Creates a String response message to represent an XML error response 
768     * message using the error specified in the message parameter. A String is
769     * created because this method ensures that a response message is reliably
770     * constructed (no exceptions are thrown) that can be sent to clients.
771     * @param errorMessage - the errormessage to be conveyed
772     * @return an XML response message containing an GS3 error element. */
773    protected String error(String errorMessage) {
774        StringBuffer buf = new StringBuffer("<" + GSXML.MESSAGE_ELEM + ">");
775        buf.append("<" + GSXML.RESPONSE_ELEM + " "
776                + GSXML.FROM_ATT + "=\"" + "Greenstone 3 Web Services\"" + ">");
777        buf.append("<" + GSXML.ERROR_ELEM + " "
778            + GSXML.ERROR_TYPE_ATT + "=\""+ GSXML.ERROR_TYPE_OTHER + "\"" + ">");
779        buf.append(errorMessage+"\n");
780        buf.append("</" + GSXML.ERROR_ELEM + ">");
781        buf.append("</" + GSXML.RESPONSE_ELEM + ">");
782        buf.append("</" + GSXML.MESSAGE_ELEM + ">");
783        return buf.toString();
784    }
785
786    /*
787    Look in file QBRWebServicesHelp.properties
788    - Have a properties file that maps methodname to help string specific
789    to the method.
790    - Read it all in statically at the start of the class, into a Properties Map.
791    - When this method is called, display the usage: "help methodname"
792    and list all the available methods by going over the keys in the Map.
793    - When the helpWithMethod(String methodname) method is called, return the
794    value of the Map for the methodname key. This value would be the help
795    description for that method.       
796    */
797    /** @return a help string for listing all the web service methods. */
798    public static String help() {
799        if(!helpErrormessage.equals("")) {
800            return helpErrormessage;
801        }
802       
803        StringBuffer helpString = new StringBuffer(
804                "USAGE: helpWithMethod(String <method name>)\n");
805        helpString.append(
806                "\nNearly all the web service operations return a String\n");
807        helpString.append(
808                "representing a Greenstone 3 XML response message.\n");
809        helpString.append("\nA list of all the method names: \n");
810       
811        Enumeration props = properties.keys();
812        while(props.hasMoreElements()){
813            String methodName = (String)props.nextElement();
814            helpString.append("\t");
815            helpString.append(methodName);
816            helpString.append("\n");
817        }
818       
819        return helpString.toString();
820    }
821   
822    /** @param methodname is the name of the method to be described. 
823     * @return a help string for the given method, explaining what the method
824     * does, what parameters it expects and their types and what it returns.
825    */
826    public static String helpWithMethod(String methodname) {
827        if(!helpErrormessage.equals("")) {
828            return helpErrormessage;
829        }
830        // else we can get the method's description from the properties
831        // map loaded from the QBRWebServicesHelp.properties file:
832        String helpString = properties.getProperty(methodname,
833            "No description for " + methodname); // if the method does not exist
834       
835        return helpString;
836    }
837} // end web service class
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