1 <?xml version="1.0" encoding="UTF-8"?>
3 <title>Ajax client development</title>
6 Pazpar2 offers programmer a simple Web Service protocol that can be
7 used (queried in a request/response fashion) from any, server- or
8 client-side, programming language with an XML support. However, when
9 programming a Web-based client to Pazpar2, to achieve certain level of
10 interactivity and instant notification of latest changes in the result
11 set, Ajax (Asynchronous JavaScript and XML) technology may be used. An
12 Ajax client allows user to browse the results before the lengthy
13 process of information retrieval from the back-end targets is
14 finished. Blocking and waiting for usually slow back-end targets is
15 one of the biggest functionality issues in a federated search engine.
18 <para><bridgehead>Pz2.js</bridgehead></para>
21 Pazpar2 comes with a small JavaScript library called pz2.js. This
22 library is designed to simplify development of an Ajax-based pazpar2
23 client and alleviate programmer from the low-level details like
24 polling the web service, fetching and parsing returned XML output or
25 managing timers, sessions and basic state variables.
29 The library supports most major browsers including Firefox 1.5+, IE
30 6+, Safari 2+, Opera 9+ and Konqueror.
34 The library can work in two modes: a session-aware mode and a
39 In the session-aware mode, the library assumes that the pazpar2
40 daemon is contacted directly (preferably via Apache proxy to avoid
41 security breaches) and tracks the session Ids internally.
45 In the session-less mode the library assumes that the client is
46 identified on the server and the session Ids are not managed
47 directly. This way of operation requires more sophisticated pazpar2
48 proxy (preferably a wrapper written in a server-side scripting
49 language like PHP that can identify clients and relate them to open
53 <para><bridgehead>Using pz2.js</bridgehead></para>
56 Client development with the pz2.js is strongly event based and the
57 style should be familiar to most JavaScript developers. A simple
58 client (jsdemo) is distributed with pazpar2's source code and shows
59 how to set-up and use pz2.js.
63 In short, programmer starts by instantiating the pz2 object and
64 passing an array of parameters to the constructor. The parameter array
65 specifies callbacks used for handling responses to the pazpar2
66 commands. Additionally, the parameter array is used to configure
67 run-time parameters of the pz2.js like polling timer time-outs,
68 session-mode and XSLT style-sheets.
71 <para><bridgehead>Command callbacks</bridgehead></para>
74 Callback naming is simple and follows “on” prefix plus command name
75 scheme (like onsearch, onshow, onrecord, ... etc.). When programmer
76 calls a function like show or record on the pz2 object, pz2.js will
77 keep on polling pazpar2 (until the backend targets are idle) and with
78 each command's response an assigned callback will be called. In case
79 of pazpar2's internal error an error callback is called.
85 "pazpar2path": "/pazpar2/search.pz2",
88 // assigning command handler, turns on automatic polling
90 // polling period for each command can be specified
94 // facet terms are specified as a comma separated list
95 "termlist": "subject,author",
97 "onrecord": my_onrecord
103 Each command callback is a user defined function that takes a hash
104 object as a parameter. The hash object contains parsed pazpar2
105 responses (hash members that correspond to the elements in the
106 response XML document). Within the handler programmer further
107 processes the data and updates the viewed document.
111 function my_onstat(data) {
112 var stat = document.getElementById("stat");
113 stat.innerHTML = '<span>Active clients: '+ data.activeclients
114 + '/' + data.clients + ' | </span>'
115 + '<span>Retrieved records: ' + data.records
116 + '/' + data.hits + '</span>';
119 function my_onshow(data) {
120 // data contains parsed show response
121 for (var i = 0; i < data.hits[0].length; i++)
122 // update page with the hits
125 function on_record(data) {
126 // if detailsstylesheet parameter was set data array
127 // will contain raw xml and xsl data
128 Element_appendTransformResult(someDiv, data.xmlDoc, data.xslDoc);
132 <para><bridgehead>pz2.js on runtime</bridgehead></para>
135 The search process is initiated by calling the search method on the
136 instantiated pz2 object. To initiate short status reports and
137 per-target status information methods stat and bytarget have to be
142 my_paz.search (query, recPergPage, 'relevance');
146 Managing the results (keeping track of the browsed results page and
147 sorting) is up to the client's programmer. At any point the show
148 method may be called to bring up the latest result set with a
149 different sorting criteria or range and without re-executing the
150 search on the back-end.
154 my_paz.show (1, 10, 'relevance');
158 To retrieve a detailed record the record command is called. When
159 calling record command one may temporarily override its default
160 callback by specifying the handler parameter. This might be useful
161 when retrieving raw records that need to be processed differently.
165 my_paz.record (recId, 2, 'opac', { “callback”: temp_callback, “args”, caller_args});
170 <para><bridgehead>PARAMATERS ARRAY</bridgehead></para>
172 <varlistentry><term>pazpar2path</term>
173 <listitem><para>server path to pazpar2 (relative to the portal), when pazpar2 is installed as a package this does not have to be set </para></listitem>
176 <varlistentry><term>usesessions</term>
177 <listitem><para>boolean, when set to true pz2.js will manage sessions internally otherwise it's left to the server-side script, default true</para></listitem>
180 <varlistentry><term>autoInit</term>
181 <listitem><para>bolean, sets auto initialization of pazpar2 session on the object instantiation, default true, valid only if usesession is set to true</para></listitem>
184 <varlistentry><term>detailstylesheet</term>
185 <listitem><para>path to the xsl presentation stylesheet (relative to the portal) used for the detailed record display</para></listitem></varlistentry>
187 <varlistentry><term>errorhandler</term>
188 <listitem><para>callback function called on any, pazpar2 or pz2.js' internal, error</para></listitem></varlistentry>
190 <varlistentry><term>oninit</term>
191 <listitem><para>specifies init response callback function</para></listitem></varlistentry>
193 <varlistentry><term>onstat</term>
194 <listitem><para>specifies stat response callback function</para></listitem></varlistentry>
196 <varlistentry><term>onshow</term>
197 <listitem><para>specifies show response callback function</para></listitem></varlistentry>
199 <varlistentry><term>onterm</term>
200 <listitem><para>specifies termlist response callback function</para></listitem></varlistentry>
202 <varlistentry><term>onrecord</term>
203 <listitem><para>specifies record response callback function</para></listitem></varlistentry>
205 <varlistentry><term>onbytarget</term>
206 <listitem><para>specifies bytarget response callback function</para></listitem></varlistentry>
208 <varlistentry><term>onreset</term>
209 <listitem><para>specifies reset method callback function</para></listitem></varlistentry>
211 <varlistentry><term>termlist</term>
212 <listitem><para>comma separated list of facets</para></listitem></varlistentry>
214 <varlistentry><term>keepAlive</term>
215 <listitem><para>ping period, should not be lower than 5000 usec</para></listitem></varlistentry>
217 <varlistentry><term>stattime</term>
218 <listitem><para>default 1000 usec</para></listitem></varlistentry>
220 <varlistentry><term>termtime</term></varlistentry>
222 <varlistentry><term>showtime</term></varlistentry>
224 <varlistentry><term>bytargettime</term></varlistentry>
230 <para><bridgehead>METHODS</bridgehead></para>
232 <varlistentry><term>stop ()</term>
233 <listitem><para>stop activity by clearing timeouts</para></listitem></varlistentry>
235 <varlistentry><term>reset ()</term>
236 <listitem><para>reset state</para></listitem></varlistentry>
238 <varlistentry><term>init (sessionId, serviceId)</term>
239 <listitem><para>session-mode, initialize new session or pick up a session already initialized</para></listitem></varlistentry>
241 <varlistentry><term>ping ()</term>
242 <listitem><para>session-mode, intitialize pinging </para></listitem></varlistentry>
244 <varlistentry><term>search (query, num, sort, filter, showfrom)</term>
245 <listitem><para>execute piggy-back search and activate polling on every command specified by assigning command callback (in the pz2 constructor)</para></listitem></varlistentry>
247 <varlistentry><term>show (start, num, sort)</term>
248 <listitem><para>start or change parameters of polling for a given window of records</para></listitem></varlistentry>
250 <varlistentry><term>record (id, offset, syntax, handler)</term>
251 <listitem><para>retrieve detailed or raw record. handler temporarily overrides default callback function.</para></listitem></varlistentry>
253 <varlistentry><term>termlist ()</term>
254 <listitem><para>start polling for termlists</para></listitem></varlistentry>
256 <varlistentry><term>bytarget ()</term>
257 <listitem><para>start polling for target status</para></listitem></varlistentry>
259 <varlistentry><term>stat ()</term>
260 <listitem><para>start polling for pazpar2 status</para></listitem></varlistentry>
265 <para>Pz2.js comes with a set of cross-browser helper classes and functions.</para>
269 <para><bridgehead>Ajax helper class</bridgehead></para>
271 <varlistentry><term>pzHttpRequest</term>
272 <listitem><para>a cross-browser Ajax wrapper class</para></listitem></varlistentry>
274 <varlistentry><term>constructor (url, errorHandler)</term>
275 <listitem><para>create new request for a given url</para></listitem></varlistentry>
277 <varlistentry><term>get (params, callback)</term>
278 <listitem><para>asynchronous, send the request with given parameters (array) and call callback with response as parameter</para></listitem></varlistentry>
280 <varlistentry><term>post (params, data, callback)</term>
281 <listitem><para>asychronous, post arbitrary data (may be XML doc) and call callback with response as parameter</para></listitem></varlistentry>
283 <varlistentry><term>load ()</term>
284 <listitem><para>synchronous, returns the response for the given request</para></listitem></varlistentry>
290 <para><bridgehead>XML helper functions</bridgehead></para>
292 <varlistentry><term>document.newXmlDoc (root)</term>
293 <listitem><para>create new XML document with root node as specified in parameter</para></listitem></varlistentry>
295 <varlistentry><term>document.parseXmlFromString (xmlString)</term>
296 <listitem><para>create new XML document from string</para></listitem></varlistentry>
298 <varlistentry><term>document.transformToDoc (xmlDoc, xslDoc)</term>
299 <listitem><para>returns new XML document as a result</para></listitem></varlistentry>
301 <varlistentry><term>Element_removeFromDoc (DOM_Element)</term>
302 <listitem><para>remove element from the document</para></listitem></varlistentry>
304 <varlistentry><term>Element_emptyChildren (DOM_Element)</term></varlistentry>
306 <varlistentry><term>Element_appendTransformResult (DOM_Element, xmlDoc, xslDoc)</term>
307 <listitem><para>append xsl transformation result to a DOM element</para></listitem></varlistentry>
309 <varlistentry><term>Element_appendTextNode (DOM_Element, tagName, textContent)</term>
310 <listitem><para>append new text node to the element</para></listitem></varlistentry>
312 <varlistentry><term>Element_setTextContent (DOM_Element, textContent)</term>
313 <listitem><para>set text content of the element</para></listitem></varlistentry>
315 <varlistentry><term>Element_getTextContent (DOM_Element)</term>
316 <listitem><para>get text content of the element</para></listitem></varlistentry>
318 <varlistentry><term>Element_parseChildNodes (DOM_Element)</term>
319 <listitem><para>parse all descendants into an associative array</para></listitem></varlistentry>
325 <!-- Keep this comment at the end of the file