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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE document PUBLIC "-//APACHE//DTD Documentation V1.0//EN" "../dtd/document-v10.dtd">
<document>
<header>
<title>Xindice within the XMLForm Framework</title>
<authors>
<person name="Josema Alonso" email="josema@simbiosystems.com"/>
</authors>
</header>
<body>
<s1 title="Notice">
<p>This How-To is based on components included in the Cocoon 2.1
distribution. If you do not have this version, you can obtain it from
the <link href="../index.html">Apache Cocoon</link> web site.
</p>
<p> Some user accessible points in the Cocoon 2.1 distribution should be
considered &#34;alpha&#34;. This means that the developer team is not
investing _any_ effort to provide backward compatibility between alpha
releases for these parts. This software will continue to be released as
&#34;alpha&#34; until its code, schemas, and APIs are considered stable.
</p>
<p>Until then, there will be no warranty that newer versions will
maintain backward compatibility for such parts, even in the most simple
cases. Of course Cocoon will be compatible to latest release, 2.0.x
release. However, once &#34;beta&#34; status is reached, backward
incompatible changes will be made only when absolutely necessary to
reach &#34;final&#34; status. </p>
<p>The Cocoon development team understands the importance of reliable
software as well protecting user investments through the creation of a
solid development platform that does not change. On the other hand,
the Cocoon project is a pioneer in many fields. Most of the technologies
it uses are at a &#34;working draft&#34; phase only. Thus, reliability
cannot be guaranteed before the software achieves its &#34;final&#34;
status. </p>
<p>Until then, no effort will be provided to guarantee backward
compatibility for any parts considered alpha. </p>
<p>You have been warned.</p>
</s1>
<s1 title="Overview">
<p>
This How-To shows you how to use Xindice as the repository for
XML resources from the XMLForm Framework. It requires prior
knowledge of Cocoon XMLForm, XSLT, Schematron, Xindice and the
XMLDB API.
</p>
</s1>
<s1 title="Purpose">
<p>
You will learn how to build a simple wizard type XMLForm that
stores XML data into a Xindice collection.
</p>
</s1>
<s1 title="Intended Audience">
<p>
Cocoon users who want to learn how to store data obtained from
XMLForms into Xindice.
</p>
</s1>
<s1 title="Prerequisites">
<p>Cocoon must be running on your system. The steps below have been
tested with Cocoon 2.1-dev.</p>
<p>You will need the following:</p>
<ul>
<li>A servlet engine such as Tomcat.</li>
<li>JDK 1.2 or later</li>
<li>Xindice 1.0 installed (create a collection named
<code>Artist</code>)</li>
</ul>
<p>Cocoon 2.1 CVS to be installed with the command:</p>
<source>build -Dinclude.webapp.libs=true webapp</source>
<p>
You will need to understand and be familiar with XSL, XForms,
XPath, Schematron and Xindice. Some knowledge about JXPath and the
XMLDB API would be helpful, too. If you are unfamiliar with these
technologies, it is advised that you learn these related concepts
first. If you are unfamiliar with XMLForm, check out the
<link href="xmlform-wizard/howto-xmlform-wizard.html">XMLForm
Wizard How-To</link> first.
</p>
</s1>
<s1 title="Steps">
<p>
We will follow the needed steps in order to add a document like
the one below to a Xindice collection named <code>Artist</code>.
</p>
<source><![CDATA[
<Artist id="pearljam">
<Name>Pearl Jam</Name>
</Artist>]]></source>
<p>
We will get the identifier and name data using a XMLForm and
store them in Xindice. We will build this XMLForm very similar to
the one in the XMLForm Wizard How-To.
</p>
<s2 title="1. Building the XMLForm files">
<p>
Create the files and name them as specified below.
</p>
<s3 title="start.xform">
<source><![CDATA[
<?xml version="1.0"?>
<document>
<h1>This is the New Artist Wizard!</h1>
<info>Steps from here on, will let you insert a new
Artist in the database.
</info>
<h3>
<a href="Artist.xform?cocoon-action-start=true">
Start!
</a>
</h3>
</document>]]></source>
</s3>
<p/>
<s3 title="artist.xform">
<source><![CDATA[
<?xml version="1.0"?>
<document xmlns:xf="http://apache.org/cocoon/xmlform/1.0">
<xf:form id="artist-insert" view="artist"
action="Artist.xform" method="post">
<xf:caption>New Artist</xf:caption>
<error>
<xf:violations class="error"/>
</error>
<xf:textbox ref="/Artist/@id">
<xf:caption>Artist identifier:</xf:caption>
</xf:textbox>
<xf:textbox ref="/Artist/Name">
<xf:caption>Artist Name:</xf:caption>
</xf:textbox>
<xf:submit id="prev" class="button">
<xf:caption>Prev</xf:caption>
<xf:hint>Go to previous page</xf:hint>
</xf:submit>
<xf:submit id="next" class="button">
<xf:caption>Next</xf:caption>
<xf:hint>Go to next page</xf:hint>
</xf:submit>
</xf:form>
</document>]]></source>
</s3>
<p/>
<s3 title="end.xform">
<source><![CDATA[
<?xml version="1.0"?>
<document>
<h1>You have reached the last page!</h1>
<info>
You have inserted a New Artist successfully.
</info>
<h3>
<a href="Artist.xform">Go to home page.</a>
</h3>
</document>]]></source>
</s3>
<p/>
<s3 title="error.xform">
<source><![CDATA[
<?xml version="1.0"?>
<document>
<h1>
You have reached the last page of the New Artist Wizard!
</h1>
<info>
There have been problems and the Artist could not be added to the
database. Please try again.
</info>
<h3>
<a href="Artist.xform">Please, start again.</a>
</h3>
</document>]]></source>
</s3>
<p/>
</s2>
<s2 title="2. Validation">
<p>
For the sake of simplicity we just validate one property against
one condition. We require the identifier to be at least two
characters in length; the validation file,
<strong><code>artist-validator.xml</code></strong> is as follows:
</p>
<source><![CDATA[
<?xml version="1.0"?>
<schema ns="http://xml.apache.cocoon/xmlform"
xmlns="http://www.ascc.net/xml/schematron">
<phase id="artist">
<active pattern="artval"/>
</phase>
<pattern name="Artist Identifier Validation" id="artval">
<rule context="/Artist/@id">
<assert test="string-length(.) > 1">
Artist Name should be at least 2 characters.
</assert>
</rule>
</pattern>
</schema>]]></source>
<p/>
<s3 title="Extended Validation">
<p>
There could be more complicated rules in Schematron but we
could also require the identifier to be unique in the
database. In this case we should query the database and see
if it already exists. If so, a new violation can be added to
the form. Since these kinds of violations are out of the scope
of Schematron, these operations should be accomplished in the
Action using Java code.
</p>
</s3>
<p/>
</s2>
<s2 title="3. The Model">
<p>
Here is where we will take a different approach to the one in
the XMLForm Wizard How-To. We will not use a separate Bean.
In order to have an XML document model we will create an XML
file with the empty structure we want to fill with data from
the form. Create the file
<strong><code>artist-model.xml</code></strong> and fill it with:
</p>
<source><![CDATA[
<Artist id="">
<Name></Name>
</Artist>]]></source>
<p>
Persistence for the data will be accomplished by using a
<link href="http://jakarta.apache.org/commons/jxpath/apidocs/org/apache/commons/jxpath/Container.html">JXPath Container</link>.
The XML document model created above will be loaded into the
Container. We will use the <code>xmlform-model</code> parameter
in the sitemap to point to the XML file.
The Container is created and manipulated by the Action in its
<code>getFormModel()</code> method, so we need to override it
and write it this way (we will see the whole Action in the next
step):
</p>
<source><![CDATA[
/**
* Extract xmlform-model parameter and
* instantiate a new form model from it.
*/
protected Object getFormModel() {
//to load the XML model
Container DOMModel = null;
Source modelSrc = null;
//this parameter holds the name of the empty XML document
//representing the model
String modelFileName =
getParameters().getParameter("xmlform-model", null);
if(modelFileName==null) return null;
try {
modelSrc = getSourceResolver().resolveURI(modelFileName);
DOMModel = new XMLDocumentContainer(new
StreamSource(modelSrc.getInputStream()));
return DOMModel;
}
catch ( Exception e) {
throw new CascadingRuntimeException(
" Failed instantiating form model ", e );
}
finally {
getSourceResolver().release(modelSrc);
}
}]]></source>
<p/>
</s2>
<s2 title="4. The Action">
<p>
In this Action we have integrated the Xindice handling code,
getting the data from the model and storing it in Xindice.
The Action that controls this form is
<strong><code>ArtistAction.java</code></strong>:
</p>
<source><![CDATA[
package com.simbiosystems.cocoon.xmlform.xindice.howto;
import java.util.Arrays;
import java.util.Map;
import javax.xml.transform.stream.StreamSource;
import org.apache.avalon.framework.CascadingRuntimeException;
import org.apache.cocoon.acting.AbstractXMLFormAction;
import org.apache.cocoon.components.validation.Violation;
import org.apache.cocoon.components.xmlform.Form;
import org.apache.cocoon.components.xmlform.FormListener;
import org.apache.commons.jxpath.Container;
import org.apache.commons.jxpath.XMLDocumentContainer;
import org.apache.excalibur.source.Source;
import org.w3c.dom.Document;
import org.w3c.dom.Node;
/**
* This action handles XMLForms for the Artist data
*/
public class ArtistAction extends AbstractXMLFormAction implements
FormListener {
// different form views participating in the form
final String VIEW_START = "start";
final String VIEW_ARTIST = "artist";
final String VIEW_END = "end";
final String VIEW_ERROR = "error";
// action commands used in the wizard
final String CMD_START = "start";
final String CMD_NEXT = "next";
final String CMD_PREV = "prev";
//constant for the XML manipulation, it holds the full name of the
//collection to be used for storing the data
final String xindiceSubCol = "/Artist";
/**
* Extract xmlform-model action parameter and
* instantiate a new form model from it.
*
* In this case it uses a JXPath Container as the model and
* there is no need for a separate model Bean.
*
* @return Form the form object this action works with.
*
*/
protected Object getFormModel() {
//to load the XML model
Container DOMModel = null;
Source modelSrc = null;
//this parameter holds the name of the empty XML document
//representing the model
String modelFileName =
getParameters().getParameter("xmlform-model", null);
if(modelFileName==null) return null;
try {
modelSrc = getSourceResolver().resolveURI(modelFileName);
DOMModel = new XMLDocumentContainer(new
StreamSource(modelSrc.getInputStream()));
return DOMModel;
}
catch ( Exception e) {
throw new CascadingRuntimeException(
" Failed instantiating form model ", e );
}
finally {
getSourceResolver().release(modelSrc);
}
}
/**
* Invoked after form population
* Take appropriate action based on the command
*
*/
public Map perform () {
// set the page control flow parameter
// according to the validation result
if ( getCommand().equals(CMD_NEXT) &&
getForm().getViolations () != null ) {
// errors, back to the same page
return page( getFormView() );
}
else {
// validation passed
// continue with control flow
// clear validation left overs in case the user
// did not press the Next button
getForm().clearViolations();
// get the user submitted command
String command = getCommand();
// get the form view which was submitted
String formView = getFormView();
// apply control flow rules
if (formView.equals (VIEW_ARTIST)) {
if (command.equals(CMD_NEXT)) {
//extended validation
//test if the ID already exists in the DB
String artistName = (String)getForm().getValue("/Artist/@id");
try {
XindiceManager xi = new XindiceManager();
Node result = xi.find(xindiceSubCol,
"/Artist[@id='"+ artistName +"']",
"Artist");
//if we do not get null the element with that ID
//already existed and we add the violation
if (result!=null) {
Violation v = new Violation();
v.setMessage("already exists in the database,
please choose another one");
v.setPath("/Artist/@id");
Violation[] va = { v };
getForm().addViolations(Arrays.asList((Object[])va));
//the ID already exists, back to the same
//page to correct the error
return page(VIEW_ARTIST);
}
}
catch (Exception e) {
getLogger().error("Cannot establish a connection to the DB", e);
}
//everything went fine, add the document to the database
try {
addDocument();
}
catch(Exception e) {
//there were errors, send it to the error page
getLogger().error("Cannot add DOM document to the database");
return page(VIEW_ERROR);
}
return page( VIEW_END);
}
if (command.equals(CMD_PREV)) {
return page(VIEW_START);
}
}
}
// should never reach this statement
return page( VIEW_START );
}
/**
* The first callback method which is called
* when an action is invoked.
*
* It is called before population.
* @return null if the Action is ready to continue.
* an objectModel map which will be returned
*/
protected Map prepare() {
if ( getCommand() == null ) {
return page(VIEW_START);
}
else if ( getCommand().equals(CMD_START)) {
// reset state by removing old form if one exists
Form.remove( getObjectModel(), getFormId() );
getForm().addFormListener( this );
return page(VIEW_ARTIST);
}
// get ready for action
// if not ready return page("whereNext");
return null;
}
/**
* Add the document to the database
*
*/
public void addDocument() throws Exception {
try {
//add the document to the database
XindiceManager xi = new XindiceManager();
//needs the DocumentRoot of the Container as a DOM Node
xi.add(xindiceSubCol,
((Document)
(((XMLDocumentContainer)
(getForm().getModel())).getValue())).getDocumentElement(),
null);
}
catch (Exception e) {
getLogger().error("DOM Document could not be created", e);
throw e;
}
}
}]]></source>
<p>
We had to use an ugly casting mechanism in the
<code>addDocument</code> method but that is what we have by now.
In future JXPath versions this will be easier to accomplish.
</p>
<s3 title="The helper class">
<p>
In order to make this work we need to use a helper class.
This class uses the XMLDB API to connect to Xindice and make
the operations available to the Action. You should extend it
to add more operations. The helper class
<strong><code>XindiceManager.java</code></strong> is as follows:
</p>
<source><![CDATA[
/**
* Helper class for Xindice related operations
*
*/
package com.simbiosystems.cocoon.xmlform.xindice.howto;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.DOMImplementation;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.xmldb.api.DatabaseManager;
import org.xmldb.api.base.Collection;
import org.xmldb.api.base.Database;
import org.xmldb.api.base.Resource;
import org.xmldb.api.base.ResourceIterator;
import org.xmldb.api.base.ResourceSet;
import org.xmldb.api.base.XMLDBException;
import org.xmldb.api.modules.XMLResource;
import org.xmldb.api.modules.XPathQueryService;
public class XindiceManager {
private static final String driver =
"org.apache.xindice.client.xmldb.DatabaseImpl";
private static final String rootCollection = "xmldb:xindice:///db/";
/**
* Constructor
*
*/
public XindiceManager() {
}
/**
* Search for a document in the DB. If not found, return null.
*
* @param subCol name of the subCollection to query if any. If blank
* or null, queries go against the rootCollection.
* @param xpath XPath expression for the query, if none, it returns
* the whole Collection
* @param resultRootelement name of the root element for the DOM
* document which will wrap the results
* @return a DOM Node with the matched documents
*
*/
public Node find(String subCol, String xpath, String resultRootElement)
throws Exception {
//prepare DOM document
DOMImplementation impl;
DocumentBuilder builder;
try {
// Find the implementation
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
factory.setNamespaceAware( false );
factory.setValidating ( false );
builder = factory.newDocumentBuilder();
impl = builder.getDOMImplementation();
}
catch (Exception ex) {
throw new RuntimeException("[XindiceManager.find]: " +
"Failed to initialize DOM factory. Root cause: \n" + ex);
}
//create the Document which will hold the results
Document resultDoc = impl.createDocument(null, resultRootElement, null);
Node root = resultDoc.getDocumentElement();
//And now the Xindice part
Collection col = null;
String strData = null;
try {
Class c = Class.forName(driver);
Database database = (Database) c.newInstance();
DatabaseManager.registerDatabase(database);
String localCol = rootCollection + subCol;
col = DatabaseManager.getCollection(localCol);
//Make the XPath query and get the resources
XPathQueryService service =
(XPathQueryService) col.getService("XPathQueryService", "1.0");
ResourceSet resultSet = service.query(xpath);
// Iterate the xpath results and add each of them to the main Document
ResourceIterator iterator = resultSet.getIterator();
//if not resources are present, just return null
if(!iterator.hasMoreResources()) return null;
while(iterator.hasMoreResources()) {
Resource r = iterator.nextResource();
Element resElement =
((Document)((XMLResource)r).getContentAsDOM()).getDocumentElement();
// Remove unwanted attributes
resElement.removeAttribute("src:col");
resElement.removeAttribute("src:key");
resElement.removeAttribute("xmlns:src");
// Add this result to the root element
Element importedElement =
(Element)resultDoc.importNode(resElement, true);
root.appendChild(importedElement);
}
//return the Document root
return root;
}
catch (Exception e) {
System.err.println("[XindiceManager.find]: Find Exception occured :" +
e.getMessage());
throw e;
}
finally {
if (col != null) {
col.close();
}
}
}
/**
* Add a document to the DB. If a key is not passed, it generates a
* unique one.
* This version uses a DOM Document.
* @param subCol name of the subCollection in which to add the resource
* if any. If blank or null, insertions go against the rootCollection.
* @param document DOM document to be inserted
* @param key unique key for the resource to be created.
* If none, one is created on the fly
*/
public void add(String subCol, Node document, String key)
throws Exception {
Collection col = null;
Node xmldoc = null;
try {
Class c = Class.forName(driver);
Database database = (Database) c.newInstance();
DatabaseManager.registerDatabase(database);
col = DatabaseManager.getCollection(rootCollection + subCol);
XMLResource document_ = (XMLResource) col.createResource(null,
"XMLResource");
document_.setContentAsDOM(document);
col.storeResource(document_);
}
catch (XMLDBException e) {
System.err.println("[XindiceManager.add]: Add Exception occured " +
e.errorCode);
throw e;
}
finally {
if (col != null) {
col.close();
}
}
}
}]]></source>
<p/>
</s3>
</s2>
<s2 title="5. The Sitemap">
<p>
Remember you should have the <code>XMLFormTransformer</code>
defined like this:
</p>
<source><![CDATA[
<map:transformer name="xmlform"
src="org.apache.cocoon.transformation.XMLFormTransformer"
logger="xmlform"/>]]></source>
<p>
Then, you must declare the Action to be used in the
corresponding section:
</p>
<source><![CDATA[
<map:action logger="xmlform"
name="ArtistAction"
src="com.simbiosystems.cocoon.xmlform.xindice.howto.ArtistAction"/>
]]></source>
<p/>
<s3 title="The Pipeline">
<p>
The following pipeline will process requests to our Form:
</p>
<source><![CDATA[
<!-- XMLForms<->Xindice pipeline -->
<map:pipeline>
<map:match pattern="Artist.xform">
<map:act type="ArtistAction">
<!-- XMLForm parameters for the Action -->
<!-- Notice how we use an XML file as the model -->
<map:parameter name="xmlform-validator-schema-ns"
value="http://www.ascc.net/xml/schematron"/>
<map:parameter name="xmlform-validator-schema"
value="artist/artist-validator.xml"/>
<map:parameter name="xmlform-id" value="artist-insert"/>
<map:parameter name="xmlform-scope" value="session"/>
<map:parameter name="xmlform-model" value="artist/artist-model.xml"/>
<!-- XMLForm document, {page} comes from Action -->
<map:generate src="artist/{page}.xform"/>
</map:act>
<!-- populating the doc with model instance data -->
<map:transform type="xmlform"/>
<!-- look and feel of the form controls -->
<map:transform src="styles/wizard2html.xsl"/>
<!-- Transforming the XMLForm controls to HTML -->
<map:transform src="styles/xmlform2html.xsl"/>
<!-- sending the HTML back to the browser -->
<map:serialize type="html"/>
</map:match>
</map:pipeline>]]></source>
<p>
Depending on where you have Cocoon installed and where you
have configured the files in this how-to, you could make a
request to a URL like
<code>http://localhost:8080/cocoon/Artist.xform</code>
and start using the Form.
</p>
</s3>
</s2>
</s1>
<s1 title="Final Considerations">
<p>
Making the operations from the Action using the helper class
seems to be the easiest way. You can think of other ways or
other operations using other Xindice tools available in Cocoon
such as the pseudo protocol. For example, you could use it to
query the DB for data that could be stored in a sitemap parameter.
You could then get the data from the Action and use it to fill a
selectbox in the form.
</p>
<p>
We did not mentioned other operations such as updates. This can
be also accomplished this way. For example, if you want to edit
the data we just stored, you could load it in the Container at
the beginning by using the find method of the helper class.
This way you get a filled form in the next step ready for editing.
Other ways or interacting with the repository include the XMLDB
Transformer. Since it uses XUpdate alike syntax, you could format
a XML String for it in the last step of the Action, making it
available to the sitemap then, so the Transformer could get it
and make the operations.
</p>
<p>
We are sure you can think of more different ways and encourage
you to contribute them if you have tested it successfully.
This how-to was refactored quite a bit from an original version
which used a regular Javabean as a wrapper for a DOM Node where
the data were persisted. This new version is much more elegant
and short. If you want to check differences, an
<link href="http://wiki.cocoondev.org/Wiki.jsp?page=XMLFormXindiceOldVersion">old version at Cocoon Wiki</link>
still exists.
</p>
</s1>
<s1 title="Summary">
<p>
This How-To makes possible the use of Xindice from XMLForms in
order to add data to the repository. You learned how to connect
to the DB from the Action, and how to make complex validation
using information stored in the DB. Remember that everything you
have just built is reusable for different user agents. You would
only need to use
<link href="../userdocs/concepts/matchers_selectors.html">matchers
and selectors</link> and to choose the appropriate transformation.
We hope this how-to was helpful for you.
</p>
</s1>
<s1 title="References">
<anchor id="references"/>
<p>
This how-to would not be possible without some ideas exchanged
with Ivelin Ivanov in the
<link href="http://cocoon.apache.org/community/mail-lists.html">Cocoon Users</link> list and
privately.
</p>
</s1>
<s1 title="Comments">
<p>
Care to comment on this How-To? Got another tip?
Help keep this How-To relevant by passing along any useful
feedback to the author,
<link href="mailto:josema|at|simbiosystems.com">Josema Alonso</link>
or via the
<link href="http://cocoon.apache.org/community/mail-lists.html">Cocoon Users</link> mail list.
</p>
</s1>
<s1 title="Revisions">
<p>
2003-02-04: First version contributed by Josema Alonso.
</p>
</s1>
</body>
</document>