Overview

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.

Purpose

You will learn how to build a simple wizard type XMLForm that stores XML data into a Xindice collection.

Intended Audience

Cocoon users who want to learn how to store data obtained from XMLForms into Xindice.

Prerequisites

Cocoon must be running on your system. The steps below have been tested with Cocoon 2.1-dev. You will need the following:

build -Dinclude.webapp.libs=true webapp 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 XMLForm Wizard How-To first.

Steps

We will follow the needed steps in order to add a document like the one below to a Xindice collection named Artist. {{{<Artist id="pearljam">

</Artist>}}} 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.

Building the XMLForm files

Create the files and name them as specified below.

start.xform

{{{<?xml version="1.0"?> <document>

</document>}}}

artist.xform

{{{<?xml version="1.0"?> <document xmlns:xf="http://xml.apache.org/cocoon/xmlform/2002">

</document>}}}

end.xform

{{{<?xml version="1.0"?> <document>

</document>}}}

error.xform

{{{<?xml version="1.0"?> <document>

</document>}}}

Validation

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, artist-validator.xml is as follows: {{{<?xml version="1.0"?> <schema ns="http://xml.apache.cocoon/xmlform" xmlns="http://www.ascc.net/xml/schematron">

</schema>}}}

Extended Validation

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.

The Model

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 artist-model.xml and fill it with: {{{<Artist id="">

</Artist>}}}

Persistence for the data will be accomplished by using a JXPath Container. The XML document model created above will be loaded into the Container. We will use the xmlform-model parameter in the sitemap to point to the XML file.
The Container is created and manipulated by the Action in its getFormModel() method, so we need to override it and write it this way (we'll see the whole Action in the next step): {{{/**

}}}

The Action

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 ArtistAction.java: {{{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;

/**

public class ArtistAction extends AbstractXMLFormAction implements FormListener {

} }}} We had to use an ugly casting mechanism in the addDocument method but that's what we have by now. In future JXPath versions this will be easier to accomplish.

The helper class

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 XindiceManager.java is as follows: {{{/**

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 {

} }}}

The Sitemap

Remember you should have the XML!FormTransformer defined like this: {{{<map:transformer name="xmlform"

Then, you must declare the Action to be used in the correspondent section: {{{<map:action logger="xmlform"

The Pipeline

{{{<!-- XMLForms<->Xindice pipeline --> <map:pipeline>

</map:pipeline>}}} Depending on where you have Cocoon installed and where you have configured the files in this howto, you could make a request to a URL like http://localhost:8080/cocoon/Artist.xform and start using the Form.

Final Considerations

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.
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.
I'm sure you can think of more different ways. I encourage you to contribute them if you have tested it succesfully.
This how-to was refactored quite a bit from its original version which used a regular Javabean as a wrapper for a DOM Node where the data were persisted. This new version version is much more elegant and short and it wouldn't be possible without some ideas exchanged with Ivelin Ivanov. Anyway if you want to see the previous version to compare we still have a copy at XMLFormXindiceOldVersion.

Summary

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. I hope it was helpful for you.

XMLFormXindice (last edited 2009-09-20 23:40:39 by localhost)