Hi,
I am trying to write a BetwixtTransformer based on CastorTransformer but have run into a problem.
Everything appears to be working Ok according to my logging messages until the XML is serialized when I get this error:
java.lang.RuntimeException: java.lang.NullPointerException
at org.apache.xalan.transformer.TransformerImpl.run(TransformerImpl.java:3231)
at java.lang.Thread.run(Thread.java:536)
To get the BetwixtTransformer up and running do the following:
1. Create an XML file to be read in via a generator:
<?xml version="1.0"?>
<document xmlns:betwixt="http://jakarta.apache.org/commons/betwixt/betwixttransfomer">
<betwixt:InsertBean name="form" scope="request"/>
</document>
2. Add the following to your sitemap.xmap:
<map:components>
<map:transformers default="xslt">
<map:transformer logger="sitemap.transformer.betwixt" name="betwixt" src="">
</map:transformers>
<map:actions>
<map:action
name ="DisplayFormAction"
src ="test.DisplayFormAction"
logger ="sitemap.action"/>
</map:actions>
</map:components>
<map:pipelines>
<map:pipeline>
<map:match pattern="form*.xml">
<map:act type="DisplayFormAction">
<map:parameter name="form-pk" value="{1}"/>
</map:act>
<map:generate src="">
<map:transform type="betwixt"/>
<map:transform type="log">
<map:parameter name="logfile" value="c:/temp/logfile.log"/>
<map:parameter name="append" value="no"/>
</map:transform>
<map:serialize type="xml"/>
</map:match>
</map:pipeline>
</map:pipelines>
3. Add the following two classes to your cocoon.war
/ ------------------ /
/ BetwixtTransformer /
/ ------------------ /
package org.apache.cocoon.transformation;
import org.apache.avalon.framework.parameters.Parameters;
import org.apache.cocoon.environment.Context;
import org.apache.cocoon.environment.Request;
import org.apache.cocoon.environment.Session;
import org.apache.cocoon.environment.SourceResolver;
import org.apache.cocoon.environment.ObjectModelHelper;
import org.apache.commons.betwixt.io.SAXBeanWriter;
import org.apache.commons.logging.impl.SimpleLog;
import org.xml.sax.Attributes;
import java.util.Map;
public class BetwixtTransformer extends AbstractTransformer
{
private static final String BETWIXT_URI =
"http://jakarta.apache.org/commons/betwixt/betwixttransfomer";
private static final String CMD_INSERT_BEAN = "InsertBean";
private static final String ATTRIB_NAME = "name";
private static final String ATTRIB_SCOPE = "scope";
private static final String VALUE_SITEMAP = "sitemap";
private static final String VALUE_SESSION = "session";
private static final String VALUE_REQUEST = "request";
private static final String VALUE_CONTEXT = "context";
private boolean in_betwixt_element = false;
private Map objectModel;
private SourceResolver resolver;
/**
* Default constructor
*/
public BetwixtTransformer()
{
}
/**
* @see org.apache.cocoon.sitemap.SitemapModelComponent#setup(SourceResolver, Map, String, Parameters)
*/
public void setup(
SourceResolver resolver,
Map objectModel,
String source,
Parameters params)
throws
org.apache.cocoon.ProcessingException,
org.xml.sax.SAXException,
java.io.IOException
{
this.objectModel = objectModel;
this.resolver = resolver;
}
/**
* @see org.xml.sax.ContentHandler#endElement(String, String, String)
*/
public void endElement(String uri, String name, String raw)
throws org.xml.sax.SAXException
{
getLogger().debug("endElement: " + name);
// Check that we are currently in the Betwixt
if (BETWIXT_URI.equals(uri))
{
in_betwixt_element = false;
return;
}
super.endElement(uri, name, raw);
}
/**
* @see org.xml.sax.ContentHandler#startElement(String, String, String, Attributes)
*/
public void startElement(
String uri,
String name,
String raw,
Attributes attr)
throws org.xml.sax.SAXException
{
getLogger().debug("startElement: " + name);
if (BETWIXT_URI.equals(uri))
{
in_betwixt_element = true;
process(name, attr);
return;
}
super.startElement(uri, name, raw, attr);
}
/**
* @see org.xml.sax.ContentHandler#characters(char[], int, int)
*/
public void characters(char[] ch, int start, int len)
throws org.xml.sax.SAXException
{
if (in_betwixt_element)
{
return;
}
super.characters(ch, start, len);
}
/**
* Method process.
* @param command
* @param attr
*/
private void process(String command, Attributes attr)
{
if (command.equals(CMD_INSERT_BEAN))
{
String sourcemap = attr.getValue(ATTRIB_SCOPE);
String name = attr.getValue(ATTRIB_NAME);
Object toInsert;
Request request = ObjectModelHelper.getRequest(objectModel);
if (name == null)
{
getLogger().error("attribut to insert not set");
}
/*
searcl all maps for the given bean
*/
else
{
if (sourcemap == null || VALUE_SITEMAP.equals(sourcemap))
{
getLogger().debug(
"Searching bean '" + name + "' in " + VALUE_SITEMAP);
toInsert = objectModel.get(name);
if (toInsert != null)
{
insertBean(toInsert);
return;
}
}
if (sourcemap == null || VALUE_REQUEST.equals(sourcemap))
{
getLogger().debug(
"Searching bean '" + name + "' in " + VALUE_REQUEST);
toInsert = request.getAttribute(name);
if (toInsert != null)
{
insertBean(toInsert);
return;
}
}
if (sourcemap == null || VALUE_SESSION.equals(sourcemap))
{
getLogger().debug(
"Searching bean '" + name + "' in " + VALUE_SESSION);
Session session = request.getSession(false);
if (session != null)
{
toInsert = session.getAttribute(name);
if (toInsert != null)
{
insertBean(toInsert);
return;
}
}
}
if (sourcemap == null || VALUE_CONTEXT.equals(sourcemap))
{
getLogger().debug(
"Searching bean '" + name + "' in " + VALUE_CONTEXT);
Context context = ObjectModelHelper.getContext(objectModel);
if (context != null)
{
toInsert = context.getAttribute(name);
if (toInsert != null)
{
insertBean(toInsert);
return;
}
}
}
}
getLogger().debug("Bean " + name + " could not be found");
return;
} // end CMD_INSERT_BEAN
getLogger().error("Unknown command: " + command);
}
/**
* Method insertBean.
* @param bean
* @param mappingpath
*/
//?? private void insertBean(Object bean, String mappingpath)
private void insertBean(Object bean)
{
// If there is a bean then marshal it into XML
if (bean != null)
{
getLogger().debug("Bean found");
try
{
SAXBeanWriter writer =
new SAXBeanWriter(
new BetwixtSAXEventHandler(
contentHandler,
getLogger()));
writer.setLog(new SimpleLog("Betwixt"));
writer.getXMLIntrospector().setAttributesForPrimitives(false);
writer.setWriteIDs(false);
writer.write(bean);
}
catch (Exception e)
{
e.printStackTrace();
}
}
else
{
getLogger().debug("No bean found");
}
}
}
/ ---------------------- /
/ BetwixtSAXEventHandler /
/ ---------------------- /
package org.apache.cocoon.transformation;
import org.apache.avalon.framework.logger.Logger;
import org.xml.sax.Attributes;
import org.xml.sax.ContentHandler;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;
public class BetwixtSAXEventHandler extends DefaultHandler
{
private ContentHandler contentHandler;
private Logger logger;
/**
* Constructor for BetwixtSAXEventHandler.
*/
public BetwixtSAXEventHandler(ContentHandler contentHandler, Logger logger)
{
super();
this.contentHandler = contentHandler;
this.logger = logger;
logger.debug("BetwixtSAXEventHandler initialised.");
}
/**
* @see org.xml.sax.ContentHandler#characters(char[], int, int)
*/
public void characters(char[] chars, int offset, int length)
throws SAXException
{
logger.debug("characters: " + new String(chars));
contentHandler.characters(chars, offset, length);
}
/**
* @see org.xml.sax.ContentHandler#endElement(String, String, String)
*/
public void endElement(String namespaceURI, String localName, String qName)
throws SAXException
{
logger.debug("endElement: " + localName + ":" + qName);
contentHandler.endElement(namespaceURI, localName, qName);
}
/**
* @see org.xml.sax.ContentHandler#startElement(String, String, String, Attributes)
*/
public void startElement(
String namespaceURI,
String localName,
String qName,
Attributes atts)
throws SAXException
{
logger.debug("startElement: " + localName + ":" + qName);
contentHandler.startElement(namespaceURI, localName, qName, atts);
}
}
4. For Betwixt to work the following jar files will need to be added to the cocoon.war:
commons-betwixt-1.0-alpha-1.jar
commons-collections.jar
commons-digester.jar
5. Finally an Action needs to be written to stick a bean object in to the request.
Just in case you are asking 'why don't you just use the CastorTransformer?' the answer is that Castor was falling over with the bean I was using (the bean was a value object created using XDoclet). This happened inside and outside of Cocoon. A quick test using Betwixt standalone worked with any problem. Therefore I thought it might be useful to write a Betwixt transformer for cocoon.
Any help is much appreciated.
Keith.
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