Re: trouble passing parameter to custom transformer

[Jorg Heymans]

you can just override setup() in your transformer and take parameters 
from there. Have a look at some existing transformers and see how they 
do it.

Francesco Rossi (Milano, Italy) wrote:
... I have trouble passing a parameter to my custom transformer

here is the code to the transformer (which is pretty straightforward: it 
just changes the attribute containing an URL, in elements of some given 
kinds):

package mypackage.transformation;

import org.apache.cocoon.transformation.AbstractTransformer;
import org.apache.cocoon.environment.SourceResolver;
import org.apache.cocoon.ProcessingException;
import org.apache.avalon.framework.parameters.*;
import org.apache.avalon.excalibur.pool.Poolable;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.AttributesImpl;
import java.io.IOException;
import java.util.Map;
import java.lang.String;
public class MyLinkRewriter
extends AbstractTransformer implements Parameterizable, Poolable {
 
 public static final String CSSLINK_ELEMENT = "link";
 public static final String IMG_ELEMENT = "img";
 public static final String ANCHOR_ELEMENT = "a";
 
 protected String absPath;
 
 protected String myUrl;
 
 public void parameterize(Parameters parameters) throws ParameterException {
  this.myUrl = parameters.getParameter("myurl");
 }
 
 public void setup(SourceResolver resolver,Map objectModel,String 
src,Parameters par)
 throws ProcessingException,SAXException,IOException {
  // salva il cammino assoluto fino alla pagina richiesta (compresa 
ultima '/')
  this.absPath = this.myUrl.substring(0,this.myUrl.lastIndexOf('/'));
 }
 
 public void startElement(String uri,String name,String 
raw,AttributesImpl attr)
 throws SAXException {
  
  int i;
  String u,l,q,t,newValue;
  
  if (name.equals(CSSLINK_ELEMENT) && attr.getLength()>0) {
   i = attr.getIndex("href");
   
   if (i==-1 || attr.getValue(i).startsWith("http://";)==true)
    super.startElement(uri, name, raw, attr);
   else {
    u = attr.getURI(i);
    l = attr.getLocalName(i);
    q = attr.getQName(i);
    t = attr.getType(i);
    newValue = "http://"; + absPath + attr.getValue(i);
    
    attr.setAttribute(i, u, l, q, t, newValue);
    super.startElement(uri, name, raw, attr);   
   }
  } else if (name.equals(IMG_ELEMENT) && attr.getLength()>0) {
   i = attr.getIndex("src");
   
   if (i==-1 || attr.getValue(i).startsWith("http://";)==true)
    super.startElement(uri, name, raw, attr);
   else {
    u = attr.getURI(i);
    l = attr.getLocalName(i);
    q = attr.getQName(i);
    t = attr.getType(i);
    newValue = "http://"; + absPath + attr.getValue(i);
    
    attr.setAttribute(i, u, l, q, t, newValue);
    super.startElement(uri, name, raw, attr);
   }
  } else if (name.equals(ANCHOR_ELEMENT) && attr.getLength()>0) {
   i = attr.getIndex("href");
   
   if (i==-1 || attr.getValue(i).startsWith("http://";)==true)
    super.startElement(uri, name, raw, attr);
   else {
    u = attr.getURI(i);
    l = attr.getLocalName(i);
    q = attr.getQName(i);
    t = attr.getType(i);
    newValue = "protected-url?myurl=" + absPath + attr.getValue(i);
    
    attr.setAttribute(i, u, l, q, t, newValue);
    super.startElement(uri, name, raw, attr);
   }
  } else // passo avanti
   super.startElement(uri, name, raw, attr);
 }
 
 public void characters(char[] buffer,int start,int length)
 throws SAXException {
  super.characters(buffer, start, length);
 }
 
 public void endElement(String uri,String name,String raw)
 throws SAXException {
  super.endElement(uri, name, raw);
 }
}

I successfully compiled it, made a .jar file containing the package, 
moved it to WEB-INF/lib.
Here is the excerpt from my sub-sitemap where I configure it:

 <map:transformers default="xslt">
    <map:transformer name="myLinkRewriter" 
src="mypackage.transformation.MyLinkRewriter"/>
 </map:transformers>

Finally, here is the excerpt from my sub-sitemap where I make use of it:

 <map:match pattern="protected-url">
    <map:generate src="http://{request-param:myurl}"; type="html"/>
    <map:transform type="myLinkRewriter">
       <map:parameter name="myurl" value="{request-param:myurl}"/>
    </map:transform>
Now, the error I get reads:

 Lookup of transformer for role 'myLinkRewriter' failed.

org.apache.cocoon.ProcessingException: Lookup of transformer for role 
'myLinkRewriter' failed.: 
org.apache.avalon.framework.component.ComponentException: 
transformers: ComponentSelector could not access the Component for hint 
[myLinkRewriter] (key [myLinkRewriter])

cause: org.apache.avalon.framework.parameters.ParameterException: The 
parameter 'myurl' does not contain a value

... can anybody help me?
thank you in advance


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