Import module into xquery with apache camel transformer EIP

问题

I have a camel route which is pretty simple, except for the used xquery which is why I extracted it into a separate file. In my camel route I call the xquery with the Transformer EIP:

.transform().xquery("resource:classpath:xquery/myCoolXQuery.xquery",String.class)

The XQuery itself works fine, but because of some functional changes I now want to import another XQuery module which I want to use as a "library" with some helping functions, because I have lots of XQuery-Files which could use them.

So what I did in my XQuery is:

xquery version "3.0" encoding "UTF-8";

declare namespace fn = 'http://www.w3.org/2005/xpath-functions';

(: Library of really helpful functions :)
import module namespace lib = "http://handofnod.com/xquery-lib" at "classpath:xquery/lib.xquery";

Question:

How can I configure Apache Camel that the StandardModuleURIResolver is able to load the imported module from the classpath?

So far investigations/ the problem

Unfortunately apache camel now throws a NullpointerException in the StandardModuleURIResolver at:

if ("classpath".equals(absoluteURI.getScheme())) {
    String path = absoluteURI.getPath();
    is = this.config.getDynamicLoader().getResourceAsStream(path);

That's because the absoluteURI (which is "classpath:xquery/lib.xquery") cannot be converted correctly and the variable path is NULL (that's pretty much code smell but not my business now).

The absoluteURI cannot be converted because the net.sf.saxon.query.XQueryParser has no value set in the this.env.getStaticBaseURI().

So I tried during debugging to set the staticBaseURI value to classpath but then the StandardModuleURIResolver also returns an absoluteURI which has a NULL value in the getPath() thus resulting in the same NullPointerException.

So now I don't have any clue how to use the Transformer-EIP with an XQuery which uses a module import for some helper functions.

Another possible solution

Another possible solution would be to not use the Transformer-EIP implemented in Apache Camel but instead use the ToDefinition because there it is possible to define a custom Saxon Configuration over an URL parameter which can use an overwritten ModuleURIResolver which then hasn't the problem.

Also, sure I could use a custom Processor implementation to achieve what I want, but that's not the point in using Camel which provides implementation for EIPs.

It would be great if I could use the Transformer-EIP with module import in my XQuery.

Project setup is:

Spring-Boot 2.1.0.RELEASE
Apache Camel 2.22.2
Build with Maven

Final question

Can anyone help me pls?

Edit 1:

I downloaded the sources from Camel and Saxon to be able to debug with more understanding what happens and tried some things:

First I tried to use an absolute path:

.transform().xquery("resource:classpath:/xquery/myCoolXQuery.xquery",String.class)

This way I don't get the NullPointerException anymore because in the StandardModuleURIResolver at getQuerySource the path is not NULL anymore:

Unfortunately the file cannot be loaded by config.getDynamicLoader().getResourceAsStream(path); and returns NULL.

So I thought I move the xquery files from the directory directly under src\main\resoures but that also didn't help and I had the same result.

回答1:

Since it seems there is no answer to my question I debugged further and further and it really just seems impossible to configure the Transformer-EIP with XQuery in any way. Also I was not able to find any way to load the imported xquery module from the classpath so I changed my code and now I call my xquery via the XQueryEndpoint which provides support for custom configuration:

.to("xquery:/xquery/myCoolXQuery.xquery?configuration=#saxonConfig&resultsFormat=String")

This way my route works. But it would have been nice to be able to use the transform() because the code would be easier to understand.

来源：https://stackoverflow.com/questions/56462217/import-module-into-xquery-with-apache-camel-transformer-eip

标签

java

apache-camel