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h2. XSLT

The *xslt:* component allows you to process a message using an [XSLT|http://www.w3.org/TR/xslt] template. This can be ideal when using [Templating] to generate respopnses for requests.

h3. URI format

{code}
xslt:templateName[?options]
{code}

Where *templateName* is the 

{code} | refers to the remote http resource |
{div}

Maven users will need to add the following dependency to their {{pom.xml}} for this component when using *Camel 2.8* or older:
{code:xml}
<dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-spring</artifactId>
    <version>x.x.x</version>
    <!-- use the same version as your Camel core version -->
</dependency>
{code}

from("activemq:My.Queue}}. |
{div}

h3. Using XSLT endpoints

For example you could use something like

{code}
from("activemq:My.Queue").
  to("xslt:com/acme/mytransform.xsl");
{code}

To use an XSLT template to formulate a response for a message for InOut message exchanges (where there is a {{JMSReplyTo}} header).

If you want to use InOnly and consume the message and send it to another destination you could use the following route:

{code}
from("activemq:My.Queue").
  to("xslt:com/acme/mytransform.xsl").
  to("activemq:Another.Queuexslt:com/acme/mytransform.xsl");
{code}

h3. Getting Parameters into the XSLT to work with

By default, all headers are added as parameters which are available in the XSLT.
To do this you will need to declare the parameter so it is then _useable_.

{code:xml}

from("activemq:My.Queue").
  to("xslt:com/acme/mytransform.xsl").
  to("activemq:Another.Queue");

<setHeader headerName="myParam"><constant>42</constant></setHeader>
<to uri="xslt:MyTransform.xsl"/>
{code}

{code:xml}
<xsl: ...... >

   <xsl:param name="myParam"/>
  
    <xsl:template ...>
{code}

h3. Spring XML versions

To use the above examples

 in Spring XML you would use something like

{code:xml}
  <camelContext xmlns="http://activemq.apache.org/camel/schema/spring">
    <route>
      <from uri="activemq:My.Queue"/>
      <to uri="xslt:org/apache/camel/spring/processor/example.xsl"/>
      <to uri="activemq:Another.Queue"/>
    </route>
  </camelContext>
{code}

<xsl:include href="staff_template.xsl"/>

<xsl:include href="staff_template.xsl"/>

.to("xslt:org/apache/camel/component/xslt/staff_include_relative.xsl")

    <xsl:include href="../staff_other_template.xsl"/>

<xsl:include href="staff_template.xsl"/>

.to("xslt:file:etc/xslt/staff_include_relative.xsl")

<xsl:include href="file:staff_template.xsl"/>

 case|http://svn.apache.org/repos/asf/camel/trunk/components/camel-spring/src/test/java/org/apache/camel/spring/processor/XsltTest.java] along with [its Spring XML|http://svn.apache.org/repos/asf/camel/trunk/components/camel-spring/src/test/resources/org/apache/camel/spring/processor/XsltTest-context.xml] if you want a concrete example.

h3. Using xsl:include
*Camel 2.2 or older*
If you use xsl:include in your XSL files then in Camel 2.2 or older it uses the default {{javax.xml.transform.URIResolver}} which means it can only lookup files from file system, and its does that relative from the JVM starting folder.

For example this include:
{code:xml}
<xsl:include href="staff_template.xsl"/>
{code}

Will lookup the {{staff_tempkalte.xsl}} file from the starting folder where the application was started.

*Camel 2.3 or newer* 
Now Camel provides its own implementation of {{URIResolver}} which allows Camel to load included files from the classpath and more intelligent than before.

For example this include:
{code:xml}
<xsl:include href="staff_template.xsl"/>
{code}

Will now be located relative from the starting endpoint, which for example could be:
{code}
.to("xslt:org/apache/camel/component/xslt/staff_include_relative.xsl")
{code}

Which means Camel will locate the file in the *classpath* as {{org/apache/camel/component/xslt/staff_template.xsl}}.
This allows you to use xsl include and have xsl files located in the same folder such as we do in the example {{org/apache/camel/component/xslt}}.

You can use the following two prefixes {{classpath:}} or {{file:}} to instruct Camel to look either in classpath or file system. If you omit the prefix then Camel uses the prefix from the endpoint configuration. If that neither has one, then classpath is assumed.

You can also refer back in the paths such as
{code}
    <xsl:include href="../staff_other_template.xsl"/>
{code}

Which then will resolve the xsl file under {{org/apache/camel/component}}.

h4. Using xsl:include and default prefix

When using xsl:include such as: 
{code:xml}
<xsl:include href="staff_template.xsl"/>
{code}

Then in Camel 2.10.3 and older, then Camel will use "classpath:" as the default prefix, and load the resource from the classpath. This works for most cases, but if you configure the starting resource to load from file, 
{code}
.to("xslt:file:etc/xslt/staff_include_relative.xsl")
{code}
.. then you would have to prefix all your includes with "file:" as well.
{code:xml}
<xsl:include href="file:staff_template.xsl"/>
{code}

From Camel 2.10.4 onwards we have made this easier as Camel will use the prefix from the endpoint configuration as the default prefix. So from Camel 2.10.4 onwards you can do:
{code:xml}
<xsl:include href="staff_template.xsl"/>
{code}

Which will load the staff_template.xsl resource from the file system, as the endpoint was configured with "file:" as prefix.
You can still though explicit configure a prefix, and then mix and match. And have both file and classpath loading. But that would be unusual, as most people either use file or classpath based resources.


h3. Dynamic stylesheets
*Available as of Camel 2.9*
Camel provides the {{CamelXsltResourceUri}} header which you can use to define a stylesheet to use instead of what is configured on the endpoint URI. This allows you to provide a dynamic stylesheet at runtime.

h3. Notes on using XSLT and Java Versions
Here are some observations from Sameer, a Camel user, which he kindly shared with us:

{quote}
In case anybody faces issues with the XSLT endpoint please review these points.

I was trying to use an xslt endpoint for a simple transformation from one xml to another using a simple xsl. The output xml kept appearing (after the xslt processor in the route) with outermost xml tag with no content within.

No explanations show up in the DEBUG logs. On the TRACE logs however I did find some error/warning indicating that the XMLConverter bean could no be initialized.

After a few hours of cranking my mind, I had to do the following to get it to work (thanks to some posts on the users forum that gave some clue):

1. Use the transformerFactory option in the route {{

  <xsl:template match="/">
    <html>
      <body>
        <xsl:for-each select="staff/programmer">
          <p>Name: <xsl:value-of select="name"/><br />
            <xsl:if test="dob=''">
              <xsl:message terminate="yes">Error: DOB is an empty string!</xsl:message>
            </xsl:if>
          </p>
        </xsl:for-each>
      </body>
    </html>
  </xsl:template>