# XSLT

The xslt: component allows you to process a message using an XSLT template. This can be ideal when using Templating to generate respopnses for requests.

## URI format

    xslt:templateName[?options]

Where templateName is the classpath-local URI of the template to invoke; or the complete URL of the remote template. Refer to the Spring Documentation for more detail of the URI syntax

You can append query options to the URI in the following format, `?option=value&option=value&...`

Here are some example URIs:

URI | Description
--- | ---
`xslt:com/acme/mytransform.xs` | Refers to the file, `com/acme/mytransform.xsl`, on the classpath.
`xslt:file:///foo/bar.xs` | Refers to the file, `/foo/bar.xsl`.
`xslt:http://acme.com/cheese/foo.xsl` | Refers to the remote HTTP resource.

## Options

Table 75 lists the XSLT uri options:

Table 75. URI options

Name | Default Value | Description
--- | --- | ---
`converter` | `null` | Option to override default XmlConverter. Will lookup for the converter in the Registry. The provided converted must be of type org.apache.camel.converter.jaxp.XmlConverter.
`transformerFactory` | `null` | New added in Apache Camel 1.6 Option to override default TransformerFactory. Will lookup for the transformerFactory in the Registry. The provided transformer factory must be of type `javax.xml.transform.TransformerFactory`.
`transformerFactoryClass` | `null` | New added in Apache Camel 1.6 Option to override default TransformerFactory. Will create a `TransformerFactoryClass` instance and set it to the converter.
`uriResolver` | `null` | Apache Camel 2.3: Allows you to use a custom `javax.xml.transformation.URIResolver`. Camel will by default use its own implementation `org.apache.camel.builder.xml.XsltUriResolver` which is capable of loading from classpath.
`resultHandlerFactory` | `null` | Apache Camel 2.3: Allows you to use a custom `org.apache.camel.builder.xml.ResultHandlerFactory` which is capable of using custom `org.apache.camel.builder.xml.ResultHandler` types.
`failOnNullBody` | `true` | Apache Camel 2.3: Whether or not to throw an exception if the input body is null.
`output` | `string` | Apache Camel 2.3: Option to specify which output type to use. Possible values are: `string, bytes, DOM, file`. The first three options are all in memory based, where as `file` is streamed directly to a `java.io.File`. For `file` you must specify the filename in the IN header with the key `Exchange.XSLT_FILE_NAME` which is also `CamelXsltFileName`. Also any paths leading to the filename must be created beforehand, otherwise an exception is thrown at runtime.
`contentCache` | `true` | Apache Camel 2.6: Cache for the resource content (the stylesheet file) when it is loaded. If set to `false` Camel will reloader the stylesheet file on each message processing. This is good for development.

## Using XSLT endpoints

For example you could use something like

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

To use an XSLT template to forumulate 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:

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

## 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.

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

And the XSLT just needs to declare it at the top level for it to be available:

    <xsl: ...... >

       <xsl:param name="myParam"/>

        <xsl:template ...>

## XML versions

To use the above examples in XML you would use something like

      <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>

There is a test case along with its Spring XML if you want a concrete example.

## Using xsl:include

Apache Camel 1.6.2/2.2 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:

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

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

Apache Camel 1.6.3/2.3 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:

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

Will now be located relative from the starting endpoint, which for example could be:

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

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

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

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