Dynamic Service Mapping

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Motivation

It is possible to create a module which hosts a set of discrete services by placing a rewrite rule into the module definition for each service which maps its external exposed address to an internal implementing service. This pattern is described here. However when a module exposes many services a better pattern is to use the XRL mapper to rewrite external requests to internal services. The advantage is that the configuration can be changed and extended during development without restarting, dynamic changes to the mapping can be performed at runtime and many abitrary mappings can be configured compactly in one location.

Structure

A single rewrite rule is used to map all external requests to the XRL mapper. The mapper uses the default link file resource located at ffcpl:/etc/XRLLinks.xml. Any external request that is not mapped will cause an exception to be returned. Both static and dynamically generated results can be returned.

Here is the example module.xml:

<module>
  <!-- put identity/info/publisher/license sections here -->
  <export>
    <uri>
      <match>ffcpl:/my_module/.*</match>
    </uri>
  </export>
  <mapping>
    <!-- rewrite all external requests to xrl mapper -->
    <rewrite>
      <match>(ffcpl:/my_module/.*)</match>
      <to>active:mapper+operand@$1</to>
    </rewrite>
    <!-- make static module resource available -->
    <this>
      <match>ffcpl:/etc/XRLLinks.xml</match>
      <match>ffcpl:/pub/.*</match>
      <match>ffcpl:/scripts/.*</match>
    </this>
    <!-- import libraries -->
    <import>
      <uri>urn:org:ten60:netkernel:ext:xrl</uri>
    </import>
    <import>
      <uri>urn:org:ten60:netkernel:ext:script</uri>
    </import>
    <super />
  </mapping>
</module>

Here is the example XRLLinks.xml:

<links basepath="ffcpl:/my_module/">
  <!-- example link to static resource from internal address space-->
  <link>
    <ext>/icon.png</ext>
    <int>ffcpl:/pub/icon.png</int>
  </link>
  <!-- example link to a dynamic resource implemented as beanshell
             that takes an optional parameter -->
  <link>
    <ext>/getData</ext>
    <int>active:beanshell+operator@ffcpl:/scripts/index.bsh</int>
    <arg>param</arg>
  </link>
</links>