xrl: mapper

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Module

The mapper accessor is exported by the urn:org:ten60:netkernel:ext:xrl module. Import this module to gain access to the accessor.

Syntax

URI

active:mapper

Argument	Rules	Description
operand	Mandatory	the external uri
operator	Optional	the links document

Example Usage

DPML

<instr>
  <type>mapper</type>
  <operator>links.xml</operator>
  <operand>ffcpl:/mysite/index.html</operand>
  <target>this:response</target>
</instr>

NetKernel Foundation API

main()
{   req=context.createSubRequest("active:mapper");
    req.addArgument("operator","links.xml");
    req.addArgument("operand","ffcpl:/mysite/index.html");
    result=context.issueSubRequest(req);
    context.createResponseFrom(result);
}

Purpose

The mapper accessor is used to map an "external" request to an internal service using a link file. For more details of the link file format see the XRL guide.

The operand URI of the incoming request is used to match the external URI of a link in the links document. The internal service is then determined which can either be a direct lookup or via a chain of named xrl: links. Any additional arguments on the request are passed through unchanged to the internal request if they match allowed arguments as specified in the args element in the link file entry. Finally the request is issued on to the internal service.

If an operand path cannot be found the mapper attempts to resolve the link xrl:404. This is useful for generating a user friendly error page. It passes a parameter doc of the form:

<error>
  <page>operand_path</page>
</error>

If the link xrl:404 cannot be found an exception is thrown by the accessor.

If an error occurs in requesting an internal uri the mapper attempts to resolve the link xrl:500 and passes a parameter doc of the form:

<error>
  <page>operand_path</page>
  <ex>netkernel_exception_fragment...</ex>
</error>

If the link xrl:500 cannot be found an unformatted raw exception is thrown by the accessor.