MarkLogic Declarative Rewriter - Simulate a Redirect using xdbc eval

ml-rewriter-redirect.txt

Demonstrate invoking the internal /eval xdbc endpoint on a HTTP server in MarkLogic to create a Redirect.

Note that there are simplier and easier ways to accomplish this, e.g using the user defined error handler or
rewriting to a endpoint that calls xdmp:redirect-response().   This example shows that it can be done 'out of the box'
by utilizing the builtin support for XDBC handling.

On Port 8000 in the default installation, and on any new REST servers a block of the declarative rewriter dispatches
XDBC requests to the internal XCDBC endpoints directly.
The xdbc.xml attached file shows the relevent block of XML.  The enableing factor is the use of <dispatch xdbc="true">.
A custom rewriter can rewrite any request to one of the builtin endpoints ( /eval, /invoke , /spawn , /insert ) and then dispatch to xdbc.
In port 8000 and REST apps this simply 'passes through' untouched XDBC requests, and also is used for the /v1/eval endpoint to support REST 
Eval requests.



The following curl command demonstrates this functionality.  Note that a POST is required to for /eval 

$ curl -i -u admin:secret --anyauth --data-urlencode 'xquery=xdmp:redirect-response("http://www.google.com")' http://localhost:8000/eval
HTTP/1.1 401 Unauthorized
Server: MarkLogic
WWW-Authenticate: Digest realm="public", qop="auth", nonce="7fc7cb2e37fa7fc000becb95b8a9bdf5", opaque="adad318baaa22742"
Content-Type: text/html; charset=utf-8
Content-Length: 209
Connection: Keep-Alive
Keep-Alive: timeout=5

HTTP/1.1 302 Found
Server: MarkLogic 8.0-20151109DL1
Location: http://www.google.com
Set-Cookie: TxnID=null; path=/
Content-Length: 0
Connection: Keep-Alive
Keep-Alive: timeout=5

redirect-snippet.xml

    <!-- XDBC -->
      <match-path  any-of="/eval /invoke /spawn /insert">
        <trace event="Rewriter Evaluator">$0</trace>
        <set-error-format>compatible</set-error-format>
       <dispatch xdbc="true">$0</dispatch>
      </match-path>
    <!-- XDBC -->