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Thursday, September 13, 2012

Using properties from within XQuery modules

Today I ran into an interesting issue. Sedna XMLDB does not support declaring external variables. But sometimes we need to have access to properties, even from a stored xquery module. We could hardcode values but some values are environment specific so no luck there.

So I was scratching my hair today and decided to get lucky on the Sedna mailinglist. Charles Foster was kind enough to share some ideas and one idea was storing the properties in the XMLDB itself.

So I quickly hacked together some prototype properties xquery support library which offers similar functionality to the Cocoon-Spring-Configurator. We can specify generic properties on the highest level and also specify environment specific properties. The nice thing is we can actually always pas the environment (prod / test/ dev) and if it can't find the property it will default to searching for a generic property by that name.
<?xml version="1.0" encoding="UTF-8"?>
<properties id="test-suite">
    <!-- default properties -->
    <property id="string1">this is text</property>
    <property id="boolean_false">false</property>
    <property id="boolean_true">true</property>
    <property id="int">5</property>
    <property id="double">3.56</property>
    <property id="decimal">6.23</property>
    <property id="float">002002.270</property>
    <property id="time">12:20:46.275+01:00</property>
    <property id="dateTime">2002-12-07T12:20:46.275+01:00</property>
    <property id="date">2002-12-07</property>
    <property id="duration">P30Y243D</property>
    <property id="anyURI">http://www.google.com</property>
    <environment id="prod">
        <property id="base_uri">http://nww.prod.spider.nxp.com</property>
        <property id="port">8513</property>

Properties XQuery library:
module namespace properties = "http://www.nxp.com/properties";

declare function properties:getPropertyFiles() as element(properties)* {

declare function properties:getPropertyFile($id as xs:string) as element(properties)? {

(:  properties:getProperty("test-suite.string1") :)
declare function properties:getProperty($expr as xs:string) {
   properties:getProperty($expr, ())

(: properties:getProperty("test-suite.base_uri", "test") :)
declare function properties:getProperty($expr as xs:string, $env as xs:string?) {
    let $tokens := tokenize($expr, "\.")
    let $fileId := $tokens[1]
    let $propertyId := $tokens[2]
    let $property := if (exists($env) and exists(properties:getPropertyFile($fileId)/environment[@id=$env]/property[@id=$propertyId]))
       then properties:getPropertyFile($fileId)/environment[@id=$env]/property[@id=$propertyId]
       else properties:getPropertyFile($fileId)/property[@id=$propertyId]
    return  if (exists($property)) then data($property)
            else fn:error(fn:QName('http://www.nxp.com/error', 'properties:doesNotExist'), concat('Property ', $expr, ' does not exist'))

import module namespace properties = "http://www.nxp.com/properties";

  <test>test-suite.base_uri      = {properties:getProperty("test-suite.base_uri", "prod")}</test>
  <test>test-suite.port          = {properties:getProperty("test-suite.port", "prod")}</test>  
  <test>test-suite.string1       = {properties:getProperty("test-suite.string1", "prod")}</test>
  <test>test-suite.boolean_false = {properties:getProperty("test-suite.boolean_false")}</test>
  <test>test-suite.boolean_true  = {properties:getProperty("test-suite.boolean_true")}</test>
  <test>test-suite.int           = {properties:getProperty("test-suite.int")}</test>
  <test>test-suite.double        = {properties:getProperty("test-suite.double")}</test>
  <test>test-suite.decimal       = {properties:getProperty("test-suite.decimal")}</test>
  <test>test-suite.float         = {properties:getProperty("test-suite.float")}</test> 
  <test>test-suite.time          = {properties:getProperty("test-suite.time")}</test>
  <test>test-suite.date          = {properties:getProperty("test-suite.date")}</test> 
  <test>test-suite.dateTime      = {properties:getProperty("test-suite.dateTime")}</test>
  <test>minutes from test-suite.dateTime = {minutes-from-dateTime(properties:getProperty("test-suite.dateTime"))}</test>
  <test>test-suite.anyURI        = {properties:getProperty("test-suite.anyURI")}</test>
  <test>test-suite.duration      = {properties:getProperty("test-suite.duration")}</test>
  <test>year from test-suite.duration      = {years-from-duration(properties:getProperty("test-suite.duration"))}</test>
Output from test-suite
  <test>test-suite.base_uri      = http://nww.prod.spider.nxp.com</test>
  <test>test-suite.port          = 8513</test>
  <test>test-suite.string1       = this is text</test>
  <test>test-suite.boolean_false = false</test>
  <test>test-suite.boolean_true  = true</test>
  <test>test-suite.int           = 5</test>
  <test>test-suite.double        = 3.56</test>
  <test>test-suite.decimal       = 6.23</test>
  <test>test-suite.float         = 002002.270</test>
  <test>test-suite.time          = 12:20:46.275+01:00</test>
  <test>test-suite.date          = 2002-12-07</test>
  <test>test-suite.dateTime      = 2002-12-07T12:20:46.275+01:00</test>
  <test>minutes from test-suite.dateTime = 20</test>
  <test>test-suite.anyURI        = http://www.google.com</test>
  <test>test-suite.duration      = P30Y243D</test>
  <test>year from test-suite.duration      = 30</test>

Now let's try and see what happens if we access a non existing property.
import module namespace properties = "http://www.nxp.com/properties";

  <test>should result in exception = {properties:getProperty("test-suite.nonexisting", "prod")}</test>

2012/09/14 09:40:17 database query/update failed (SEDNA Message: ERROR doesNotExist
    Property test-suite.nonexisting does not exist

Now we only need to make sure that the correct environment is passed. As all our environments use a different database we only need to store a specific constants library in each database and we're good to go.
module namespace constants = "http://www.nxp.com/constants";

declare variable $constants:ENVIRONMENT as xs:string := "test";

So now we can rewrite our little test-suite to use this constant
import module namespace properties = "http://www.nxp.com/properties";
import module namespace constants = "http://www.nxp.com/constants";

  <test>test-suite.boolean_false = {properties:getProperty("test-suite.boolean_false", $constants:ENVIRONMENT)}</test>


  1. I believe you could also do the following to handle types:
    <properties id="test-suite" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
    <property id="boolean_false" xsi:type="xs:boolean">false</property>

    This way you could just use fn:data and cut out the properties:typeCast function.

    Cool stuff.

  2. Hey... I will check if I can indeed simplify the code and eliminate the typecasting. Will update this article today. Thx for the comment.

  3. Thanks for giving this such nice details about properties xquery modules. This type of details is very useful for every one. You have done best work.

    Buy to Let Mortgage

  4. Hey Bojem,

    thx for checking this article out. Sharing ideas or useful stuff has 2 benefits:
    - others might find it helpful
    - others might comment useful remarks helping to improve my work

    It's win-win situation ;-)