Friday, July 8, 2011

Getting Started - XQuery Dev inside OSB Eclipse

  • Should have installed OSB 
  • Basics understanding of middleware technology.
       We can use XQuery/XSL in OSB to do the message transformation. But XQuery is preferred over the XSL because of the  performance advantage. In this post I will show how to develop an xquery using the osb workshop eclipse.

XQuery - Introduction
       XQuery is a light weight language which has got an xml like syntax. XQuery has 3 important parts as below
  1. Namespace declaration
  2. Set of function with their implementations
  3. Declaration of variables
  4. Mentioning the function with which the execution begins.
          For further understanding of the XQuery you can refer

Sample XQuery

Listing-1    xquery version "1.0" encoding "Cp1252";
Listing-2    (:: pragma  parameter="$anyType1" type="xs:anyType" ::)
Listing-3    (:: pragma  type="xs:anyType" ::)
Listing-4    declare namespace xf = "";
Listing-5    declare namespace ns1 = "";
Listing-6    declare namespace ns2 = "";
Listing-8    declare function xf:sample($requestDoc as element(*))
Listing-9                    as element(*)
Listing-10    {
Listing-11                <ns2:Address>
Listing-12                  <ns2:name>
Listing-13                  {
Listing-14                  $requestDoc/ns1:FirstName/text()
Listing-15                  }
Listing-16                  </ns2:name>
Listing-17                  <ns2:phone>
Listing-18                  {
Listing-19                  $requestDoc/ns1:PhoneNumber/text()
Listing-20                  }
Listing-21                  </ns2:phone>
Listing-22                </ns2:Address>
Listing-23    };
Listing-25    declare variable $requestDoc as element(*) external;
Listing-27    xf:sample($requestDoc)


Listing 1 - declaration of xquery
Listing 2 to 3 - comments
Listing 4 to 6 - Namespace declarations
Listing 8 to 9
     This is the code snippet for the function 'sample' which takes 'requestDoc' which is of type element(*),             that is the xml. It returns the type element(*) which is also an xml.

Listing 10 - shows the start of the xquery function
Listing 23 - shows the end of the xquery function
Listing 11 to 22 - the body of the function 'sample'
 Here we are doing the transformation.  What ever we write it in these lines will be the final output of the 
 xquery tranformation
Listing 14 or 19 - Here we are assigning the data obtained from request xml to the output response xml.

Listing 25 - declaring the request variable 'requestDoc' as 'external' as type 'element(*)'. So when we test this xquery from the OSB flow, we will bind the request xml with 'requestDoc' variable and we can transform the request xml to the response xml. 

Listing 27 - This is the last line of the xquery where the execution of the xquery begins. Suppose if we have multiple functions, what ever function is given in the last line of xquery will be the entry point of execution.

Development of XQuery in OSB Workshop - Eclipse
          Open the eclipse and create a project . Right click on the project and create a new xquery

Give some name

Now give the request binding variables.
Here I have added only one variable.
Give the 'Parameter Name' as 'requestDoc'  and click on 'Add' so that we can add the request binding variable.

Similarly mention the response also

Now we have created the xquery. It will be now opened in the osb eclipse editor. The editor has 3 parts.
  1. Design
  2. Source
  3. Test
We can use 'Design' part if we have the source and destination schemas.

Now click on 'Source' and you can see the xquery source code.

Now modify the xquery as below

xquery version "1.0" encoding "Cp1252";
(:: pragma  parameter="$anyType1" type="xs:anyType" ::)
(:: pragma  type="xs:anyType" ::)
declare namespace xf = "";
declare namespace ns1 = "";
declare namespace ns2 = "";
declare function xf:sample($requestDoc as element(*))
    as element(*)
declare variable $requestDoc as element(*) external;

Sample request xml for Testing

<ns1:AddressDetails xmlns:ns1="">

Testing the application

Now Click on the 'Test' tab inside the xquery editor for testing

Now we have successfully created an xquery and tested it. 

 Testing the XQuery inside OSB Message Flow

      Create a new sample osb project. If you are a beginner you can refer the below post

 In the request flow drag one 'replace' node 

     Click on 'XPath' and enter the value as '*'

     In Variable : body
     Now click on 'Expresssion' and click on 'XQuery Resource' and browse to the sample xquery
     and enter $body/* into the 'requestDoc'.

Now you  can deploy the application and test it.

   This topic is intended to give an introduction to Xquery development and using the same inside the osb message flow. You can better explore more.


    please contact Sajeev Ramakrishnan




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