Getting in a lather Ian Pearce Sybase Professional Services ipearcesybase'com

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Getting in a latherIan PearceSybase
Professional Servicesipearce_at_sybase.com
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Agenda

• What is it
• What does it do
• Why do I need to use it
• How can I use it

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What is it

• SOAP means
• Simple Object Access Protocol
• Rationale ?
• Invented as a language-independent method for
  invoking business methods by wrapping them up as
  XML documents

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What is it (cont.) ?

• Operates across process boundaries
• Uses HTTP as its transport protocol
• Quite a popular protocol !!!
• Allows us to do Remote Procedure Calls
• (Get someone else to do the work !)

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XML again ???

• All we hear about these days is XML !!!
• Good point !
• Is it any use to me ?

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Any old data, any old data, any, any, any old
data
Your/Data/0xCC
Your Enterprise (but Legacy format) Application
That you always have to make the changes to
because youre the last one left from the team
that originally wrote it
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XML cont.

• OK, good point
• Why do I need XML when I can just throw an
  Integer or a Blob across the wire ?
• Portability
• Byte-swapping

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Why do I need to use it ?

• OK, but I dont need that if Im talking to
  EAServer from PowerBuilder, or Java !
• Agreed, but what if someone chose another
  Application Server ?
• What if someone has already written some code
  that you can just invoke, with a minimum of
  effort ?

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eGP Demo
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eGP Demo
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How does it do it ?

• At its most simple level SOAP works like this

Wrap request as XML and dispatch
Invoke Service
SOAP Container
Java Class
Decode
Collect results
Convert to XML and dispatch
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How does it do it ?

• The client wraps up a request and sends it to the
  SOAP container
• The SOAP container then
• unwraps the request
• calls the required service
• wraps up the result and dispatches it
• The client then unwraps it

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What we really do

• To make the call to the SOAP container, we need
  to pass across an ENVELOPE
• This contains a BODY, which itself contains
• the request
• the parameters

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And the SOAP container is ?

• The SOAP container can be anything
• But well use the Apache SOAP server from
  http//xml.apache.org/dist/soap/
• Easy to install
• See http//my.sybase.com/detail?id1013352

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And the SOAP container does ?

• Once installed, the SOAP service deals with all
  your requests
• We can easily administer it by using the
  SOAPAdmin web application
• We can easily define our own services

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How can I use it ?

• Here comes the science part

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Using SOAP with PowerBuilder

• In order to use SOAP, you need to establish an
  HTTP connection with the SOAP server
• Luckily, we have that facility, using the GetUrl
  function

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Using SOAP with PowerBuilder

• Or do we ????
• SOAP complains when you use the GET HTTP method
• it wants you to use the POST HTTP method

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GET/POST whats the difference ?

• Brief reminder ..
• The GET method is used when you want to pass
  parameters over to an HTTP server
• but these parameters are appended to the URL
• i.e. http//my.sybase.com/detail?id1013352
• The id parameter is appended

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GET/POST whats the difference ?

• Remember, SOAP wants you to POST parameters
• Why cant we use GET
• Because what would happen if were passing a HUGE
  amount of information across to the SOAP Server
• Overloaded anyone ?

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GET/POST whats the difference ?

• We therefore need to use the POST method
• Internet banking ever seen you UID/PWD in the
  URL ?
• Unlikely -)
• So we need to use the POST HTTP method

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PowerBuilder to the rescue !!

• Luckily, PowerBuilder has the posturl method
• Its been there since version 6.0 actually !
• The postURL method is a method in the inet system
  object

Actually, it might have been an addition to
Version 5 whos counting -)
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The inet System object

• The postURL method works like this
• Where linet_base is an instance of the inet
  object
• lblob_data is a BLOB that contains the XML
• ls_headers is the HTTP header set
• lnv_id is an instance of the internetresult object

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Catching the response

• After dispatching the request to the server, we
  just lie back and think of ltinsert_applicable_coun
  trygt
• When the server responds, we see the response as
  a STRING argument to the internetdata event in
  the internetresult object
• Et voila !

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Building a generic PBSoapService

• If we want to call PB Components from a SOAP
  client, we can do one of two things
• 1. Wait for the PBWebServices addition to EAS
• 2. Roll our own !!!!

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Rolling our own

• Things to remember
• 1. We need a skeleton service on the SOAP
  container to handle our requests
• 2. We only ever want strings passed back

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Rolling our own

• Steps
• Create a PB component that retrieves a row based
  on an argument
• Generate Java stubs (and compile)
• Create a Java wrapper which will pass-through any
  requests
• Create a deployment descriptor for the wrapper
• Deploy it (using the sample that comes with the
  SOAP service from Apache)

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More information

• For more information, please feel free to contact
  me
• ian.pearce_at_sybase.com
• 01628 597395
• 07977 257395

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Getting in a latherIan PearceSybase
Professional Servicesipearce_at_sybase.com