1. Consuming Web Services with 2E Generated Objects

2. Speakers
Jonathan R Bolton
C&D Technologies, Inc.

3. Presentation Objectives
This presentation will demonstrate how a combination of user source objects in conjunction with standard CA 2E action diagram processes can create a program to consume a web service.

4. System Prerequisites

5. System Prerequisites
The following functions and freeware libraries are required to successfully created 2E objects that will consume web services:
Generation mode must be ILE RPG (RP4)
The 2E compiler preprocessor must be present and active
The following freeware libraries must be installed on the System i:
HTTPAPI HTTP API library
YAJL JSON Parser library
The SOAPUI web service exerciser application

6. SOAP Web Services
Web services using Simple Object Access Protocol (SOAP) were quite popular several years ago but have been displaced by RESTful web services
SOAP services utilize an XML-based interface for both the request to the service and the response
SOAPUi allows you to interrogate the service to determine the XML request format and verify the format of the response

7. SOAP Request
This example shows the request for a SOAP web service that accepts a manifest ID and a manifest line number as input data. Note that, as a web service powered by a 2E-generated service program, the default 2E 7A return code parameter (P0Rtn) is included. It however does not need to be populated.

8. SOAP Response
This is the response from the web service request shown in the previous slide. The service returns the customer order number (WP0003), the item number (WP0004) and the item description (WP0005). Note the 7A return code is referenced but without a full tag pair.

9. RESTful Web Services
The Representational State Transfer (REST) service is becoming the protocol of choice for web services
Javascript Object Notation (JSON) is the preferred vehicle for the response and is a simplified name:value pair
In its simplest form, the request is just a URL with parameters

10. RESTful Example The URL in this example is the following:
This is the response:

11. A More Complex SOAP Service
This service returns multiple sets of data where there are 8 subfields in each data set. Since the service is powered by a 2E generated program object, the response is populated by an *arrays object . Also note that the input parameter (WP0001) comes after the definition of the return parameter.

12. Request and Response

13. Creating a consumption process in 2E
Both SOAP and RESTful web services can be consumed by a 2E-generated program
Execute User Source objects are needed for coding of these two functions:
The call to the web service via HTTP
The parsing of the response returned by the service

14. Execute User Source objects
Execute User Source (EXCUSRSRC) objects are needed to manage these functions/activities:
Definition statements pertaining to variables needed in the object that are not part of the 2E model database
Definition of the XML request packet
Coding of the HTTP call
Coding of the appropriate parser, based on the service type
XML-INTO for SOAP services
DATA-INTO (with YAJLINTO) for RESTful services

15. Required Definition Specifications

16. Required Definition Specifications
Use the Y* compiler directive to dynamically add additional libraries needed for compilation.
If using SQL and not DDS, ensure that the compiler preprocessor option (RPGPPOPT) is set to *LVL2 and not *NONE. If this is not done, the compiles will fail.
Definition specifications allow the easy setup for the HTTP call using the HTTPAPI functions.
Use the /include directive to add the required header files. Don’t use /copy directives. These are not correctly understood by the compile preprocessor.

17. SOAP Request User Source

18. SOAP Array Data Structure

19. SOAP Array Data Structure
This user source defines a data structure that can be accessed by the XML-INTO process and 2E generated source code
The data structure array dimension value must match that of the 2E array parameter you are using
The key take away here is that the user source must define the data structure parameters using the names discovered by testing the web service with SOAPUi

20. SOAP Response Data Update

21. SOAP Response Data Update
This user source is the connection point between the user source added to work with the data parsers and 2E generated source code
The input parameter defines the index value for the data set being processed
The output parameters receive the parser results

22. The Execute External Function object

23. RESTful Web Service Differences
The HTTP call does not require a formal request set in XML, just a URL with parameter(s)
The response can be parsed into a qualified data structure

24. RESTful Web Service Response

25. RESTful Qualified Data Structure

26. RESTful Web Service Call and Parse

27. Demonstration

28. Conclusions . . .
Web services are a powerful tool that extends the versatility of the IBM i platform, both as a provider of services or a consumer of services
CA 2E can easily be used to both create and consume web services
Imaginative use of Execute User Source objects makes sophisticated programming techniques possible
Web services help dispel the notion that the IBM i and CA 2E are “legacy” systems ready for retirement

29. Useful links . . .
HTTPAPI Library :
YAJL JSON Parser:

30. Thank you for attending!