Use IBM's Web Services Client for ILE to consume a web service in an ILE RPG program.
Web services serve many purposes—from utilizing external web services for things like retrieving exchange rates or tracking shipments, to using internal web services as a means of communicating between applications within your organization. The task of writing a program to consume a web service can be relatively simple or very complicated, depending on the requirements of the web service that you're consuming. In this article, we'll explore how to use Web Service Definition Language (WSDL) to easily consume a web service in an RPGLE program.
WSDL is intended to provide developers and applications a means by which to determine what data is to be exchanged with a web service. IBM's Web Services Client for ILE gives you a utility to create a stub ILE service program in RPG to allow you to easily consume a web service. WSDL2RPG can generate an RPGLE service program that provides a means by which you can easily consume a web service from within an RPGLE program. The process is fairly simple. First and foremost, you need to make sure that you have the required PTF that adds the WSDL2RPG script to your system. Below is a table that shows the PTFs for each release of the OS from V5R4 forward.
Once you've ensured that you have the appropriate PTF for your release installed, you're ready to go. The Qshell script for WSDL2RPG is created in this folder:
Before you can execute the script, you'll need the location of the WSDL document that describes the web service. That location can be either the HTTP location of the WSDL or a local WSDL document on the IFS. The WSDL2RPG.SH script is executed using the following format:
/QIBM/ProdData/OS/WebServices/V1/client/bin/wsdl2rpg.sh <options> URI-To-WSDL
The options available for this script are listed below:
- -h/-help—Displays help text for the script/command.
- -o [path] —Sets the output directory for the source to be created.
- -ms [number] —Defines the maximum size for RPG character fields used to hold string data. For V5R4, the value can be between 16 and 650004. For V6R1 and higher, the range is 16 to 80000004. The default value is 128.
- -mb [number] —Defines the maximum size for binary fields holding character data. The range is 48 to 650004 for V5R4 and 48 to 160000004 for V6R1 and higher.
- -ma [number] —Defines the maximum array size for RPG arrays. The range is from 1 to 320004 for V5R4 and 1 to 80000004 for V6R1 and higher. The default value is 20.
- -s [path] —This value is the full /qsys.lib path to the service program to be created.
- -d—This option indicates that the resulting service program should be generated with debugging views.
As I mentioned earlier, you can specify the WSDL document as either a local IFS resource or using a full URI to the WSDL on web service. As an example of this, we'll use a free currency convertor web service. Enter the Qshell command line by typing QSH at the command line. Next, we need to create a folder to contain the source for the service programs. Type the following command inside the Qshell command line:
Now use the WSDL2RPG.sh script to generate our service program.
In this example, our output source will be generated in the /CurrConv IFS folder. The resulting service program will be created in the library MYLIB and will be named CURRENCY. The source members created by the script will be named based on the portType value from the provided WSDL document. In our example, this value is CurrencyConvertor. After executing the script above, you should see the following documents in the /CurrConv folder:
- CurrencyConvertorSoap.cl—CL to create the service program
- CurrencyConvertorSoap.rpleinc—Include RPGLE source member
- CurrencyConvertorSoap.rpgle—Service program RPGLE source
- CurrencyConvertorSoap_util.rpgleinc—RPGLE utility include source
- CurrencyConvertorSoap_util.rpgle—RPGLE utility source code
- CurrencyConvertorSoap_xsdtypes.rpgleinc—XSD data type include source
The source for all of the examples for this tip can be downloaded here. In addition to these, you'll find the C language includes and source for the C stub that is used by the RPGLE stub to access the web service. After executing the WSDL2RPG.sh script, you will also have an RPG service program named CURRENCY in the library specified as MYLIB above. For each operation supported by the web service, the created service program will contain a stub subprocedure. The naming convention will be stub_op_ followed by the name of the web service operation. In our example, that sub-procedure is stub_op_ConversionRate. To consume that service program, we simply need to include the "rpgleinc" source in our RPG program and then initiate a call to three subprocedures inside of the service program:
- Stub_create_CurrencyConvertorSoap(webService_ds)—Create a connection to the web service and store the details in the data structure webService_ds.
- Stub_op_ConversionRate(webService_ds: fromRate_stringDS: toRate_stringDS: rateAmount_DS)—Perform the conversion operation on the supplied web service and return the rate.
- Stub_destroy_CurrencyConvertorSoap(webService_ds) —Disconnect from the supplied web service.
In each of these examples, the webService_ds value identifies a data structure that contains information about the web service itself. This data structure contains the following:
- Endpoint URL—The URL for the web service as a 2048 character field. If this value is blank, the endpoint from the WSDL is used.
- Handle—A pointer to the C stub handle when invoking AXIS API.
- Exception Indicator —An indicator variable that identifies that an exception has occurred.
- Exception Code—An integer code associated with the error condition.
- Exception String—A 2048-character description of the error.
- Reserved—Reserved 1024 character field.
The program below utilizes the CURRENCY service program to retrieve the exchange rate from U.S. dollars to Canadian dollars.
// Sample Program To Consume the CurrencyConversion Web Service
// Using the RPGLE Stub Service Program "CURRENCY"
// Create using: CRTRPGMOD MODULE(mylib/CURRCONV)
// CRTPGM PGM(mylib/CURRCONV)
// The include members below are created by WSDL2RPG
d ws_ds ds likeds(This_t) inz
d amount ds likeds(xsd_double)
d fromCode ds likeds(xsd_string)
d toCode ds likeds(xsd_string)
d decAmt s 13 2
d rtnInd s 1n
// Define our "FROM" and "TO" Currency Codes based on
// Constants defined to the web service stub
fromCode.value = Currency_USD;
toCode.value = Currency_CAD;
// Create a connection to the web service
// Call the web service conversion rate operation
rtnInd = stub_op_ConversionRate( ws_ds
// Convert and display the returned conversion rate
decAmt = %dec(amount.value: 13:2);
if rtnInd and not amount.isNil;
// Close the web service connection
*inlr = *on;
This simple example illustrates a few things about the web service stub. First off, you'll notice the Currency_USD and Currency_CAD constants used to identify the currency codes to convert from and to. All of the currency code constants are defined in the RPGLEINC source created by the WSDL2RPG script. You'll also see the xsd_double and xsd_string types used to define the variables used in the program. These variables are actually qualified data structures that are defined in the CurrencyConvertorSoap_xsdtypes.rpgleinc source. These data structures contain an isNil subfield that is an indicator variable which identifies that the value is null along with a value subfield that contains the actual value of the element. Note that we do not provide a value in the ws_ds parameter. If for some reason we needed to provide a different URI for the web service endpoint from that defined in the WSDL, we would define that alternate URI in the ws_ds.endpoint value.
Simple but Powerful
This simple example illustrates how easy it is to consume a web service in an RPGLE program using the WSDL2RPG script. For more information on this powerful functionality, check out the Web Services Client for ILE Programming Guide.