Tip 3: How to call a low-code module from an RPG program

This tip documents how to:

1. Create a low-code module to consume a REST API.
2. Call the low-code module from an RPG program, by using the PJSCALL program.

Create a low-code module to consume a REST API

• Navigate to the workspace "pjstips".
• Click New/Module File.

• Click Edit/Source, to bring up the Source view.

• Clear the current default code, and enter the code below.
• pjstips_03_1.module.json

  {
    "routines": [
      {
        "name": "routine1",
        "inputs": [
          {
            "type": "decimal",
            "ibmiLength": 4,
            "name": "custno",
            "ibmiDecimals": 0
          }
        ],
        "outputs": [
          {
            "type": "string",
            "ibmiLength": 30,
            "name": "name"
          }
        ],
        "steps": [
          {
            "text": "Consume REST service",
            "answers": {
              "plugin": "Custom:web-service",
              "uri": "http://localhost:8081/run/pjstips/pjstips_02_3",
              "method": "POST",
              "headers": "",
              "body": "{\n  \"custno\": input[\"custno\"]\n}",
              "json": true,
              "auth": "",
              "capture_response": true,
              "capture_on_error": false,
              "capture_as": "Value",
              "specific_property": "",
              "destination": "Work variable",
              "work_variable": "myres"
            }
          },
          {
            "text": "Set Module output",
            "answers": {
              "plugin": "Program Data:set-module-output",
              "module-output-values": {
                "name": "myres[\"name\"]"
              }
            }
          }
        ]
      }
    ]
  }

• Click Edit/Design, to bring up the Design view.
• If needed, in the "Consume REST service" step, change the Endpoint URL to point to the correct host/port.
• Click Home/Save As, and save as pjstips_03_1.module.json.
• You've created a low-code module, as shown below, with a routine named "routine1" that:
  
  • Takes an input parameter of "custno".
  • Uses plugin "Consume REST service" to issue a POST request to URL http://localhost:8081/run/pjstips/pjstips_02_3 (created in a previous example).
  • The input "custno" is specified in the "body" of the POST request.
  • The returned JSON object from the REST web service is saved in a work variable named "myres".
  • The value of myres["name"] is used to set the output value output["name"].
• 

Call the low-code module from an RPG program

• You can call this low-module from another low-code module, from another "regular" (i.e. NOT low-code) PJS module, or from an RPG program. To call it from an RPG program, use the code generated in the panel "IBM i Call Interface" panel.

• Below is an example, where the input custno is set to 1234 to pass to the low-code module, which calls the REST service to get the customer name, which is then returned to the RPG program, which is then displayed on the screen.

**free

  Dcl-PR PJSCALL ExtPgm;
    ParmType        Char(30)          Const;
    ModuleID        VarUCS2(500)      Const;
    RoutineName     VarUCS2(70)       Const;
    InputParms      Char(16773104)    Const Options(*Varsize:*Omit:*NoPass);
    InputParmSize   Int(10)           Const Options(*Omit:*NoPass);
    OutputParms     Char(16773104)    Options(*Varsize:*Omit:*NoPass);
    OutputParmSize  Int(10)           Const Options(*Omit:*NoPass);
  End-PR;

  Dcl-DS InputDS Qualified Inz;
    custno  Zoned(4: 0);
  End-DS;

  Dcl-DS OutputDS Qualified Inz;
    name  VarChar(30);
  End-DS;

  InputDS.custno = 1234;			// pass input to the low-code module in "InputDS"

  Monitor;

    PJSCALL('*MODULE'
      : 'pjstips:pjstips_03_1.module.json'
      : 'routine1'
      : InputDS
      : %Size(InputDS)
      : OutputDS
      : %Size(OutputDS)
    );

  On-Error;


  EndMon;

  dsply  OutputDS.name;				// output from the low-code module in "OutputDS"		
  *inlr = *on;
  return;