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Building JSON with RPG and YAJL and Writing to Standard Output

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Building JSON with RPG and YAJL and Writing to Standard Output

This example is meant to explain how to use the YAJL toolkit from Scott Klement, RPG, and the Apache server to easily create JSON and write it out to standard output.  This sort of functionality is nice if you're creating a web service for others to consume.

The HTTP Server Configuration

First, we need to set up an Apache server configuration.  This is really simple and would look similar to this:

Listen x.x.x.x:80

CGIConvMode %%EBCDIC/EBCDIC%%

<Directory />
   Options None
   Order Deny,Allow
   Deny From all
</Directory>

<Directory /www/bvsdemo/html>
   Order Allow,Deny
   Allow From all
   <FilesMatch "\.html(\..+)?$">
       Options +Includes
       SetOutputFilter Includes
  </FilesMatch>
</Directory>

ScriptAliasMatch ^/cgi-bin/(.*) /qsys.lib/bvsdemo.lib/$1.pgm

<Directory /qsys.lib/bvsdemo.lib>
   allow from all
   order allow,deny
   Options +ExecCGI +Includes
   SetOutputFilter Includes
</Directory>

With this configuration we are basically telling the Apache server to run any program requested to the /cgi-bin directory.  The actual library the program is in will be BVSDEMO.

The RPG Program

Next, we need the program (caution... full free format following!)

**free
ctl-opt DFTACTGRP(*NO) ACTGRP('BVSDEMO') BNDDIR('YAJL') DECEDIT('0.');

// Imports
/include yajl_h

// Global Definitions
dcl-ds CSTMSTDS extname('CSTMSTPF') end-ds;

// Work Variables
dcl-s yajl_errMsg varchar(500) inz('');

//**********************************************************************
yajl_genOpen(*ON);
yajl_beginObj(); //main JSON object

exsr $Data;

yajl_endObj(); // Main JSON Object

// Write JSON to Standard Output
yajl_writeStdout(200:yajl_errMsg);

if (yajl_errMsg <> '');
   // handle error
endif;

yajl_genClose();

*inlr = *on;

//***************************************************************
//* Build JSON
//***************************************************************
begsr $Data;

  exec SQL declare C1 cursor for
      select email, bname, name, add1, add2,
             city, state, zip
        from CSTMSTPF;

  exec SQL open C1;
  exec SQL fetch next from C1 into
      :email, :bname, :name, :add1, :add2,
      :city, :state, :zip;

  yajl_beginArray('customerList');

  dow (sqlCode = 0);
    yajl_beginObj();  //Customer Object
    yajl_addChar('email':%trimr(email));
    yajl_addChar('bname':%trimr(bname));
    yajl_addChar('name':%trimr(name));
    yajl_addChar('add1':%trimr(add1));
    yajl_addChar('add2':%trimr(add2));
    yajl_addChar('city':%trim(city));
    yajl_addChar('state':%trimr(state));
    yajl_addChar('zip':%trimr(zip));
    yajl_endObj();  //Customer Object

    exec SQL fetch next from C1 into
        :email, :bname, :name, :add1, :add2,
        :city, :state, :zip;
  enddo;

  exec SQL close C1;

  yajl_endArray(); //customerList

endsr;

As show by this program, we simply build the JSON using YAJL and then use the yajl_WritestdOut() function to output that JSON to the browser.

The Results

An example of this exact program can be seen here by clicking here.

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Last edited 07/12/2019 at 10:50:43




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