Rest Web Services for Everyday RPG and SQL

Copyright Central Park Data Systems, Inc. 1

Looking Inside the Developer’s Toolkit:REST Web Services for Everyday RPG and SQL Consumption

Charles Guarino

Charles GuarinoTwitter @charlieguarino

Central Park Data Systems, Inc.

REST SERVICES

About The Speaker

With an IT career spanning over 30 years, Charles Guarino

has been a consultant for most of them. Since 1995 he has

been founder and President of Central Park Data Systems,

Inc., a New York area based IBM midrange consulting

company. In addition to being a professional speaker, he is a

frequent contributor of technical and strategic articles and

webcasts for the IT community. He is a proud member of

COMMON’s Speaker Excellence Hall of Fame and also Long

Island Software and Technology Network’s Twenty Top

Techies of 2009. Charles currently serves as a member of

COMMON’s Strategic Education Team (SET) and is also

Immediate Past President and monthly Q&A host of LISUG,

a Long Island IBM i User’s Group www.lisug.org.

Charles can be reached at [email protected].

LinkedIn - http://www.linkedin.com/in/guarinocharles


What We’ll Cover …

• Web services 101

• XML versus JSON

• Real life web services

• XML using native SQL

• XML using native RPG

• JSON to XML using native RPG

• JSON to XML using native SQL

• Wrap-up

Local System

Program “A” Program “B”

How Do They Work?

Consumer Provider

PARAMETERS


The Cloud

Power System

running IBM I

Program “A”

Web Services Server

on some other

system

Program “B”

How Do They Work?

Consumer Provider

More Web Services Fun Facts

• A STATELESS connection

• Can be sent in the clear or securely

• Can be public or private between companies or individuals

• Hardware, programming language and platform agnostic

• Can save you lots of $ - pre-written and tested and documented services

• Can be FREE, Restricted Access, Pay-For-Each-Use or Subscription Based

• Extends your applications in ways you may have never known possible, providing real time information.

• Can be many and simultaneous points of failure

• See the end of this presentation for useful links!!!!


Methods of Transport

REST(Representational State Transfer)

URL http://.....

Web Services for the masses


How do they track your usage?

But how do they make money?




• XML versus JSON






• Wrap-up

Data Format XML

XML – IBM i has native parsing tools

Extensible Markup Language


Data Format JSON

JSON

Java Script Object Notation



• XML versus JSON






• Wrap-up


http://wiki.cdyne.com/wiki/index.php?title=CDYNE_Weather




http://wsf.cdyne.com/WeatherWS/Weather.asmx?op=GetCityForecastByZIP


http://wsf.cdyne.com/WeatherWS/Weather.asmx/GetCityForecastByZIP?Zip=10038

Header Data

First Day’s Forecast

Second Day’s Forecast

First screen prompts for zip code:


Subfile displayed with fully parsed data for zipcode 10038:



• XML versus JSON






• Wrap-up


Definitions For Using SQL and XML

SYSTOOLS

CCSID 37

CCSID 65535

CLOB versus BLOB

XPATH

A Review Once Again of the XML Data

Header Data

First Day’s Forecast

Second Day’s Forecast

Starting point for SQL statement

“ForecastReturn/ForecastResult/Forecast”


http://www.ibm.com/developerworks/data/library/techarticle/dm-1105httprestdb2/

HTTPGETCLOB !!!

IBM i Navigator Using 7.1 Technology Refresh 6


The NEW Power of the SQL Select Statement

Select *

from XMLTABLE(xmlnamespaces(default

'http://ws.cdyne.com/WeatherWS/'),

'ForecastReturn/ForecastResult/Forecast'

passing XMLPARSE(document(

systools.httpGetClob('http://wsf.cdyne.com/WeatherWS/Weather.asmx/Ge

tCityForecastByZIP?Zip=10038','')))

Columns

State VarChar(3) path '../../State',

City VarChar(30) path '../../City',

Station VarChar(30) path '../../WeatherStationCity',

DateTime VarChar(50) path 'Date',

Description VarChar(30) path 'Desciption',

MorningLow VarChar(3) path 'Temperatures/MorningLow',

DayTimeHigh VarChar(3) path 'Temperatures/DaytimeHigh',

Nighttime VarChar(3)

path 'ProbabilityOfPrecipiation/Nighttime',

Daytime VarChar(3)

path 'ProbabilityOfPrecipiation/Daytime')x;

Prompt for zip code

Concatenate zip code and execute HTTPGETCLOB,

place XML into variable “BigVar”

Declare cursor, read 7 rows into data structure

Load parsed data into subfile and display

WEATHRRSQL Basic Program Flow


Program WEATHRRSQL

Stepping through the code, zip code 10038 was keyed.


Stepping through subprocedure ConsumeWebService

Data structure XMLINDATA after SQL Fetch


Loading the subfile:



• XML versus JSON






• Wrap-up


Prompt for zip code

Concatenate zip code and execute HTTPGETCLOB,


Parse XML into data structures using RPG’s XML-INTO

Load parsed data into subfile and display

WEATHRINTO Basic Program Flow

Program WEATHRINTO


1

2

3

4

Header data – A Closer Look

1

2

3

Detail Data – A Closer Look

If you want to capture the data, the names must match – misspellings and all!


Immediately after HTTPGETCLOB, loaded BigVar

xml-into HeaderData:


Loaded data structure HeaderData:

Loaded data structure WeatherData:


Loading the subfile:



• XML versus JSON






• Wrap-up


www.openweathermap.org

Sample API call using London, UK

http://api.openweathermap.org/data/2.5/weather?q=London,uk&appid=2de143494c0b295

cca9337e1e96b00e0


http://www.scottklement.com/yajl

http://www.mcpressonline.com/programming/techtip-json-and-xml-conversion-in-db2-for-i.html


API key stored in data area WEATHERMAP

This is invalid XML data, needs to be fixed

<1aaa>

</1aaa>


Prepare URL from JSON web service,

include app key from data area

Execute HTTPGETCLOB, place JSON into “Jsonstring”


Call program to convert JSON to XML

Fix any bad XML tags

WEATHRJSON Basic Program Flow

Invoke XML SAX parser and

write selected data elements to table WEBSVCDATA

Program WEATHRJSON


Program call with parameter “Costa Mesa, CA”

URL is loaded, appended with API key


Variable JSONSTRING

Variable JSONSTRING converted to XMLSTRING


Parsed data in table WEBSVCDATA



• XML versus JSON






• Wrap-up


Prepare URL from JSON web service,

include app key from data area

Execute HTTPGETCLOB, place JSON into “Jsonstring”


Call program to convert JSON to XML

Fix any bad XML tags

WTHRJSONXT Basic Program Flow

Invoke XML SAX parser and INSERT rows

from selected data elements to table WEATHERDATA

Program WTHRJSONXT


JSONSTRING is loaded from web service

XMLSTRING is loaded from web service


At the beginning of subprocedure processXML

Insert row into table WeatherData


Table WeatherData (Weath00001) after insert



• XML versus JSON






• Wrap-up


Looking Inside the Developer’s Toolkit:REST Web Services for Everyday RPG and SQL Consumption

Charles Guarino

Charles GuarinoTwitter @charlieguarino

REST SERVICES

THANK YOU !!!

Definitions

• XML (eXtensible Markup Language)• Unlike HTML which has pre-defined tags, the tags can have any

value you wish. This is what makes it extensible.

• Your document must still be well-formed to be parsed, meaning each start tag must have a corresponding end tag.

• The actual data is stored between the tags.

• Parsing• The “shredding” or extraction of the XML data from its tags.

• SOAP • Simple Object Access Protocol

• Message-based, you create a message similar to an email using a pre-defined language, Web Services Definition Language, or WSDL (“wiz-dul”).


Definitions (cont.)

• REST (Representation State Transfer)• HTTP based, no need to create a message

• Web service can be consumed using a browser

• U.R.I. (Universal Resource Identifier)• More broadly based than a URL, which refers to a website, is

used to identify any object in the cloud

Helpful resources• The basics of RESTful web services

http://www.ibm.com/developerworks/webservices/librar

y/ws-restful

• XML Name Spaces

http://www.w3schools.com/xml/xml_namespaces.asp

• SQL Messages and Codes When Using SQL With DB2 for i

http://pic.dhe.ibm.com/infocenter/iseries/v7r1m0/index.j

sp?topic=%2Frzala%2Frzalakickoff.htm


Helpful resources

• A good primer on understanding CCSID

http://www.itjungle.com/mpo/mpo091103-

story03.html

• A beginner’s definition of BLOB

http://www.techterms.com/definition/blob

• A beginner’s definition of CLOB

http://www.techterms.com/definition/clob

Helpful resources

• What is SYSTOOLS?http://pic.dhe.ibm.com/infocenter/iseries/v7r1m0/index.jsp?topic=%2Frzajq%2Frzajqsystools.htm

• IBM developerWorks website discussing new SQL HTTP functions, including HTTPGETCLOB https://www.ibm.com/developerworks/community/wikis/home?lang=en#!/wiki/IBM%20i%20Technology%20Updates/page/New%20HTTP%20functions%20added%20to%20SYSTOOLS

• A beginner’s tutorial on XPATH

http://www.w3schools.com/xsl/xpath_intro.asp


Additional Session Information

• To Run SQL Scripts in IBM i Navigator

Open your connection in Navigator

Open “Databases”

When your database name appears, right click on it.

In the menu, click on “Run SQL Scripts”

• When you are in the SQL Scripts window, click on “Connection”

and select “Temporary JDBC Settings”

In the “Translation” tab, make sure “Translate CCSID 65535” is

CHECKED.

Software Disclaimer

DISCLAIMER OF WARRANTIES AND LIMITATION OF LIABILITY

The software is supplied “as is” and all use is at your own

risk.

Central Park Data Systems Inc. and/or Charles Guarino

disclaims all warranties of any kind, either express or

implied, as to the software, including, but not limited to,

implied warranties of fitness for a particular purpose,

merchantability or non‐infringement of proprietary rights.

No documentation furnished is intended to express or imply

any warranty that the operation of the software will be

uninterrupted, timely, or error‐free.

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Rest Web Services for Everyday RPG and SQL

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