January 5th, 2009Article Introducing PHP Data Services

Now you can view the article I wrote titling “Introduction to PHP Data Services“. There I explain how you can design and implement Data Services in PHP using WSF/PHP Data Services Library.

This article covers,

  1. Designing your Data Service API.
  2. Writing the Data Service.
  3. Deploying and Testing Data Service.
  4. Make the Data Service available in both SOAP and RESTful form.
  5. Use of WS-* features in your Data Service.

If you are thinking of adapting SOA in to your database backed PHP applications, this article will be a good starting point.

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DataServices, REST, RESTful, SOA, SQL, Tutorial/Guide, WSDL, database, design, php, web services, wsf/php, wso2, xml No Comments »

December 21st, 2008Introduction to WSO2 Carbon - Componentized SOA Platform

“WSO2 carbon is a componentized, customizable SOA Platform, You can adapt the middleware to your enterprise architecture, rather than adapt your architecture to the middleware”.

The Carbon Story
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DataServices, SOA, Tutorial/Guide, carbon, web services, wso2 1 Comment »

December 18th, 2008Data Services Best Practices

In simple term, data services are exposing data as web services. Anyway it is not a complete definition. Actually there are situations where we use data services not only to read data, but also to create, update or delete data. So it is better say data services are doing CRUD (Create, Read, Update, Delete) operations for data through web services. Simply it is like providing a web service interface for the database.

Anyway exposing  a database directly as a web service is like violating the first principles of software engineering. It will tightly couple the database structure with the interface, so whenever you do a simple change to the database schema, you will have to change the web service interface which will no doubt break all the clients depending on it.

So first of all, you have to design the service interface independent of the database schema you have. Most of the time you will able to find some query that would map the service interface to the database schema.

For an example think of publishing data in database table (say for table name “Games”) like this.

Teams
GameID Venue Date Team1 Team2 Team1Score Team2Score
1 xxx stadium 2008-12-18 Italy Sweden 34 33
2 yyy stadium 2008-12-19 France Spain 51 50

You will directly able to map these data to data service. So the response payload for a “getGames” operation would be something like,

<getGamesResponse>
   <Game>
      <Venue>
         xxx stadium
      </Venue>
      <Date>
         2008-12-18
      </date>
      <Team1>
          Italy
      </Team1>
      <Team2>
          Sweden
      </Team2>
      <Team1Score>
          34
      </Team1Score>
      <Team2Score>
          33
      </Team2Score>
   </Game>
   <Game>
      <Venue>
         yyy stadium
      </Venue>
      <Date>
         2008-12-19
      </date>
      <Team1>
          France
      </Team1>
      <Team2>
          Spain
      </Team2>
      <Team1Score>
          51
      </Team1Score>
      <Team2Score>
          50
      </Team2Score>
   </Game>
</getGamesResponse>

You can get this done with a SQL query simply as this,

SELECT * FROM `Games`

Say later if you decided to restructure the database table so the new database schema would be like this,





Games




GameId
Venue
Date




1
xxx stadium
2008-12-18




1
yyy stadium
2008-12-19










GamesTeams




GameId
TeamId
score




1
1
70




1
2
33




2
1
51




2
3
50
Teams
TeamId Name Coach
1 Italy Mr. ABC
1 Canada Mr. PQR
2 Spain Mr. XYZ

(Note here the Games and Teams are associated in the GamesTeams table.)

You can still use a query like the one in following to provide the same service interface, because it returns the same result set as the earlier one.

   SELECT Games.Venue,
              Games.Date,
              Team1.Name AS Team1,
              Team2.Name AS Team2,
              GameTeam1.Score AS Score1,
              GameTeam2.Score AS Score2
         FROM Teams Team1,
              Teams Team2,
              GamesTeams GameTeam1,
              GamesTeams GameTeam2,
              Games
        WHERE GameTeam1.gameId = Games.gameId  AND
              GameTeam2.gameId = Games.gameId AND
              GameTeam1.teamId = Team1.teamId AND
              GameTeam2.teamId = Team2.teamId AND
              Team1.teamId <> Team2.teamId AND
              Team1.name=?

This allows you to keep the ser