If you want to write some code that makes the Pentaho BI Platform talk to an external system, this may be what you are looking for, so read on...

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What is an Action?

Actions are the lightweight alternative to Pentaho BI Components.  For an understanding of how and why they are different, let's take a step back and examine what a BI Component is and how it is used.  A BI Component is historically a Java class that does some work, yielding some output, when it is provided certain inputs and resources.  The work done as well as the inputs and resources required are entirely up to the component developer.  It's purpose is to perform some work in a sequential success-based workflow (action sequence).  A saavy BI Platform user with a bit of inclination for Java coding can implement his or her own custom component to do just about anything.  However, this is not an easy endeavour since developing your own BI Component requires intimate knowledge of internal Pentaho APIs.  When you are done writing your custom component, the code you have written will be tightly coupled to the Pentaho BI Platform, so much so, that it will be difficult to unit test and may be difficult to maintain.

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The Action framework expects Action objects to be Java bean compliant with respect to setting inputs, setting resources, and getting outputs.  In other words, if your action needs takes a string input, the action definition in the xaction solution file will specify this string input, and the Action framework will cause that value to be set via a setter method on the Action object.  You do not see parameter Maps and such in the Action API for this reason.  All inputs, output, and resources IO will involve Java bean reflection on your Action object to find the appropriate IO methods.

See the Echo Plugin - a sample plugin for the BI PlatformBIServer project for examples of how to get data into your IAction and how to expose the output of your IAction so something else can do something with it (i.e. display the results of your IAction, pipe them to another step in an action sequence, or bind them to a session parameter).

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public class MyAction implements IAction {
public void setAttachments(int index, Object o)
{     //do something   }
public Object getAttachments(int index)
 { //will not be called }
public void execute() throws Exception {}
}

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Plugging in Actions

Of course writing an Action does no good unless you can use it in an action sequence, right? Well the way you make the Pentaho BI Platform aware of your Action is to write a plugin. See the wiki page on developing plugins for more information.