Primarily parameters capture the data that accompany events.

However, the usage of parameters could be general in nature.  For example, for platforms that have dynamic object creation and life cycle management, these parameters could be used to represent dependant object as well as data keys.

For dynamic segment composition schemes, these parameters could be used to customize included segments at runtime.

The point here is that apart from event parameters, the general implementation implications of parameters would differ from platforms to platforms.

For events the id for the parameters descriptors would be registered against the event. For page composition, the parameters would have a parent, which would the segment that represents the included page.

The parameters descriptor could describe 1) an object that hold the properties that would be used as parameters, 2) or map object, or collection of objects that hold the key and value parameter pairs. 3) In addition, it could be a parent to one or more parameter descriptors.  The latter "parameter" singular descriptor, affords a finer grain parameter binding of individual key and value pair; whereas the "parameters" are bound to collection, or whole object.

Apart for the introduction of custom programming, Struts usage parameters is tied to the events and page compositions. These are the implementations of the three modes listed above.

1. Single Object exposing attributes: A parameters descriptor could hold reference to a single object. This could be the form-bean.
2. Single Map object: The parameters descriptor would hold reference to an object that contains a Map containing the individual key and value pairs of parameters.
3. Group of Parameter Descriptors: A set of individual key and value pairs would be captured each with a parameter descriptor.

For use with Struts these alternatives are illustrated below, as used in connection with the event descriptor.

1)  Single Object.

This is used to specify objects passed for events, typically form bean for an action event

2)  Map Object.

The implementation for the form bean as parameter for POST events is discussed in event and behavior-define descriptors. This is reflected in the Struts configuration file.

For the GET events it is the Map object that would be specified. The implementation would be as shown below.

  <html:link action="/referToAssociates"
    	name="object" property="property" >
  	Go back to referrer
  </html:link>
  

The referenced {object.property} would resolve into map object.

3)  There is the finer grain specification. Whereby the "parameters" descriptor would be a parent to one or more "parameter" descriptors, as shown below.

The implementation of the singular parameter descriptor is discussed in the parameter description section.

More details are available in the attributes descriptions