To support using GPO within JSP a number of custom tags are provided.

These have been designed to make iniitialization and access to the GPO system as simple as possible, and in conjunction with the Alchemist system generation dramatically simplifies the amount of code that needs to be written.

System Initialization

The normal java initialization using OMClient and derived classes is support by the gpo:init tag, that can be used as follows:

<%@ taglib uri="/tags/gpo" prefix="gpo" %>

<gpo:init store='/db/test.rw' />

For Alchemist generated systems the derived client class should be provided:

<%@ taglib uri="/tags/gpo" prefix="gpo" %>

<gpo:init
  clientClass='alchemy.contacts.client.ContactsClient' 
  store='/db/test.rw' />

This stores the client in the application context, and opens the associated database.

The optional parameters are as follows:

parameter	Description
clientClass	The OMClient derived class
om	Specific IObjectManager implementation
store	Specific store file
desc	Xml description file

Root Object

The OMClient provides a method to getDefaultRoot that by default returns the NameManager used to remember and recall keyed values. The Alchemist generated OMClient specializations will return the root object of the defiend model.

<%@ taglib uri="/tags/gpo" prefix="gpo" %>

<gpo:root>
  <%= root.toString() %>
</gpo:root>

The single optional id parameter supports the specification of variable name:

<gpo:root id='myRoot'>
  <%= myRoot.toString() %>
</gpo:root>

GPO Tag

Accessing the GPO objects is the base requirement for any GPO based application. The gpo tag provides just that - either from an explicit object reference - gpoId or a parameter in the current request:

<%@ taglib uri="/tags/gpo" prefix="gpo" %>

<gpo:gpo id='gpo' parameter='id'>
  <h2>Inspect <%=gpo.getID()%></h2>
</gpo:metaSpec>

...or:

<gpo:gpo id='gpo' gpoId='12'>
  <h2>Inspect <%=gpo.toString()%></h2>
</gpo:metaSpec>

GPO MetaSpec

When browsing a GPO model, the MetaSpec object can provide a generic protocol to discover key aspects of the target object.

The metaspec tag provides access to the MetaSpec object either from a provided src GPO object or via an external parameter.

<%@ taglib uri="/tags/gpo" prefix="gpo" %>

<gpo:metaSpec id='metaSpec' parameter='id'>
  <h2>Inspect <%=metaSpec.getLabel()%></h2>
</gpo:metaSpec>

Alternatively, the metaSpec tag can be nested within a gpo tag:

<%@ taglib uri="/tags/gpo" prefix="gpo" %>

<gpo:gpo parameter='id'>
  <gpo:metaSpec id='metaSpec'>
    <h2>Inspect <%=metaSpec.getLabel()%></h2>
  </gpo:metaSpec>
</gpo:gpo>

Remember and Recall

The remember and recall tags support the IObjectManager protocol to remember and recall values.

These can be used straightforwardly to persistently retain certain values:

<%@ taglib uri="/tags/gpo" prefix="gpo" %>

<gpo:remember key='name' value='Cut The Crap'/>

To recall you must provide the key and the id of the variable. Optionally you can provide the type of the data to avoid any casting in your code.

<%@ taglib uri="/tags/gpo" prefix="gpo" %>

<gpo:recall id='name' key='name' type='java.lang.String'>
  <h2>Length of name is <%=name.length()%></h2>
</gpo:recall>

An additional option controls the scope of the variable created, although it will default to nested if a scope='page' is declared the variable will be available to any script following the start tag.