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Subject: cvs commit: jakarta-ant/proposal/myrmidon/src/xdocs configuring.xml
From: donaldp () apache ! org
Date: 2002-03-31 5:17:27
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donaldp 02/03/30 21:17:27
Added: proposal/myrmidon/docs configuring.html
proposal/myrmidon/src/xdocs configuring.xml
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Add a basic page about configuring tasks in myrmidon.
Revision Changes Path
1.1 jakarta-ant/proposal/myrmidon/docs/configuring.html
Index: configuring.html
===================================================================
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" \
"http://www.w3.org/TR/html4/loose.dtd">
<!-- Content Stylesheet for Site -->
<!-- start the processing -->
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"/>
<meta name="author" value="Peter Donald">
<meta name="email" value="peter@apache.org">
<title>Apache Myrmidon - On Task Configuring in Ant2</title>
</head>
<body bgcolor="#ffffff" text="#000000" link="#525D76">
<table border="0" width="100%" cellspacing="0">
<!-- TOP IMAGE -->
<tr>
<td> <td colspan="2">
<a href="http://jakarta.apache.org"><img \
src="http://jakarta.apache.org/images/jakarta-logo.gif" align="left" border="0"/></a> \
</td> </td>
<td valign="bottom"><div align="right"><b><font size="+3" \
color="#525D76">Apache Myrmidon</font></b></div></td> </tr>
</table>
<table border="0" width="100%" cellspacing="4">
<tr><td colspan="2">
<hr noshade="" size="1"/>
</td></tr>
<tr>
<!-- LEFT SIDE NAVIGATION -->
<td valign="top" nowrap="true">
<p><strong>Myrmidon</strong></p>
<ul>
<li> <a href="./index.html">Introduction</a>
</li>
<li> <a href="./getinvolved.html">Get Involved</a>
</li>
<li> <a href="./user.html">Building Myrmidon</a>
</li>
<li> <a href="./todo.html">Todo List</a>
</li>
</ul>
<p><strong>User Guide</strong></p>
<ul>
<li> <a href="./buildfile.html">Build file</a>
</li>
<li> <a href="./vfs.html">Virtual File System</a>
</li>
<li> <a href="./ant1compat.html">Ant1 Compatibility Layer</a>
</li>
<li> <a href="./differences.html">Differences to Ant1</a>
</li>
<li> <a href="./task.html">My First Task</a>
</li>
</ul>
<p><strong>Extending Ant</strong></p>
<ul>
<li> <a href="./configuring.html">Configuration HOWTO</a>
</li>
<li> <a href="./converter.html">Converter HOWTO</a>
</li>
<li> <a href="./type.html">Type HOWTO</a>
</li>
<li> <a href="./classloader.html">ClassLoader HOWTO</a>
</li>
<li> <a href="./librarys.html">Library HOWTO</a>
</li>
</ul>
<p><strong>Container Design</strong></p>
<ul>
</ul>
</td>
<td align="left" valign="top">
<table border="0" cellspacing="0" cellpadding="2" width="100%">
<tr><td bgcolor="#525D76">
<font color="#ffffff" face="arial,helvetica,sanserif">
<a name="Introduction"><strong>Introduction</strong></a>
</font>
</td></tr>
<tr><td>
<blockquote>
<p>This section will describe in detail the mechanism via \
which tasks are
configured. Configuration is the name given to the stage in tasks
lifecycle via which the XML representation is mapped onto the task
object.</p>
</blockquote>
</td></tr>
</table>
<table border="0" cellspacing="0" cellpadding="2" width="100%">
<tr><td bgcolor="#525D76">
<font color="#ffffff" face="arial,helvetica,sanserif">
<a name="Names"><strong>Names</strong></a>
</font>
</td></tr>
<tr><td>
<blockquote>
<p>When mapping the XML representation on to the task \
object you
need to be able map the names as they appear in the XML to the
names as they appear in the Java code. The process is for generating
a java name from the xml name is as follows.</p>
<ol>
<li>Capitalize the first character of name.</li>
<li>Find any '-' characters in XML name and remove character and
capitalize the following letter. (And there must be a following
letter)</li>
</ol>
<p>Some example mappings;</p>
<div align="left">
<table cellspacing="4" cellpadding="0" border="0">
<tr>
<td bgcolor="#023264" width="1" height="1"><img src="/images/void.gif" \
width="1" height="1" vspace="0" hspace="0" border="0"/></td>
<td bgcolor="#023264" height="1"><img src="/images/void.gif" width="1" \
height="1" vspace="0" hspace="0" border="0"/></td>
<td bgcolor="#023264" width="1" height="1"><img src="/images/void.gif" \
width="1" height="1" vspace="0" hspace="0" border="0"/></td> </tr>
<tr>
<td bgcolor="#023264" width="1"><img src="/images/void.gif" width="1" \
height="1" vspace="0" hspace="0" border="0"/></td> <td bgcolor="#ffffff"><pre>
my-name ===> MyName
aString ===> AString
Basedir ===> Basedir
baseDir ===> BaseDir
url ===> Url</pre></td>
<td bgcolor="#023264" width="1"><img src="/images/void.gif" width="1" \
height="1" vspace="0" hspace="0" border="0"/></td> </tr>
<tr>
<td bgcolor="#023264" width="1" height="1"><img src="/images/void.gif" \
width="1" height="1" vspace="0" hspace="0" border="0"/></td>
<td bgcolor="#023264" height="1"><img src="/images/void.gif" width="1" \
height="1" vspace="0" hspace="0" border="0"/></td>
<td bgcolor="#023264" width="1" height="1"><img src="/images/void.gif" \
width="1" height="1" vspace="0" hspace="0" border="0"/></td> </tr>
</table>
</div>
<p>Note that the above transformation is lossy and \
as such the
following XML names all map to the same Java name. The ant1.x mapping
is similarly lossy and in practice this has not been an issue.</p>
<div align="left">
<table cellspacing="4" cellpadding="0" border="0">
<tr>
<td bgcolor="#023264" width="1" height="1"><img src="/images/void.gif" \
width="1" height="1" vspace="0" hspace="0" border="0"/></td>
<td bgcolor="#023264" height="1"><img src="/images/void.gif" width="1" \
height="1" vspace="0" hspace="0" border="0"/></td>
<td bgcolor="#023264" width="1" height="1"><img src="/images/void.gif" \
width="1" height="1" vspace="0" hspace="0" border="0"/></td> </tr>
<tr>
<td bgcolor="#023264" width="1"><img src="/images/void.gif" width="1" \
height="1" vspace="0" hspace="0" border="0"/></td> <td bgcolor="#ffffff"><pre>
base-dir ===> BaseDir
Base-dir ===> BaseDir
baseDir ===> BaseDir
BaseDir ===> BaseDir</pre></td>
<td bgcolor="#023264" width="1"><img src="/images/void.gif" width="1" \
height="1" vspace="0" hspace="0" border="0"/></td> </tr>
<tr>
<td bgcolor="#023264" width="1" height="1"><img src="/images/void.gif" \
width="1" height="1" vspace="0" hspace="0" border="0"/></td>
<td bgcolor="#023264" height="1"><img src="/images/void.gif" width="1" \
height="1" vspace="0" hspace="0" border="0"/></td>
<td bgcolor="#023264" width="1" height="1"><img src="/images/void.gif" \
width="1" height="1" vspace="0" hspace="0" border="0"/></td> </tr>
</table>
</div>
<p><i>NOTE: We should really resolve this and \
either disallow '-' characters or disallow uppercase or something. (PD)</i></p>
</blockquote>
</td></tr>
</table>
<table border="0" cellspacing="0" cellpadding="2" width="100%">
<tr><td bgcolor="#525D76">
<font color="#ffffff" face="arial,helvetica,sanserif">
<a name="Resolving Values"><strong>Resolving Values</strong></a>
</font>
</td></tr>
<tr><td>
<blockquote>
<p>The first stage of mapping the XML representation to the \
task
is resolving all text data. The text data that needs to be resolved
include the values of attributes and the content.</p>
<p>Resolution consists of expanding any property \
references in the text
data. Property references are identified as starting with the token
"${" and finishing with another "}" token. The text
in between is the name of a property. The value of the property \
replaces
the sequence of text starting with the "${" token and finishing
with the "}" token.</p>
<p>Note that the value of the property may not be a \
string. If the text data
contains text (or other property references) to either side of the \
property
reference then it must be <a href="converter.html">converted</a> to a
String.</p>
</blockquote>
</td></tr>
</table>
<table border="0" cellspacing="0" cellpadding="2" width="100%">
<tr><td bgcolor="#525D76">
<font color="#ffffff" face="arial,helvetica,sanserif">
<a name="Modeller"><strong>Modeller</strong></a>
</font>
</td></tr>
<tr><td>
<blockquote>
<p>Currently the representation of object are stored in a \
hierarchial
tree of <code>org.apache.myrmidon.api.metadata.ModelElement</code>
objects. Each ModelElement has a number of attributes and can have
either content or sub-elements.</p>
<p>In most cases it is the responsibility of the \
runtime to map
the ModelElement onto an object. However in some cases it may be useful \
for the object to get access to it's own model and for it to explicitly
manage it's own configuration. In this case the object should implement
the <code>org.apache.myrmidon.api.metadata.Modeller</code> interface
which will provide the mechanism for the object to receive its own
representation and configure itself.</p>
<p>Note that the Modeller mechanism should be \
avoided if possible
as it adds considerable complexity to the implementing object.</p>
</blockquote>
</td></tr>
</table>
<table border="0" cellspacing="0" cellpadding="2" width="100%">
<tr><td bgcolor="#525D76">
<font color="#ffffff" face="arial,helvetica,sanserif">
<a name="Attributes"><strong>Attributes</strong></a>
</font>
</td></tr>
<tr><td>
<blockquote>
<p>To map an XML attribute on to a Java object, the name of \
the
attribute is mapped to a java name and prefixed with the string
"set". The resulting string is then used to look up a
method with a single parameter.</p>
<p>For example, for the attribute "world" would \
result in a lookup of a method named "setWorld" with a single
parameter.</p>
<p>If multiple methods were matched during the \
lookup then an
exception is thrown indicating ambiguity. Theres is an exception
to this rule that allows 2 methods to be matched if one of the
methods takes a <code>java.lang.String</code> parameter. The method
that has the <code>java.lang.String</code> parameter is ignored and
the other method would be chosen. This exception is allowed as it is
common practice for a task to evolve from String parameters to more
strongly typed parameters.</p>
<p>The resolved text data of the attribute must be
<a href="converter.html">converted</a> to the type of the matched
methods parameter. For example, if the "setWorld" method
took a parameter of type <code>java.io.File</code> then the resolved
text data must be converted into a <code>java.io.File</code>. The
conversion is done by the Converter architecture that is more fully
described in the <a href="converter.html">Converter HOWTO</a>.</p>
<p>After the value is converted to the correct type \
the method is invoked with the converted value.</p>
</blockquote>
</td></tr>
</table>
<table border="0" cellspacing="0" cellpadding="2" width="100%">
<tr><td bgcolor="#525D76">
<font color="#ffffff" face="arial,helvetica,sanserif">
<a name="Content"><strong>Content</strong></a>
</font>
</td></tr>
<tr><td>
<blockquote>
<p>The XML representation of object can have either have \
nested
elements or nested text (content) but not both. To add the content
to an object a method named "content" with one parameter is looked
up. The resolved text data for content is then
<a href="converter.html">converted</a> to the type of the parameter
and passed in via the method.</p>
</blockquote>
</td></tr>
</table>
<table border="0" cellspacing="0" cellpadding="2" width="100%">
<tr><td bgcolor="#525D76">
<font color="#ffffff" face="arial,helvetica,sanserif">
<a name="Element"><strong>Element</strong></a>
</font>
</td></tr>
<tr><td>
<blockquote>
<p>Mapping an ModelElement onto a java object is a series \
of steps. If the ModelElement name ends with the string "-ref" then
it is treated as a reference element - see the <em>Referrenced
Elements</em> section. Otherwise, the element is first attempted to
be mapped as a <em>Named Element</em> and if no match is found via
that method it tries to treat the element as a <em>Typed \
Element</em>.</p>
<table border="0" cellspacing="0" cellpadding="2" \
width="100%"> <tr><td bgcolor="#828DA6">
<font color="#ffffff" face="arial,helvetica,sanserif">
<a name="Named Elements"><strong>Named Elements</strong></a>
</font>
</td></tr>
<tr><td>
<blockquote>
<p>To map a named ModelElement on to a Java object, the \
name of
the element is mapped to a java name and prefixed with the string
"add". The resulting string is then used to look up a
method with a single parameter.</p>
<p>For example, for the attribute "geometry" would \
result in a lookup of a method named "addGeometry" with a single
parameter. If multiple methods were matched during the lookup then an
exception is thrown indicating ambiguity. If no methods were found that
match name then skip down to configuring "typed" elements.</p>
<p>The type of the methods single parameter is then \
examined to determine
what happens next. There are two valid situations, if neither of these \
are satisfied, then an exception is thrown.</p>
<ul>
<li>The parameters type is \
<code>org.apache.myrmidon.api.metadata.ModelElement</code></li> <li>The parameters \
type is a concrete class</li> </ul>
<p>1. If the parameter has a type of \
<code>org.apache.myrmidon.api.metadata.ModelElement</code>
then the un-modified model representation of element is passed to \
object by invoking the adder method.</p>
<p>2. If the parameters type is concrete then an \
instance of the parameter is
instantiated using the default constructor. This created object is then \
configured
in the same manner as task using the elements representation as the \
model. After
the object is configured it is passed into object by invoking the adder \
method.</p> </blockquote>
</td></tr>
</table>
<table border="0" cellspacing="0" cellpadding="2" \
width="100%"> <tr><td bgcolor="#828DA6">
<font color="#ffffff" face="arial,helvetica,sanserif">
<a name="Referrenced Elements"><strong>Referrenced Elements</strong></a>
</font>
</td></tr>
<tr><td>
<blockquote>
<p>A referenced element is one that has a name ending in
"-ref" and has a single attribute "name"
and no content or child elements.</p>
<p>The value of the "name" attribute is the name of \
a property.
The value of this property is retrieved from the TaskContext.</p>
<p>Like with <em>Named Elements</em> the name of \
the element (minus
the "-ref" part) is mapped to a java name and prefixed with the string
"add". The resulting string is then used to look up a
method with a single parameter. If multiple methods were matched during \
the lookup then an exception is thrown indicating ambiguity.</p>
<p>The value retrieved from the TaskContext is then \
converted to the type
of the methods parameter and the add method is invoked with the \
converted value.</p>
<p>An example usage is the following;</p>
<div align="left">
<table cellspacing="4" cellpadding="0" border="0">
<tr>
<td bgcolor="#023264" width="1" height="1"><img src="/images/void.gif" \
width="1" height="1" vspace="0" hspace="0" border="0"/></td>
<td bgcolor="#023264" height="1"><img src="/images/void.gif" width="1" \
height="1" vspace="0" hspace="0" border="0"/></td>
<td bgcolor="#023264" width="1" height="1"><img src="/images/void.gif" \
width="1" height="1" vspace="0" hspace="0" border="0"/></td> </tr>
<tr>
<td bgcolor="#023264" width="1"><img src="/images/void.gif" width="1" \
height="1" vspace="0" hspace="0" border="0"/></td> <td bgcolor="#ffffff"><pre>
<my-task ...>
<classpath-ref name="project.class.path"/>
</my-task>
</pre></td>
<td bgcolor="#023264" width="1"><img src="/images/void.gif" width="1" \
height="1" vspace="0" hspace="0" border="0"/></td> </tr>
<tr>
<td bgcolor="#023264" width="1" height="1"><img src="/images/void.gif" \
width="1" height="1" vspace="0" hspace="0" border="0"/></td>
<td bgcolor="#023264" height="1"><img src="/images/void.gif" width="1" \
height="1" vspace="0" hspace="0" border="0"/></td>
<td bgcolor="#023264" width="1" height="1"><img src="/images/void.gif" \
width="1" height="1" vspace="0" hspace="0" border="0"/></td> </tr>
</table>
</div>
</blockquote>
</td></tr>
</table>
<table border="0" cellspacing="0" cellpadding="2" \
width="100%"> <tr><td bgcolor="#828DA6">
<font color="#ffffff" face="arial,helvetica,sanserif">
<a name="Typed Elements"><strong>Typed Elements</strong></a>
</font>
</td></tr>
<tr><td>
<blockquote>
<p>"Typed" elements can also be added to an object. A typed \
element
is one in which the name of the element actually refers to a type \
rather than the name of the adder to call.</p>
<p>For example, you may wish to allow a task to add \
arbitrary instances of the
Condition role to a task. So instead of adding methods such as
<code>addAnd(AndCondition)</code>, <code>addOr(OrCondition)</code> and
<code>addXor(XorCondition)</code> you can instead add a single method
<code>add(Condition)</code>. This vastly simplifies the amount of work \
required
to write tasks that take conditions. More importantly it allows \
end-users to
extend the number of elements selected by task. For instance if the \
user wanted
a "nand" condition they could write the Nand type use it in their build
file. For a discussion on roles and types see the <a \
href="types.html">Types HOWTO</a>.</p>
<p>To use a Typed adder there must be a single \
method named "add" that
has a single parameter. The parameter <em>MUST</em> be an abstract \
interface and
must be registered as a role. The name of the element is then used to \
lookup the
a type in the TypeManager with a role matching the interface name.</p>
<p>For example if an element named "nand" was added \
to an object that had
an adder with the signature <code>void add( Condition condition \
)</code> then
the type named "nand" in the role "Condition" would be looked up.
An instance of the type would then be created using the default \
constructor and the
created object would be configured and then adder to object using \
adder.</p> </blockquote>
</td></tr>
</table>
</blockquote>
</td></tr>
</table>
</td>
</tr>
<!-- FOOTER -->
<tr><td colspan="2">
<hr noshade="" size="1"/>
</td></tr>
<tr><td colspan="2">
<div align="center"><font color="#525D76" size="-1"><em>
Copyright © 2000-2002, Apache Software Foundation
</em></font></div>
</td></tr>
</table>
</body>
</html>
<!-- end the processing -->
1.1 jakarta-ant/proposal/myrmidon/src/xdocs/configuring.xml
Index: configuring.xml
===================================================================
<?xml version="1.0"?>
<document>
<properties>
<title>On Task Configuring in Ant2</title>
<author email="peter@apache.org">Peter Donald</author>
</properties>
<body>
<section name="Introduction">
<p>This section will describe in detail the mechanism via which tasks \
are
configured. Configuration is the name given to the stage in tasks
lifecycle via which the XML representation is mapped onto the task
object.</p>
</section>
<section name="Names">
<p>When mapping the XML representation on to the task object you
need to be able map the names as they appear in the XML to the
names as they appear in the Java code. The process is for generating
a java name from the xml name is as follows.</p>
<ol>
<li>Capitalize the first character of name.</li>
<li>Find any '-' characters in XML name and remove character and
capitalize the following letter. (And there must be a following
letter)</li>
</ol>
<p>Some example mappings;</p>
<source>
my-name ===> MyName
aString ===> AString
Basedir ===> Basedir
baseDir ===> BaseDir
url ===> Url</source>
<p>Note that the above transformation is lossy and as such the
following XML names all map to the same Java name. The ant1.x mapping
is similarly lossy and in practice this has not been an issue.</p>
<source>
base-dir ===> BaseDir
Base-dir ===> BaseDir
baseDir ===> BaseDir
BaseDir ===> BaseDir</source>
<p><i>NOTE: We should really resolve this and either disallow '-' \
characters or disallow uppercase or something. (PD)</i></p>
</section>
<section name="Resolving Values">
<p>The first stage of mapping the XML representation to the task
is resolving all text data. The text data that needs to be resolved
include the values of attributes and the content.</p>
<p>Resolution consists of expanding any property references in the text
data. Property references are identified as starting with the token
"${" and finishing with another "}" token. The text \
in between is the name of a property. The value of the property \
replaces
the sequence of text starting with the "${" token and \
finishing with the "}" token.</p>
<p>Note that the value of the property may not be a string. If the text \
data
contains text (or other property references) to either side of the \
property
reference then it must be <a href="converter.html">converted</a> to a
String.</p>
</section>
<section name="Modeller">
<p>Currently the representation of object are stored in a hierarchial
tree of <code>org.apache.myrmidon.api.metadata.ModelElement</code>
objects. Each ModelElement has a number of attributes and can have
either content or sub-elements.</p>
<p>In most cases it is the responsibility of the runtime to map
the ModelElement onto an object. However in some cases it may be useful \
for the object to get access to it's own model and for it to explicitly
manage it's own configuration. In this case the object should implement
the <code>org.apache.myrmidon.api.metadata.Modeller</code> interface
which will provide the mechanism for the object to receive its own
representation and configure itself.</p>
<p>Note that the Modeller mechanism should be avoided if possible
as it adds considerable complexity to the implementing object.</p>
</section>
<section name="Attributes">
<p>To map an XML attribute on to a Java object, the name of the
attribute is mapped to a java name and prefixed with the string
"set". The resulting string is then used to look up a
method with a single parameter.</p>
<p>For example, for the attribute "world" would result
in a lookup of a method named "setWorld" with a single
parameter.</p>
<p>If multiple methods were matched during the lookup then an
exception is thrown indicating ambiguity. Theres is an exception
to this rule that allows 2 methods to be matched if one of the
methods takes a <code>java.lang.String</code> parameter. The method
that has the <code>java.lang.String</code> parameter is ignored and
the other method would be chosen. This exception is allowed as it is
common practice for a task to evolve from String parameters to more
strongly typed parameters.</p>
<p>The resolved text data of the attribute must be
<a href="converter.html">converted</a> to the type of the matched
methods parameter. For example, if the "setWorld" method
took a parameter of type <code>java.io.File</code> then the resolved
text data must be converted into a <code>java.io.File</code>. The
conversion is done by the Converter architecture that is more fully
described in the <a href="converter.html">Converter HOWTO</a>.</p>
<p>After the value is converted to the correct type the method is
invoked with the converted value.</p>
</section>
<section name="Content">
<p>The XML representation of object can have either have nested
elements or nested text (content) but not both. To add the content
to an object a method named "content" with one parameter is looked
up. The resolved text data for content is then
<a href="converter.html">converted</a> to the type of the parameter
and passed in via the method.</p>
</section>
<section name="Element">
<p>Mapping an ModelElement onto a java object is a series of steps.
If the ModelElement name ends with the string "-ref" then
it is treated as a reference element - see the <em>Referrenced
Elements</em> section. Otherwise, the element is first attempted to
be mapped as a <em>Named Element</em> and if no match is found via
that method it tries to treat the element as a <em>Typed \
Element</em>.</p> <subsection name="Named Elements">
<p>To map a named ModelElement on to a Java object, the name of
the element is mapped to a java name and prefixed with the string
"add". The resulting string is then used to look up a
method with a single parameter.</p>
<p>For example, for the attribute "geometry" would result
in a lookup of a method named "addGeometry" with a single
parameter. If multiple methods were matched during the lookup then an
exception is thrown indicating ambiguity. If no methods were found that
match name then skip down to configuring "typed" \
elements.</p>
<p>The type of the methods single parameter is then examined to \
determine
what happens next. There are two valid situations, if neither of these \
are satisfied, then an exception is thrown.</p>
<ul>
<li>The parameters type is \
<code>org.apache.myrmidon.api.metadata.ModelElement</code></li> <li>The parameters \
type is a concrete class</li> </ul>
<p>1. If the parameter has a type of \
<code>org.apache.myrmidon.api.metadata.ModelElement</code>
then the un-modified model representation of element is passed to \
object by invoking the adder method.</p>
<p>2. If the parameters type is concrete then an instance of the \
parameter is
instantiated using the default constructor. This created object is then \
configured
in the same manner as task using the elements representation as the \
model. After
the object is configured it is passed into object by invoking the adder \
method.</p> </subsection>
<subsection name="Referrenced Elements">
<p>A referenced element is one that has a name ending in
"-ref" and has a single attribute "name"
and no content or child elements.</p>
<p>The value of the "name" attribute is the name of a \
property.
The value of this property is retrieved from the TaskContext.</p>
<p>Like with <em>Named Elements</em> the name of the element (minus
the "-ref" part) is mapped to a java name and prefixed with \
the string
"add". The resulting string is then used to look up a
method with a single parameter. If multiple methods were matched during \
the lookup then an exception is thrown indicating ambiguity.</p>
<p>The value retrieved from the TaskContext is then converted to the \
type
of the methods parameter and the add method is invoked with the \
converted value.</p>
<p>An example usage is the following;</p>
<source><![CDATA[
<my-task ...>
<classpath-ref name="project.class.path"/>
</my-task>
]]></source>
</subsection>
<subsection name="Typed Elements">
<p>"Typed" elements can also be added to an object. A typed \
element
is one in which the name of the element actually refers to a type \
rather than the name of the adder to call.</p>
<p>For example, you may wish to allow a task to add arbitrary instances \
of the
Condition role to a task. So instead of adding methods such as
<code>addAnd(AndCondition)</code>, <code>addOr(OrCondition)</code> and
<code>addXor(XorCondition)</code> you can instead add a single method
<code>add(Condition)</code>. This vastly simplifies the amount of work \
required
to write tasks that take conditions. More importantly it allows \
end-users to
extend the number of elements selected by task. For instance if the \
user wanted
a "nand" condition they could write the Nand type use it in \
their build
file. For a discussion on roles and types see the <a \
href="types.html">Types HOWTO</a>.</p>
<p>To use a Typed adder there must be a single method named \
"add" that
has a single parameter. The parameter <em>MUST</em> be an abstract \
interface and
must be registered as a role. The name of the element is then used to \
lookup the
a type in the TypeManager with a role matching the interface name.</p>
<p>For example if an element named "nand" was added to an \
object that had
an adder with the signature <code>void add( Condition condition \
)</code> then
the type named "nand" in the role "Condition" would \
be looked up.
An instance of the type would then be created using the default \
constructor and the
created object would be configured and then adder to object using \
adder.</p>
</subsection>
</section>
</body>
</document>
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