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extract and expand property documentation 

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@828198 13f79535-47bb-0310-9956-ffa450edef68
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Stefan Bodewig 16 years ago
parent
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      docs/manual/CoreTasks/property.html
  2. +1
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  3. +1
    -0
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  4. +326
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      docs/manual/properties.html
  5. +2
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  6. +2
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  7. +20
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  8. +2
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@@ -57,7 +57,7 @@ instance.</p>
properties. These references are resolved at the time these properties are set.
This also holds for properties loaded from a property file.</p>
<p>A list of predefined properties can be found <a
href="../using.html#built-in-props">here</a>.</p>
href="../properties.html#built-in-props">here</a>.</p>
<p>Since Ant 1.7.1 it is possible to load properties defined in xml
according to <a href="http://java.sun.com/dtd/properties.dtd">Suns DTD</a>,
if Java5+ is present. For this the name of the file, resource or url has


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@@ -31,7 +31,7 @@
<b>(b)</b> (hopefully more often) install one or more PropertyHelper Delegates into the
PropertyHelper active on the current Project. This is somewhat advanced Ant usage and
assumes a working familiarity with the modern Ant APIs. See the description of Ant's
<a href="../using.html#propertyHelper">Property Helper</a> for more information.
<a href="../properties.html#propertyHelper">Property Helper</a> for more information.
<b>Since Ant 1.8.0</b></p>

<h3>Parameters specified as nested elements</h3>


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@@ -28,6 +28,7 @@
<h2><a href="toc.html" target="navFrame">Table of Contents</a></h2>

<h3>Concepts</h3>
<a href="properties.html">Properties and PropertyHelpers</a>
<a href="clonevm.html">ant.build.clonevm</a><br/>
<a href="sysclasspath.html">build.sysclasspath</a><br/>
<a href="javacprops.html">Ant properties controlling javac</a><br/>


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@@ -0,0 +1,326 @@
<!--
Licensed to the Apache Software Foundation (ASF) under one or more
contributor license agreements. See the NOTICE file distributed with
this work for additional information regarding copyright ownership.
The ASF licenses this file to You under the Apache License, Version 2.0
(the "License"); you may not use this file except in compliance with
the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
-->
<html>

<head>
<meta http-equiv="Content-Language" content="en-us"/>
<link rel="stylesheet" type="text/css" href="stylesheets/style.css"/>
<title>Properties and PropertyHelpers</title>
</head>

<body>
<h1>Properties</h1>

<p>Properties are key-value-pairs where Ant tries to
expand <code>${key}</code> to <code>value</code> at runtime.</p>

<p>There are many tasks that can set properties, the most common one
is the <a href="CoreTasks/property.html">property</a> task. In
addition properties can be defined
via <a href="running.html">command line arguments</a> or similar
mechanisms from outside of Ant.</p>

<p>Normally property values can not be changed, once a property is
set, most tasks will not allow its value to be modified. In
general properties are of global scope, i.e. once they have been
defined they are available for any task or target invoked
subsequently - it is not possible to set a property in a child
build process created via
the <a href="CoreTasks/ant.html">ant</a>, antcall or subant tasks
and make it available to the calling build process, though.</p>

<p>Starting with Ant 1.8.0
the <a href="CoreTasks/local.html">local</a> task can be used to
create properties that are locally scoped to a target or
a <a href="CoreTasks/sequential.html">sequential</a> element like
the one of the <a href="CoreTasks/macrodef.html">macrodef</a>
task.</p>

<a name="built-in-props"><h2>Built-in Properties</h2></a>

<p>Ant provides access to all system properties as if they had been
defined using a <code>&lt;property&gt;</code> task. For
example, <code>${os.name}</code> expands to the name of the
operating system.</p>
<p>For a list of system properties see
<a href="http://java.sun.com/j2se/1.3/docs/api/java/lang/System.html#getProperties()">the Javadoc of System.getProperties</a>.
</p>

<p>In addition, Ant has some built-in properties:</p>
<pre>
basedir the absolute path of the project's basedir (as set
with the basedir attribute of <a href="using.html#projects">&lt;project&gt;</a>).
ant.file the absolute path of the buildfile.
ant.version the version of Ant
ant.project.name the name of the project that is currently executing;
it is set in the name attribute of &lt;project&gt;.
ant.project.default-target
the name of the currently executing project's
default target; it is set via the default
attribute of &lt;project&gt;.
ant.project.invoked-targets
a comma separated list of the targets that have
been specified on the command line (the IDE,
an &lt;ant&gt; task ...) when invoking the current
project.
ant.java.version the JVM version Ant detected; currently it can hold
the values &quot;1.2&quot;, &quot;1.3&quot;,
&quot;1.4&quot;, &quot;1.5&quot; and &quot;1.6&quot;.
ant.core.lib the absolute path of the <code>ant.jar</code> file.
</pre>

<p>There is also another property, but this is set by the launcher
script and therefore maybe not set inside IDEs:</p>
<pre>
ant.home home directory of Ant
</pre>

<p>The following property is only set if Ant is started via the
Launcher class (which means it may not be set inside IDEs
either):</p>
<pre>
ant.library.dir the directory that has been used to load Ant's
jars from. In most cases this is ANT_HOME/lib.
</pre>

<a name="propertyHelper"><h1>PropertyHelpers</h1></a>

<p>Ant's property handling is accomplished by an instance of
<code>org.apache.tools.ant.PropertyHelper</code> associated with
the current Project. You can learn more about this class by
examining Ant's Java API. In Ant 1.8 the PropertyHelper class was
much reworked and now itself employs a number of helper classes
(actually instances of
the <code>org.apache.tools.ant.PropertyHelper$Delegate</code>
marker interface) to take care of discrete tasks such as property
setting, retrieval, parsing, etc. This makes Ant's property
handling highly extensible; also of interest is the
new <a href="CoreTasks/propertyhelper.html">propertyhelper</a>
task used to manipulate the PropertyHelper and its delegates from
the context of the Ant buildfile.

<p>There are three sub-interfaces of <code>Delegate</code> that may be
useful to implement.</p>

<ul>
<li><code>org.apache.tools.ant.property.PropertyExpander</code> is
responsible for finding the property name inside a string in the
first place (the default extracts <code>foo</code>
from <code>${foo}</code>).

<p>This is the interface you'd implement if you wanted to invent
your own property syntax - or allow nested property expansions
since the default implementation doesn't balance braces
(see <a href="http://svn.apache.org/viewvc/ant/antlibs/props/trunk/src/main/org/apache/ant/props/NestedPropertyExpander.java?view=log"><code>NestedPropertyExpander</code>
in the "props" Antlib</a> for an example).</p>
</li>

<li><code>org.apache.tools.ant.PropertyHelper$PropertyEvaluator</code>
is used to expand <code>${some-string}</code> into
an <code>Object</code>.

<p>This is the interface you'd implement if you want to provide
your own storage independent of Ant's project instance - the
interface represents the reading end. An example for this
would
be <code>org.apache.tools.ant.property.LocalProperties</code>
which implements storage
for <a href="CoreTasks/local.html">local properties</a>.</p>

<p>Another reason to implement this interface is if you wanted
to provide your own "property protocol" like
expanding <code>toString:foo</code> by looking up the project
reference foo and invoking <code>toString()</code> on it
(which is already implemented in Ant, see below).</p>
</li>

<li><code>org.apache.tools.ant.PropertyHelper$PropertySetter</code>
is responsible for setting properties.

<p>This is the interface you'd implement if you want to provide
your own storage independent of Ant's project instance - the
interface represents the reading end. An example for this
would
be <code>org.apache.tools.ant.property.LocalProperties</code>
which implements storage
for <a href="CoreTasks/local.html">local properties</a>.</p>
</li>

</ul>

<p>The default <code>PropertyExpander</code> looks similar to:</p>

<pre>
public class DefaultExpander implements PropertyExpander {
public String parsePropertyName(String s, ParsePosition pos,
ParseNextProperty notUsed) {
int index = pos.getIndex();
if (s.indexOf("${", index) == index) {
int end = s.indexOf('}', index);
if (end < 0) {
throw new BuildException("Syntax error in property: " + s);
}
int start = index + 2;
pos.setIndex(end + 1);
return s.substring(start, end);
}
return null;
}
}
</pre>

<p>The logic that replaces <code>${toString:some-id}</code> with the
stringified representation of the object with
id <code>some-id</code> inside the current build is contained in a
PropertyEvaluator similar to the following code:</p>

<pre>
public class ToStringEvaluator implements PropertyHelper.PropertyEvaluator {
private static final String prefix = "toString:";
public Object evaluate(String property, PropertyHelper propertyHelper) {
Object o = null;
if (property.startsWith(prefix) && propertyHelper.getProject() != null) {
o = propertyHelper.getProject().getReference(property.substring(prefix.length()));
}
return o == null ? null : o.toString();
}
}
</pre>


<h1>Property Expansion</h1>

<p>When Ant encounters a construct <code>${some-text}</code> the
exact parsing semantics are subject to the configured property
helper delegates.</p>

<h2><code>$$</code> Expansion</h2>

<p>In its default configuration Ant will expand the
text <code>$$</code> to a single <code>$</code> and suppress the
normal property expansion mechanism for the text immediately
following it, i.e. <code>$${key}</code> expands
to <code>${key}</code> and not <code>value</code> even though a
property named <code>key</code> was defined and had the
value <code>value</code>. This can be used to escape
literal <code>$</code> characters and is useful in constructs that
only look like property expansions or when you want to provide
diagnostic output like in</p>

<pre> &lt;echo&gt;$${builddir}=${builddir}&lt;/echo&gt;</pre>

<p>which will echo this message:</p>

<pre> ${builddir}=build/classes</pre>

<p>if the property <code>builddir</code> has the
value <code>build/classes</code>.</p>
<p>In order to maintain backward compatibility with older Ant
releases, a single '$' character encountered apart from a
property-like construct (including a matched pair of french
braces) will be interpreted literally; that is, as '$'. The
"correct" way to specify this literal character, however, is by
using the escaping mechanism unconditionally, so that "$$" is
obtained by specifying "$$$$". Mixing the two approaches yields
unpredictable results, as "$$$" results in "$$".</p>

<h2>Nesting of Braces</h2>

<p>In its default configuration Ant will not try to ballance braces
in property expansions, it will only consume the text up to the
first closing brace when creating a property name. I.e. when
expanding something like <code>${a${b}}</code> it will be
translated into two parts:</p>

<ol>
<li>the expansion of property <code>a${b</code> - likely nothing
useful.</li>
<li>the literal text <code>}</code> resulting from the second
closing brace</li>
</ol>

<p>This means you can't use easily expand properties whose names are
given by properties, but there
are <a href="http://ant.apache.org/faq.html#propertyvalue-as-name-for-property">some
workarounds</a> for older versions of Ant. With Ant 1.8.0 and the
<a href="http://ant.apache.org/antlib/props/">the props Antlib</a>
you can configure Ant to use
the <code>NestedPropertyExpander</code> defined there if you need
such a feature.</p>

<h2>Expanding a "Property Name"</h2>

<p>In its most simple form <code>${key}</code> is supposed to look
up a property named <code>key</code> and expand to the value of
the property. Additional <code>PropertyEvaluator</code>s may
result in a different interpretation of <code>key</code>,
though.</p>

<p>The <a href="http://ant.apache.org/antlibs/props/">props
Antlib</a> provides a few interesting evaluators but there are
also a few built-in ones.</p>

<a name="toString"><h3>Getting the value of a Reference with
${toString:}</h3></a>

<p>Any Ant type which has been declared with a reference can also
its string value extracted by using the <code>${toString:}</code>
operation, with the name of the reference listed after
the <code>toString:</code> text. The <code>toString()</code>
method of the Java class instance that is referenced is invoked
-all built in types strive to produce useful and relevant output
in such an instance.</p>

<p>For example, here is how to get a listing of the files in a fileset,<p>

<pre>
&lt;fileset id=&quot;sourcefiles&quot; dir=&quot;src&quot; includes=&quot;**/*.java&quot; /&gt;
&lt;echo&gt; sourcefiles = ${toString:sourcefiles} &lt;/echo&gt;
</pre>

<p>There is no guarantee that external types provide meaningful
information in such a situation</p>

<h3><a name="ant.refid">Getting the value of a Reference with
${ant.refid:}</a></h3>

<p>Any Ant type which has been declared with a reference can also be
used as a property by using the <code>${ant.refid:}</code>
operation, with the name of the reference listed after
the <code>ant.refid:</code> text. The difference between this
operation and <a href="#toString"><code>${toString:}</code></a> is
that <code>${ant.refid:}</code> will expand to the referenced
object itself. In most circumstances the toString method will be
invoked anyway, for example if the <code>${ant.refid:}</code> is
surrounded by other text.</p>

<p>This syntax is most useful when using a task with attribute
setters that accept objects other than String. For example if the
setter accepts a Resource object as in</p>
<pre>
public void setAttr(Resource r) { ... }
</pre>

<p>then the syntax can be used to pass in resource subclasses
preciously defined as references like</p>
<pre>
&lt;url url="http://ant.apache.org/" id="anturl"/&gt;
&lt;my:task attr="${ant.refid:anturl}"/&gt;
</pre>

</body>

+ 2
- 2
docs/manual/tutorial-tasks-filesets-properties.html View File

@@ -317,7 +317,7 @@ whithout being complex :-)</p>

<p>The test case uses the ant property <i>ant.home</i> as reference. This property is set by the
<tt>Launcher</tt> class which starts ant. We can use that property in our buildfiles as a
<a href="using.html#built-in-props">build-in property [3]</a>. But if we create a new ant
<a href="properties.html#built-in-props">build-in property [3]</a>. But if we create a new ant
environment we have to set that value for our own. And we use the <code>&lt;junit&gt;</code> task in fork-mode.
Therefore we have do modify our buildfile:
<pre class="code">
@@ -952,7 +952,7 @@ Now the new task is uploaded into the bug database.
<h2><a name="resources">Resources</a></h2>
&nbsp;&nbsp;[1] <a href="tutorial-writing-tasks.html">tutorial-writing-tasks.html</a><br>
&nbsp;&nbsp;[2] <a href="tutorial-tasks-filesets-properties.zip">tutorial-tasks-filesets-properties.zip</a><br>
&nbsp;&nbsp;[3] <a href="using.html#built-in-props">using.html#built-in-props</a><br>
&nbsp;&nbsp;[3] <a href="properties.html#built-in-props">properties.html#built-in-props</a><br>
&nbsp;&nbsp;[4] <a href="http://ant-contrib.sourceforge.net/">http://ant-contrib.sourceforge.net/</a><br>
&nbsp;&nbsp;[5] <a href="CoreTasks/java.html">CoreTasks/java.html</a><br>
&nbsp;&nbsp;[6] <a href="http://ant.apache.org/ant_task_guidelines.html">http://ant.apache.org/ant_task_guidelines.html</a><br>


+ 2
- 2
docs/manual/tutorial-writing-tasks.html View File

@@ -102,7 +102,7 @@ the execution of some steps bofore. So the refactored code is:
&lt;/project&gt;
</pre>
<i>ant.project.name</i> is one of the
<a href="http://ant.apache.org/manual/using.html#built-in-props" target="_blank">
<a href="http://ant.apache.org/manual/properties.html#built-in-props" target="_blank">
build-in properties [1]</a> of Ant.


@@ -755,7 +755,7 @@ The last sources and the buildfile are also available


Used Links:<br>
&nbsp;&nbsp;[1] <a href="http://ant.apache.org/manual/using.html#built-in-props">http://ant.apache.org/manual/using.html#built-in-props</a><br>
&nbsp;&nbsp;[1] <a href="http://ant.apache.org/manual/properties.html#built-in-props">http://ant.apache.org/manual/properties.html#built-in-props</a><br>
&nbsp;&nbsp;[2] <a href="http://ant.apache.org/manual/CoreTasks/taskdef.html">http://ant.apache.org/manual/CoreTasks/taskdef.html</a><br>
&nbsp;&nbsp;[3] <a href="http://ant.apache.org/manual/develop.html#set-magic">http://ant.apache.org/manual/develop.html#set-magic</a><br>
&nbsp;&nbsp;[4] <a href="http://ant.apache.org/manual/develop.html#nested-elements">http://ant.apache.org/manual/develop.html#nested-elements</a><br>


+ 20
- 209
docs/manual/using.html View File

@@ -267,170 +267,27 @@ task instances at all, only proxies.
</p>

<h3><a name="properties">Properties</a></h3>
<p>A project can have a set of properties. These might be set in the buildfile
by the <a href="CoreTasks/property.html">property</a> task, or might be set outside Ant. A
property has a name and a value; the name is case-sensitive. Properties may be used in the value of
task attributes. This is done by placing the property name between
&quot;<code>${</code>&quot; and &quot;<code>}</code>&quot; in the
attribute value. For example,
if there is a &quot;builddir&quot; property with the value
&quot;build&quot;, then this could be used in an attribute like this:
<code>${builddir}/classes</code>.
This is resolved at run-time as <code>build/classes</code>.</p>
<p>In the event you should need to include this construct literally
(i.e. without property substitutions), simply "escape" the '$' character
by doubling it. To continue the previous example:
<pre> &lt;echo&gt;$${builddir}=${builddir}&lt;/echo&gt;</pre>
will echo this message:
<pre> ${builddir}=build/classes</pre></p>
<p>In order to maintain backward compatibility with older Ant releases,
a single '$' character encountered apart from a property-like construct
(including a matched pair of french braces) will be interpreted literally;
that is, as '$'. The "correct" way to specify this literal character,
however, is by using the escaping mechanism unconditionally, so that "$$"
is obtained by specifying "$$$$". Mixing the two approaches yields
unpredictable results, as "$$$" results in "$$".</p>

<h3><a name="built-in-props">Built-in Properties</a></h3>
<p>Ant provides access to all system properties as if they had been
defined using a <code>&lt;property&gt;</code> task.
For example, <code>${os.name}</code> expands to the
name of the operating system.</p>
<p>For a list of system properties see
<a href="http://java.sun.com/j2se/1.3/docs/api/java/lang/System.html#getProperties()">the Javadoc of System.getProperties</a>.
</p>
<p>In addition, Ant has some built-in properties:</p>
<pre>
basedir the absolute path of the project's basedir (as set
with the basedir attribute of <a href="#projects">&lt;project&gt;)</a>.
ant.file the absolute path of the buildfile.
ant.version the version of Ant
ant.project.name the name of the project that is currently executing;
it is set in the name attribute of &lt;project&gt;.
ant.project.default-target
the name of the currently executing project's
default target; it is set via the default
attribute of &lt;project&gt;.
ant.project.invoked-targets
a comma separated list of the targets that have
been specified on the command line (the IDE,
an &lt;ant&gt; task ...) when invoking the current
project.
ant.java.version the JVM version Ant detected; currently it can hold
the values &quot;1.2&quot;, &quot;1.3&quot;,
&quot;1.4&quot;, &quot;1.5&quot; and &quot;1.6&quot;.
ant.core.lib the absolute path of the <code>ant.jar</code> file.
</pre>
<p>There is also another property, but this is set by the launcher script and therefore
maybe not set inside IDEs:</p>
<pre>
ant.home home directory of Ant
</pre>
<p>The following property is only set if Ant is started via the
Launcher class (which means it may not be set inside IDEs
either):</p>
<pre>
ant.library.dir the directory that has been used to load Ant's
jars from. In most cases this is ANT_HOME/lib.
</pre>

<a name="propertyHelper"><h3>Property Helpers</h3></a>
Ant's property handling is accomplished by an instance of
<code>org.apache.tools.ant.PropertyHelper</code> associated with the current Project.
You can learn more about this class by examining Ant's Java API. In Ant 1.8 the
PropertyHelper class was much reworked and now itself employs a number of helper
classes (actually instances of the <code>org.apache.tools.ant.PropertyHelper$Delegate</code>
marker interface) to take care of discrete tasks such as property setting, retrieval,
parsing, etc. This makes Ant's property handling highly extensible; also of interest is the
new <a href="CoreTasks/propertyhelper.html">propertyhelper</a> task used to manipulate the
PropertyHelper and its delegates from the context of the Ant buildfile.

<p>There are three sub-interfaces of <code>Delegate</code> that may be
useful to implement.</p>

<ul>
<li><code>org.apache.tools.ant.property.PropertyExpander</code> is
responsible for finding the property name inside a string in the
first place (the default extracts <code>foo</code>
from <code>${foo}</code>).

<p>This is the interface you'd implement if you wanted to invent
your own property syntax - or allow nested property expansions
since the default implementation doesn't balance braces
(see <a href="http://svn.apache.org/viewvc/ant/sandbox/antlibs/props/trunk/src/main/org/apache/ant/props/NestedPropertyExpander.java?view=log"><code>NestedPropertyExpander</code>
in the "props" Antlib in Ant's sandbox</a> for an
example).</p>
</li>

<li><code>org.apache.tools.ant.PropertyHelper$PropertyEvaluator</code>
is used to expand <code>${some-string}</code> into
an <code>Object</code>.

<p>This is the interface you'd implement if you want to provide
your own storage independent of Ant's project instance - the
interface represents the reading end. An example for this would
be <code>org.apache.tools.ant.property.LocalProperties</code>
which implements storage
for <a href="CoreTasks/local.html">local properties</a>.</p>

<p>Another reason to implement this interface is if you wanted to
provide your own "property protocol" like
expanding <code>toString:foo</code> by looking up the project
reference foo and invoking <code>toString()</code> on it (which
is already implemented in Ant, see below).</p>
</li>

<li><code>org.apache.tools.ant.PropertyHelper$PropertySetter</code>
is responsible for setting properties.

<p>This is the interface you'd implement if you want to provide
your own storage independent of Ant's project instance - the
interface represents the reading end. An example for this would
be <code>org.apache.tools.ant.property.LocalProperties</code>
which implements storage
for <a href="CoreTasks/local.html">local properties</a>.</p>
</li>

</ul>

<p>The default <code>PropertyExpander</code> looks similar to:</p>

<pre>
public class DefaultExpander implements PropertyExpander {
public String parsePropertyName(String s, ParsePosition pos,
ParseNextProperty notUsed) {
int index = pos.getIndex();
if (s.indexOf("${", index) == index) {
int end = s.indexOf('}', index);
if (end < 0) {
throw new BuildException("Syntax error in property: " + s);
}
int start = index + 2;
pos.setIndex(end + 1);
return s.substring(start, end);
}
return null;
}
}
</pre>

<p>The logic that replaces <code>${toString:some-id}</code> with the
stringified representation of the object with
id <code>some-id</code> inside the current build is contained in a
PropertyEvaluator similar to the following code:</p>

<pre>
public class ToStringEvaluator implements PropertyHelper.PropertyEvaluator {
private static final String prefix = "toString:";
public Object evaluate(String property, PropertyHelper propertyHelper) {
Object o = null;
if (property.startsWith(prefix) && propertyHelper.getProject() != null) {
o = propertyHelper.getProject().getReference(property.substring(prefix.length()));
}
return o == null ? null : o.toString();
}
}
</pre>
<p>Properties are an important way to customize a build process or
to just provide shortcuts for strings that are used repeatedly
inside a build file.</p>

<p>In its most simple form properties are defined in the build file
(for example by the <a href="CoreTasks/property.html">property</a>
task) or might be set outside Ant. A property has a name and a
value; the name is case-sensitive. Properties may be used in the
value of task attributes or in the nested text of tasks that support
them. This is done by placing the property name between
&quot;<code>${</code>&quot; and &quot;<code>}</code>&quot; in the
attribute value. For example, if there is a &quot;builddir&quot;
property with the value &quot;build&quot;, then this could be used
in an attribute like this: <code>${builddir}/classes</code>. This
is resolved at run-time as <code>build/classes</code>.</p>

<p>With Ant 1.8.0 property expansion has become much more powerful
than simple key value pairs, more details can be
found <a href="properties.html">in the concepts section</a> of this
manual.</p>

<a name="example"><h3>Example Buildfile</h3></a>
<pre>
@@ -784,52 +641,6 @@ implementation of the element upon which it is specified. Some tasks (the
deliberately assign a different meaning to <code>refid</code>.</p>


<h3><a name="toString">Getting the value of a Reference with ${toString:}</a></h3>
<p>
Any Ant type which has been declared with a reference can also its string
value extracted by using the <code>${toString:}</code> operation,
with the name of the reference listed after the <code>toString:</code> text.
The <code>toString()</code> method of the Java class instance that is
referenced is invoked -all built in types strive to produce useful and relevant
output in such an instance.
</p>
<p>
For example, here is how to get a listing of the files in a fileset,
<p>
<pre>
&lt;fileset id=&quot;sourcefiles&quot; dir=&quot;src&quot; includes=&quot;**/*.java&quot; /&gt;
&lt;echo&gt; sourcefiles = ${toString:sourcefiles} &lt;/echo&gt;
</pre>
<p>
There is no guarantee that external types provide meaningful information in such
a situation</p>

<h3><a name="ant.refid">Getting the value of a Reference with
${ant.refid:}</a></h3>

<p>Any Ant type which has been declared with a reference can also be
used as a property by using the <code>${ant.refid:}</code>
operation, with the name of the reference listed after
the <code>ant.refid:</code> text. The difference between this
operation and <a href="#toString"><code>${toString:}</code></a> is
that <code>${ant.refid:}</code> will expand to the referenced object
itself. In most circumstances the toString method will be invoked
anyway, for example if the <code>${ant.refid:}</code> is surrounded
by other text.</p>

<p>This syntax is most useful when using a task with attribute setters
that accept objects other than String. For example if the setter
accepts a Resource object as in</p>
<pre>
public void setAttr(Resource r) { ... }
</pre>
<p>then the syntax can be used to pass in resource subclasses
preciously defined as references like</p>
<pre>
&lt;url url="http://ant.apache.org/" id="anturl"/&gt;
&lt;my:task attr="${ant.refid:anturl}"/&gt;
</pre>

<h3><a name="external-tasks">Use of external tasks</a></h3>
Ant supports a plugin mechanism for using third party tasks. For using them you
have to do two steps:


+ 2
- 2
docs/manual/usinglist.html View File

@@ -34,8 +34,8 @@
<a href="using.html#targets">Targets</a><br/>
<a href="using.html#tasks">Tasks</a><br/>
<a href="using.html#properties">Properties</a><br/>
<a href="using.html#built-in-props">Built-in Properties</a><br/>
<a href="using.html#propertyHelper">Property Helpers</a><br />
<a href="properties.html#built-in-props">Built-in Properties</a><br/>
<a href="properties.html#propertyHelper">Property Helpers</a><br />
<a href="using.html#example">Example Buildfile</a><br/>
<a href="using.html#filters">Token Filters</a><br/>
<a href="using.html#path">Path-like Structures</a><br/>


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