2006-09-11 04:19:00 +00:00
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Licensed to the Apache Software Foundation (ASF) under one or more
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this work for additional information regarding copyright ownership.
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(the "License"); you may not use this file except in compliance with
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the License. You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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-->
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<html>
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<head>
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<meta http-equiv="Content-Language" content="en-us">
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<link rel="stylesheet" type="text/css" href="../stylesheets/style.css">
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<title>Custom Components</title>
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</head>
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<body>
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<h2>Custom Components</h2>
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<h3>Overview</h3>
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<p>
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Custom components are conditions, selectors, filters and other objects
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that are defined outside Apache Ant core.
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</p>
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<p>
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In Ant 1.6 custom conditions, selectors and filters has been
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overhauled.
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</p>
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<p>
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It is now possible to define custom conditions, selectors and filters
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that behave like Ant Core components. This is achieved by allowing
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datatypes defined in build scripts to be used as custom components if
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the class of the datatype is compatible, or has been adapted by an
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adapter class.
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</p>
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<p>
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The old methods of defining custom components are still supported.
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</p>
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<h3>Definition and use</h3>
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<p>
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A custom component is a normal Java class that implements a particular
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interface or extends a particular class, or has been adapted to the
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interface or class.
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</p>
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<p>
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It is exactly like writing
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a <a href="../develop.html#writingowntask">custom task</a>. One
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defines attributes and nested elements by writing <em>setter</em>
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methods and <em>add</em> methods.
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</p>
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<p>
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After the class has been written, it is added to the ant system by
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using <code><typedef></code>.
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</p>
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<h3 id="customconditions">Custom Conditions</h3>
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<p>
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Custom conditions are datatypes that
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implement <code>org.apache.tools.ant.taskdefs.condition.Condition</code>.
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For example a custom condition that returns true if a string is all
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upper case could be written as:
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</p>
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<pre>
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package com.mydomain;
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import org.apache.tools.ant.BuildException;
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import org.apache.tools.ant.taskdefs.condition.Condition;
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public class AllUpperCaseCondition implements Condition {
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private String value;
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// The setter for the "value" attribute
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public void setValue(String value) {
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this.value = value;
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}
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// This method evaluates the condition
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public boolean eval() {
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if (value == null) {
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throw new BuildException("value attribute is not set");
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}
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return value.toUpperCase().equals(value);
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}
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}</pre>
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<p>
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Adding the condition to the system is achieved as follows:
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</p>
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<pre>
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<typedef
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name="alluppercase"
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classname="com.mydomain.AllUpperCaseCondition"
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classpath="${mydomain.classes}"/></pre>
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<p>
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This condition can now be used wherever a Core Ant condition is used.
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</p>
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<pre>
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<condition property="allupper">
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<alluppercase value="THIS IS ALL UPPER CASE"/>
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</condition></pre>
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<h3 id="customselectors">Custom Selectors</h3>
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<p>
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Custom selectors are datatypes that
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implement <code>org.apache.tools.ant.types.selectors.FileSelector</code>.
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</p>
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<p>
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There is only one method required, <code>public boolean
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isSelected(File basedir, String filename, File file)</code>. It
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returns true or false depending on whether the given file should be
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selected or not.
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</p>
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<p>
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An example of a custom selection that selects filenames ending
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in <samp>.java</samp> would be:
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</p>
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<pre>
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package com.mydomain;
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import java.io.File;
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import org.apache.tools.ant.types.selectors.FileSelector;
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public class JavaSelector implements FileSelector {
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public boolean isSelected(File b, String filename, File f) {
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return filename.toLowerCase().endsWith(".java");
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}
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}</pre>
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<p>
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Adding the selector to the system is achieved as follows:
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</p>
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<pre>
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<typedef
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name="javaselector"
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classname="com.mydomain.JavaSelector"
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classpath="${mydomain.classes}"/></pre>
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<p>
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This selector can now be used wherever a Core Ant selector is used,
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for example:
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</p>
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<pre>
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<copy todir="to">
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<fileset dir="src">
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<javaselector/>
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</fileset>
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</copy></pre>
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<p>
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One may
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use <code>org.apache.tools.ant.types.selectors.BaseSelector</code>, a
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convenience class that provides reasonable default behaviour. It has
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some predefined behaviours you can take advantage of. Any time you
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encounter a problem when setting attributes or adding tags, you can
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call <code>setError(String errmsg)</code> and the class will know that
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there is a problem. Then, at the top of your <code>isSelected()</code>
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method call <code>validate()</code> and a BuildException will be
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thrown with the contents of your error
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message. The <code>validate()</code> method also gives you a last
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chance to check your settings for consistency because it
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calls <code>verifySettings()</code>. Override this method and
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call <code>setError()</code> within it if you detect any problems in
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how your selector is set up.
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</p>
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<p>
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To write custom selector containers one should
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extend <code>org.apache.tools.ant.types.selectors.BaseSelectorContainer</code>.
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Implement the <code>public boolean isSelected(File baseDir, String
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filename, File file)</code> method to do the right thing. Chances are
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you'll want to iterate over the selectors under you, so
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use <code>selectorElements()</code> to get an iterator that will do
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that.
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</p>
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<p>
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For example to create a selector container that will select files if a
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certain number of contained selectors select, one could write a
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selector as follows:
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</p>
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<pre>
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public class MatchNumberSelectors extends BaseSelectorContainer {
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private int number = -1;
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public void setNumber(int number) {
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this.number = number;
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}
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public void verifySettings() {
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if (number < 0) {
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throw new BuildException("Number attribute should be set");
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}
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}
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public boolean isSelected(File baseDir, String filename, File file) {
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validate();
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int numberSelected = 0;
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for (Enumeration e = selectorElements(); e.hasNextElement();) {
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FileSelector s = (FileSelector) e.nextElement();
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if (s.isSelected(baseDir, filename, file)) {
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numberSelected++;
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}
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}
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return numberSelected == number;
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}
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}</pre>
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<p>
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To define and use this selector one could do:
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</p>
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<pre>
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<typedef name="numberselected"
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classname="com.mydomain.MatchNumberSelectors"/>
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...
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<fileset dir="${src.path}">
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<numberselected number="2">
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<contains text="script" casesensitive="no"/>
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<size value="4" units="Ki" when="more"/>
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<javaselector/>
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</numberselected>
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</fileset></pre>
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<p>
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<em>The custom selector</em>
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</p>
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<p>
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The custom selector was the pre Ant 1.6 way of defining custom
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selectors. This method is still supported for backward compatibility.
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</p>
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<p>
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You can write your own selectors and use them within the selector
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containers by specifying them within the <code><custom></code>
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tag.
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</p>
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<p>
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To create a new Custom Selector, you have to create a class that
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implements <code>org.apache.tools.ant.types.selectors.ExtendFileSelector</code>.
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The easiest way to do that is through the convenience base
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class <code>org.apache.tools.ant.types.selectors.BaseExtendSelector</code>,
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which provides all of the methods for
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supporting <code><param></code> tags. First, override
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the <code>isSelected()</code> method, and optionally
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the <code>verifySettings()</code> method. If your custom selector
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requires parameters to be set, you can also override
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the <code>setParameters()</code> method and interpret the parameters
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that are passed in any way you like. Several of the core selectors
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demonstrate how to do that because they can also be used as custom
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selectors.
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</p>
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<p>
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Once that is written, you include it in your build file by using
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the <code><custom></code> tag.
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</p>
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2018-02-28 07:58:59 +01:00
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<table class="attr">
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<tr>
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<th>Attribute</th>
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<th>Description</th>
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<th>Required</th>
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</tr>
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<tr>
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<td>classname</td>
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<td>
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The name of your class that
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implements <code>org.apache.tools.ant.types.selectors.FileSelector</code>.
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</td>
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<td>Yes</td>
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</tr>
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<tr>
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<td>classpath</td>
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<td>
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The classpath to use in order to load the custom selector
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class. If neither <var>classpath</var> nor
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<var>classpathref</var> are specified, the class will be
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loaded from the classpath that Ant uses.
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</td>
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<td>No</td>
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</tr>
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<tr>
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<td>classpathref</td>
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<td>
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A reference to a classpath previously defined. If
|
|
|
|
|
neither <var>classpathref</var> nor <var>classpath</var> above are
|
|
|
|
|
specified, the class will be loaded from the classpath that Ant
|
|
|
|
|
uses.
|
2003-08-13 08:35:50 +00:00
|
|
|
</td>
|
2018-02-28 07:58:59 +01:00
|
|
|
<td>No</td>
|
2003-08-13 08:35:50 +00:00
|
|
|
</tr>
|
|
|
|
|
</table>
|
|
|
|
|
|
2018-02-28 07:58:59 +01:00
|
|
|
<p>
|
|
|
|
|
Here is how you use <code><custom></code> to use your class as a
|
|
|
|
|
selector:
|
2003-08-13 08:35:50 +00:00
|
|
|
</p>
|
2018-02-09 06:54:03 +01:00
|
|
|
<pre>
|
2003-09-23 22:12:36 +00:00
|
|
|
<fileset dir="${mydir}" includes="**/*">
|
|
|
|
|
<custom classname="com.mydomain.MySelector">
|
|
|
|
|
<param name="myattribute" value="myvalue"/>
|
2003-08-13 08:35:50 +00:00
|
|
|
</custom>
|
2018-02-28 07:58:59 +01:00
|
|
|
</fileset></pre>
|
|
|
|
|
<p>The core selectors that can also be used as custom selectors are</p>
|
2003-08-13 08:35:50 +00:00
|
|
|
|
|
|
|
|
<ul>
|
|
|
|
|
<li><a href="selectors.html#containsselect">Contains Selector</a> with
|
2018-02-28 07:58:59 +01:00
|
|
|
classname <code>org.apache.tools.ant.types.selectors.ContainsSelector</code></li>
|
2003-08-13 08:35:50 +00:00
|
|
|
<li><a href="selectors.html#dateselect">Date Selector</a> with
|
2018-02-28 07:58:59 +01:00
|
|
|
classname <code>org.apache.tools.ant.types.selectors.DateSelector</code></li>
|
2003-08-13 08:35:50 +00:00
|
|
|
<li><a href="selectors.html#depthselect">Depth Selector</a> with
|
2018-02-28 07:58:59 +01:00
|
|
|
classname <code>org.apache.tools.ant.types.selectors.DepthSelector</code></li>
|
2003-08-13 08:35:50 +00:00
|
|
|
<li><a href="selectors.html#filenameselect">Filename Selector</a> with
|
2018-02-28 07:58:59 +01:00
|
|
|
classname <code>org.apache.tools.ant.types.selectors.FilenameSelector</code></li>
|
2003-08-13 08:35:50 +00:00
|
|
|
<li><a href="selectors.html#sizeselect">Size Selector</a> with
|
2018-02-28 07:58:59 +01:00
|
|
|
classname <code>org.apache.tools.ant.types.selectors.SizeSelector</code></li>
|
2003-08-13 08:35:50 +00:00
|
|
|
</ul>
|
|
|
|
|
|
2018-02-28 07:58:59 +01:00
|
|
|
<p>
|
|
|
|
|
Here is the example from the Depth Selector section rewritten to use
|
|
|
|
|
the selector through <code><custom></code>.
|
|
|
|
|
</p>
|
2018-02-09 06:54:03 +01:00
|
|
|
<pre>
|
2003-09-23 22:12:36 +00:00
|
|
|
<fileset dir="${doc.path}" includes="**/*">
|
|
|
|
|
<custom classname="org.apache.tools.ant.types.selectors.DepthSelector">
|
|
|
|
|
<param name="max" value="1"/>
|
2003-08-13 08:35:50 +00:00
|
|
|
</custom>
|
2018-02-28 07:58:59 +01:00
|
|
|
</fileset></pre>
|
|
|
|
|
<p>Selects all files in the base directory and one directory below that.</p>
|
2003-08-13 08:35:50 +00:00
|
|
|
|
2018-02-08 16:59:52 +01:00
|
|
|
<h3 id="filterreaders">Custom Filter Readers</h3>
|
2003-08-13 08:35:50 +00:00
|
|
|
<p>
|
2018-02-28 07:58:59 +01:00
|
|
|
Custom filter readers selectors are datatypes that
|
|
|
|
|
implement <code>org.apache.tools.ant.types.filters.ChainableReader</code>.
|
2003-08-13 08:35:50 +00:00
|
|
|
</p>
|
2018-02-28 07:58:59 +01:00
|
|
|
<p>
|
|
|
|
|
There is only one method required. <code>Reader chain(Reader
|
|
|
|
|
reader)</code>. This returns a reader that filters input from the
|
|
|
|
|
specified reader.
|
2003-08-13 08:35:50 +00:00
|
|
|
</p>
|
|
|
|
|
<p>
|
2018-02-28 07:58:59 +01:00
|
|
|
For example a filterreader that removes every second character could
|
|
|
|
|
be:
|
2003-08-13 08:35:50 +00:00
|
|
|
</p>
|
2018-02-09 06:54:03 +01:00
|
|
|
<pre>
|
2003-08-13 08:35:50 +00:00
|
|
|
public class RemoveOddCharacters implements ChainableReader {
|
2018-02-28 07:58:59 +01:00
|
|
|
public Reader chain(Reader reader) {
|
|
|
|
|
return new BaseFilterReader(reader) {
|
|
|
|
|
int count = 0;
|
|
|
|
|
public int read() throws IOException {
|
|
|
|
|
while (true) {
|
|
|
|
|
int c = in.read();
|
|
|
|
|
if (c == -1) {
|
|
|
|
|
return c;
|
|
|
|
|
}
|
|
|
|
|
count++;
|
|
|
|
|
if ((count % 2) == 1) {
|
|
|
|
|
return c;
|
|
|
|
|
}
|
2003-09-23 11:35:53 +00:00
|
|
|
}
|
2018-02-28 07:58:59 +01:00
|
|
|
}
|
|
|
|
|
}
|
|
|
|
|
}
|
|
|
|
|
}</pre>
|
2003-08-13 08:35:50 +00:00
|
|
|
<p>
|
2018-02-28 07:58:59 +01:00
|
|
|
For line oriented filters it may be easier to
|
|
|
|
|
extend <code>ChainableFilterReader</code> an inner class
|
|
|
|
|
of <code>org.apache.tools.ant.filters.TokenFilter</code>.
|
2003-08-13 08:35:50 +00:00
|
|
|
</p>
|
|
|
|
|
<p>
|
|
|
|
|
For example a filter that appends the line number could be
|
|
|
|
|
</p>
|
2018-02-09 06:54:03 +01:00
|
|
|
<pre>
|
2003-08-13 08:35:50 +00:00
|
|
|
public class AddLineNumber extends ChainableReaderFilter {
|
2018-02-28 07:58:59 +01:00
|
|
|
private void lineNumber = 0;
|
|
|
|
|
public String filter(String string) {
|
|
|
|
|
lineNumber++;
|
|
|
|
|
return "" + lineNumber + "\t" + string;
|
|
|
|
|
}
|
|
|
|
|
}</pre>
|
2003-09-23 11:35:53 +00:00
|
|
|
|
2003-08-13 08:35:50 +00:00
|
|
|
</body>
|
|
|
|
|
</html>
|
