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Java > Open Source Codes > net > sf > antcontrib > logic > IfTask


1 /*
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4  * Copyright (c) 2002 Ant-Contrib project. All rights reserved.
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21  * Ant-Contrib project (http://sourceforge.net/projects/ant-contrib)."
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48
49 package net.sf.antcontrib.logic;
50
51 import org.apache.tools.ant.BuildException;
52 import org.apache.tools.ant.taskdefs.Sequential;
53 import org.apache.tools.ant.taskdefs.condition.Condition;
54 import org.apache.tools.ant.taskdefs.condition.ConditionBase;
55
56 /**
57  * Perform some tasks based on whether a given condition holds true or
58  * not.
59  *
60  * <p>This task is heavily based on the Condition framework that can
61  * be found in Ant 1.4 and later, therefore it cannot be used in
62  * conjunction with versions of Ant prior to 1.4.</p>
63  *
64  * <p>This task doesn't have any attributes, the condition to test is
65  * specified by a nested element - see the documentation of your
66  * <code>&lt;condition&gt;</code> task (see
67  * <a HREF="http://jakarta.apache.org/ant/manual/CoreTasks/condition.html">the
68  * online documentation</a> for example) for a complete list of nested
69  * elements.</p>
70  *
71  * <p>Just like the <code>&lt;condition&gt;</code> task, only a single
72  * condition can be specified - you combine them using
73  * <code>&lt;and&gt;</code> or <code>&lt;or&gt;</code> conditions.</p>
74  *
75  * <p>In addition to the condition, you can specify two different
76  * child elements, <code>&lt;then&gt;</code> and
77  * <code>&lt;else&gt;</code>. Both are optional and both must not be
78  * used more than once inside the same task. Both elements are
79  * containers for Ant tasks, just like Ant's
80  * <code>&lt;parallel&gt;</code> and <code>&lt;sequential&gt;</code>
81  * tasks - in fact they are implemented using the same class as Ant's
82  * <code>&lt;sequential&gt;</code> task.</p>
83  *
84  * <p>Use the following task to define the <code>&lt;if&gt;</code>
85  * task before you use it the first time:</p>
86  *
87  * <pre><code>
88  * &lt;taskdef name="if" classname="net.sf.antcontrib.logic.IfTask" /&gt;
89  * </code></pre>
90  *
91  * <h3>Crude Example</h3>
92  *
93  * <pre><code>
94  * &lt;if&gt;
95  * &lt;equals arg1=&quot;${foo}&quot; arg2=&quot;bar&quot; /&gt;
96  * &lt;then&gt;
97  * &lt;echo message=&quot;The value of property foo is bar&quot; /&gt;
98  * &lt;/then&gt;
99  * &lt;else&gt;
100  * &lt;echo message=&quot;The value of property foo is not bar&quot; /&gt;
101  * &lt;/else&gt;
102  * &lt;/if&gt;
103  * </code></pre>
104  *
105  * @author <a HREF="mailto:stefan.bodewig@epost.de">Stefan Bodewig</a>
106  */
107 public class IfTask extends ConditionBase {
108
109     private Sequential thenTasks = null;
110     private Sequential elseTasks = null;
111
112     /**
113      * A nested &lt;then&gt; element - a container of tasks that will
114      * be run if the condition holds true.
115      *
116      * <p>Not required.</p>
117      */
118     public void addThen(Sequential t) {
119         if (thenTasks != null) {
120             throw new BuildException("You must not nest more than one <then> into <if>");
121         }
122         thenTasks = t;
123     }
124
125     /**
126      * A nested &lt;else&gt; element - a container of tasks that will
127      * be run if the condition doesn't hold true.
128      *
129      * <p>Not required.</p>
130      */
131     public void addElse(Sequential e) {
132         if (elseTasks != null) {
133             throw new BuildException("You must not nest more than one <else> into <if>");
134         }
135         elseTasks = e;
136     }
137
138     public void execute() throws BuildException {
139         if (countConditions() > 1) {
140             throw new BuildException("You must not nest more than one condition into <if>");
141         }
142         if (countConditions() < 1) {
143             throw new BuildException("You must nest a condition into <if>");
144         }
145         Condition c = (Condition) getConditions().nextElement();
146         if (c.eval()) {
147             if (thenTasks != null) {
148                 thenTasks.perform();
149             }
150         } else {
151             if (elseTasks != null) {
152                 elseTasks.perform();
153             }
154         }
155     }
156 }
157
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