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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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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-->
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2003-08-21 00:34:27 +00:00
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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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2005-04-29 18:58:16 +00:00
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<link rel="stylesheet" type="text/css" href="../stylesheets/style.css">
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2003-08-21 00:34:27 +00:00
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<title>Assertions type</title>
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</head>
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<body>
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<h2><a name="assertions">Assertions</a></h2>
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<p>
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2004-02-02 14:33:08 +00:00
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The <tt>assertions</tt> type enables or disables the Java 1.4 assertions feature,
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on a whole Java program, or components of a program. It can be used
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in <a href="../Tasks/java.html"><code><java></code></a> and
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<a href="../Tasks/junit.html"><code><junit></code></a> to add extra validation to code.
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<p>
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Assertions are covered in the
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2013-09-13 13:40:23 +00:00
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<a href="http://docs.oracle.com/javase/7/docs/technotes/guides/language/assert.html">Java SE documentation</a>,
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and the
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<a href="http://docs.oracle.com/javase/specs/jls/se7/html/jls-14.html#jls-14.10">Java Language Specification</a>.
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<p>
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The key points to note are that a <tt>java.lang.AssertionError</tt>
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is thrown when an assertion fails, and that the facility is only available
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on Java 1.4 and later. To enable assertions one must set <tt>source="1.4"</tt>
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(or later) in <tt><javac></tt> when the source is being compiled, and
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that the code must contain <tt>assert</tt> statements to be tested. The
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result of such an action is code that neither compiles or runs on earlier
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versions of Java. For this reason Apache Ant itself currently contains no assertions.
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<p>
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When assertions are enabled (or disabled) in a task through nested
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assertions elements, the class loader or command line is modified with the
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appropriate options. This means that the JVM executed must be a Java 1.4
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or later JVM, even if there are no assertions in the code. Attempting to
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enable assertions on earlier VMs will result in an "Unrecognized option"
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error and the JVM will not start.
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<p>
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<h4>Attributes</h4>
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<p>
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</p>
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<table border="1" cellpadding="2" cellspacing="0">
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<tr>
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<td valign="top"><b>Attribute</b></td>
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<td valign="top"><b>Description</b></td>
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<td align="center" valign="top"><b>Required</b></td>
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</tr>
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<tr>
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<td valign="top">enableSystemAssertions</td>
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<td valign="top">Flag to turn system assertions on or off.</td>
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<td valign="top" align="center">No; default is "unspecified"</td>
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</tr>
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</table>
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<p>
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When system assertions have been neither enabled nor disabled, then
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the JVM is not given any assertion information - the default action of the
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current JVMs is to disable system assertions.
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<p>
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Note also that there is no apparent documentation for what parts of the
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JRE come with useful assertions.
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<h3>Nested elements</h3>
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<h4>enable</h4>
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<p>
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Enable assertions in portions of code.
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If neither a package nor class is specified, assertions are turned on in <i>all</i> (user) code.
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</p>
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<table border="1" cellpadding="2" cellspacing="0">
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<tr>
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<td valign="top"><b>Attribute</b></td>
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<td valign="top"><b>Description</b></td>
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<td align="center" valign="top"><b>Required</b></td>
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</tr>
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<tr>
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<td valign="top">class</td>
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<td valign="top">The name of a class on which to enable assertions.</td>
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<td valign="top" align="center">No</td>
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</tr>
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<tr>
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<td valign="top">package</td>
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<td valign="top">
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The name of a package in which to enable assertions on all classes. (Includes subpackages.)
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Use "<tt>...</tt>" for the anonymous package.
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</td>
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<td valign="top" align="center">No</td>
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</tr>
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</table>
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<h4>disable</h4>
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<p>
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Disable assertions in portions of code.
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</p>
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<table border="1" cellpadding="2" cellspacing="0">
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<tr>
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<td valign="top"><b>Attribute</b></td>
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<td valign="top"><b>Description</b></td>
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<td align="center" valign="top"><b>Required</b></td>
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</tr>
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<tr>
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<td valign="top">class</td>
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<td valign="top">The name of a class on which to disable assertions.</td>
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<td valign="top" align="center">No</td>
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</tr>
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<tr>
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<td valign="top">package</td>
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<td valign="top">
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The name of a package in which to disable assertions on all classes. (Includes subpackages.)
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Use "<tt>...</tt>" for the anonymous package.
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</td>
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<td valign="top" align="center">No</td>
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</tr>
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</table>
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<p>
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Because assertions are disabled by default, it only makes sense to disable
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assertions where they have been enabled in a parent package.
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<h4>Examples</h4>
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2004-02-02 14:33:08 +00:00
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<h5>Example: enable assertions in all user classes</h5>
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All classes not in the JRE (i.e. all non-system classes) will have assertions turned on.
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<pre>
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<assertions>
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<enable/>
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</assertions>
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</pre>
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2003-08-21 00:34:27 +00:00
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<h5>Example: enable a single class</h5>
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Enable assertions in a class called Test
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<pre>
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<assertions>
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<enable class="Test"/>
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</assertions>
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</pre>
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<h5>Example: enable a package</h5>
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2004-02-02 14:33:08 +00:00
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Enable assertions in the <tt>org.apache</tt> package
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and all packages starting with the <tt>org.apache.</tt> prefix
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<pre>
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<assertions>
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<enable package="org.apache"/>
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</assertions>
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</pre>
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<h5>Example: System assertions</h5>
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2004-02-02 14:33:08 +00:00
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Example: enable system assertions and assertions in all <tt>org.apache</tt> packages except
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for Ant (but including <tt>org.apache.tools.ant.Main</tt>)
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<pre>
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<assertions enableSystemAssertions="true">
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<enable package="org.apache"/>
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<disable package="org.apache.tools.ant"/>
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<enable class="org.apache.tools.ant.Main"/>
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</assertions>
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</pre>
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<h5>Example: disabled and anonymous package assertions</h5>
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Disable system assertions; enable those in the anonymous package
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<pre>
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<assertions enableSystemAssertions="false">
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<enable package="..."/>
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</assertions>
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</pre>
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<h5>Example: referenced assertions</h5>
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This type is a datatype, so you can declare assertions and use them later
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<pre>
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<assertions id="project.assertions">
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<enable package="org.apache.test"/>
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</assertions>
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2004-02-02 14:33:08 +00:00
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<assertions refid="project.assertions"/>
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</pre>
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2003-08-22 09:20:12 +00:00
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2006-09-11 04:33:25 +00:00
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2003-08-22 09:20:12 +00:00
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</body>
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</html>
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