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| <html> |
| <head> |
| <meta http-equiv="Content-Language" content="en-us"> |
| <link rel="stylesheet" type="text/css" href="../stylesheets/style.css"> |
| <title>Programming Selectors in Ant</title> |
| </head> |
| |
| <body> |
| <h2>Programming your own Selectors</h2> |
| |
| <h3>Selector Programming API</h3> |
| |
| <p>Want to define your own selectors? It's easy!</p> |
| |
| <p>First, pick the type of selector that you want to define. There |
| are three types, and a recipe for each one follows. Chances are |
| you'll want to work with the first one, Custom Selectors.</p> |
| |
| <ol> |
| <li>Custom Selectors |
| |
| <p>This is the category that Ant provides specifically for you to |
| define your own Selectors. Anywhere you want to use your selector |
| you use the <code><custom></code> element and specify |
| the class name of your selector within it. See the |
| <a href="selectors.html#customselect">Custom Selectors</a> |
| section of the Selector page for details. The |
| <code><custom></code> element can be used anywhere |
| the core selectors can be used. It can be contained within |
| <a href="selectors.html#selectcontainers">Selector Containers</a>, |
| for example.</p> |
| |
| <p>To create a new Custom Selector, you have to create a class that |
| implements |
| <code>org.apache.tools.ant.types.selectors.ExtendFileSelector</code>. |
| The easiest way to do that is through the convenience base class |
| <code>org.apache.tools.ant.types.selectors.BaseExtendSelector</code>, |
| which provides all of the methods for supporting |
| <code><param></code> tags. First, override the |
| <code>isSelected()</code> method, and optionally the |
| <code>verifySettings()</code> method. If your custom |
| selector requires parameters to be set, you can also override |
| the <code>setParameters()</code> method and interpret the |
| parameters that are passed in any way you like. Several of the |
| core selectors demonstrate how to do that because they can |
| also be used as custom selectors.</p> |
| |
| <li>Core Selectors |
| |
| <p>These are the selectors used by Ant itself. To implement one of |
| these, you will have to alter some of the classes contained within |
| Ant.</p> |
| |
| <ul> |
| <li><p>First, create a class that implements |
| <code>org.apache.tools.ant.types.selectors.FileSelector</code>. |
| You can either choose to implement all methods yourself from |
| scratch, or you can extend |
| <code>org.apache.tools.ant.types.selectors.BaseSelector</code> |
| instead, a convenience class that provides reasonable default |
| behaviour for many methods.</p> |
| |
| <p>There is only one method required. |
| <code>public boolean isSelected(File basedir, String filename, |
| File file)</code> |
| is the real purpose of the whole exercise. It returns true |
| or false depending on whether the given file should be |
| selected from the list or not.</p> |
| |
| <p>If you are using |
| <code>org.apache.tools.ant.types.selectors.BaseSelector</code> |
| there are also some predefined behaviours you can take advantage |
| of. Any time you encounter a problem when setting attributes or |
| adding tags, you can call setError(String errmsg) and the class |
| will know that there is a problem. Then, at the top of your |
| <code>isSelected()</code> method call <code>validate()</code> and |
| a BuildException will be thrown with the contents of your error |
| message. The <code>validate()</code> method also gives you a |
| last chance to check your settings for consistency because it |
| calls <code>verifySettings()</code>. Override this method and |
| call <code>setError()</code> within it if you detect any |
| problems in how your selector is set up.</p> |
| |
| <p>You may also want to override <code>toString()</code>.</p> |
| |
| <li><p>Put an <code>add</code> method for your selector in |
| <code>org.apache.tools.ant.types.selectors.SelectorContainer</code>. |
| This is an interface, so you will also have to add an implementation |
| for the method in the classes which implement it, namely |
| <code>org.apache.tools.ant.types.AbstractFileSet</code>, |
| <code>org.apache.tools.ant.taskdefs.MatchingTask</code> and |
| <code>org.apache.tools.ant.types.selectors.BaseSelectorContainer</code>. |
| Once it is in there, it will be available everywhere that core |
| selectors are appropriate.</p> |
| </ul> |
| |
| <li>Selector Containers |
| <p>Got an idea for a new Selector Container? Creating a new one is |
| no problem:</p> |
| <ul> |
| <li><p>Create a new class that implements |
| <code>org.apache.tools.ant.types.selectors.SelectorContainer</code>. |
| This will ensure that your new |
| Container can access any new selectors that come along. Again, there |
| is a convenience class available for you called |
| <code>org.apache.tools.ant.types.selectors.BaseSelectorContainer</code>. |
| </p> |
| <li><p>Implement the |
| <code>public boolean isSelected(String filename, File file)</code> |
| method to do the right thing. Chances are you'll want to iterate |
| over the selectors under you, so use |
| <code>selectorElements()</code> to get an iterator that will do |
| that.</p> |
| <li><p>Again, put an <code>add</code> method for your container in |
| <code>org.apache.tools.ant.types.selectors.SelectorContainer</code> |
| and its implementations |
| <code>org.apache.tools.ant.types.AbstractFileSet</code> and |
| <code>org.apache.tools.ant.types.selectors.BaseSelectorContainer</code>. |
| </p> |
| </ul> |
| </ol> |
| |
| <h3>Testing Selectors</h3> |
| |
| <p>For a robust component (and selectors are (Project)Components) tests are |
| necessary. For testing Tasks we use JUnit TestCases - more specific |
| <tt>org.apache.tools.ant.BuildFileTest extends junit.framework.TestCase</tt>. |
| Some of its features like configure the (test) project by reading its buildfile and |
| execute targets we need for selector tests also. Therefore we use that BuildFileTest. |
| But testing selectors requires some more work: having a set of files, instantiate |
| and configure the selector, check the selection work and more. Because we usually |
| extend <tt>BaseExtendSelector</tt> its features have to be tested also (e.g. setError()). |
| </p> |
| |
| <p>That's why we have a base class for doing our selector tests: |
| <tt>org.apache.tools.ant.types.selectors.BaseSelectorTest</tt>.</p> |
| |
| <p>This class extends TestCase and therefore can included in the set of Ant's |
| unit tests. It holds an instance of preconfigured BuildFileTest. Configuration |
| is done by parsing the src/etc/testcases/types/selectors.xml. BaseSelectorTest |
| then gives us helper methods for handling multiple selections. </p> |
| |
| <p>Because the term "testcase" or "testenvironment" are so often used, this |
| special testenvironment got a new name: <i>bed</i>. Like you initialize the |
| test environment by calling setUp() and cleaning by calling tearDown() (<i>or like |
| to make your bed before go sleeping</i>) you have to do that work with your |
| <i>bed</i> by calling <tt>makeBed()</tt> respecitive <tt>cleanupBed()</tt>.</p> |
| |
| <p>A usual test scenario is<ol> |
| <li>make the bed</li> |
| <li>instantiate the selector</li> |
| <li>configure the selector</li> |
| <li>let the selector do some work</li> |
| <li>verify the work</li> |
| <li>clean the bed</li> |
| </ol> |
| </p> |
| |
| <p>For common way of instantiation you have to override the <tt>getInstance()</tt> |
| simply by returning a new object of your selector. For easier "selection and verification work" |
| BaseSelectorTest provides the method <tt>performTests()</tt> which |
| iterates over all files (and directories) in the String array <tt>filenames</tt> |
| and checks whether the given selector returns the expected result. If an error |
| occurred (especially the selector does not return the expected result) the test |
| fails and the failing filenames are logged.</p> |
| |
| <p>An example test would be:<pre> |
| package org.apache.tools.ant.types.selectors; |
| |
| public class MySelectorTest extends BaseSelectorTest { |
| |
| public MySelectorTest(String name) { |
| super(name); |
| } |
| |
| public BaseSelector getInstance() { |
| return new MySelector(); |
| } |
| |
| public void testCase1() { |
| try { |
| // initialize test environment 'bed' |
| makeBed(); |
| |
| // Configure the selector |
| MySelector s = (MySelector)getSelector(); |
| s.addParam("key1", "value1"); |
| s.addParam("key2", "value2"); |
| s.setXX(true); |
| s.setYY("a value"); |
| |
| // do the tests |
| performTests(s, "FTTTTTTTTTTT"); // First is not selected - rest is |
| |
| } finally { |
| // cleanup the environment |
| cleanupBed(); |
| } |
| } |
| } |
| </pre> |
| As an example of an error JUnit could log<pre> |
| [junit] FAILED |
| [junit] Error for files: <font color=blue>.;copy.filterset.filtered;tar/gz/asf-logo.gif.tar.gz</font> |
| [junit] expected:<<font color=blue>FTTTFTTTF...</font>> but was:<TTTTTTTTT...> |
| [junit] junit.framework.ComparisonFailure: Error for files: .;copy.filterset.filtered;tar/gz/asf-logo.gif.tar.gz |
| [junit] expected:<FTTTFTTTF...> but was:<TTTTTTTTT...> |
| [junit] at junit.framework.Assert.assertEquals(Assert.java:81) |
| [junit] at org.apache.tools.ant.types.selectors.BaseSelectorTest.performTest(BaseSelectorTest.java:194) |
| </pre></p> |
| |
| <p>Described above the test class should provide a <tt>getInstance()</tt> |
| method. But that isn't used here. The used <tt>getSelector()</tt> method is |
| implemented in the base class and gives an instance of an Ant Project to |
| the selector. This is usually done inside normal build file runs, but not |
| inside this special environment, so this method gives the selector the |
| ability to use its own Project object (<tt>getProject()</tt>), for example |
| for logging.</p> |
| |
| |
| <h3>Logging</h3> |
| |
| <p>During development and maybe later you sometimes need the output of information. |
| Therefore Logging is needed. Because the selector extends BaseExtendSelector or directly |
| BaseSelector it is an Ant <tt>DataType</tt> and therefore a <tt>ProjectComponent</tt>. <br> |
| That means that you have access to the project object and its logging capability. |
| <tt>ProjectComponent</tt> itself provides <i>log</i> methods which will do the |
| access to the project instance. Logging is therefore done simply with: |
| <pre> |
| log( "message" ); |
| </pre> |
| or |
| <pre> |
| log( "message" , loglevel ); |
| </pre> |
| where the <tt>loglevel</tt> is one of the values <ul> |
| <li> org.apache.tools.ant.Project.MSG_ERR </li> |
| <li> org.apache.tools.ant.Project.MSG_WARN </li> |
| <li> org.apache.tools.ant.Project.MSG_INFO (= default) </li> |
| <li> org.apache.tools.ant.Project.MSG_VERBOSE </li> |
| <li> org.apache.tools.ant.Project.MSG_DEBUG </li> |
| </ul> |
| </p> |
| |
| |
| </body> |
| |
| </html> |
