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| <h1>InputHandler</h1> |
| |
| <h2>Overview</h2> |
| |
| <p>When a task wants to prompt a user for input, it doesn't simply |
| read the input from the console as this would make it impossible to |
| embed Ant in an IDE. Instead it asks an implementation of the |
| <code>org.apache.tools.ant.input.InputHandler</code> interface to |
| prompt the user and hand the user input back to the task.</p> |
| |
| <p>To do this, the task creates an <code>InputRequest</code> object |
| and passes it to the <code>InputHandler</code> Such an |
| <code>InputRequest</code> may know whether a given user input is valid |
| and the <code>InputHandler</code> is supposed to reject all invalid |
| input.</p> |
| |
| <p>Exactly one <code>InputHandler</code> instance is associated with |
| every Ant process, users can specify the implementation using the |
| <code>-inputhandler</code> command line switch.</p> |
| |
| <h2>InputHandler</h2> |
| |
| <p>The <code>InputHandler</code> interface contains exactly one |
| method</p> |
| |
| <pre> |
| void handleInput(InputRequest request) |
| throws org.apache.tools.ant.BuildException; |
| </pre> |
| |
| <p>with some pre- and postconditions. The main postcondition is that |
| this method must not return unless the <code>request</code> considers |
| the user input valid, it is allowed to throw an exception in this |
| situation.</p> |
| |
| <p>Ant comes with two built-in implementations of this interface:</p> |
| |
| <h3><a name="defaulthandler">DefaultInputHandler</a></h3> |
| |
| <p>This is the implementation you get, when you don't use the |
| <code>-inputhandler</code> command line switch at all. This |
| implementation will print the prompt encapsulated in the |
| <code>request</code> object to Ant's logging system and re-prompt for |
| input until the user enters something that is considered valid input |
| by the <code>request</code> object. Input will be read from the |
| console and the user will need to press the Return key.</p> |
| |
| <h3>PropertyFileInputHandler</h3> |
| |
| <p>This implementation is useful if you want to run unattended build |
| processes. It reads all input from a properties file and makes the |
| build fail if it cannot find valid input in this file. The name of |
| the properties file must be specified in the Java system property |
| <code>ant.input.properties</code>.</p> |
| |
| <p>The prompt encapsulated in a <code>request</code> will be used as |
| the key when looking up the input inside the properties file. If no |
| input can be found, the input is considered invalid and an exception |
| will be thrown.</p> |
| |
| <p><strong>Note</strong> that <code>ant.input.properties</code> must |
| be a Java system property, not an Ant property. I.e. you cannot |
| define it as a simple parameter to <code>ant</code>, but you can |
| define it inside the <code>ANT_OPTS</code> environment variable.</p> |
| |
| <h2>InputRequest</h2> |
| |
| <p>Instances of <code>org.apache.tools.ant.input.InputRequest</code> |
| encapsulate the information necessary to ask a user for input and |
| validate this input.</p> |
| |
| <p>The instances of <code>InputRequest</code> itself will accept any |
| input, but subclasses may use stricter validations. |
| <code>org.apache.tools.ant.input.MultipleChoiceInputRequest</code> |
| should be used if the user input must be part of a predefined set of |
| choices.</p> |
| |
| <hr> |
| <p align="center">Copyright © 2002 Apache Software Foundation. All rights |
| Reserved.</p> |
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