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| <title>Tutorial: Hello World with Ant</title> |
| <meta name="author" content="Jan Matèrne"> |
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| <h1>Tutorial: Hello World with Ant</h1> |
| |
| <p>This document provides a step by step tutorial for starting java programming with Ant. |
| It does <b>not</b> contain deeper knowledge about Java or Ant. This tutorial has the goal |
| to let you see, how to do the easiest steps in Ant.</p> |
| |
| |
| |
| <h2>Content</h2> |
| <p><ul> |
| <li><a href="#prepare">Preparing the project</a></li> |
| <li><a href="#four-steps">Enhance the build file</a></li> |
| <li><a href="#enhance">Enhance the build file</a></li> |
| <li><a href="#ext-libs">Using external libraries</a></li> |
| </ul></p> |
| |
| |
| |
| <a name="prepare"></a> |
| <h2>Preparing the project</h2> |
| <p>We want to separate the source from the generated files, so our java source files will |
| be in <tt>src</tt> folder. All generated files should be under <tt>build</tt>, and there |
| splitted into several subdirectories for the individual steps: <tt>classes</tt> for our compiled |
| files and <tt>jar</tt> for our own JAR-file.</p> |
| <p>The later directories are created by our buildfile, so we have to create only the <tt>src</tt> |
| directory. (Because I am working on Windows, here is the win-syntax - translate to your shell):</p> |
| |
| <pre class="code"> |
| md src |
| </pre> |
| |
| <p>This is not a Java tutorial, so just write this code into <tt>src/oata/HelloWorld.java</tt> - |
| you should guess it's meaning ;-)</p> |
| |
| <pre class="code"> |
| package oata; |
| |
| public class HelloWorld { |
| public static void main(String[] args) { |
| System.out.println("Hello World"); |
| } |
| } |
| </pre> |
| |
| |
| |
| <a name="four-steps"></a> |
| <h2>Four steps to a running application</h2> |
| <p>Oki-doki - now we have to think about our build process. We <i>have</i> to compile our code, otherwise we couldn't |
| start the program. Oh - "start" - yes, we could provide a target for that. We <i>should</i> package our application. |
| Now it's only one class - but if you want to provide a download, no one would download several hundreds files ... |
| (think about a complex Swing GUI :) - so let us create a jar file. A startable jar file would be nice ... And it's a |
| good practise to have a "clean" target, which deletes all the generated stuff. Many failures could be solved just |
| by a "clean build" :-)</p> |
| |
| <p>The buildfile describing that would be:</p> |
| <pre class="code"> |
| <project> |
| |
| <target name="clean"> |
| <delete dir="build"/> |
| </target> |
| |
| <target name="compile"> |
| <mkdir dir="build/classes"/> |
| <javac srcdir="src" destdir="build/classes"/> |
| </target> |
| |
| <target name="jar"> |
| <mkdir dir="build/jar"/> |
| <jar destfile="build/jar/HelloWorld.jar" basedir="build/classes"> |
| <manifest> |
| <attribute name="Main-Class" value="oata.HelloWorld"/> |
| </manifest> |
| </jar> |
| </target> |
| |
| <target name="run"> |
| <java jar="build/jar/HelloWorld.jar" fork="true"/> |
| </target> |
| |
| </project> |
| </pre> |
| |
| <p>Now you can compile, package and run the application via</p> |
| <pre class="code"> |
| ant compile |
| ant jar |
| ant run |
| </pre> |
| <p>Or shorter with</p> |
| <pre class="code"> |
| ant compile jar run |
| </pre> |
| |
| |
| |
| <a name="enhance"></a> |
| <h2>Enhance the build file</h2> |
| </p>Ok, the build works - but it is not as nice as it should: many time you are referencing the same directories, |
| main-class and jar-name are hard coded, and while invocation you have to remember the right order of build steps.</p> |
| <p>The first and second point would be adressed with <i>properties</i>, the thirs with a special property - an attribute |
| of the <project>-tag and the fourth problem can be solved using dependencies.</p> |
| |
| <pre class="code"> |
| <project name="HelloWorld" basedir="." default="main"> |
| |
| <property name="src.dir" value="src"/> |
| |
| <property name="build.dir" value="build"/> |
| <property name="classes.dir" value="${build.dir}/classes"/> |
| <property name="jar.dir" value="${build.dir}/jar"/> |
| |
| <property name="main-class" value="oata.HelloWorld"/> |
| |
| |
| |
| <target name="clean"> |
| <delete dir="${build.dir}"/> |
| </target> |
| |
| <target name="compile"> |
| <mkdir dir="${classes.dir}"/> |
| <javac srcdir="${src.dir}" destdir="${classes.dir}"/> |
| </target> |
| |
| <target name="jar" depends="compile"> |
| <mkdir dir="${jar.dir}"/> |
| <jar destfile="${jar.dir}/${ant.project.name}.jar" basedir="${classes.dir}"> |
| <manifest> |
| <attribute name="Main-Class" value="${main-class}"/> |
| </manifest> |
| </jar> |
| </target> |
| |
| <target name="run" depends="jar"> |
| <java jar="${jar.dir}/${ant.project.name}.jar" fork="true"/> |
| </target> |
| |
| <target name="clean-build" depends="clean,jar"/> |
| |
| <target name="main" depends="clean,run"/> |
| |
| </project> |
| </pre> |
| |
| <p>Now it's easier, just do a <tt>ant</tt> and you will get</p> |
| <pre class="output"> |
| Buildfile: build.xml |
| |
| clean: |
| |
| compile: |
| [mkdir] Created dir: C:\...\build\classes |
| [javac] Compiling 1 source file to C:\...\build\classes |
| |
| jar: |
| [mkdir] Created dir: C:\...\build\jar |
| [jar] Building jar: C:\...\build\jar\HelloWorld.jar |
| |
| run: |
| [java] Hello World |
| |
| main: |
| |
| BUILD SUCCESSFUL |
| </pre> |
| |
| |
| <a name="ext-libs"></a> |
| <h2>Using external libraries</h2> |
| <p>Somehow told us not to use syso-statements. For log-Statements we should use a Logging-API - customizable on a high |
| degree (including switching off during usual life (= not development) execution). We use Log4J, because <ul> |
| <li>it is not part of the JDK (1.4+) and we want to show how to use external libs</li> |
| <li>it can run under JDK 1.2 (as Ant)</li> |
| <li>it's highly configurable</li> |
| <li>it's from Apache :-)</li> |
| </ul></p> |
| <p>We store our external libraries in a new directory <tt>lib</tt>. Log4J can be |
| <a href="http://www.apache.org/dist/logging/log4j/1.2.9/logging-log4j-1.2.9.zip">downloaded</a> from Logging's Homepage. |
| Create the <tt>lib</tt> directory and extract the log4j-1.2.9.jar into that lib-directory. After that we have to modify |
| our java source to use that library and our buildfile so that this library could be accessed during compilation and run. |
| </p> |
| <p>Working with Log4J is documented inside its manual. Here we use the <i>MyApp</i>-example from the |
| <a href="http://logging.apache.org/log4j/docs/manual.html">Short Manual</a>. First we have to modify the java source to |
| use the logging framework:</p> |
| |
| <pre class="code"> |
| package oata; |
| |
| <b>import org.apache.log4j.Logger;</b> |
| <b>import org.apache.log4j.BasicConfigurator;</b> |
| |
| public class HelloWorld { |
| <b>static Logger logger = Logger.getLogger(HelloWorld.class);</b> |
| |
| public static void main(String[] args) { |
| <b>BasicConfigurator.configure();</b> |
| <font color="blue"><b>logger.info("Hello World");</b></font> |
| } |
| } |
| </pre> |
| |
| <p>Most of the modifications are "framework overhead" which has to be done once. The red line is our "old System-out" |
| statement.</p> |
| <p>Don't try to run <tt>ant</tt> - you will only get lot of compiler errors. Log4J is not inside the classpath so we have |
| to do a little work here. But do not change the CLASSPATH environment variable! This is only for this project and maybe |
| you would break other environments (this is one of the most famous mistakes when working with Ant). We introduce Log4J |
| into our buildfile:</p> |
| |
| <pre class="code"> |
| <project name="HelloWorld" basedir="." default="main"> |
| ... |
| <b><property name="lib.dir" value="lib"/></b> |
| |
| <b><path id="classpath"></b> |
| <b><fileset dir="${lib.dir}" includes="**/*.jar"/></b> |
| <b></path></b> |
| |
| ... |
| |
| <target name="compile"> |
| <mkdir dir="${classes.dir}"/> |
| <javac srcdir="${src.dir}" destdir="${classes.dir}" <b>classpathref="classpath"</b>/> |
| </target> |
| |
| <target name="run" depends="jar"> |
| <java fork="true" <b>classname="${main-class}"</b>> |
| <b><classpath></b> |
| <b><path refid="classpath"/></b> |
| <font color="blue"><b><path location="${jar.dir}/${ant.project.name}.jar"/></b></font> |
| <b></classpath></b> |
| </java> |
| </target> |
| |
| ... |
| |
| </project> |
| </pre> |
| |
| <p>In this example we start our application not via its Main-Class manifest-attribute, because we could not provide |
| a jarname <i>and</i> a classpath. So add our class in the red line to the already defined path and start as usual. Running |
| <tt>ant</tt> would give (after the usual compile stuff):</p> |
| |
| <pre class="output"> |
| [java] 0 [main] INFO oata.HelloWorld - Hello World |
| </pre> |
| |
| <p>What's that? <ul> |
| <li><i>[java]</i> Ant task running at the moment</li> |
| <li><i>0</i> <font size="-1">sorry don't know - some Log4J stuff</font></li> |
| <li><i>[main]</i> the running thread from our application </li> |
| <li><i>INFO</i> log level of that statement</i> |
| <li><i>oata.HelloWorld</i> source of that statement</i> |
| <li><i>-</i> <font size="-1">sorry don't know - some Log4J stuff</font></li> |
| <li><i>Hello World</i> the message</li> |
| </ul> |
| For another layout ... have a look inside Log4J's documentation about using other PatternLayout's.</p> |
| |
| |
| <a name="config-files"> |
| <h2>Configuration files</h2> |
| <p>Why we have used Log4J? "It's highly configurable"? No - all is hard coded! But that is not the debt of Log4J - it's |
| ours. We had coded <tt>BasicConfigurator.configure();</tt> which implies a simple, but hard coded configuration. More |
| confortable would be using a property file. In the java source delete the BasicConfiguration-line from the main() method. |
| Log4J will search then for a configuration as described in it's manual. Then create a new file <tt>src/log4j.properties</tt>. |
| That's the default name for Log4J's configuration and using that name would make life easier - not only the framework knows |
| what is inside, you too!</p> |
| |
| <pre class="code"> |
| log4j.rootLogger=DEBUG, <b>stdout</b> |
| |
| log4j.appender.<b>stdout</b>=org.apache.log4j.ConsoleAppender |
| |
| log4j.appender.<b>stdout</b>.layout=org.apache.log4j.PatternLayout |
| log4j.appender.<b>stdout</b>.layout.ConversionPattern=<font color="blue"><b>%m%n</b></font> |
| </pre> |
| |
| <p>This configuration creates an output channel ("Appender") to console named as <tt>stdout</tt> which prints the |
| message (%m) followed by a line feed (%n) - same as the earlier System.out.println() :-) Oooh kay - but we haven't |
| finished yet. We should deliver the configuration file, too. So we change the buildfile:</p> |
| |
| <pre class="code"> |
| ... |
| <target name="compile"> |
| <mkdir dir="${classes.dir}"/> |
| <javac srcdir="${src.dir}" destdir="${classes.dir}" classpathref="classpath"/> |
| <b><copy todir="${classes.dir}"></b> |
| <b><fileset dir="${src.dir}" excludes="**/*.java"/></b> |
| <b></copy></b> |
| </target> |
| ... |
| </pre> |
| |
| <p>This copies all resources (as long as they haven't the suffix ".java") to the build directory, so we could |
| start the application from that directory and these files will included into the jar.</p> |
| |
| <hr> |
| <p align="center">Copyright © 2005 The Apache Software Foundation. All rights Reserved.</p> |
| |
| </body> |
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