Apache Ant


Lately I’ve gleened some “real world” Apache Ant tips and tricks from some really impressive Java EE developers I’ve had the opportunity of working with over the last year.

Apache Ant is a Java library and command-line tool whose mission is to drive processes described in build files as targets and extension points dependent upon each other. Ant supplies a number of built-in tasks allowing to compile, assemble, test and run Java applications.

Makefiles on steroids. Its XML based, and rather verbose. None the less, its powerful, and mature.

To get a birds-eye feel on what’s possible, checkout the Overview of Apache Ant Tasks.

Getting setup

  • Java home. The “go-to” JDK in other words. Add a system variable JAVA_HOME if not exists, and point it to the desired JDK.
  • Ant home. Make sure the Ant is installed, and then point to your Ant installation by defining the ANT_HOME environment variable, for example /usr/local/apache-ant-1.9.4.
  • Path. Update the path to make sure both %JAVA_HOME%\bin and %ANT_HOME%\bin are included.

Here’s my ~/.bash_profile:

export JAVA_HOME=/usr/libexec/java_home
export MYSQL_HOME=/usr/local/mysql
export GROOVY_HOME=/usr/local/groovy-2.1.4
export M2_HOME=/usr/local/apache-maven-3.0.4
export ANT_HOME=/usr/local/apache-ant-1.9.4
export PATH=$PATH:$M2_HOME/bin:$MYSQL_HOME/bin:$GROOVY_HOME/bin:$ANT_HOME/bin

OK, you should be up and running. Check Java is happy.

MacBook:/ ben$ java -version
java version "1.7.0_13"
Java(TM) SE Runtime Environment (build 1.7.0_13-b20)
Java HotSpot(TM) 64-Bit Server VM (build 23.7-b01, mixed mode)

And then Ant:

MacBook:/ ben$ ant -version
Apache Ant(TM) version 1.9.4 compiled on April 29 2014

Getting started

We have adopted a divide-and-conquer style pattern, which helps provide structure and to modularise concerns; basically the following targets are created for each module:

  • clean - destroy all generated artifacts for the module.
  • init - setup file system and other needed dependencies to support the build of the module.
  • compile - you guessed it, all work needed to compile module, taking care of things like dependencies.
  • assemble - package bytecode into JAR’s, WAR’s, EAR’s, whatever.

For example, module1-clean, module1-init, module1-compile, module1-assemble. This makes life debugging much simplier, as you can work through the script chunk by chunk.

build.properties

Next, its nice to extract public facing properties into a dedidcated build.properties. It’s a nicer way of controlling the build process, without going under the hood into the (overwhelming) build.xml.

# General application infomation
application.name=ant-spike
application.version=1.0
application.vendor=bEncode

# Server settings
jboss.home=/usr/local/wildfly-8.2.0.Final

# Core Java compiler settings
javac.debug=true
javac.failonerror=true
javac.source=1.7
javac.target=1.7

Properties can injected into the build.xml like so:

<property file="build.properties" />

Build number management

The out of the box buildnumber will create a tiny file to hold an integer which gets incremented from build to build, helping to uniquely identify each build.

<buildnumber file="build.number" />

This will create a file called build.number, if one doesn’t already exist.

#Build Number for ANT. Do not edit!
#Fri Jan 30 22:34:30 EST 2015
build.number=24

Obviously you can create and manage this manually if desired.

You can then “stamp” this number into the MANIFEST.MF in your target package format (e.g. EAR):

<property name="build.version" value="${application.version}.${build.number}" />

<target name="ear-assemble" depends="ear-init" description="Assemble the EAR">
    <!-- Ommitted for clarity -->

    <manifest file="${dist.dir}/META-INF/MANIFEST.MF">
        <attribute name="Built-By" value="${user.name}" />
        <section name="${application.name}">
            <attribute name="Specification-Title" value="${ant.project.name}" />
            <attribute name="Specification-Version" value="${application.version}" />
            <attribute name="Specification-Vendor" value="${application.vendor}" />
            <attribute name="Implementation-Title" value="${application.name}" />
            <attribute name="Implementation-Version" value="${build.version} ${TODAY}, ${TSTAMP}" />
            <attribute name="Implementation-Vendor" value="${application.vendor} " />
        </section>
    </manifest>

    <zip destfile="${dist.dir}/${versioned.ear.file}" basedir="${dist.dir}" />
</target>

Classpath management

Using Ant’s path and pathelement tasks, you can define all the file system cludge needed to get your code building. For example, I’ve bundled all the EE libraries into jboss.classpath, for quick and easy referencing throughout the rest of the build definition.

<!-- Class path entries -->
<path id="jboss.classpath">
  <pathelement location="${jboss.home}/modules/system/layers/base/javax/annotation/api/main/jboss-annotations-api_1.2_spec-1.0.0.Final.jar" />
  <pathelement location="${jboss.home}/modules/system/layers/base/javax/ejb/api/main/jboss-ejb-api_3.2_spec-1.0.0.Final.jar" />
  <pathelement location="${jboss.home}/modules/system/layers/base/javax/enterprise/api/main/cdi-api-1.1.jar" />
  <pathelement location="${jboss.home}/modules/system/layers/base/javax/inject/api/main/javax.inject-1.jar" />
  <pathelement location="${jboss.home}/modules/system/layers/base/javax/interceptor/api/main/jboss-interceptors-api_1.2_spec-1.0.0.Final.jar" />
  <pathelement location="${jboss.home}/modules/system/layers/base/javax/servlet/api/main/jboss-servlet-api_3.1_spec-1.0.0.Final.jar" />
  <pathelement location="${jboss.home}/modules/system/layers/base/javax/servlet/jsp/api/main/jboss-jsp-api_2.3_spec-1.0.1.Final.jar" />
</path>

<!-- Required library class path entries -->
<path id="common.libs">
    <pathelement location="${lib.dir}/logging/logback-classic-1.1.2.jar" />
    <pathelement location="${lib.dir}/logging/logback-core-1.1.2.jar" />
</path>

<path id="common.classpath">
    <path refid="common.libs" />
    <path refid="jboss.classpath" />
</path>

<path id="ejb.classpath">
    <path refid="jboss.classpath" />
    <path refid="common.classpath" />
</path>

<path id="web.classpath">
    <pathelement path="${ejb.build.dir}" />
    <path refid="jboss.classpath" />
    <path refid="common.classpath" />
</path>

<path id="findbugs.classpath">
    <fileset dir="${findbugs.home}/lib">
        <include name="*.jar" />
    </fileset>
</path>

Custom task definition

Ant is also very extensible. Third party providers can be easily plugged in via the taskdef directive, like so:

<taskdef name="findbugs" classname="edu.umd.cs.findbugs.anttask.FindBugsTask" classpathref="findbugs.classpath" />

The above for example, plugs in the excellent FindBugs Java static analyser, which will produce an HTML report of “dodgy code” as part of the build. More on this later.

Example end-to-end module

This particular module is an EJB. First a clean target is made. You can see lots of file system related cleanup happen here via the delete task. Of course, it supports things like recursive deletion and more.

<target name="ejb-clean" depends="" description="Clean up the classes folder and any generated jars">
  <delete dir="${ejb.build.dir}" failonerror="false" quiet="true" />
  <delete dir="${common.build.dir}" failonerror="false" quiet="true" />
  <delete failonerror="false" quiet="true">
    <fileset file="${build.dir}/${ejb.name}.jar" />
  </delete>
</target>

OK, clean up is taken care of. Next what setup activity is need to facilitate the build work. Here just one directory need to be created:

<target name="ejb-init" depends="ejb-clean" description="Setup required repositories for the ejb build">
  <mkdir dir="${ejb.build.dir}" />
</target>

Next, the real grunt work. The javac task is the heavy lifter here. Everything is quite self documenting. One thing to note is the exclude filter <exclude name="**/*Test.java" />, using a GLOB filter this will strip all unit tests (classes ending in ‘*Test.java”) out of the build.

<target name="ejb-compile" depends="ejb-init" description="Compile main source java files for jars">
  <javac destdir="${ejb.build.dir}" source="${javac.source}" target="${javac.target}" debug="${javac.debug}" failonerror="${javac.failonerror}">
    <src path="${ejb.src.dir}" />
    <exclude name="**/*Test.java"/>
    <classpath refid="ejb.classpath" />
  </javac>
  <copy todir="${ejb.build.dir}/META-INF">
    <fileset dir="${ejb.src.dir}/META-INF">
      <include name="**/*.*" />
    </fileset>
  </copy>
</target>

Finally we package the bytecode (class files) into a JAR.

<target name="ejb-assemble" depends="ejb-compile" description="Assemble the classes into jars">
  <jar destfile="${build.dir}/${ejb.name}.jar" basedir="${ejb.build.dir}" />
</target>

Done, we have our EJB project neatly packed up in a tidy little JAR.

Bonus bits

The next target shows off the built-in javadoc task, which will generate detailed HTML based code documentation about the solution, by simply running “ant javadoc”:

<target name="ant-spike-javadoc" depends="build">
  <delete dir="${dist.javadoc.dir}" failonerror="false" quiet="true" />
  <mkdir dir="${dist.javadoc.dir}" />
  <javadoc destdir="${dist.javadoc.dir}" author="true" version="true" use="true" windowtitle="Ben's Ant Spike" package="true" useexternalfile="yes">
    <fileset dir="${ejb.src.dir}" />
    <fileset dir="${web.src.dir}" />
    <tag description="To Do:" name="TODO" scope="all" />
  </javadoc>
</target>

And finally my personal favourite, this shows off the custom FindBugs Ant task that was registered via the taskdef directive. This will point FindBugs at the necessary code and classpaths, to perform a static analysis of the solution. It will convert findings into a stand-alone HTML report using the fancy.xslt transform.

<target name="findbugs">
  <delete dir="${dist.findbugs.dir}" failonerror="false" quiet="true" />
  <mkdir dir="${dist.findbugs.dir}" />
  <findbugs home="${findbugs.home}"
      output="html"
      effort="max"
      reportLevel="low"
      stylesheet="fancy.xsl"
      outputFile="${dist.findbugs.dir}/ant-spike-findbugs.html" >
    <auxClasspath refid="common.classpath" />
    <sourcePath path="${ejb.src.dir}" />
    <sourcePath path="${web.src.dir}" />
    <class location="${build.dir}/${ejb.dir}.jar" />
    <class location="${build.dir}/${web.dir}.war" />
  </findbugs>
</target>