Problem with Java Ant build.xml

Question

I am writing an assembly file for its basic properties of starting, cleaning, and compiling. Here is what I have:

<?xml version="1.0" encoding="ISO-8859-1"?> <project default="compile"> <description> Compile and run the Java files for Lab7 </description> <target name="prob1" depends='compile'> <java classname='prob1'> <classpath path='./'/> <arg value='Gertrude'/> <arg value='Justin'/> </java> </target> <target name="prob2" depends='compile'> <java classname='prob2'> <classpath path='./'/> <arg value='28'/> </java> </target> <target name="prob3" depends='compile'> <java classname='prob3'> <classpath path='./'/> <arg value='2000'/> </java> </target> <target name="prob4" depends='compile'> <java classname='prob4'> <classpath path='./'/> <arg value='2'/> </java> </target> <target name="compile"> <javac srcdir='./' includeantruntime="false"/> </target> <target name="clean"> <delete> <fileset dir="./"> <include name='*.class'/> </fileset> </delete> </target> </project> 

I am trying to run each problem with different arguments one at a time. Like in prob1, I want to run it with a name and then with a middle name, how to do it?

Answer 1

Yes, something like this is possible with antlib, which offers a wide range of functions, for example, for loops, if conditions and macros. You can define a macro as

 <macrodef name="call-cc"> <attribute name="target"/> <attribute name="param1"> <attribute name="param2"> <element name="yourtask"> <java classname='$name'> <classpath path='./'/> <arg value='@{param1}'/> <arg value='@{param2}'/> </java> </element> </macrodef> 

and then you can call it like that

 <call-cc target="unittests" param1="bla" param2="blabla"/> 

You can read about antlib in the manual.

Answer 2

As explained by @Moataz and @jheddings, ANT macrodef is the best way to abstract these repetitive and parameterized actions.

The following working example also demonstrates some additional enhancements to your build, such as using properties to abstract the location of your project files and using ANT paths to manage runtime class paths.

 <project default="compile"> <description> Example build file. Demonstrates the following - Properties - Build paths - Running java programs using a macrodef </description> <property name="src.dir" location="src/main/java"/> <property name="build.dir" location="build"/> <property name="classes.dir" location="build/classes"/> <path id="runtime.path"> <pathelement location="${classes.dir}"/> </path> <macrodef name="call-prog"> <attribute name="classname"/> <attribute name="arg1"/> <attribute name="arg2" default=""/> <sequential> <java classname='@{classname}' classpathref="runtime.path"> <arg value='@{arg1}'/> <arg value='@{arg2}'/> </java> </sequential> </macrodef> <target name="compile"> <mkdir dir="${classes.dir}"/> <javac destdir="${classes.dir}" srcdir='${src.dir}' includeantruntime="false"/> </target> <target name="clean"> <delete dir="${build.dir}"/> </target> <target name="prob1" depends='compile'> <call-prog classname="org.demo.App" arg1="Justin" arg2="Gertrude"/> </target> <target name="prob2" depends='compile'> <call-prog classname="org.demo.App" arg1="28"/> </target> .. .. </project> 

Finally, when you have created a repository of common macro codes that you use in all your assemblies, you can consider them as ANTlib . The best way to share assembly logic in ANT, in my opinion. For this simple example, this would be redundant.

Answer 3

You can do this using antcall or macrodef as follows:

 <target name="run-prob" depends="compile"> <fail unless="prob-class" /> <fail unless="prob-args" /> <java classname="${prob-class}"> <classpath path="./"/> <arg line="${prob-args}"/> </java> </target> <target name="prob1" depends="compile"> <antcall target="run-prob"> <param name="prob-class">prob1</param> <param name="prob-args">justin gertrude</param> </antcall> </target> <target name="prob2" depends="compile"> <prob class="prob2"> <arg value='28'/> </prob> </target> <macrodef name="prob"> <attribute name="class" /> <element name="args" implicit="true" /> <sequential> <java classname="@{class}"> <classpath path="./"/> <args /> </java> </sequential> </macrodef> 

The advantage of using antcall is that you can make calls from the command line, for example:

 ant -Dprob-class=prob3 -Dprob-args=2000 run-prob 

The advantage of using macrodef is that it looks a little cleaner and more obvious in the ant file. Of course, you can also mix the two methods and call the macro from the antcall target or vice versa.