Re: just not getting it

Thu, 14 Aug 2003 11:50:52 -0700

One suggested addition to Conor MacNeill's example buildfile:

It's worth considering adding to the "compile" target so that it includes a "<depend>" task right before the "<javac>" task. "<javac>" alone does an OK but imperfect job of dependency checking and recompiling; preceding it with the appropriate <depend> makes the dependency checking almost perfect (though nothing can detect things like dependencies introduced because of run-time reflection...)

For example, say class A imports and uses class B. Then say everything is compiled and brought up to date. Next, say B is changed. Without a preceding <depend> invocation, <javac> will see that B.java is newer than B.class, so it'll recompile B. However, <javac> will not determine that A should also be recompiled, even though A might call a method in B whose signature has changed. When <depend> is used though, it will remove A.class when it sees that B has been modified, since <depend> (unlike <javac>) "knows" that A uses B.

Anyway, here's the documentation for <depend> :

http://ant.apache.org/manual/OptionalTasks/depend.html

Unfortunately, I don't have the time to add the exact <depend> element to the sample buildfile, but roughly speaking, the structure of the <depend> task mirrors that of the <javac> that follows it (especially in terms of the source and destination directories/files). In addition though, I like to add "closure=true" and "cache=${cacheDir}" attributes to the <depend> task.

Anyway, I also encourage people to take the time to learn about Ant features. I recently switched from using "make" to Ant, and I think Ant is far better...

Hope this helps,
Rich Wagner


From: Conor MacNeill <[EMAIL PROTECTED]>
Reply-To: "Ant Users List" <[EMAIL PROTECTED]>
To: "Ant Users List" <[EMAIL PROTECTED]>
Subject: Re: just not getting it
Date: Mon, 11 Aug 2003 11:25:34 +1000

Here is a complete and relatively simple example of a full build file to
compile and build a jar. This particular example uses a set of external
libraries in the build. If you don;t need that, you can drop out the
lib.classpath related stuff.

<project name="piston" default="jar">
  <property name="src.dir" value="src"/>
  <property name="build.dir" value="build"/>
  <property name="lib.dir" value="lib"/>
  <property name="jar.dir" value="jar"/>

  <path id="lib.classpath">
    <fileset dir="${lib.dir}"/>
  </path>

  <target name="compile">
    <mkdir dir="${build.dir}"/>
    <javac srcdir="${src.dir}" destdir="${build.dir}" debug="on">
      <classpath refid="lib.classpath"/>
    </javac>
  </target>

  <target name="jar" depends="compile">
    <mkdir dir="${jar.dir}"/>
    <jar destfile="${jar.dir}/piston.jar">
      <fileset dir="${build.dir}"/>
      <manifest>
        <attribute name="Main-Class" value="com.codefeed.piston.Piston"/>
      </manifest>
    </jar>
  </target>
</project>


On Mon, 11 Aug 2003 06:44 am, Gregory Seidman wrote:
>
> Would someone please explain how to handle the simple example of a
> directory/package tree full of .java source files to be built into a JAR?
> Once I have that toehold, I think I can start learning the rest.
>

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