如何强制ant javac任务覆盖目标目录中的类文件？

Question

Here is a very simplified version of what I am trying to achieve. I have two directories, Directory1 and Directory2 . Both directories contain Java source files. Some of the files in Directory2 can have the same fully qualified class name as the files in Directory1 .

Using ant, the files are compiled to a directory called CompileDirectory , first from Directory1 and then from Directory2 . I want the files in Directory2 to be compiled and overwrite the compiled class files from Directory1 . However, ant seems to ignore the classes that have the same fully qualified class name.

Here's a simple example -

Directory structure

$ ls -R
.:
build.xml  CompileDirectory  Directory1  Directory2

./CompileDirectory:

./Directory1:
A.java

./Directory2:
A.java

build.xml

<project name="TestProject" default="build" basedir=".">

<target name="build" depends="javac1, javac2" />

<target name="javac1">
     <javac srcdir="${basedir}/Directory1" destdir="CompileDirectory" includeantruntime="false"/>
</target>

<target name="javac2">
     <javac srcdir="${basedir}/Directory2" destdir="CompileDirectory" includeantruntime="false"/>
</target>

</project>

Ant run

$ ant -buildfile build.xml 

Buildfile: ...(path).../build.xml

javac1:
    [javac] Compiling 1 source file to ...(path).../CompileDirectory

javac2:

build:

BUILD SUCCESSFUL
Total time: 0 seconds

As can be seen, the javac2 target above does nothing.

When I run the Java program, I see that the class file is the one from Directory1.

$ cd CompileDirectory/
$ java A 
I am class A from directory 1

Is there a way to force the javac task in the javac2 target to compile the source file in Directory2 and overwrite the class file in the CompileDirectory ?

Answer 1

It has to do with timestamp of files and whether the compiler thinks the source is newer than class file.

<project name="TestProject" default="build" basedir=".">

<target name="build" depends="javac1, touch2, javac2" />

<target name="javac1">
     <javac srcdir="${basedir}/Directory1" destdir="CompileDirectory" includeantruntime="false"/>
</target>

<target name="touch2">
     <sleep seconds="2" />
     <touch datetime="now">
    <fileset dir="${basedir}/Directory2" />
     </touch>
</target>

<target name="javac2">
     <javac srcdir="${basedir}/Directory2" destdir="CompileDirectory" includeantruntime="false"/>
</target>

</project>

Answer 2

Other possible way to avoid this is create a stage directory and compile the classes there and copy back to original directory using overwrite option.

  <project name="TestProject" default="build" basedir=".">

<target name="build" depends="javac1, javac2, copy1" />

<target name="javac1">
     <javac srcdir="${basedir}/Directory1" destdir="CompileDirectory" includeantruntime="false"/>
</target>

<target name="javac2">
     <javac srcdir="${basedir}/Directory2" destdir="CompileDirectory1" includeantruntime="false"/>
</target>
<target name="copy1">
   <copy overwrite="on" todir="CompileDirectory">
       <fileset dir="CompileDirectory1">
                <include name ="**/*.*"/>
       </fileset>
   </copy>
</target>