<javac> rebuilds even if source not changed

[Jean-Rene David-3]

Hello,

When a class is in a package, the <javac> target
always rebuilds it even if the source hasn't
changed. Here's a test case:

$ ant -version
Apache Ant version 1.7.0 compiled on December 13 2006

$ ls
build.xml
Welcome.java

$ cat Welcome.java
package My.Class;
public class Welcome
{
   public static void main(String[] args)
   {
      System.out.println("Hello World!");
   }
}

$ cat build.xml
<?xml version="1.0"?>
<project name="test" default="build" basedir=".">
   <target name="build">
      <mkdir dir="foo" />
      <javac srcdir="." destdir="foo" />
   </target>
</project>

$ ant
Buildfile: build.xml

build:
    [mkdir] Created dir: /tmp/testcase/foo
    [javac] Compiling 1 source file to /tmp/testcase/foo

BUILD SUCCESSFUL
Total time: 1 second

Now I just run it again:

$ ant
Buildfile: build.xml

build:
    [javac] Compiling 1 source file to /tmp/testcase/foo

BUILD SUCCESSFUL
Total time: 0 seconds

And it recompiles but the source file hasn't
changed.

My class is part of the My.Class package, so javac
put it in: foo/My/Class:

$ find
.
./Welcome.java
./build.xml
./foo
./foo/My
./foo/My/Class
./foo/My/Class/Welcome.class

But the <javac> task doesn't recurse the hierarchy
to find the class file. It only looks in the
"destdir" itself. So if I just:

$ touch foo/Welcome.class

Then <javac> doesn't rebuild the file:

$ ant
Buildfile: build.xml

build:

BUILD SUCCESSFUL
Total time: 0 seconds

What idiom am I missing?

Thanks for any input,

--
JR

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[Steve Loughran]

Jean-Rene David wrote:

> Hello,
>
> When a class is in a package, the <javac> target
> always rebuilds it even if the source hasn't
> changed. Here's a test case:
>
> $ ant -version
> Apache Ant version 1.7.0 compiled on December 13 2006
>
> $ ls
> build.xml
> Welcome.java
>
> $ cat Welcome.java
> package My.Class;
> public class Welcome
> {
>    public static void main(String[] args)
>    {
>       System.out.println("Hello World!");
>    }
> }
>
> $ cat build.xml
> <?xml version="1.0"?>
> <project name="test" default="build" basedir=".">
>    <target name="build">
>       <mkdir dir="foo" />
>       <javac srcdir="." destdir="foo" />
>    </target>
> </project>
>
> $ ant
> Buildfile: build.xml
>
> build:
>     [mkdir] Created dir: /tmp/testcase/foo
>     [javac] Compiling 1 source file to /tmp/testcase/foo
>
> BUILD SUCCESSFUL
> Total time: 1 second
>
> Now I just run it again:
>
> $ ant
> Buildfile: build.xml
>
> build:
>     [javac] Compiling 1 source file to /tmp/testcase/foo
>
> BUILD SUCCESSFUL
> Total time: 0 seconds
>
> And it recompiles but the source file hasn't
> changed.
>
> My class is part of the My.Class package, so javac
> put it in: foo/My/Class:
>
> $ find
> .
> ./Welcome.java
> ./build.xml
> ./foo
> ./foo/My
> ./foo/My/Class
> ./foo/My/Class/Welcome.class

>
> But the <javac> task doesn't recurse the hierarchy
> to find the class file. It only looks in the
> "destdir" itself. So if I just:
>
> $ touch foo/Welcome.class

you must move the class under the package name it is in. Without that
not only does ant not do any dependency checking (is it expected to
remember where every .class file comes from?) and sun's javac compiler
wont build files in the correct order.
--
Steve Loughran                  http://www.1060.org/blogxter/publish/5
Author: Ant in Action           http://antbook.org/

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[Jean-Rene David-3]

* Steve Loughran [2008.04.28 06:00]:
> Jean-Rene David wrote:
>> [...]
>> But the <javac> task doesn't recurse the hierarchy
>> to find the class file. It only looks in the
>> "destdir" itself. So if I just:
>>
>> $ touch foo/Welcome.class
>
> you must move the class under the package name it is in.

Of course. It works now. Thanks.

For posterity:

$ find
.
./build.xml
./src
./src/My
./src/My/Class
./src/My/Class/Welcome.java

$ ant
Buildfile: build.xml

build:
    [mkdir] Created dir: /data/home/jrdavid/work/java-practice/build
    [javac] Compiling 1 source file to /data/home/jrdavid/work/java-practice/build

BUILD SUCCESSFUL
Total time: 0 seconds

$ ant
Buildfile: build.xml

build:

BUILD SUCCESSFUL
Total time: 0 seconds

--
JR

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