[Scons-users] Questions about building Java code

[Dirk Bächle]

Hi Dirk,

On 26.04.2013 12:08, Dirk Heinrichs wrote:

> Hi,

>

> I'm doing a little evaluation of Scons as a possible replacement for

> Ant. I've setup a small test build containing two .java files and did a

> typical build, edit, build cycle. This is what I got:

>

> % scons -Q

> /usr/bin/javac -d classes -sourcepath src src/ExtraClass.java src/MainClass.java

> % vim src/MainClass.java

> % scons -Q

> Retrieved `classes/ExtraClass.class' from cache

> /usr/bin/javac -d classes -sourcepath src src/ExtraClass.java src/MainClass.java

>

> Two things look strange here:

>

> 1) Why is classes/ExtraClass.class retrieved from the cache although its

> source file didn't change?

> 2) Why is anything retrieved from the cache at all when javac

> recompiles all the files afterwards?


I'm no Java expert but here's what I see: You are obviously using 
CacheDir to share created files. This is why an up-to-date version of 
'classes/ExtraClass.class' can be retrieved from the CacheDir, instead 
of recompiling ExtraClass.java. So that's what SCons is doing in 1).

ad 2): You changed "MainClass.java", so SCons has to recompile it...also 
using ExtraClass.class, since it might contain definitions MainClass 
depends on.

So it all makes sense to me.

Best regards,

Dirk