[CMake] FindJava.cmake update

[Hendrik Sattler]

Zitat von Mathieu Malaterre <mathieu.malaterre at gmail.com>:

> Hendrik,
>
> On Mon, Nov 2, 2009 at 3:19 PM, Hendrik Sattler   
> <post at hendrik-sattler.de> wrote:
>> Zitat von Mathieu Malaterre <mathieu.malaterre at gmail.com>:
>>
>>> I updated the FindJava.cmake. It now implements the VERSION* stuff,
>>> and I fixed the naming convention as per the readme.txt. I tested on
>>> linux/gcj, linux/sun-java and linux/openjdk-6
>>
>> Why are you using NO_DEFAULT_PATH and but listing /usr/bin and
>> /usr/local/bin? This is wrong and breaks "/usr/local/bin before /usr/bin".
>> Just drop those from the list and also your NO_DEFAULT_PATH. If you want
>> your list first, use HINTS instead of PATHS.
>
> Fixed. Thanks !

Thanks, too.

However, it can still be improved. The current (partial) list is:
   /usr/lib/java/bin
   /usr/share/java/bin
   /usr/local/java/bin
   /usr/local/java/share/bin
   /usr/java/j2sdk1.4.2_04
   /usr/lib/j2sdk1.4-sun/bin
   /usr/java/j2sdk1.4.2_09/bin
   /usr/lib/j2sdk1.5-sun/bin
   /opt/sun-jdk-1.5.0.04/bin

I am still not sure that the path list is good. Newer version should  
come first to possibly match the version criteria. OTOH, if there is a  
version request for EXACT 1.4, finding version 1.5 is wrong when 1.4  
is also installed (remember: more than one can be installed at the  
same time). Same applies for the registry entries. The list should be  
assembled according to the version requested. There's no point in  
looking for other versions than the requested one(s).
The odd paths like /usr/java/j2sdk1.4.2_04 (actually the whole list  
above) should just go away: why only list those specific versions and  
locations? If java is installed there, it is likely to either have  
symlinks to the normal bin locations or to be in PATH or JAVA_HOME.

I also think that caching $ENV{CLASSPATH} should be part of the  
module. This can be done like this:
if ( NOT Java_CLASSPATH )
   set ( Java_CLASSPATH $ENV{CLASSPATH} CACHE STRING "java classpath" )
endif ( NOT Java_CLASSPATH )
if ( NOT CMAKE_SYSTEM_NAME STREQUAL "Windows" )
   # Non-Windows classpath may use : instead of ;
   # so make this a cmake list here by always using ;
   string ( REPLACE ":" ";" Java_CLASSPATH "${Java_CLASSPATH}" )
endif ( NOT CMAKE_SYSTEM_NAME STREQUAL "Windows" )
mark_as_advanced ( Java_CLASSPATH )

This makes it easier to call java with:
set(foo_CP "${Java_CLASSPATH})
list(APPEND foo_CP /location/to/foo.jar)
add_custom_command (
   OUTPUT ${foo}
   COMMAND "${Java_JAVA_EXECUTABLE}" -cp "${foo_CP}" ${foo_main_class}
   DEPENDS "${bar}"
   VERBATIM
)

HS

PS: For the registry keys that try to guess future versions of java:  
cmake-2.8 would have been a great chance to allow getting all entries  
of a directory or registry group. Besides FindJava.cmake, many other  
cmake modules would benefit from such a feature (e.g. boost).