Including large number of jars in classpath...

Question

Hello,
I have an application that relies on over 100 jars and a set of classes - I have been using an IDE to set the classpath so far, which has been fine, but I need to distribute the application to others, and so need to bundle the classes, preferably as a jar. I have tried multiple variations of setting the classpath within the manifest for the jar file (that includes only my source), and have finally resorted to setting the classpath using a batch file and running directly using the classes. Neither method works - the classpath seems to be too long - the best results I've got are with the bat file, but this loads all but the last 8 jars - taking out a few jars adds one or two more, so this seems to confirm a maximum length for the classpath. (FYI, I have previously used the manifest to set the classpath and this has been fine, but in this case I had only two jars.)
Has anyone come across this problem, and if so, have you managed to find a solution - I've combed through the relevant postings to this forum and have found similar problems but no actual Manifest or bat file example apart from a description of what was done, all of which I've tried, and none of which worked. The option to use the wildcard * in the classpath environment variable doesn't work because I cannot use JDK1.6 - the external libraries need to run on JDK1.5 - I have actually tried this but it is not expanded.
Aba-Sah

Answer 1

Another option is to package (or "flatten") all the dependencies into a single JAR. I use the following Groovy script in ANT builds to copy files from many JARs to a single location ...
<!-- set up a groovy task -->
<taskdef name="groovy"
          classname="org.codehaus.groovy.ant.Groovy"
     classpathref="compile-cp"/>
<!-- you'll need to adapt this to your environment -->
<target name="flattenLibs">
          <mkdir dir="${dist-temp}"/>
          <groovy>
               import java.io.*;
               import java.util.zip.*;
               import java.util.jar.*;
               def copyBinary(isDir, dfile, is) {
                    def file = new File( dfile )
                    if ( isDir ) {
                         file.mkdirs()
                    else {
                         def preIndex = Math.max( dfile.lastIndexOf( "/" ), dfile.lastIndexOf( "\\" ) )
                         if ( preIndex > 0 )
                              new File( dfile.substring( 0, preIndex + 1 ) ).mkdirs()
                         def fout = new BufferedOutputStream( new FileOutputStream( file ) )
                         try {
                              byte[] buffer = new byte[ 1024 ]
                              int i
                              while ( ( i = is.read( buffer, 0, buffer.length ) ) > 0 )
                                   fout.write( buffer, 0, i )
                              fout.close()
                         finally {
                              fout.close()
               def destDir = project.getProperty( "dist-temp" )
               if ( destDir.endsWith( "\\" ) || destDir.endsWith( "/" ) )
                    destDir = destDir.subString( 0, destDir.length() - 1 )
               // Look at "core-cp"
               def libs = []
               project.getReference( "core-cp" ).list().each { pe ->
                    if ( pe.endsWith( ".jar" ) )
                         libs.add( pe )
               def noisy = "true".equalsIgnoreCase( project.getProperty( "noisy" ) )
               // Copy:
               libs.each { lib ->
                    def jfile = new JarFile( new File( lib ) )
                    def e = jfile.entries()
                    while ( e.hasMoreElements() ) {
                         def entry = e.nextElement()
                         def name = entry.getName()
                         if ( noisy )
                              println "Copying \"${name}\" ..."
                         def is = new BufferedInputStream( jfile.getInputStream( entry ) )
                         try {
                              copyBinary( entry.isDirectory(), "${destDir}/${name}", is )
                         finally {
                              is.close()
          </groovy>
     </target>