Update Jar file by adding new ones with Groovy

JarUpdater.groovy

import java.util.jar.*

def outputFile = new File("path/to/mylib/MyLib.jar")
def newFile1 = new File("path/to/new/file/NewClass1.class")
def newFile2 = new File("path/to/new/file/NewClass2.class")

updateJarFile(outputFile, newFile1, newFile2)

def updateJarFile(File jarFile, File... files){
	def tmpFile = File.createTempFile('tempJar', '.tmp')
	def jarTemp = new JarOutputStream(new FileOutputStream(tmpFile))
	JarFile outputJar = new JarFile(jarFile)
	boolean jarUpdated = false
	try {
		for (File f in files){
			def entry = new JarEntry(f.name)
			jarTemp.putNextEntry(entry)
			f.eachByte{def buf ->
				jarTemp.write(buf)
			}
			jarTemp.closeEntry()
		}
		// Copy original jar file to the temporary one.
		def jarEntries = outputJar.entries()
		for (JarEntry entry in jarEntries) {
			jarTemp.putNextEntry(entry)
			outputJar.getInputStream(entry).eachByte { def buf ->
				jarTemp.write(buf)			
			}
		}		
		jarUpdated = true
	} catch (Exception e){
		println("ERROR: ${e.message}")
	} finally {
		outputJar.close()
		jarTemp.close()
		if (!jarUpdated) {
			tmpFile.delete()
		}
	}
	if (jarUpdated){
		jarFile.delete()
		tmpFile.renameTo(jarFile)
	}
}