Jar files can create a number of problems. Just today, I was playing with locating resources within jar files and that can be a pain. Also there is the creation and maintenance of manifest files. There also can be a problem when the jar contains multiple levels of jar files and this does not always work out of the box. What is a good tool for creating jar files, particularly of the case where jars need to be packaged inside of jars?

I am looking for a JAR file generator fitting these requirements:

• Able to create jar files containing other jar files
• Makes creation and maintenance of manifest files easy.