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Java Forum / General / February 2007Specify lib dir on command line
My java app needs to put a directory of jar files on the classpath. It's a pain to specify every jar file explicitly on the command line, because the files are going to change from time to time. I've seen a variety of ways to automatically include all the jar files in a directory using batch files and shell scripts. The trouble is that these scripts look like real hacks, and people are really doing backflips to do what should be very simple. Do more recent versions of java have a command line option to do what I'm looking for? Something like "java -mylibdir=/mylib"? I don't see it, but sometimes these things are easy to miss. > ... put a directory of jar files on the classpath. > ... > Do more recent versions of java have a command line option to do what > I'm looking for? Something like "java -mylibdir=/mylib"? It's been available for a long time. http://www.google.com/search?q=java+ext+dirs > http://www.google.com/search?q=java+ext+dirs I doesn't really mean the same thing as loading stuff from the normal classpath, though. Code loaded as a "standard extension" is loaded by a different classloader in a different security context. I'd avoid using the extension mechanism completely. -- chris >> Do more recent versions of java have a command line option to do what >> I'm looking for? Something like "java -mylibdir=/mylib"? > > It's been available for a long time. > > http://www.google.com/search?q=java+ext+dirs That is a global thing and just like CLASSPATH env var should be general avoided and only used where it is really needed. Arne Chris wrote on 25.02.2007 10:17: > My java app needs to put a directory of jar files on the classpath. It's > a pain to specify every jar file explicitly on the command line, because [quoted text clipped - 8 lines] > I'm looking for? Something like "java -mylibdir=/mylib"? I don't see it, > but sometimes these things are easy to miss. The preferred way is to create a manifest file in your "main" jar, that references all other jars in the directory. This step can be automated during build (NetBeans for one, will automatically do that for you, but it's quite easy to do with Ant as well). Having said that, the documentation for Java6 at http://java.sun.com/javase/6/docs/technotes/tools/windows/java.html http://java.sun.com/javase/6/docs/technotes/tools/solaris/java.html contains a description that might be what you are looking for: "As a special convenience, a class path element containing a basename of * is considered equivalent to specifying a list of all the files in the directory with the extension .jar or .JAR (a java program cannot tell the difference between the two invocations). " I haven't used it though. A third option is to write your own classloader that simply includes all files from the base directory. Thomas > My java app needs to put a directory of jar files on the classpath. It's > a pain to specify every jar file explicitly on the command line, because [quoted text clipped - 8 lines] > I'm looking for? Something like "java -mylibdir=/mylib"? I don't see it, > but sometimes these things are easy to miss. Java 1.6 supports wildcards in classpath to mean all jars in dir. Arne Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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