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September 10, 2013

Groovy Goodness: Running Scripts from a JAR Archive

We can run Groovy scripts from the command-line with the groovy command followed by the name of Groovy script file. We could already run script with the http: protocol as described in this blog post. Since Groovy 2.1 we can even run scripts that are packaged in an archive with the jar: protocol.

Let's create first a simple Groovy script and package it in a sample.jar file.

// File: cookies.groovy

println 'Running from inside a JAR: '
def cookies = ['Cookie', 'Biscuit'].collect { it.toUpperCase() }.join(',')
println cookies

We can use the jar command to place the file cookies.groovy in sample.jar:

$ jar cvf sample.jar cookies.groovy
added manifest
adding: cookies.groovy(in = 153) (out= 126)(deflated 17%)
$ jar tvf sample.jar
     0 Fri Sep 06 14:50:24 CEST 2013 META-INF/
    68 Fri Sep 06 14:50:24 CEST 2013 META-INF/MANIFEST.MF
   153 Fri Sep 06 14:48:44 CEST 2013 cookies.groovy

We now have a single Groovy script, but we can place more scripts inside the JAR file if we want to. To run a specific Groovy script file we must use the jar: protocol. We must specify the location of the JAR file with the file: or http: protocols followed by !/. In some shells the ! symbol is a special character and we might need to escape it. For example on Mac OSX we need to invoke the following command to run our script placed in the JAR file:

$ groovy jar:file:sample.jar'!'/cookies.groovy
Running from inside a JAR:

We can place the JAR file on a web server and use the jar:http://<address>/sample.jar!/cookies.groovy syntax to run the scripts remotely.

Code written with Groovy 2.1.6