BeanShell Tutorial: Quick Start On Invoking Your Own Or External Java Code From The Shell

bshsplash3BeanShell is a lightweight scripting language that’s compatible with the Java language.
It provides a dynamic environment for executing Java code in its standard syntax but also allow common scripting conveniences such as loose types, commands, and method closures like those in Perl and JavaScript. It is considered so useful that it should became part of the J2SE at some time in the future (the BeanShell Scripting Language JSR-274 , has passed the voting process with flying colors).

Here I simply describe how to call you own code or any external existing code directly from the bean shell. You first have to download the last bean shell jar release. Let’s suppose that you put it in the directory “C:libs” along with the famous Apache commons lang library. So we suppose that “C:libs” contains two jars called bsh-2.0b4.jar and commons-lang-2.4.jar.

Open a command prompt and type:

java -cp C:libsbsh-2.0b4.jar;C:libscommons-lang-2.3.jar bsh.Interpreter

You should see a prompt “bsh %” indicating that the bean shell session has started. So here an example of session using the method getLevenshteinDistance from the StringUtils utility class of the apache commons lang package:

bsh % import  org.apache.commons.lang.StringUtils;
bsh % d = StringUtils.getLevenshteinDistance("Louisville Slugger", "Lousiville Slugger");
bsh % print(d);

Note that instead of having to type the precise import, you can type instead:

bsh % import *;

This will trigger a set of “mappings” between the shell and the external jars that you specified in your classpath. By doing this, just remember that you are importing every possible class accessible from the classpath so it may force you to type the full path of classes in the case that two classes exists with the same name in different packages (it happens more often than one may think).

A good intermediary solution is to define a file called .bshrc and to put there all the specific imports that you are usually using. Then, while invoking the interpreter, just set the java system property user.home to the directory containing the .bshrc file. Let’s say for example that it is located in “C:appbshconfig”, you just have to type:

java -Duser.home=C:appbshconfig -cp C:libsbsh-2.0b4.jar;C:libscommons-lang-2.3.jar bsh.Interpreter

Note that you can add to the java command any options that you need (for instance you can use -Xmx if you need to).

For a complete doc of bean shell commands, consult the bean shell documentation page.

For an eclipse plugin allowing you to perform auto-complete from the bean shell and other nice features, take a look at EclipseShell (I didn’t tested it yet but the site contains nice screencasts and documentation).

One thought on “BeanShell Tutorial: Quick Start On Invoking Your Own Or External Java Code From The Shell

Comments are closed.