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javabeanshell

BeanShell command line interpreter features

I'm trying to test BeanShell's command line interpreter in how it processes basic Java commands and syntax on my machine, and see if I can customise its behavior in any way. I've installed version 2.0b4 on my machine running OS X 10.10.1 (the JAR file is in /Library/Java/Extensions as per the instructions).

It's the closest thing to what I've been looking for, an interactive Java interpreter, but it doesn't have some standard features which a good interpreter should have.

  1. I'd like to be able to use the Up arrow key to reuse a previous command, but at the moment it doesn't recognise it, it just shows a control sequence. Is there a way to customise this for BeanShell?

  2. Is there a way to get BeanShell to print out the value of a variable if I've created it beforehand, just by naming it, like

    String s = new String( "Hello World!" ); s; Hello World!.

This is possible in Python for example.

  1. According to the documentation on importing Java classes which(<java class>); should return the classpath location of the specified Java class. But which( java.lang.String ); does not work for me, I get a NullPointerException:

    bsh % which(java.lang.String);
    Start ClassPath Mapping Mapping: Directory /Users/srm // Error: // Uncaught Exception: Method Invocation cp.getClassSource : at Line: 42 : in file: /bsh/commands/which.bsh : cp .getClassSource ( className )

    Called from method: which : at Line: 8 : in file: : which ( java .lang .String ) Target exception: java.lang.NullPointerException

    java.lang.NullPointerException

Any pointers or help would be appreciated.

Solution
    1. Run beanshell with jline.

    Download jline jar from http://jline.sourceforge.net/index.html and then you can do: 

    java -cp jline-1.0.jar:bsh-2.0b4.jar jline.ConsoleRunner bsh.Interpreter

    Line editing capability will be provided by jline. I found this hint here.

    There are issues running with jline2. First, you'll get:

     $ java -cp jline-2.12.jar:bsh-2.0b4.jar jline.ConsoleRunner bsh.Interpreter
 Exception in thread "main" java.lang.NoClassDefFoundError: jline/ConsoleRunner

    Due to this issue which is fixed. But then, use the new class and you still get: 

    $ java -cp jline-2.12.jar:bsh-2.0b4.jar jline.console.internal.ConsoleRunner bsh.Interpreter
Exception in thread "main" java.lang.IllegalArgumentException: wrong number of arguments

    due to this issue which is not fixed yet.

    1. Use show() command which will trigger showing of value.
    bsh % show();
bsh % String s = new String("Hello World");
bsh % s;
<Hello World>
bsh %

    It is mentioned in the Useful BeanShell Commands section of the documentation.

    1. Doesn't work for me either

    It doesn't fail in my case, but it didn't find it either. 

    bsh % which(java.lang.String);
Start ClassPath Mapping
Mapping: Archive: file:/Users/me/beanshell/jline-1.0.jar
Mapping: Archive: file:/Users/me/beanshell/bsh-2.0b4.jar
Mapping: Archive: file:/System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents/Classes/classes.jar
End ClassPath Mapping
null
bsh %