BeanShell Language

Website Developer
7 min readJan 5, 2024

Researching BeanShell has proven to be worth my time. It is a handy Java source interpreter. BeanShell is very versatile in Java regarding what it can be used for and its Benefits. BeanShell has been around for almost as long as Java has, growing and helping code ever since.

What is BeanShell?

BeanShell is a lightweight, embeddable Java source interpreter that includes features in object scripting. BeanShell is written in the Java Language. BeanShell is exceptional in the way it can execute standard Java syntax. It can extend the syntaxes with popular scripting techniques that include loose types, commands, and method closures like those found in Perl and JavaScript.

BeanShell History

During 1993, Patrick Niemeyer was heavily interested in the Tcl/Tk scripting. He was working at Southwestern Bell Technology Resources at the time. With the advice of a friend, Patrick picked up a coding language called Oak, which would later become Java. Patrick unknowingly became one of the first book writers for the language that went mainstream. The book was called “Exploring Java, O’Reilly & Associates.” Patrick also created Java’s first scripting language, BeanShell.

BeanShell was not ready to be released to the public until 1997. It didn’t do anything special before Java’s 1.1 updates, where it had helped create updates for Patrick’s book. Because BeanShell started to help code in Java, Patrick decided to “Polish it up and release it.”

Who Uses BeanShell and Trends of BeanShell’s Popularity.

Since its release, BeanShell has slowly accumulated more popularity. Though BeanShell has had its ups and downs in trending popularity, it has leveled out in growth. BeanShell is bundled in a bunch of programming software nowadays, so much so that it might be hard to find a Java scripting language that doesn’t include some aspect of BeanShell. Some notable bundles with BeanShell integrated into their product include Emacs as part of their JDE, NetBeans for Sun Microsystems, Forte for Java IDEs, and BEA’s WebLogic application server. With the logic of BeanShell being bundled in all these programs, it makes sense that BeanShell has found its home in many places. The most significant discrepancy between the people who use BeanShell recorded is very wild. Scientists from CERN in their super techy laboratories are recorded to have used BeanShell in their software. While at the other end of the spectrum, BeanShell is being used to teach nine-year-olds how to code. Another significant discrepancy includes BeanShell being integrated into “Large financial applications.” While on the other end of the spectrum, BeanShell can be embedded into remote floating Buoys.

Examples of Code


BeanShell can support Java 1.5 for-loops for anything that covers arrays and collections. Even though BeanShell is not limited to Java 1.5

List foo = aRandomList();
for ( someElement : foo )
print( someElement );
for ( Object anotherElement: foo )
print( anotherElement );
int [] array = new int [] { 1, 2, 3 };
for( i : array )
for( char c : "some string" )
print( c );


All the regular Java statements will work for BeanShell. BeanShell only really builds upon Java and improves the quality of life features. Even so, here is an example of a very simple if statement.

if ( something happening ) {
int x = 1;
y = x*5;

For all variables, they are assigned a type. Like for instance, “JButton.” BeanShell can support these types, as is the norm in other programming languages like Java. For these types of assigned-type variables, assigning a different type to those variables will always result in an error message. This kind of situation is best suited for Bean Shell. One of BeanShell’s most prominent features is the ability to assign variables without declaring them first or assigning any type. This process would also classify these variables as dynamic. BeanShell will check those variables when the code is run at that time. Here are some examples where Java syntax is typed loosely.

// Loosely Typed Java syntax. 
// Use a hashtable
hashtable = new Hashtable();
date = new Date();
hashtable.put( "today", date );
// Print the current clock value
print( System.currentTimeMillis() );
// Loop
for (i=0; i<5; i++)
// Pop up a frame with a button in it
button = new JButton( "My Button" );
frame = new JFrame( "My Frame" );
frame.getContentPane().add( button, "Center" );

Looking directly at the code from a glance, the difference between traditionally assigned and loosely typed Java syntax doesn’t seem like much. But it is amazing. The technique proves helpful when scripting is part of the development and testing process. It is beneficial when the software is interactable.

A “loose” variable can be assigned to a type, and then its type can be overwritten to another later. The opposite can also be true. There can be no variable, but BeanShell can hold the Java Primitive values like int and Boolean. BeanShell is also brilliant when it comes to assigning those primitive values. It knows the real types and will only allow the appropriate use of those values. This includes doing the correct “numeric promotion” akin to what Java usually does when used in an expression.

What is BeanShell used for?

BeanShell can interactively test Java code, find bugs in code, and find ways to improve upon the code through testing. Scripting Java allows it to be used in many applications.

Those applications include:

  • Rapid Prototyping is a group of techniques that makes it easier to create a scale model of something — frequently done to create three-dimensional computer-aided design data (CAD). The data is then used to make 3D visual renders or printed with a 3D printer.
  • User Scripting Extension is a program frequently written in JavaScript for modifying web pages to customize the browsing experience. A user script manager browser extension like Greasemonkey is standard to run smoothly on the Firefox internet browser.
  • Rule Engines is a program that surveys data provided and then executes actions corresponding to the conditions matched in the provided data. Rule engines are used for many reasons. One reason is that its code is straightforward to read, even for people unfamiliar with coding. Another reason is that all rules are in one place for easy organization. Code maintenance is easy since rules can easily be updated.
  • Testing BeanShell is easily testable with its debug() command. Allowing for easy revisions in code.
  • Dynamic Deployment: BeanShell can deploy, redeploy, and un-deploy an application or module without restarting the server. This is very useful for developers since they can bring an application or module to life without wasting time restarting the server for the app or module. Whenever a redeployment usually happens, it breaks every session — forcing every client to restart their session.
  • Embedded systems are a godsend of a feature. Embed BeanShell into systems makes it very flexible in what kind of code can be included. BeanShell can upgrade the system to be highly customizable without all the hardships of compiling Java classes and knowing Java syntax.
  • Java education, BeanShell is very versatile, so much so that the difference between the super technical and the most simple developers ranges from high-energy physics laboratories at CERN to programming classrooms for nine-year-olds.

How does BeanShell work exactly?

BeanShell is very lightweight and embeddable. This means BeanShell can be called into Java applications to execute code dynamically. It can also be running at run-time or provide extensibility to the application. BeanShell can also manipulate Java applications. Allowing for work with Java objects and application programming interfaces dynamically. Thanks to BeanShell being written in Java and running in the same Virtual Machine as an application, references to live objects can freely pass into scripts and return them as results. BeanShell is a combination of dynamically interpreted Java, a scripting language, and a flexible environment. All in one.

What are some benefits of BeanShell?

The most significant benefits of BeanShell are as follows:

  • BeanShell can execute the entirety of Java syntax dynamically. It can also run Java code written as only fragments. Even loosely typed Java is different from BeanShell. BeanShell has more convenient benefits, but these are the most prominent.
  • Full transparent access to all Java objects as well as application programming interfaces.
  • BeanShell can be run in four modes:
  • Command Line
  • Console
  • Applet
  • Remote Session Server
  • Works well with secure environments. Does not need a class loader or bytecode generation for the most part.
  • The BeanShell interpreter is a tiny file. BeanShell is around one hundred fifty kilobytes as a jar file.
  • BeanShell is 100% Java and nothing else.
  • BeanShell is 100% Free!!
  • Java Evaluation Benefits
  • BeanShell can dynamically evaluate entire Java source classes and isolate Java methods, statements, and expressions.
  • Scripting Benefits
  • Variables can be typed optionally.
  • Scripted methods can have optionally typed arguments and can also return values.
  • Scripted objects using method closures.
  • Scripted interfaces that can also include event handlers.
  • Convenience syntax for handling Properties, hash tables, and primitive wrapper types in JavaBean.
  • Variables can be auto-allocated to emulate Java property files.
  • An extensible set of utility and shell-like commands
  • Dynamic classpath management useful for fine-grained class reloading
  • Dynamic command loading along with user command path
  • Sophisticated namespace and call stack management
  • Detailed error reporting

BeanShell is one crazy helpful Java source interpreter. It is almost a necessity when coding with Java. A Java coder made beanShell for coding with Java. It has been around since the beginning! (although not released to the public until later) Many benefits and quality-of-life changes come with working with BeanShell that only a fool wouldn’t use!