Executing JavaScript on the JVMΒΆ

As you will see in subsequent sections, navigating and manipulating the JVM’s class and object structure can result in verbose and cumbersome Python code. Therefore, Javabridge ships with the JavaScript interpreter Rhino, which runs on the JVM. In many cases, the most convienient way to interact with the JVM is to execute a piece of JavaScript.

For more information on using Rhino with the JVM see https://developer.mozilla.org/en-US/docs/Rhino/Scripting_Java


>>> javabridge.run_script("2 + 2")
>>> javabridge.run_script("a + b", bindings_in={"a": 2, "b": 3})
>>> outputs = {"result": None}
>>> javabridge.run_script("var result = 2 + 2;", bindings_out=outputs)
>>> outputs["result"]
>>> javabridge.run_script("java.lang.Math.abs(v)", bindings_in=dict(v=-1.5))

A conversion is necessary when converting from Python primitives and objects to Java and JavaScript primitives and objects. Python primitives are boxed into Java objects - Javascript will automatically unbox them when calling a method that takes primitive arguments (e.g. the call to Math.abs(double) as in the above example. The following is a table of bidirectional translations from Python to Java / Javascript and vice-versa:

Python Java - boxed Java-primitive
bool java.lang.Boolean boolean
int java.lang.Integer int
long java.lang.Long long
float java.lang.Double double
unicode java.lang.String N/A
str (Python->java only) java.lang.String N/A
None null N/A