JavaFunction.java

/*
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 *
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 *
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 *     notice, this list of conditions and the following disclaimer.
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 *   - Redistributions in binary form must reproduce the above copyright
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 *     from this software without specific prior written permission.
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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
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 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
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 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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 */

import javax.script.*;

import org.openjdk.engine.python.PythonScriptEngine;
import org.openjdk.engine.python.AbstractPythonScriptEngine.PyExecMode;
import org.openjdk.engine.python.PyJavaFunction;

void main() throws ScriptException {
    ScriptEngineManager m = new ScriptEngineManager();
    var e = (PythonScriptEngine) m.getEngineByName("python");

    PyJavaFunction.OneArgFunc pyFunc = (arg) -> {
        System.out.println("one arg Java function called with: " + arg);
        try {
            return e.fromJava(System.getProperty(arg.toString()));
        } catch (ScriptException ex) {
            throw new RuntimeException(ex);
        }
    };

    PyJavaFunction.VarArgsFunc pyVarArgsFunc = (args) -> {
        System.out.println("varargs Java function called with: " + args.length  + " args");
        var buf = new StringBuilder();
        for (var arg : args) {
            buf.append(arg.toString());
            buf.append(':');
        }
        try {
            return e.fromJava(buf.toString());
        } catch (ScriptException ex) {
            throw new RuntimeException(ex);
        }
    };


    e.put("getJavaProp", pyFunc);
    e.eval("print('func __name__ =', getJavaProp.__name__)");
    e.eval("print(getJavaProp('java.home'))");

    e.put("concat", pyVarArgsFunc);
    e.eval("print('func __name__ =', concat.__name__)");
    e.eval("print(concat('hello', 233, { 'x' : 42 }))");

    PyJavaFunction.NoArgFunc thrower = ()-> {
        System.out.println("Going to throw exception!");
        throw new RuntimeException("Java Error!!");
    };
    e.put("jexceptionFunc", thrower);
    e.setExecMode(PyExecMode.FILE);
    e.eval("""
    try:
        jexceptionFunc()
    except Exception as e:
        print("Caught exception from Java function call")
        print(e)
    """);
}