Common Embedding Techniques Cheat Sheet

This document contains quick code snippets for common script embedding operations. The idea for this section came from the paper Embedding APIs of Java-Based Scripting Engines available at: http://pnuts.org/~tomatsu/embedding.html

Evaluate an Expression Reading from a String

ScriptEnvironment env = script.getScriptEnvironment();
Scalar value = env.evaluateExpression("3 * (10 / 2)");

Evaluate an Expression Reading from a String

ScriptEnvironment env = script.getScriptEnvironment();
Scalar value = env.evaluateExpression("3 * (10 / 2)");

Execute a Script Reading from a Stream (without creating a String)

ScriptLoader   loader = new ScriptLoader();
ScriptInstance script = loader.loadScript("name", inputStream);
script.runScript();

Catch a Runtime Script Error

public class Watchdog implements RuntimeWarningWatcher
{
   public void processScriptWarning(ScriptWarning warning)
   {
      String message = warning.getMessage();
      int    lineNo  = warning.getLineNumber();
      String script  = warning.getNameShort(); // name of script
   }
}

script.addWarningWatcher(new Watchdog());

Catch a Syntax Error when loading a Script

try
{
   ScriptInstance script;
   script = loader.loadScript("name", inputStream);
}
catch (YourCodeSucksException ex)
{
   Iterator i = ex.getErrors().iterator();
   while (i.hasNext())
   {
      SyntaxError error = (SyntaxError)i.next();

      String description = error.getDescription();
      String code        = error.getCodeSnippet();
      int    lineNumber  = error.getLineNumber();
   }
}

Set/Get a Variable without Parsing

script.getScriptVariables().putScalar("$var", SleepUtils.getScalar("value"));
Scalar value  = script.getScriptVariables().getScalar("$var");

Call a function/method without parsing scripts

script.callFunction("&functionName", new Stack());