Question

So I’m trying to run a server in Eclipse and get this error when I run it.

    java.lang.NullPointerException
[1/19/13 9:07 PM]:  at com.rs2.util.Misc.loadScripts(Misc.java:544)
[1/19/13 9:07 PM]:  at com.rs2.Server.run(Server.java:129)
[1/19/13 9:07 PM]:  at java.lang.Thread.run(Thread.java:662)

Here is line 129 in Server.java:

Misc.loadScripts(new File("./data/ruby/"));

And here is the line 544 in loadScripts:

engine.eval(new FileReader(file));

And, in case it’s needed, here is the rest of the loadScripts class:

public static void loadScripts(File directory) {
        try {
            ScriptEngine engine = new ScriptEngineManager().getEngineByName("jruby");
            if (!directory.exists() || !directory.isDirectory()) {
                throw new IllegalArgumentException("Missing scripts folder! " + directory.getAbsolutePath());
            }
            for (File file : directory.listFiles()) {
                if (file.isDirectory()) {
                    loadScripts(file);
                } else {
                    if (file.getName().endsWith(".rb")) {
                        engine.eval(new FileReader(file));
                    }
                }
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (ScriptException e) {
            e.printStackTrace();
        }
    }

If anyone can help, please answer. Thanks in advance.

Answer 1

This happens because engine is null when line 544 is executed:

engine.eval(new FileReader(file));

And it’s null because the ScriptEngineManager didn’t find the JRuby scripting engine, that you were trying to load in this line:

ScriptEngine engine = new ScriptEngineManager().getEngineByName("jruby");

Make sure that the JRuby script engine is included on the classpath when you run this program.

You should also add a check in your program, for example like this:

ScriptEngine engine = new ScriptEngineManager().getEngineByName("jruby");
if (engine == null) {
    throw new UnsupportedOperationException("JRuby scripting engine not found");
}