Question

I wanted to boot up a Jython interpreter inside the plugin, then execute files inside the interpreter.

package com.jakob.jython;

import org.bukkit.plugin.java.JavaPlugin;
import org.python.core.PyObject;
import org.python.util.PythonInterpreter;

import java.io.IOException;
import java.io.InputStream;
import java.util.logging.Logger;

public class EmbeddedJython extends JavaPlugin {

    private static final Logger log = Logger.getLogger("Minecraft");
    private PythonInterpreter interpreter;
    private PyObject plugin;


    public void onEnable() {
        log.info("JythonTest enabled");
        this.interpreter = new PythonInterpreter();
        log.info("Jython interpreter fired up and cooking on gas");

        log.info("Loading Python Plugin");

        InputStream pythonScript = EmbeddedJython.class.getResourceAsStream("MyPlugin.py");
        this.interpreter.execfile(pythonScript, "MyPlugin.py");

        log.info("Getting plg method.");
        this.plugin = this.interpreter.get("plg");
        log.info("Plugin loaded");
        log.info(plugin.invoke("onEnable").toString());
    }

    public void onDisable() {
        log.info(plugin.invoke("onDisable").toString());
        log.info("Jython disabled");
    }

}

In other tests I can get the Jython interpreter up and running strings I hand it but when I use the above snippet I end up with an exception that looks something like this:

11:03:38 [SEVERE] Error occurred while enabling JythonTest v0.12 (Is it up to da
te?): null
java.io.IOException: Stream closed
        at java.io.BufferedInputStream.getInIfOpen(Unknown Source)
        at java.io.BufferedInputStream.fill(Unknown Source)
        at java.io.BufferedInputStream.read(Unknown Source)
        at org.python.core.ParserFacade.adjustForBOM(ParserFacade.java:371)
        at org.python.core.ParserFacade.prepBufReader(ParserFacade.java:298)
        at org.python.core.ParserFacade.prepBufReader(ParserFacade.java:288)
        at org.python.core.ParserFacade.parse(ParserFacade.java:183)
        at org.python.core.Py.compile_flags(Py.java:1717)
        at org.python.util.PythonInterpreter.execfile(PythonInterpreter.java:235
)
        at com.jakob.jython.EmbeddedJython.onEnable(EmbeddedJython.java:26)
        at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:125)
        at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader
.java:750)
        at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManage
r.java:253)
        at org.bukkit.craftbukkit.CraftServer.loadPlugin(CraftServer.java:132)
        at org.bukkit.craftbukkit.CraftServer.loadPlugins(CraftServer.java:110)
        at net.minecraft.server.MinecraftServer.e(MinecraftServer.java:218)
        at net.minecraft.server.MinecraftServer.a(MinecraftServer.java:205)
        at net.minecraft.server.MinecraftServer.init(MinecraftServer.java:145)
        at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:265)
        at net.minecraft.server.ThreadServerApplication.run(SourceFile:394)

java.io.IOException: java.io.IOException: Stream closed

        at org.python.core.PyException.fillInStackTrace(PyException.java:70)
        at java.lang.Throwable.<init>(Throwable.java:181)
        at java.lang.Exception.<init>(Unknown Source)
        at java.lang.RuntimeException.<init>(Unknown Source)
        at org.python.core.PyException.<init>(PyException.java:46)
        at org.python.core.PyException.<init>(PyException.java:43)
        at org.python.core.Py.JavaError(Py.java:481)
        at org.python.core.ParserFacade.fixParseError(ParserFacade.java:104)
        at org.python.core.ParserFacade.parse(ParserFacade.java:186)
        at org.python.core.Py.compile_flags(Py.java:1717)
        at org.python.util.PythonInterpreter.execfile(PythonInterpreter.java:235
)
        at com.jakob.jython.EmbeddedJython.onEnable(EmbeddedJython.java:26)
        at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:125)
        at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader
.java:750)
        at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManage
r.java:253)
        at org.bukkit.craftbukkit.CraftServer.loadPlugin(CraftServer.java:132)
        at org.bukkit.craftbukkit.CraftServer.loadPlugins(CraftServer.java:110)
        at net.minecraft.server.MinecraftServer.e(MinecraftServer.java:218)
        at net.minecraft.server.MinecraftServer.a(MinecraftServer.java:205)
        at net.minecraft.server.MinecraftServer.init(MinecraftServer.java:145)
        at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:265)
        at net.minecraft.server.ThreadServerApplication.run(SourceFile:394)
Caused by: java.io.IOException: Stream closed
        at java.io.BufferedInputStream.getInIfOpen(Unknown Source)
        at java.io.BufferedInputStream.fill(Unknown Source)
        at java.io.BufferedInputStream.read(Unknown Source)
        at org.python.core.ParserFacade.adjustForBOM(ParserFacade.java:371)
        at org.python.core.ParserFacade.prepBufReader(ParserFacade.java:298)
        at org.python.core.ParserFacade.prepBufReader(ParserFacade.java:288)
        at org.python.core.ParserFacade.parse(ParserFacade.java:183)
        ... 13 more

Could it be I’m using execfile wrong?
Or is it an error or something I’m missing in how InputStream works?

Answer 1

Are you sure that EmbeddedJython.class.getResourceAsStream("MyPlugin.py"); is finding the resource?

If it can’t find the resource, getResourceAsStream will return a null, and it is possible that the Jython interpreter will treat that as an empty (closed) stream.

Your application should probably check this, rather than assuming that getResourceAsStream has succeeded.

---

If I private File pythonFile = new File('MyScirpt.py'); and then hand getResourceAsStream(pythonFile.getAbsolutePath());

That won’t work. The getResourceAsStream method looks for resources on the classloader’s classpath, and expects a path that can be resolved relative to some entry on the classpath.

You probably want to do this:

private File pythonFile = new File('MyScirpt.py');
InputStream is = new FileInputStream(pythonFile);

and pass the is to the interpreter. You also need to arrange that the stream is always closed when the interpreter has finished … by whatever mechanism that happens.