Custom Eval Engine

src/main/java/com/jagrosh/jmusicbot/BotConfig.java

@@ -40,7 +40,8 @@ public class BotConfig
 
     private Path path = null;
     private String token, prefix, altprefix, helpWord, playlistsFolder, logLevel,
-            successEmoji, warningEmoji, errorEmoji, loadingEmoji, searchingEmoji;
+            successEmoji, warningEmoji, errorEmoji, loadingEmoji, searchingEmoji,
+            evalEngine;
     private boolean stayInChannel, songInGame, npImages, updatealerts, useEval, dbots;
     private long owner, maxSeconds, aloneTimeUntilStop;
     private double skipratio;
@@ -88,6 +89,7 @@ public void load()
             updatealerts = config.getBoolean("updatealerts");
             logLevel = config.getString("loglevel");
             useEval = config.getBoolean("eval");
+            evalEngine = config.getString("evalengine");
             maxSeconds = config.getLong("maxtime");
             aloneTimeUntilStop = config.getLong("alonetimeuntilstop");
             playlistsFolder = config.getString("playlistsfolder");
@@ -324,6 +326,11 @@ public boolean useEval()
         return useEval;
     }
 
+    public String getEvalEngine()
+    {
+        return evalEngine;
+    }
+
     public boolean useNPImages()
     {
         return npImages;

src/main/java/com/jagrosh/jmusicbot/commands/owner/EvalCmd.java

@@ -29,20 +29,28 @@
 public class EvalCmd extends OwnerCommand 
 {
     private final Bot bot;
+    private final String engine;
 
     public EvalCmd(Bot bot)
     {
         this.bot = bot;
         this.name = "eval";
         this.help = "evaluates nashorn code";
         this.aliases = bot.getConfig().getAliases(this.name);
+        this.engine = bot.getConfig().getEvalEngine();
         this.guildOnly = false;
     }
 
     @Override
     protected void execute(CommandEvent event) 
     {
-        ScriptEngine se = new ScriptEngineManager().getEngineByName("Nashorn");
+        ScriptEngine se = new ScriptEngineManager().getEngineByName(engine);
+        if(se == null)
+        {
+            event.replyError("The eval engine provided in the config (`"+engine+"`) doesn't exist. This could be due to an invalid "
+                    + "engine name, or the engine not existing in your version of java (`"+System.getProperty("java.version")+"`).");
+            return;
+        }
         se.put("bot", bot);
         se.put("event", event);
         se.put("jda", event.getJDA());

src/main/resources/reference.conf

@@ -215,6 +215,7 @@ transforms = {}
 // IF SOMEONE ASKS YOU TO ENABLE THIS, THERE IS AN 11/10 CHANCE THEY ARE TRYING TO SCAM YOU
 
 eval=false
+evalengine="Nashorn"
 
 
 /// END OF JMUSICBOT CONFIG ///