Optimize bookie usage information while using command line option --help (#4241)

Author: tmzk1005

bookkeeper-server/src/main/java/org/apache/bookkeeper/server/Main.java

@@ -109,12 +109,13 @@ private static ServerConfiguration parseArgs(String[] args)
             BasicParser parser = new BasicParser();
             CommandLine cmdLine = parser.parse(BK_OPTS, args);
 
+            ServerConfiguration conf = new ServerConfiguration();
+
             if (cmdLine.hasOption('h')) {
-                throw new IllegalArgumentException();
+                conf.setProperty("help", true);
+                return conf;
             }
 
-            ServerConfiguration conf = new ServerConfiguration();
-
             if (cmdLine.hasOption('c')) {
                 String confFile = cmdLine.getOptionValue("c");
                 loadConfFile(conf, confFile);
@@ -210,6 +211,11 @@ static int doMain(String[] args) {
             return ExitCode.INVALID_CONF;
         }
 
+        if (conf.getBoolean("help", false)) {
+            printUsage();
+            return ExitCode.OK;
+        }
+
         // 1. building the component stack:
         LifecycleComponent server;
         try {
@@ -244,6 +250,11 @@ private static ServerConfiguration parseCommandLine(String[] args)
             printUsage();
             throw iae;
         }
+
+        if (conf.getBoolean("help", false)) {
+            return conf;
+        }
+
         String hello = String.format(
             "Hello, I'm your bookie, bookieId is %1$s, listening on port %2$s. Metadata service uri is %3$s."
                 + " Journals are in %4$s. Ledgers are stored in %5$s. Indexes are stored in %6$s.",