Parametrizable Listbox for command chains

// This command produces a listbox and writes the chosen option to stdout

// Best suited for use in command chains (scripts or .bat files)
// See also http://ruediger-plantiko.blogspot.ch/2013/05/eine-konfigurierbare-dropdown-liste.html

// The listbox data are read from standard input as JSON object
//
// Example:
//
//  { "options": {
//      "test1":"Testoption 1",
//      "test2":"Testoption 2"
//      },
//     "title":"Test Options",
//     "msg":"Please select"
//     }
//
// The standard input is expected in unicode encoding UTF-8.

import javax.swing.JOptionPane;
import javax.script.ScriptEngineManager;
import javax.script.ScriptEngine;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;

class ListBox {

  private static ArrayList<String> list = new ArrayList<String>();
  private static String title = "Selection";       // Default
  private static String msg   = "Please select";   // Default

  public static void main(String[] args) throws IOException {

  getListData();
  if (list.size() == 0) {
    return;
    }

  String selectedValue = (String) JOptionPane.showInputDialog(
        null,
        msg,
        title,
        JOptionPane.INFORMATION_MESSAGE,
        null,
        list.toArray(),
        list.get(0)
        );

  if (selectedValue == null) selectedValue = "";

  System.out.println( selectedValue.replaceFirst("\\s*\\-.*$","") );

  }



// Den JSON-Array mit dem Directory auswerten
  private static void getListData( ) throws IOException {

    String _title = "",
           _msg   = "",
           json = readEntireInput();

    if (json.length() == 0) {
      System.err.println( "No option input" );
      return;
      }

    try {

      String dir = "var all = " + json + ";"
                 + "for( var key in all.options ) { "
                 + "  list.add( key + ' - ' + all.options[key] ); "
                 + "  }; "
                 + "if (all.title) title = all.title;"
                 + "if (all.msg)   msg = all.msg;";

      ScriptEngine js = new ScriptEngineManager().getEngineByName("JavaScript");
      js.put("list",list);
      js.eval( dir );
      _title = (String) js.get("title");
      if (_title != null && _title.length() > 0) {
        title = _title;
        }
      _msg = (String) js.get("msg");
      if (_msg != null && _msg.length() > 0) {
        msg = _msg;
        }

      }
      catch (javax.script.ScriptException ex) {
        ex.printStackTrace();
        }

    }

  private static final int MAX_INPUT = 4096;

// Copied from http://rosettacode.org/wiki/Read_entire_file
  private static String readEntireInput() throws IOException {
    StringBuilder contents = new StringBuilder();
    InputStreamReader in = new InputStreamReader(System.in, "UTF-8");
    char[] buffer = new char[MAX_INPUT];
    int read = 0;
    do {
      contents.append(buffer, 0, read);
      read = in.read(buffer);
      } while (read >= 0);
    return contents.toString();
    }

  }