BSFHelper.java

package com.ociweb.bsf;

import java.io.*;
import org.apache.bsf.BSFException;
import org.apache.bsf.BSFManager;

/**
 * This class provides methods that make it easier to
 * use the BSF to work with JRuby code.
 * jruby.jar and bsf.jar must be in the classpath.
 */
public class BSFHelper {
  
  private static final String LANGUAGE = "ruby";
  private static final int COLUMN_NO = -1;
  private static final int LINE_NO = -1;

  private BSFManager manager;

  public BSFHelper() {
    // Register the JRuby engine with BSF.
    String engine = "org.jruby.javasupport.bsf.JRubyEngine";
    String[] extensions = {"rb"};
    BSFManager.registerScriptingEngine(LANGUAGE, engine, extensions);

    manager = new BSFManager();
  }

  /**
   * Declares a global variable that Ruby code can use
   * to access a given Java object.
   */
  public void declareBean(String name, Object bean)
  throws BSFException {
    manager.declareBean(name, bean, bean.getClass());
  }

  /**
   * Evaluates a Ruby expression and returns its value.
   */
  public Object evalExpression(String expression)
  throws BSFException {
    String source = "(java)";
    return manager.eval(LANGUAGE, source, LINE_NO, COLUMN_NO, expression);
  }

  /**
   * Evaluates a file of Ruby code and
   * returns the value of the last expression.
   */
  public Object evalFile(String rubyFilePath)
  throws BSFException, IOException {
    String source = rubyFilePath;
    String expression = readFile(rubyFilePath);
    return manager.eval(
      LANGUAGE, source, LINE_NO, COLUMN_NO, expression);
  }

  /**
   * Executes a file of Ruby code.
   */
  public void execExpression(String expression)
  throws BSFException {
    String source = "(java)";
    manager.exec(LANGUAGE, source, LINE_NO, COLUMN_NO, expression);
  }

  /**
   * Executes a file of Ruby code.
   */
  public void execFile(String rubyFilePath)
  throws BSFException, IOException {
    String source = rubyFilePath;
    String expression = readFile(rubyFilePath);
    manager.exec(LANGUAGE, source, LINE_NO, COLUMN_NO, expression);
  }

  /**
   * Reads the entire content of a given file into a String and returns it.
   */
  private static String readFile(String filePath)
  throws IOException {
    FileReader fr = new FileReader(filePath);
    BufferedReader br = new BufferedReader(fr);
    String content = "";

    while (true) {
      String line = br.readLine();
      if (line == null) break;
      content += line + '\n';
    }

    return content;
  }
}

Copyright © 2007 Object Computing, Inc. All rights reserved.