ScriptExecutionController.java

/* vim: set ts=2 et sw=2 cindent fo=qroca: */

package com.globant.katari.console.view;

import java.io.ByteArrayOutputStream;
import java.io.IOException;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.lang.StringUtils;
import org.apache.commons.lang.Validate;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.mvc.AbstractController;

import com.globant.katari.console.application.ScriptingEngine;

/** Handles the execution of code sent by the console's client code.
 * @author juan.pereyra@globant.com
 */
public class ScriptExecutionController extends AbstractController {

  /** Request parameter key for the code to be executed. */
  private static final String SCRIPT_CODE_REQ_PARAM = "script";

  /** Content type to be used in the response. */
  private static final String JSON_CONTENT_TYPE = "application/json";

  /** Scripting engine used to execute the code. */
  private ScriptingEngine scriptingEngine;

  /** Builds a new instance of the controller.
   * @param theScriptingEngine Scripting engine used to execute the code. It
   * can't be null.
   */
  public ScriptExecutionController(final ScriptingEngine theScriptingEngine) {
    Validate.notNull(theScriptingEngine,
        "The the scripting engine cannot be null.");
    scriptingEngine = theScriptingEngine;
  }

  /** {@inheritDoc}
   */
  @Override
  protected ModelAndView handleRequestInternal(final HttpServletRequest
      request, final HttpServletResponse response) throws IOException {

    String code = request.getParameter(SCRIPT_CODE_REQ_PARAM);

    ByteArrayOutputStream output = new ByteArrayOutputStream();
    ByteArrayOutputStream error = new ByteArrayOutputStream();

    scriptingEngine.execute(code, output, error);

    String result = "{\"output\":\"" + escapeForJson(output.toString())
        + "\",\"error\":\"" + escapeForJson(error.toString()) + "\"}";

    response.setContentType(JSON_CONTENT_TYPE);
    response.getWriter().print(result);

    response.flushBuffer();

    return null;
  }

  /** Escapes non-JSON characters.
   *
   * Inspired by <a
   * href="http://code.google.com/p/json-simple/">JSON-Simple</a>.
   * @param input The text to be escaped. It can be null or empty, in
   * both cases the result will be an empty string.
   * @return An escaped version of the input string. It can return an empty
   * string if the input is either null or empty.
   */
  private String escapeForJson(final String input) {
    if (null == input || StringUtils.isEmpty(input)) {
      return "";
    }

    StringBuffer output = new StringBuffer();
    for (int i = 0; i < input.length(); i++) {
      char ch = input.charAt(i);
      switch(ch) {
      case '"':
        output.append("\\\"");
        break;
      case '\\':
        output.append("\\\\");
        break;
      case '\b':
        output.append("\\b");
        break;
      case '\f':
        output.append("\\f");
        break;
      case '\n':
        output.append("\\n");
        break;
      case '\r':
        output.append("\\r");
        break;
      case '\t':
        output.append("\\t");
        break;
      case '/':
        output.append("\\/");
        break;
      default:
        // Reference: http://www.unicode.org/versions/Unicode5.1.0/
        boolean isUnicodeChar = (ch >= '\u0000' && ch <= '\u001F')
          || (ch >= '\u007F' && ch <= '\u009F')
          || (ch >= '\u2000' && ch <= '\u20FF');

        if (isUnicodeChar) {
          String ss = Integer.toHexString(ch);
          output.append("\\u");
          for (int k = 0; k < 4 - ss.length(); k++) {
            output.append('0');
          }
          output.append(ss.toUpperCase());
        } else {
          output.append(ch);
        }
      }
    }
    return output.toString();
  }
}