NutchController.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.nutch.webapp.controller;

import java.io.IOException;
import java.util.Enumeration;
import java.util.Iterator;

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

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.nutch.util.LogUtil;
import org.apache.nutch.webapp.common.ServiceLocator;
import org.apache.nutch.webapp.common.ServletContextServiceLocator;
import org.apache.nutch.webapp.common.WebappInstanceServiceLocator;
import org.apache.struts.tiles.ComponentContext;
import org.apache.struts.tiles.Controller;

/**
 *  Base class for nutch Tiles controllers.
 */
public abstract class NutchController implements Controller {

  public static final Log LOG = LogFactory.getLog(NutchController.class);

  public final void execute(ComponentContext tileContext,
      HttpServletRequest request, HttpServletResponse response,
      ServletContext servletContext) throws ServletException, IOException {

    request.setCharacterEncoding("UTF-8");

    try {
      nutchPerform(tileContext, request, response, servletContext);
    } catch (Exception e) {
      LOG.info("Exception occured while executing nutch controller:");
      e.printStackTrace(LogUtil.getInfoStream(LOG));
    }
  }

  /**
   * Nutch controllers overwrite this method.
   * 
   * @param tileContext
   * @param request
   * @param response
   * @param servletContext
   * @throws ServletException
   * @throws IOException
   */
  public abstract void nutchPerform(ComponentContext tileContext,
      HttpServletRequest request, HttpServletResponse response,
      ServletContext servletContext) throws ServletException, IOException;

  /**
   * Get Active service locator from request or create on if none exists.
   *
   * @param request
   * @return
   */
  protected ServiceLocator getServiceLocator(HttpServletRequest request) {
    return WebappInstanceServiceLocator.getFrom(request);
  }

  /**
   * Log request attributes. used for debugging
   * 
   * @param request
   */
  void logRequestAttributes(HttpServletRequest request) {
    Enumeration e = request.getAttributeNames();

    while (e.hasMoreElements()) {
      String name = (String) e.nextElement();
      LOG.info("request attrs:" + name + " = " + request.getAttribute(name));
    }
  }

  /**
   * Log tiles context. used for debugging
   * 
   * @param context
   */
  void logComponentContext(ComponentContext context) {
    Iterator i = context.getAttributeNames();

    while (i.hasNext()) {
      String name = (String) i.next();
      LOG.info("context attrs:" + name + " = " + context.getAttribute(name));
    }
  }

  public void perform(ComponentContext tileContext, HttpServletRequest request,
      HttpServletResponse response, ServletContext servletContext)
      throws ServletException, IOException {
    execute(tileContext, request, response, servletContext);
  }

  /**
   * Get servlet context service locator, this one cannot access request
   * specific information as preferences etc.
   *
   * @param servletContext
   * @return
   */
  public ServiceLocator getServiceLocator(ServletContext servletContext){
    return ServletContextServiceLocator.getInstance(servletContext);
  }
}