package com.landsoft.filter;

import java.io.*;
import javax.servlet.*;

/**
 * Example filter that unconditionally sets the character encoding to be used
 * in parsing the incoming request to a value specified by the
 * <strong>encoding</string> filter initialization parameter in the web app
 * deployment descriptor (</code>/WEB-INF/web.xml</code>).  This filter could
 * easily be extended to be more intelligent about what character encoding to
 * set, based on characteristics of the incoming request (such as the values
 * of the <code>Accept-Language</code> and <code>User-Agent</code> headers,
 * or a value stashed in the current user's session).
 *
 * <p>Title: Chinaspis Future</p>
 * <p>Description: Web-Based Integerated Project Management System</p>
 * <p>Copyright: Copyright (c) 2003</p>
 * <p>Company: www.chinaspis.com</p>
 * @author not attributable
 * @version 1.0
 */

public class SetCharacterEncodingFilter
    implements Filter {

  // ----------------------------------------------------- Instance Variables

  /**
   * The default character encoding to set for requests that pass through
   * this filter.
   */
  protected String encoding = null;

  /**
   * The filter configuration object we are associated with.  If this value
   * is null, this filter instance is not currently configured.
   */
  protected FilterConfig filterConfig = null;

  // --------------------------------------------------------- Public Methods

  /**
   * Take this filter out of service.
   */
  public void destroy() {

    this.encoding = null;
    this.filterConfig = null;

  }

  /**
   * Select and set (if specified) the character encoding to be used to
   * interpret request parameters for this request.
   *
   * @param request The servlet request we are processing
   * @param result The servlet response we are creating
   * @param chain The filter chain we are processing
   *
   * @exception IOException if an input/output error occurs
   * @exception ServletException if a servlet error occurs
   */
  public void doFilter(ServletRequest request, ServletResponse response,
                       FilterChain chain) throws IOException,
      ServletException {

    // Select and set (if needed) the character encoding to be used
    String encoding = selectEncoding(request);
    if (encoding != null) {
      request.setCharacterEncoding(encoding);

      // Pass control on to the next filter
    }
    chain.doFilter(request, response);
  }

  /**
   * Place this filter into service.
   *
   * @param filterConfig The filter configuration object
   */
  public void init(FilterConfig filterConfig) throws ServletException {

    this.filterConfig = filterConfig;
    this.encoding = filterConfig.getInitParameter("encoding");

  }

  // ------------------------------------------------------ Protected Methods


  /**
   * Select an appropriate character encoding to be used, based on the
   * characteristics of the current request and/or filter initialization
   * parameters.  If no character encoding should be set, return
   * <code>null</code>.
   * <p>
   * The default implementation unconditionally returns the value configured
   * by the <strong>encoding</strong> initialization parameter for this
   * filter.
   *
   * @param request The servlet request we are processing
   */
  protected String selectEncoding(ServletRequest request) {

    return (this.encoding);

  }

}