MultipartFilter.java

// Copyright (C) 2001 by Jason Hunter <jhunter_AT_acm_DOT_org>.
// All rights reserved.  Use of this class is limited.
// Please see the LICENSE for more information.

package com.oreilly.servlet;

import java.io.File;
import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;

/**
 * A filter for easy semi-automatic handling of multipart/form-data requests 
 * (file uploads).  The filter capability requires Servlet API 2.3.
 * <p>
 * See Jason Hunter's June 2001 article in JavaWorld for a full explanation of
 * the class usage.
 *
 * @author <b>Jason Hunter</b>, Copyright © 2001
 * @version 1.0, 2001/06/19
 */
public class MultipartFilter implements Filter {

  private FilterConfig config = null;
  private String dir = null;

  public void init(FilterConfig config) throws ServletException {
    this.config = config;

    // Determine the upload directory.  First look for an uploadDir filter
    // init parameter.  Then look for the context tempdir.
    dir = config.getInitParameter("uploadDir");
    if (dir == null) {
      File tempdir = (File) config.getServletContext()
                  .getAttribute("javax.servlet.context.tempdir");
      if (tempdir != null) {
        dir = tempdir.toString();
      }
      else {
        throw new ServletException(
          "MultipartFilter: No upload directory found: set an uploadDir " +
          "init parameter or ensure the javax.servlet.context.tempdir " +
          "directory is valid");
      }
    }
  }

  public void destroy() {
    config = null;
  }

  public void doFilter(ServletRequest request, ServletResponse response,
                     FilterChain chain) throws IOException, ServletException {
    HttpServletRequest req = (HttpServletRequest) request;
    String type = req.getHeader("Content-Type");

    // If this is not a multipart/form-data request continue
    if (type == null || !type.startsWith("multipart/form-data")) {
      chain.doFilter(request, response);
    }
    else {
      MultipartWrapper multi = new MultipartWrapper(req, dir);
      chain.doFilter(multi, response);
    }
  }
}