httpserverutil.java

这是外国一个开源推理机

/*  Sesame - Storage and Querying architecture for RDF and RDF Schema
 *  Copyright (C) 2001-2005 Aduna
 *
 *  Contact:
 *  	Aduna
 *  	Prinses Julianaplein 14 b
 *  	3817 CS Amersfoort
 *  	The Netherlands
 *  	tel. [phone]
 *  	fax. [phone]
 *
 *  	http://aduna.biz/
 *  	http://www.openrdf.org/
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public
 *  License as published by the Free Software Foundation; either
 *  version 2.1 of the License, or (at your option) any later version.
 *
 *  This library is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public
 *  License along with this library; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

package org.openrdf.util.http;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.UnsupportedEncodingException;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.zip.GZIPOutputStream;

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

import org.apache.commons.fileupload.DefaultFileItemFactory;
import org.apache.commons.fileupload.DiskFileUpload;
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadBase;
import org.apache.commons.fileupload.FileUploadException;

/**
 * Utility methods for HTTP servers/servlets.
 **/
public class HttpServerUtil {

	private static File _tmpDir = null;
	private static DefaultFileItemFactory _fileItemFactory = null;
	private static DiskFileUpload _fileUpload = null;
	
	private static DiskFileUpload _getDiskFileUpload() {
		if (_fileUpload == null) {
			_fileItemFactory = new DefaultFileItemFactory();

			if (_tmpDir != null) {
				// Try setting the tmp directory for _fileUpload
				_fileItemFactory.setRepository(_tmpDir);
			}

			_fileUpload = new DiskFileUpload(_fileItemFactory);
		}

		return _fileUpload;
	}

	public static void setTmpDir(File tmpDir) {
		_tmpDir = tmpDir;
		if (_fileItemFactory != null) {
			_fileItemFactory.setRepository(tmpDir);
		}
	}

	/**
	 * Checks whether the supplied request is a <tt>multipart/form-data</tt>
	 * POST request.
	 **/
	public static boolean isMultipartFormRequest(HttpServletRequest request) {
		return FileUploadBase.isMultipartContent(request);
	}

	/**
	 * Gets the trimmed value of a request parameter as a String. If the
	 * specified parameter does not exist or if it has a white-space-only value,
	 * <tt>null</tt> will be returned.
	 *
	 * @param request The request object to get the parameter from.
	 * @param paramName The name of the parameter.
	 * @return The trimmed value, or <tt>null</tt> if the specified parameter
	 * does not have a value.
	 **/
	public static String getParameter(HttpServletRequest request, String paramName) {
		return getParameter(request, paramName, null);
	}

	/**
	 * Gets the trimmed value of a request parameter as a String. If the
	 * specified parameter does not exist or if it has a white-space-only value,
	 * the supplied <tt>defaultValue</tt> will be returned.
	 *
	 * @param request The request object to get the parameter from.
	 * @param paramName The name of the parameter.
	 * @param defaultValue The value that should be returned when the specified
	 * parameter did not have a value.
	 * @return The trimmed value, or <tt>defaultValue</tt> if the specified
	 * parameter does not have a value.
	 **/
	public static String getParameter(HttpServletRequest request, String paramName, String defaultValue) {
		String result = request.getParameter(paramName);

		if (result == null) {
			result = defaultValue;
		}
		else {
			result = result.trim();
			
			if (result.length() == 0) {
				result = defaultValue;
			}
		}

		return result;
	}

	/**
	 * Parses a <tt>multipart/form-data</tt> POST request and returns its
	 * parameters as set of FileItems, mapped using their field name.
	 *
	 * @param request The request.
	 * @return a Map of FileItem objects, mapped using their field name (Strings).
	 * @exception IOException If the request could not be read/parsed.
	 **/
	public static Map parseMultipartFormRequest(HttpServletRequest request)
		throws IOException
	{
		try {
			List fileItems = _getDiskFileUpload().parseRequest(request);
			Map resultMap = new HashMap(fileItems.size() * 2);

			Iterator iter = fileItems.iterator();
			while (iter.hasNext()) {
				FileItem fileItem = (FileItem)iter.next();
				resultMap.put(fileItem.getFieldName(), fileItem);
			}

			return resultMap;
		}
		catch (FileUploadException e) {
			IOException ioe = new IOException();
			ioe.initCause(e);
			throw ioe;
		}
	}

	/**
	 * Gets the trimmed value of a request parameter from a Map of FileItem
	 * objects, as returned by <tt>parseMultipartFormRequest()</tt>. If the
	 * specified parameter does not exist or if it has a white-space-only value,
	 * <tt>null</tt> will be returned. The values are assumed to be using the
	 * UTF-8 encoding.
	 *
	 * @param fileItemMap A Map of FileItem objects, mapped using their field
	 * name (Strings).
	 * @param paramName The name of the parameter.
	 * @return The trimmed value, or <tt>null</tt> if the specified parameter
	 * does not have a value.
	 **/
	public static String getParameter(Map fileItemMap, String paramName) {
		return getParameter(fileItemMap, paramName, null);
	}

	/**
	 * Gets the trimmed value of a request parameter from a Map of FileItem
	 * objects, as returned by <tt>parseMultipartFormRequest()</tt>. If the
	 * specified parameter does not exist or if it has a white-space-only value,
	 * the supplied <tt>defaultValue</tt> will be returned. The values are
	 * assumed to be using the UTF-8 encoding.
	 *
	 * @param fileItemMap A Map of FileItem objects, mapped using their field
	 * name (Strings).
	 * @param paramName The name of the parameter.
	 * @param defaultValue The value that should be returned when the specified
	 * parameter did not have a value.
	 * @return The trimmed value, or <tt>null</tt> if the specified parameter
	 * does not have a value.
	 **/
	public static String getParameter(Map fileItemMap, String paramName, String defaultValue) {
		String result = defaultValue;

		FileItem fileItem = (FileItem)fileItemMap.get(paramName);
		if (fileItem != null) {
			try {
				result = fileItem.getString("UTF-8").trim();
			}
			catch (UnsupportedEncodingException e) {
				// UTF-8 must be supported by all compliant JVM's,
				// this exception should never be thrown.
				throw new RuntimeException("UTF-8 character encoding not supported on this platform");
			}

			if (result.length() == 0) {
				result = defaultValue;
			}
		}

		return result;
	}

	/**
	 * Gets the binary value of a request parameter from a Map of FileItem
	 * objects, as returned by <tt>parseMultipartFormRequest()</tt>.
	 *
	 * @param fileItemMap A Map of FileItem objects, mapped using their field
	 * name (Strings).
	 * @param paramName The name of the parameter.
	 * @return The binary value, or <tt>null</tt> if the specified parameter
	 * does not have a value.
	 **/
	public static byte[] getBinaryParameter(Map fileItemMap, String paramName) {
		byte[] result = null;

		FileItem fileItem = (FileItem)fileItemMap.get(paramName);
		if (fileItem != null) {
			result = fileItem.get();
		}

		return result;
	}

	/**
	 * Gets the value of a request parameter as an InputStream from a Map of
	 * FileItem objects, as returned by <tt>parseMultipartFormRequest()</tt>.
	 *
	 * @param fileItemMap A Map of FileItem objects, mapped using their field
	 * name (Strings).
	 * @param paramName The name of the parameter.
	 * @return The value, or <tt>null</tt> if the specified parameter does not
	 * have a value.
	 **/
	public static InputStream getStreamParameter(Map fileItemMap, String paramName)
		throws IOException
	{
		InputStream result = null;

		FileItem fileItem = (FileItem)fileItemMap.get(paramName);
		if (fileItem != null) {
			result = fileItem.getInputStream();
		}

		return result;
	}

	/**
	 * Sets headers on the supplied response that prevent all kinds of
	 * browsers to cache it.
	 **/
	public static void setNoCacheHeaders(HttpServletResponse response) {
		//
		// according to http://vancouver-webpages.com/META/FAQ.html
		//
		response.setHeader("Cache-Control", "must-revalidate");
		response.setHeader("Cache-Control", "max-age=1");
		response.setHeader("Cache-Control", "no-cache");
		response.setIntHeader("Expires", 0);
		response.setHeader("Pragma", "no-cache");
	}

	/**
	 * Checks whether the sender of the supplied request can handle
	 * gzip-encoded data.
	 *
	 * @param request A HTTP request
	 * @return <tt>true</tt> if the sender of the request can handle
	 * gzip-encoded data, <tt>false</tt> otherwise.
	 **/
	public static boolean acceptsGZIPEncoding(HttpServletRequest request) {
		boolean result = false;

		String acceptEncoding = request.getHeader("accept-encoding");
		if (acceptEncoding != null) {
			// Microsoft Internet Explorer indicates that it accepts gzip
			// encoding, but it fails to handle it properly (see issue
			// [SES-28] in Sesame issue tracker).
			boolean isInternetExplorer = false;

			String userAgent = request.getHeader("user-agent");
			if (userAgent != null) {
				isInternetExplorer = userAgent.indexOf("MSIE") != -1;
			}

			result = isInternetExplorer == false &&
					acceptEncoding.toLowerCase().indexOf("gzip") != -1;
		}
		
		return result;
	}

	/**
	 * Opens an gzip-encoded output stream for the specified response. This
	 * method also sets the required header(s) to indicate that the response
	 * is gzip-encoded.
	 **/
	public static OutputStream openGZIPOutputStream(HttpServletResponse response)
		throws IOException
	{
		response.setHeader("Content-Encoding", "gzip");
		return new GZIPOutputStream(response.getOutputStream(), 4096);
	}
}