Useful HttpServlet utilities
/* * net/balusc/util/HttpServletUtil.java * * Copyright (C) 2007 BalusC * * This program is free software; you can redistribute it and/or modify it under the terms of the * GNU General Public License as published by the Free Software Foundation; either version 2 of the * License, or (at your option) any later version. * * This program 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 * General Public License for more details. * * You should have received a copy of the GNU General Public License along with this program; if * not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA * 02110-1301, USA. */ package net.balusc.util; import java.io.BufferedInputStream; import java.io.BufferedOutputStream; import java.io.ByteArrayInputStream; import java.io.File; import java.io.FileInputStream; import java.io.InputStream; import java.io.IOException; import java.io.OutputStreamWriter; import java.io.UnsupportedEncodingException; import java.net.MalformedURLException; import java.net.URL; import java.net.URLConnection; import java.net.URLEncoder; import java.util.Iterator; import java.util.Map; import javax.servlet.http.Cookie; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * Useful HttpServlet utilities. * * @author BalusC * @link http://balusc.blogspot.com/2006/05/httpservletutil.html */ public final class HttpServletUtil { // Init --------------------------------------------------------------------------------------- private HttpServletUtil() { // Utility class, hide the constructor. } // Cookies ------------------------------------------------------------------------------------ /** * Retrieve the cookie value from the given servlet request based on the given * cookie name. * @param request The HttpServletRequest to be used. * @param name The cookie name to retrieve the value for. * @return The cookie value associated with the given cookie name. */ public static String getCookieValue(HttpServletRequest request, String name) { Cookie[] cookies = request.getCookies(); if (cookies != null) { for (Cookie cookie : cookies) { if (cookie != null && name.equals(cookie.getName())) { return cookie.getValue(); } } } return null; } /** * Set the cookie value in the given servlet response based on the given cookie * name and expiration interval. * @param response The HttpServletResponse to be used. * @param name The cookie name to associate the cookie value with. * @param value The actual cookie value to be set in the given servlet response. * @param maxAge The expiration interval in seconds. If this is set to 0, * then the cookie will immediately expire. */ public static void setCookieValue( HttpServletResponse response, String name, String value, int maxAge) { Cookie cookie = new Cookie(name, value); cookie.setMaxAge(maxAge); response.addCookie(cookie); } /** * Remove the cookie from the given servlet response based on the given cookie * name. It actually sets the cookie expiration interval to zero, resulting the * cookie being expired immediately. * @param response The HttpServletResponse to be used. * @param name The cookie name of the cookie to be removed. */ public static void removeCookie(HttpServletResponse response, String name) { setCookieValue(response, name, null, 0); } // Downloads ---------------------------------------------------------------------------------- /** * Send the given file as a byte array to the servlet response. If attachment * is set to true, then show a "Save as" dialogue, else show the file inline * in the browser or let the operating system open it in the right application. * @param response The HttpServletResponse to be used. * @param bytes The file contents in a byte array. * @param fileName The file name. * @param attachment Download as attachment? */ public static void downloadFile( HttpServletResponse response, byte[] bytes, String fileName, boolean attachment) throws IOException { // Wrap the byte array in a ByteArrayInputStream and pass it through another method. downloadFile(response, new ByteArrayInputStream(bytes), fileName, attachment); } /** * Send the given file as a File object to the servlet response. If attachment * is set to true, then show a "Save as" dialogue, else show the file inline * in the browser or let the operating system open it in the right application. * @param response The HttpServletResponse to be used. * @param file The file as a File object. * @param attachment Download as attachment? */ public static void downloadFile( HttpServletResponse response, File file, boolean attachment) throws IOException { // Prepare stream. BufferedInputStream input = null; try { // Wrap the file in a BufferedInputStream and pass it through another method. input = new BufferedInputStream(new FileInputStream(file)); downloadFile(response, input, file.getName(), attachment); } finally { // Gently close stream. if (input != null) { try { input.close(); } catch (IOException e) { String message = "Closing file " + file.getPath() + " failed."; // Do your thing with the exception and the message. Print it, log it or mail it. System.err.println(message); e.printStackTrace(); } } } } /** * Send the given file as an InputStream to the servlet response. If attachment * is set to true, then show a "Save as" dialogue, else show the file inline * in the browser or let the operating system open it in the right application. * @param response The HttpServletResponse to be used. * @param input The file contents in an InputStream. * @param fileName The file name. * @param attachment Download as attachment? */ public static void downloadFile( HttpServletResponse response, InputStream input, String fileName, boolean attachment) throws IOException { // Prepare stream. BufferedOutputStream output = null; try { // Prepare. int contentLength = input.available(); String contentType = URLConnection.guessContentTypeFromName(fileName); String disposition = attachment ? "attachment" : "inline"; // If content type is unknown, then set the default value. // For all content types, see: http://www.w3schools.com/media/media_mimeref.asp if (contentType == null) { contentType = "application/octet-stream"; } // Init servlet response. response.reset(); response.setContentLength(contentLength); response.setContentType(contentType); response.setHeader( "Content-disposition", disposition + "; filename=\"" + fileName + "\""); output = new BufferedOutputStream(response.getOutputStream()); // Write file contents to response. while (contentLength-- > 0) { output.write(input.read()); } // Finalize task. output.flush(); } finally { // Gently close stream. if (output != null) { try { output.close(); } catch (IOException e) { String message = "Closing HttpServletResponse#getOutputStream() failed."; // Do your thing with the exception and the message. Print it, log it or mail it. System.err.println(message); e.printStackTrace(); } } } } // Queriers ----------------------------------------------------------------------------------- /** * Invoke a GET request on the given URL with the given parameter map which will be encoded as * UTF-8. It is highly recommended to close the obtained inputstream after processing! * @param url The URL to be invoked. * @param parameterMap The parameter map to be processed as query parameters. * @return The result of the GET request as an InputStream. * @throws MalformedURLException If the given URL is invalid. * @throws IOException If the given URL cannot be connected nor written. */ public static InputStream doGet(String url, Map<String, String[]> parameterMap) throws MalformedURLException, IOException { return doGet(url, parameterMap, "UTF-8"); } /** * Invoke a GET request on the given URL with the given parameter map and the given charset * encoding. It is highly recommended to close the obtained inputstream after processing! * @param url The URL to be invoked. * @param parameterMap The parameter map to be processed as query parameters. * @param charset The encoding to be applied. * @return The result of the GET request as an InputStream. * @throws MalformedURLException If the given URL is invalid. * @throws IOException If the given URL cannot be connected nor written. * @throws UnsupportedEncodingException If the given charset is not supported. */ public static InputStream doGet(String url, Map<String, String[]> parameterMap, String charset) throws MalformedURLException, IOException, UnsupportedEncodingException { String query = createQuery(parameterMap, charset); URLConnection urlConnection = new URL(url + "?" + query).openConnection(); urlConnection.setUseCaches(false); return urlConnection.getInputStream(); } /** * Invoke a POST request on the given URL with the given parameter map which will be encoded as * UTF-8. It is highly recommended to close the obtained inputstream after processing! * @param url The URL to be invoked. * @param parameterMap The parameter map to be processed as query parameters. * @return The result of the POST request as an InputStream. * @throws MalformedURLException If the given URL is invalid. * @throws IOException If the given URL cannot be connected nor written. */ public static InputStream doPost(String url, Map<String, String[]> parameterMap) throws MalformedURLException, IOException { return doPost(url, parameterMap, "UTF-8"); } /** * Invoke a POST request on the given URL with the given parameter map and the given charset * encoding. It is highly recommended to close the obtained inputstream after processing! * @param url The URL to be invoked. * @param parameterMap The parameter map to be processed as query parameters. * @param charset The encoding to be applied. * @return The result of the POST request as an InputStream. * @throws MalformedURLException If the given URL is invalid. * @throws IOException If the given URL cannot be connected nor written. * @throws UnsupportedEncodingException If the given charset is not supported. */ public static InputStream doPost(String url, Map<String, String[]> parameterMap, String charset) throws MalformedURLException, IOException, UnsupportedEncodingException { String query = createQuery(parameterMap, charset); URLConnection urlConnection = new URL(url).openConnection(); urlConnection.setUseCaches(false); urlConnection.setDoOutput(true); // Triggers POST. urlConnection.setRequestProperty("accept-charset", charset); urlConnection.setRequestProperty("content-type", "application/x-www-form-urlencoded"); OutputStreamWriter writer = null; try { writer = new OutputStreamWriter(urlConnection.getOutputStream()); writer.write(query); } finally { if (writer != null) { try { writer.close(); } catch (IOException e) { String message = "Closing URLConnection#getOutputStream() of " + url + " failed."; // Do your thing with the exception and the message. Print it, log it or mail it. System.err.println(message); e.printStackTrace(); } } } return urlConnection.getInputStream(); } /** * Create a query string based on the given parameter map and the given charset encoding. * @param parameterMap The parameter map to be processed as query parameters. * @param charset The encoding to be applied. * @return The parameter map as query string. * @throws UnsupportedEncodingException If the given charset is not supported. */ public static String createQuery(Map<String, String[]> parameterMap, String charset) throws UnsupportedEncodingException { StringBuilder query = new StringBuilder(); for (Iterator<String> names = parameterMap.keySet().iterator(); names.hasNext();) { String name = names.next(); String[] values = parameterMap.get(name); for (int i = 0; i < values.length;) { query.append(URLEncoder.encode(name, charset)); query.append("="); query.append(URLEncoder.encode(values[i], charset)); if (++i < values.length) { query.append("&"); } } if (names.hasNext()) { query.append("&"); } } return query.toString(); } }
Copyright - GNU General Public License
(C) May 2006, BalusC
0 comments:
Post a Comment