Java tutorial
/** * 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.hadoop.util; import java.io.*; import java.util.Calendar; import javax.servlet.*; import javax.servlet.http.HttpServletRequest; import org.apache.commons.httpclient.URIException; import org.apache.commons.httpclient.util.URIUtil; import org.apache.hadoop.classification.InterfaceAudience; import org.apache.hadoop.classification.InterfaceStability; import com.google.common.base.Preconditions; @InterfaceAudience.Private @InterfaceStability.Unstable public class ServletUtil { /** * Initial HTML header */ public static PrintWriter initHTML(ServletResponse response, String title) throws IOException { response.setContentType("text/html"); PrintWriter out = response.getWriter(); out.println("<html>\n" + "<link rel='stylesheet' type='text/css' href='/static/hadoop.css'>\n" + "<title>" + title + "</title>\n" + "<body>\n" + "<h1>" + title + "</h1>\n"); return out; } /** * Get a parameter from a ServletRequest. * Return null if the parameter contains only white spaces. */ public static String getParameter(ServletRequest request, String name) { String s = request.getParameter(name); if (s == null) { return null; } s = s.trim(); return s.length() == 0 ? null : s; } /** * @return a long value as passed in the given parameter, throwing * an exception if it is not present or if it is not a valid number. */ public static long parseLongParam(ServletRequest request, String param) throws IOException { String paramStr = request.getParameter(param); if (paramStr == null) { throw new IOException("Invalid request has no " + param + " parameter"); } return Long.parseLong(paramStr); } public static final String HTML_TAIL = "<hr />\n" + "<a href='http://hadoop.apache.org/core'>Hadoop</a>, " + Calendar.getInstance().get(Calendar.YEAR) + ".\n" + "</body></html>"; /** * HTML footer to be added in the jsps. * @return the HTML footer. */ public static String htmlFooter() { return HTML_TAIL; } /** * Generate the percentage graph and returns HTML representation string * of the same. * * @param perc The percentage value for which graph is to be generated * @param width The width of the display table * @return HTML String representation of the percentage graph * @throws IOException */ public static String percentageGraph(int perc, int width) throws IOException { assert perc >= 0; assert perc <= 100; StringBuilder builder = new StringBuilder(); builder.append("<table border=\"1px\" width=\""); builder.append(width); builder.append("px\"><tr>"); if (perc > 0) { builder.append("<td cellspacing=\"0\" class=\"perc_filled\" width=\""); builder.append(perc); builder.append("%\"></td>"); } if (perc < 100) { builder.append("<td cellspacing=\"0\" class=\"perc_nonfilled\" width=\""); builder.append(100 - perc); builder.append("%\"></td>"); } builder.append("</tr></table>"); return builder.toString(); } /** * Generate the percentage graph and returns HTML representation string * of the same. * @param perc The percentage value for which graph is to be generated * @param width The width of the display table * @return HTML String representation of the percentage graph * @throws IOException */ public static String percentageGraph(float perc, int width) throws IOException { return percentageGraph((int) perc, width); } /** * Escape and encode a string regarded as within the query component of an URI. * @param value the value to encode * @return encoded query, null if the default charset is not supported */ public static String encodeQueryValue(final String value) { try { return URIUtil.encodeWithinQuery(value, "UTF-8"); } catch (URIException e) { throw new AssertionError("JVM does not support UTF-8"); // should never happen! } } /** * Escape and encode a string regarded as the path component of an URI. * @param path the path component to encode * @return encoded path, null if UTF-8 is not supported */ public static String encodePath(final String path) { try { return URIUtil.encodePath(path, "UTF-8"); } catch (URIException e) { throw new AssertionError("JVM does not support UTF-8"); // should never happen! } } /** * Parse and decode the path component from the given request. * @param request Http request to parse * @param servletName the name of servlet that precedes the path * @return decoded path component, null if UTF-8 is not supported */ public static String getDecodedPath(final HttpServletRequest request, String servletName) { try { return URIUtil.decode(getRawPath(request, servletName), "UTF-8"); } catch (URIException e) { throw new AssertionError("JVM does not support UTF-8"); // should never happen! } } /** * Parse the path component from the given request and return w/o decoding. * @param request Http request to parse * @param servletName the name of servlet that precedes the path * @return path component, null if the default charset is not supported */ public static String getRawPath(final HttpServletRequest request, String servletName) { Preconditions.checkArgument(request.getRequestURI().startsWith(servletName + "/")); return request.getRequestURI().substring(servletName.length()); } }