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.nutch.searcher.response.xml; import java.io.ByteArrayOutputStream; import java.io.IOException; import java.text.SimpleDateFormat; import java.util.HashSet; import java.util.Set; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.xml.parsers.DocumentBuilderFactory; import javax.xml.transform.OutputKeys; import javax.xml.transform.Transformer; import javax.xml.transform.TransformerFactory; import javax.xml.transform.dom.DOMSource; import javax.xml.transform.stream.StreamResult; import org.apache.commons.lang.StringUtils; import org.apache.hadoop.conf.Configuration; import org.apache.nutch.html.Entities; import org.apache.nutch.searcher.Hit; import org.apache.nutch.searcher.HitDetails; import org.apache.nutch.searcher.Summary; import org.apache.nutch.searcher.response.ResponseWriter; import org.apache.nutch.searcher.response.SearchResults; import org.w3c.dom.Attr; import org.w3c.dom.Document; import org.w3c.dom.Element; import org.w3c.dom.Node; /** * A ResponseWriter implementation that returns search results in XML format. */ public class XMLResponseWriter implements ResponseWriter { private String contentType = null; private Configuration conf; private int maxAgeInSeconds; private boolean prettyPrint; /** * Creates and returns a new node within the XML document. * * @param doc The XML document. * @param parent The parent Node. * @param name The name of the new node. * * @return The newly created node Element. */ private static Element addNode(Document doc, Node parent, String name) { Element child = doc.createElement(name); parent.appendChild(child); return child; } /** * Creates and returns a new node within the XML document. The node contains * the text supplied as a child node. * * @param doc The XML document. * @param parent The parent Node. * @param name The name of the new node. * @param text A text string to append as a child node. * * @return The newly created node Element. */ private static void addNode(Document doc, Node parent, String name, String text) { Element child = doc.createElement(name); child.appendChild(doc.createTextNode(getLegalXml(text))); parent.appendChild(child); } /** * Adds an attribute name and value to a node Element in the XML document. * * @param doc The XML document. * @param node The node Element on which to attach the attribute. * @param name The name of the attribute. * @param value The value of the attribute. */ private static void addAttribute(Document doc, Element node, String name, String value) { Attr attribute = doc.createAttribute(name); attribute.setValue(getLegalXml(value)); node.getAttributes().setNamedItem(attribute); } /** * Transforms and returns the text string as legal XML text. * * @param text The text to transform. * * @return The text string in the form of legal XML text. */ protected static String getLegalXml(String text) { if (text == null) { return null; } StringBuffer buffer = null; for (int i = 0; i < text.length(); i++) { char c = text.charAt(i); if (!isLegalXml(c)) { if (buffer == null) { buffer = new StringBuffer(text.length()); buffer.append(text.substring(0, i)); } } else { if (buffer != null) { buffer.append(c); } } } return (buffer != null) ? buffer.toString() : text; } /** * Determines if the character is a legal XML character. * * @param c The character to check. * * @return True if the character is legal xml, false otherwise. */ private static boolean isLegalXml(final char c) { return c == 0x9 || c == 0xa || c == 0xd || (c >= 0x20 && c <= 0xd7ff) || (c >= 0xe000 && c <= 0xfffd) || (c >= 0x10000 && c <= 0x10ffff); } public void setContentType(String contentType) { this.contentType = contentType; } public Configuration getConf() { return conf; } public void setConf(Configuration conf) { this.conf = conf; this.maxAgeInSeconds = conf.getInt("searcher.response.maxage", 86400); this.prettyPrint = conf.getBoolean("searcher.response.prettyprint", true); } public void writeResponse(SearchResults results, HttpServletRequest request, HttpServletResponse response) throws IOException { try { // create the xml document and add the results and search nodes DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); Document xmldoc = factory.newDocumentBuilder().newDocument(); Element resEl = addNode(xmldoc, xmldoc, "results"); Element searchEl = addNode(xmldoc, resEl, "search"); // add common nodes String query = results.getQuery(); addNode(xmldoc, searchEl, "query", query); addNode(xmldoc, searchEl, "totalhits", String.valueOf(results.getTotalHits())); String lang = results.getLang(); if (lang != null) { addNode(xmldoc, searchEl, "lang", lang); } String sort = results.getSort(); if (sort != null) { addNode(xmldoc, searchEl, "sort", sort); } addNode(xmldoc, searchEl, "reverse", results.isReverse() ? "true" : "false"); addNode(xmldoc, searchEl, "start", String.valueOf(results.getStart())); addNode(xmldoc, searchEl, "end", String.valueOf(results.getEnd())); addNode(xmldoc, searchEl, "rows", String.valueOf(results.getRows())); addNode(xmldoc, searchEl, "totalhits", String.valueOf(results.getTotalHits())); addNode(xmldoc, searchEl, "withSummary", String.valueOf(results.isWithSummary())); String[] searchFields = results.getFields(); Set<String> fieldSet = new HashSet<String>(); if (searchFields != null && searchFields.length > 0) { addNode(xmldoc, searchEl, "fields", StringUtils.join(searchFields, ",")); for (int i = 0; i < searchFields.length; i++) { fieldSet.add(searchFields[i]); } } // add documents Element documents = addNode(xmldoc, resEl, "documents"); HitDetails[] details = results.getDetails(); Hit[] hits = results.getHits(); Summary[] summaries = results.getSummaries(); for (int i = 0; i < details.length; i++) { // every document has an indexno and an indexdocno Element document = addNode(xmldoc, documents, "document"); addAttribute(xmldoc, document, "indexno", String.valueOf(hits[i].getIndexNo())); addAttribute(xmldoc, document, "indexkey", String.valueOf(hits[i].getUniqueKey())); // don't add summaries not including summaries if (summaries != null && results.isWithSummary()) { String encSumm = Entities.encode(summaries[i].toString()); addNode(xmldoc, document, "summary", encSumm); } // add the fields from hit details Element fields = addNode(xmldoc, document, "fields"); HitDetails detail = details[i]; for (int j = 0; j < detail.getLength(); j++) { String fieldName = detail.getField(j); String[] fieldValues = detail.getValues(fieldName); // if we specified fields to return, only return those fields if (fieldSet.size() == 0 || fieldSet.contains(fieldName)) { Element field = addNode(xmldoc, fields, "field"); addAttribute(xmldoc, field, "name", fieldName); for (int k = 0; k < fieldValues.length; k++) { String encFieldVal = Entities.encode(fieldValues[k]); addNode(xmldoc, field, "value", encFieldVal); } } } } // get the xml source and a transformer to print it out DOMSource source = new DOMSource(xmldoc); TransformerFactory transFactory = TransformerFactory.newInstance(); Transformer transformer = transFactory.newTransformer(); // pretty printing can be set through configuration if (prettyPrint) { transformer.setOutputProperty("indent", "yes"); transformer.setOutputProperty(OutputKeys.INDENT, "yes"); transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "2"); } // write out the content to a byte array ByteArrayOutputStream baos = new ByteArrayOutputStream(); StreamResult result = new StreamResult(baos); transformer.transform(source, result); baos.flush(); baos.close(); // cache control headers SimpleDateFormat sdf = new SimpleDateFormat("E, d MMM yyyy HH:mm:ss 'GMT'"); long relExpiresInMillis = System.currentTimeMillis() + (1000 * maxAgeInSeconds); response.setContentType(contentType); response.setHeader("Cache-Control", "max-age=" + maxAgeInSeconds); response.setHeader("Expires", sdf.format(relExpiresInMillis)); // write out the content to the response response.getOutputStream().write(baos.toByteArray()); response.flushBuffer(); } catch (Exception e) { throw new IOException(e); } } }