Java tutorial
/** * The contents of this file are subject to the license and copyright * detailed in the LICENSE and NOTICE files at the root of the source * tree and available online at * * http://www.dspace.org/license/ */ package org.dspace.content.authority; import java.io.IOException; import javax.xml.parsers.SAXParserFactory; import javax.xml.parsers.SAXParser; import javax.xml.parsers.ParserConfigurationException; import org.xml.sax.XMLReader; import org.xml.sax.InputSource; import org.xml.sax.helpers.DefaultHandler; import org.xml.sax.Attributes; import org.xml.sax.SAXException; import org.xml.sax.SAXParseException; import org.apache.log4j.Logger; import org.dspace.core.ConfigurationManager; import org.apache.commons.httpclient.HttpClient; import org.apache.commons.httpclient.methods.GetMethod; import org.apache.commons.httpclient.util.EncodingUtil; import org.apache.commons.httpclient.NameValuePair; import org.apache.commons.httpclient.HttpException; /** * Choice Authority based on SHERPA/RoMEO - for Publishers and Journals * See the subclasses SHERPARoMEOPublisher and SHERPARoMEOJournalTitle * for actual choice plugin implementations. This is a superclass * containing all the common protocol logic. * * Reads these DSpace Config properties: * * # contact URL for server * sherpa.romeo.url = http://www.sherpa.ac.uk/romeoapi11.php * * WARNING: This is a very crude and incomplete implementation, done mainly * as a proof-of-concept. Any site that actually wants to use it will * probably have to refine it (and give patches back to dspace.org). * * @see SHERPARoMEOPublisher * @see SHERPARoMEOJournalTitle * @author Larry Stone * @version $Revision $ */ public abstract class SHERPARoMEOProtocol implements ChoiceAuthority { private static Logger log = Logger.getLogger(SHERPARoMEOProtocol.class); // contact URL from configuration private static String url = null; public SHERPARoMEOProtocol() { if (url == null) { url = ConfigurationManager.getProperty("sherpa.romeo.url"); // sanity check if (url == null) { throw new IllegalStateException("Missing DSpace configuration keys for SHERPA/RoMEO Query"); } } } // this implements the specific RoMEO API args and XML tag naming public abstract Choices getMatches(String text, int collection, int start, int limit, String locale); public Choices getBestMatch(String field, String text, int collection, String locale) { return getMatches(field, text, collection, 0, 2, locale); } // XXX FIXME just punt, returning value, never got around to // implementing a reverse query. public String getLabel(String field, String key, String locale) { return key; } // NOTE - ignore limit and start for now protected Choices query(String result, String label, String authority, NameValuePair[] args, int start, int limit) { HttpClient hc = new HttpClient(); String srUrl = url + "?" + EncodingUtil.formUrlEncode(args, "UTF8"); GetMethod get = new GetMethod(srUrl); log.debug("Trying SHERPA/RoMEO Query, URL=" + srUrl); try { int status = hc.executeMethod(get); if (status == 200) { SAXParserFactory spf = SAXParserFactory.newInstance(); SAXParser sp = spf.newSAXParser(); XMLReader xr = sp.getXMLReader(); SRHandler handler = new SRHandler(result, label, authority); // XXX FIXME: should turn off validation here explicitly, but // it seems to be off by default. xr.setFeature("http://xml.org/sax/features/namespaces", true); xr.setContentHandler(handler); xr.setErrorHandler(handler); xr.parse(new InputSource(get.getResponseBodyAsStream())); int confidence; if (handler.total == 0) { confidence = Choices.CF_NOTFOUND; } else if (handler.total == 1) { confidence = Choices.CF_UNCERTAIN; } else { confidence = Choices.CF_AMBIGUOUS; } return new Choices(handler.result, start, handler.total, confidence, false); } } catch (HttpException e) { log.error("SHERPA/RoMEO query failed: ", e); return null; } catch (IOException e) { log.error("SHERPA/RoMEO query failed: ", e); return null; } catch (ParserConfigurationException e) { log.warn("Failed parsing SHERPA/RoMEO result: ", e); return null; } catch (SAXException e) { log.warn("Failed parsing SHERPA/RoMEO result: ", e); return null; } finally { get.releaseConnection(); } return null; } // SAX handler to grab SHERPA/RoMEO (and eventually other details) from result private static class SRHandler extends DefaultHandler { private Choice result[] = null; int rindex = 0; // result index int total = 0; // name of element containing a result, e.g. <journal> private String resultElement = null; // name of element containing the label e.g. <name> private String labelElement = null; // name of element containing the authority value e.g. <issn> private String authorityElement = null; protected String textValue = null; public SRHandler(String result, String label, String authority) { super(); resultElement = result; labelElement = label; authorityElement = authority; } // NOTE: text value MAY be presented in multiple calls, even if // it all one word, so be ready to splice it together. // BEWARE: subclass's startElement method should call super() // to null out 'value'. (Don't you miss the method combination // options of a real object system like CLOS?) public void characters(char[] ch, int start, int length) throws SAXException { String newValue = new String(ch, start, length); if (newValue.length() > 0) { if (textValue == null) { textValue = newValue; } else { textValue += newValue; } } } // if this was the FIRST "numhits" element, it's size of results: public void endElement(String namespaceURI, String localName, String qName) throws SAXException { if (localName.equals("numhits")) { String stotal = textValue.trim(); if (stotal.length() > 0) { total = Integer.parseInt(stotal); result = new Choice[total]; if (total > 0) { result[0] = new Choice(); log.debug("Got " + total + " records in results."); } } } else if (localName.equals(resultElement)) { // after start of result element, get next hit ready if (++rindex < result.length) { result[rindex] = new Choice(); } } else if (localName.equals(labelElement) && textValue != null) { // plug in label value result[rindex].value = textValue.trim(); result[rindex].label = result[rindex].value; } else if (authorityElement != null && localName.equals(authorityElement) && textValue != null) { // plug in authority value result[rindex].authority = textValue.trim(); } else if (localName.equals("message") && textValue != null) { // error message log.warn("SHERPA/RoMEO response error message: " + textValue.trim()); } } // subclass overriding this MUST call it with super() public void startElement(String namespaceURI, String localName, String qName, Attributes atts) throws SAXException { textValue = null; } public void error(SAXParseException exception) throws SAXException { throw new SAXException(exception); } public void fatalError(SAXParseException exception) throws SAXException { throw new SAXException(exception); } } }