Java tutorial
/** * '$RCSfile$' * Copyright: 2000-2005 Regents of the University of California and the * National Center for Ecological Analysis and Synthesis * * '$Author: harris $' * '$Date: 2006-01-26 10:42:52 +1000 (Thu, 26 Jan 2006) $' * '$Revision: 2904 $' * * 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */ package edu.ucsb.nceas.metacat.lsid; import java.io.BufferedReader; import java.io.ByteArrayInputStream; import java.io.ByteArrayOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.io.Reader; import java.io.StringReader; import java.util.Hashtable; import java.util.ResourceBundle; import java.util.Enumeration; import javax.xml.transform.Transformer; import javax.xml.transform.TransformerFactory; import javax.xml.transform.stream.StreamResult; import javax.xml.transform.stream.StreamSource; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import com.ibm.lsid.LSID; import com.ibm.lsid.MalformedLSIDException; import com.ibm.lsid.MetadataResponse; import com.ibm.lsid.server.LSIDMetadataService; import com.ibm.lsid.server.LSIDRequestContext; import com.ibm.lsid.server.LSIDServerException; import com.ibm.lsid.server.LSIDServiceConfig; import edu.ucsb.nceas.metacat.client.Metacat; import edu.ucsb.nceas.metacat.client.MetacatFactory; import edu.ucsb.nceas.metacat.client.MetacatInaccessibleException; public class LSIDAuthorityMetaData implements LSIDMetadataService { private LSIDDataLookup lookup = null; private static Hashtable currentLSIDs = new Hashtable(); private static Log logger = LogFactory.getLog("edu.ucsb.nceas.metacat.lsid"); public void initService(LSIDServiceConfig cf) throws LSIDServerException { logger.info("Starting LSIDAuthorityMetadata."); lookup = new LSIDDataLookup(); } private static final String RDF_NS = "http://www.w3.org/1999/02/22-rdf-syntax-ns#"; private static final String DC_NS = "http://purl.org/dc/elements/1.1/"; private static final String I3CP_NS = "urn:lsid:i3c.org:predicates:"; private static final String I3C_CONTENT = "urn:lsid:i3c.org:types:content"; private static final String DEFAULT_STYLESHEET = "default.xslt"; public MetadataResponse getMetadata(LSIDRequestContext req, String[] formats) throws LSIDServerException { LSID lsid = req.getLsid(); ByteArrayInputStream theMetadata = doMetadataRequest(lsid); return new MetadataResponse(theMetadata, null, MetadataResponse.RDF_FORMAT); } private ByteArrayInputStream doMetadataRequest(LSID lsid) throws LSIDServerException { logger.debug("getting metadata for lsid " + lsid.getLsid()); try { LSIDDataLookup myLookup = new LSIDDataLookup(); InputStream content = myLookup.lsidData(lsid); InputStream content2 = myLookup.lsidData(lsid); if (!isEML(content2)) { content = getEML(lsid); } content2.close(); setCurrentLSID(lsid); // based on the doctype choose the appropriate stylesheet String styleSheetName = null; String _docType = myLookup.getDocType(lsid); try { ResourceBundle rb = ResourceBundle.getBundle("metacat-lsid"); styleSheetName = rb.getString(_docType.replaceAll(":", "")); } catch (java.util.MissingResourceException mre) { logger.warn("there is no style corresponding to: '" + _docType + "' -- using default"); styleSheetName = this.DEFAULT_STYLESHEET; mre.getMessage(); } InputStream styleSheet = getClass().getResourceAsStream(styleSheetName); TransformerFactory factory = TransformerFactory.newInstance(); Transformer transformer = factory.newTransformer(new StreamSource(styleSheet)); ByteArrayOutputStream out = new ByteArrayOutputStream(); transformer.transform(new StreamSource(content), new StreamResult(out)); content.close(); clearState(); return new ByteArrayInputStream(out.toByteArray()); } catch (Exception e) { throw new LSIDServerException(e, "Error transforming XML for: " + lsid); } } public static String getStringFromInputStream(InputStream input) { StringBuffer result = new StringBuffer(); BufferedReader in = new BufferedReader(new InputStreamReader(input)); String line; try { while ((line = in.readLine()) != null) { result.append(line); } } catch (IOException e) { logger.error("IOexception " + e); } return result.toString(); } /** * figure out is this inputstream is an eml document or not * TODO: need a better way to figure out if this is an eml document */ private boolean isEML(InputStream input) { if (input == null) { return false; } int loop = 0; boolean itIsEML = false; String line = ""; try { BufferedReader in = new BufferedReader(new InputStreamReader(input)); while ((loop < 20) && (line != null) && (!itIsEML)) { line = in.readLine(); line = line.toLowerCase(); if (line.indexOf("eml:eml") != -1) { itIsEML = true; } loop++; } } catch (IOException e) { logger.error("ioerror in LSIDAuthorityMetadata: " + e); } return itIsEML; } /** * this lsid points to a data object - get the metadata objects which refer * to this document */ private InputStream getEML(LSID theLSID) { InputStream response = null; // need to find things with this object in any of the elements // using the metacat api // get back dataset/docid and dataset/title // create the query String theQuery = getMetaCatQuery(theLSID); // get the metacat record Reader metaCatResponse = getMetaCatResponse(theQuery); // parse the metadata to get the applicable rdf information response = parseMetaCatResponse(metaCatResponse, theLSID); return response; } /** * given an LSID return a metacat query which will return docs mentioning * this LSID */ private String getMetaCatQuery(LSID lsid) { logger.debug("getting Metacat Query for: " + lsid.toString()); String ns = lsid.getNamespace(); String id = lsid.getObject(); String ver = lsid.getRevision(); String theName = ns + "." + id + "." + ver; String theQuery = null; theQuery = "<?xml version=\"1.0\"?>\n" + "<pathquery version=\"1.2\">\n" + " <querytitle>" + theName + " search</querytitle>\n" + " <returnfield>dataset/docid</returnfield>\n" + " <returnfield>dataset/title</returnfield>\n" + " <querygroup operator=\"UNION\">\n" + " <queryterm searchmode=\"contains\" casesensitive=\"false\">\n" + " <value>" + theName + "</value>\n" + " <pathexpr>anyfield</pathexpr>\n" + " </queryterm>\n" + " </querygroup>\n" + "<pathquery>\n"; return theQuery; } /** * given a query string, query MetaCat and return the response */ private Reader getMetaCatResponse(String query) { logger.debug("Querying the metacat server."); // get the metacat server from the configuration file // ResourceBundle rb = ResourceBundle.getBundle("metacat-lsid"); String url = rb.getString("metacatserver"); Reader r = null; try { Metacat m = MetacatFactory.createMetacatConnection(url); r = m.query(new StringReader(query)); } catch (MetacatInaccessibleException mie) { logger.error("Metacat Inaccessible:\n" + mie.getMessage()); } catch (Exception e) { logger.error("General exception:\n" + e.getMessage()); } return r; } /** * Given a reader which is a metacat response, parse it and return the * appropriate rdf */ private InputStream parseMetaCatResponse(Reader reader, LSID theLSID) { InputStream response = null; logger.debug("Parsing the metacat response."); // if there's more than one document, then return rdf listing the // documents // otherwise get the document and return rdf based on it String contents = getStringFromReader(reader); if (numberDocuments(contents) < 1) { response = noMetaDataResponse(theLSID); } else if (numberDocuments(contents) > 1) { response = metaDataList(contents, theLSID); } else { response = getMetaData(contents, theLSID); } return response; } /** * There's no metadata for this document */ private ByteArrayInputStream noMetaDataResponse(LSID theLSID) { ResourceBundle rb = ResourceBundle.getBundle("metacat-lsid"); String metadataLabels = rb.getString("metadatalabels"); String result = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n" + "<rdf:RDF xmlns:rdf=\"http://www.w3.org/1999/02/22-rdf-syntax-ns#\" \n" + " xmlns:dc=\"http://purl.org/dc/elements/1.1/\" \n" + " xmlns:pred=\"urn:lsid:i3c.org:predicates:\" xmlns=\"urn:lsid:" + metadataLabels + ":predicates:\"> \n" + "<rdf:Description rdf:about=\"" + theLSID.getLsid() + "\"> \n" + " <pred:title xmlns:pred=\"http://purl.org/dc/elements/1.1/\">There is no metadata for this LSID.</pred:title>\n" + "</rdf:Description>\n" + "</rdf:RDF>\n"; return new ByteArrayInputStream(result.getBytes()); } /** * There's more than one metdata document */ private ByteArrayInputStream metaDataList(String contents, LSID theLSID) { ResourceBundle rb = ResourceBundle.getBundle("metacat"); String metadataLabels = rb.getString("metadatalabels"); String result = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n" + "<rdf:RDF xmlns:rdf=\"http://www.w3.org/1999/02/22-rdf-syntax-ns#\" \n" + " xmlns:dc=\"http://purl.org/dc/elements/1.1/\" \n" + " xmlns:pred=\"urn:lsid:i3c.org:predicates:\" xmlns=\"urn:lsid:" + metadataLabels + ":predicates:\"> \n" + "<rdf:Description rdf:about=\"" + theLSID.getLsid() + "\"> \n" + " <pred:title xmlns:pred=\"http://purl.org/dc/elements/1.1/\">There is more than one metadata document for this LSID - which confuses me right now. Try again soon and I'll be less confused.</pred:title>\n" + "</rdf:Description>\n" + "</rdf:RDF>\n"; return new ByteArrayInputStream(result.getBytes()); } /** * There's just one metadata document */ private ByteArrayInputStream getMetaData(String contents, LSID theLSID) { String paramString = "<param name=\"dataset/title\">"; ByteArrayInputStream result = null; if (contents.indexOf(paramString) == -1) { return noMetaDataResponse(theLSID); } else { String parts[] = contents.split(paramString); String parts2[] = parts[1].split("</param>"); try { LSID newLSID = new LSID(parts2[0]); result = doMetadataRequest(newLSID); } catch (MalformedLSIDException e) { logger.error("problem generating LSID: " + e); e.printStackTrace(); } catch (LSIDServerException e) { logger.error("problem generating LSID: " + e); e.printStackTrace(); } } return result; } /** * Find out how many contents are in this metacat response I'm just using * string stuff for this - sort of lame, but does the trick more cool would * be to use xml stuff */ private int numberDocuments(String contents) { String[] docSplit = contents.split("<document>"); return (docSplit.length - 1); } /** * Given a reader, return a string */ private String getStringFromReader(Reader reader) { StringBuffer response = new StringBuffer(); try { BufferedReader bufReader = new BufferedReader(reader); String line = null; while ((line = bufReader.readLine()) != null) { response.append(line); } bufReader.close(); } catch (IOException e) { logger.error("error getting string from reader " + e); } return response.toString(); } /** * set the LSID for the current thread */ static void setCurrentLSID(LSID lsid) { currentLSIDs.put(Thread.currentThread(), lsid); } static void clearState() { currentLSIDs.remove(Thread.currentThread()); } /** * get the current LSID for the given thread, for use in XSLT so return a * string */ public static String getLSID(org.apache.xalan.extensions.XSLProcessorContext foo, org.apache.xalan.templates.ElemExtensionCall bar) throws MalformedLSIDException { return ((LSID) currentLSIDs.get(Thread.currentThread())).toString(); } public static String getLSID() throws MalformedLSIDException { return ((LSID) currentLSIDs.get(Thread.currentThread())).toString(); } }