Java tutorial
/* The contents of this file are subject to the license and copyright terms * detailed in the license directory at the root of the source tree (also * available online at http://fedora-commons.org/license/). */ package org.fcrepo.server.storage; import java.io.BufferedReader; import java.io.InputStream; import java.io.InputStreamReader; import java.net.MalformedURLException; import java.net.URL; import java.net.URLEncoder; import java.util.Map; import org.apache.commons.httpclient.UsernamePasswordCredentials; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.fcrepo.common.http.HttpInputStream; import org.fcrepo.common.http.WebClient; import org.fcrepo.common.http.WebClientConfiguration; import org.fcrepo.server.Context; import org.fcrepo.server.Server; import org.fcrepo.server.errors.ModuleInitializationException; import org.fcrepo.server.errors.ServerException; import org.fcrepo.server.storage.types.DigitalObject; /** * DefaultDOManager extension that updates a GSearch (Fedora Generic Search) * service as object changes are committed. * <p> * To use, simply change fedora.fcfg, replacing "DefaultDOManager" with * "GSearchDOManager", and add the following xml param elements: * </p> * <p> * Required: * <ul> * <li> <param name="gSearchRESTURL" * value="http://localhost:8080/fedoragsearch/rest"/></li> * </ul> * </p> * <p> * Optional (only needed if basic auth is required for GSearch REST access): * <ul> * <li> <param name="gSearchUsername" value="exampleUsername"/></li> * <li> <param name="gSearchPassword" value="examplePassword"/></li> * </ul> * </p> * * @author Chris Wilper */ public class GSearchDOManager extends DefaultDOManager { private static final Logger logger = LoggerFactory.getLogger(GSearchDOManager.class); /** Required param: URL of GSearch REST interface. */ public static final String GSEARCH_REST_URL = "gSearchRESTURL"; /** Optional param: User to authenticate to GSearch as. */ public static final String GSEARCH_USERNAME = "gSearchUsername"; /** Optional param: Password to use for GSearch authentication. */ public static final String GSEARCH_PASSWORD = "gSearchPassword"; /** Configured value for GSEARCH_REST_URL parameter. */ private String _gSearchRESTURL; /** Credentials we'll use for GSearch authentication, if enabled. */ private UsernamePasswordCredentials _gSearchCredentials; /** HTPP client configuration */ private WebClientConfiguration _webClientConfig; /** HTTP client we'll use for sending GSearch update signals. */ private WebClient _webClient; /** * Delegates construction to the superclass. */ public GSearchDOManager(Map moduleParameters, Server server, String role) throws ModuleInitializationException { super(moduleParameters, server, role); } // // Overrides of DefaultDOManager methods // /** * Performs superclass post-initialization, then completes initialization * using GSearch-specific parameters. */ @Override public void postInitModule() throws ModuleInitializationException { super.postInitModule(); // validate required param: GSEARCH_REST_URL _gSearchRESTURL = getParameter(GSEARCH_REST_URL); if (_gSearchRESTURL == null) { throw new ModuleInitializationException( "Required parameter, " + GSEARCH_REST_URL + " was not specified", getRole()); } else { try { new URL(_gSearchRESTURL); logger.debug("Configured GSearch REST URL: " + _gSearchRESTURL); } catch (MalformedURLException e) { throw new ModuleInitializationException( "Malformed URL given " + "for " + GSEARCH_REST_URL + " parameter: " + _gSearchRESTURL, getRole()); } } // validate credentials: if GSEARCH_USERNAME is given, GSEARCH_PASSWORD // should also be. String user = getParameter(GSEARCH_USERNAME); if (user != null) { logger.debug("Will authenticate to GSearch service as user: " + user); String pass = getParameter(GSEARCH_PASSWORD); if (pass != null) { _gSearchCredentials = new UsernamePasswordCredentials(user, pass); } else { throw new ModuleInitializationException( GSEARCH_PASSWORD + " must be specified because " + GSEARCH_USERNAME + " was specified", getRole()); } } else { logger.debug( GSEARCH_USERNAME + " unspecified; will not attempt " + "to authenticate to GSearch service"); } // finally, init the http client we'll use _webClientConfig = getServer().getWebClientConfig(); _webClient = new WebClient(_webClientConfig); } /** * Commits the changes to the given object as usual, then attempts to * propagate the change to the GSearch service. */ @Override public void doCommit(boolean cachedObjectRequired, Context context, DigitalObject obj, String logMessage, boolean remove) throws ServerException { super.doCommit(cachedObjectRequired, context, obj, logMessage, remove); // determine the url we need to invoke StringBuffer url = new StringBuffer(); url.append(_gSearchRESTURL + "?operation=updateIndex"); String pid = obj.getPid(); url.append("&value=" + urlEncode(pid)); if (remove) { logger.info("Signaling removal of " + pid + " to GSearch"); url.append("&action=deletePid"); } else { if (logger.isInfoEnabled()) { if (obj.isNew()) { logger.info("Signaling add of " + pid + " to GSearch"); } else { logger.info("Signaling mod of " + pid + " to GSearch"); } } url.append("&action=fromPid"); } // send the signal sendRESTMessage(url.toString()); } // // Private utility methods // /** * Performs the given HTTP request, logging a warning if we don't get a 200 * OK response. */ private void sendRESTMessage(String url) { HttpInputStream response = null; try { logger.debug("Getting " + url); response = _webClient.get(url, false, _gSearchCredentials); int code = response.getStatusCode(); if (code != 200) { logger.warn("Error sending update to GSearch service (url=" + url + "). HTTP response code was " + code + ". " + "Body of response from GSearch follows:\n" + getString(response)); } } catch (Exception e) { logger.warn("Error sending update to GSearch service via URL: " + url, e); } finally { if (response != null) { try { response.close(); } catch (Exception e) { logger.warn("Error closing GSearch response", e); } } } } /** * Read the remainder of the given stream as a String and return it, or an * error message if we encounter an error. */ private static String getString(InputStream in) { try { StringBuffer out = new StringBuffer(); BufferedReader reader = new BufferedReader(new InputStreamReader(in)); String line = reader.readLine(); while (line != null) { out.append(line + "\n"); line = reader.readLine(); } return out.toString(); } catch (Exception e) { return "[Error reading response body: " + e.getClass().getName() + ": " + e.getMessage() + "]"; } } /** * URL-encode the given string using UTF-8 encoding. */ private static final String urlEncode(String s) { try { return URLEncoder.encode(s, "UTF-8"); } catch (Exception e) { logger.warn("Failed to encode '" + s + "'", e); return s; } } }