package com.emprogria.rs.converter; import javax.ws.rs.WebApplicationException; import java.net.HttpURLConnection; import java.net.URI; import java.net.URL; import javax.xml.bind.JAXBContext; /** * Utility class for resolving an uri into an entity. */ public class UriResolver { private static ThreadLocal<UriResolver> instance = new ThreadLocal<UriResolver>() { @Override protected UriResolver initialValue() { return new UriResolver(); } }; private boolean inProgress = false; private UriResolver() { } /** * Returns an instance of UriResolver. * * @return an instance of UriResolver. */ public static UriResolver getInstance() { return instance.get(); } private static void removeInstance() { instance.remove(); } /** * Returns the entity associated with the given uri. * * @param type the converter class used to unmarshal the entity from XML * @param uri the uri identifying the entity * @return the entity associated with the given uri */ public <T> T resolve(Class<T> type, URI uri) { if (inProgress) return null; inProgress = true; try { if (uri == null) { throw new RuntimeException("No uri specified in a reference."); } URL url = uri.toURL(); HttpURLConnection conn = (HttpURLConnection)url.openConnection(); conn.setRequestMethod("GET"); if (conn.getResponseCode() == 200) { JAXBContext context = JAXBContext.newInstance(type); return (T) context.createUnmarshaller().unmarshal(conn.getInputStream()); } else { throw new WebApplicationException(new Throwable("Resource for " + uri + " does not exist."), 404); } } catch (WebApplicationException ex) { throw ex; } catch (Exception ex) { throw new WebApplicationException(ex); } finally { removeInstance(); } } }