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<%@ page contentType="text/plain;charset=ISO-8859-1" import="java.io.*" %>
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<% 
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/************************************************
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 * This is an example implementation of a Kepler AuthNamespace web service.
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 * 
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 * The output parameters are
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 *   error, namespace
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 * The optional input parameters are
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 *   username, password, namespace
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 *
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 ************************************
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 * Kepler AuthNamespace Web Service *
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 ************************************
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 *
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 * The namespace that is returned shall always be unique for the given URL regardless of URI input parameters
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 * The file type returned by the webservice shall be text/plain and shall contain the two output parameters
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 *      formatted in accordance with the java.util.Properties specification.
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 *
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 * Optionally a username and password parameter may be supplied to the webservice for authenticating users
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 *      or simply for disallowing robots from accessing the service.
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 * Implementations of the AuthNamespace service may also optionally accept a namespace as an input,
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 *      check to see if that namespace is available, and return it if it is available or return an error if it is not.
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 *
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 ************************************************/
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try {
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	/*
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	 * The authority string should exactly match the URL this service is accessed by.
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	 * This prevents having multiple URLs accessing this same JSP page which would be bad
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	 *   since the namespaces generated by an authority must be unique to that authority.
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	 */
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	String authority = "http://library.kepler-project.org/kepler/style/skins/kepler/keplerAuthNameSpace.jsp";
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	String accessedAuthority = request.getRequestURL().toString();
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	/*
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	 * Get username and password inputs.
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	 */
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	String user = request.getParameter( "username" );
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	String pass = request.getParameter( "password" );
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	/*
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	 * Make sure the URL used to access this service is the correct authority URL.
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	 */
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	if ( accessedAuthority != null && accessedAuthority.equals( authority )) {
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		/* 
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		 * Check to make sure the "kepler" username/password was given
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		 * This will prevent stray robots or users from incrementing namespaces arbitrarily.
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		 */
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		if ( user != null && user.equals("kepler") ) {
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			if ( pass != null && pass.equals("kepler") ) {
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				if ( request.getParameter( "namespace" ) != null ) {
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					// TODO query a database for the requested namespace
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					// print namespace if it is not already taken and insert it into the database
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					// return an error if the namespace has already been reserved
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				} else {
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					/* Store an incrementing integer in a file.
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					 * This approach may fail due to collisions under high load conditions.
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					 * But works fine for this example implementation.
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					 */
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					ServletContext context = session.getServletContext();
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					String fname = "/var/kepler/last_issued_namespace.txt";
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					Integer inc = new Integer(0);
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					File f = new File( fname );
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					if (f.exists()) {
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						// Read in the previous Integer
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						InputStream is = new FileInputStream(fname);
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						ObjectInput oi = new ObjectInputStream(is);
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						inc = (Integer) oi.readObject();
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						oi.close();
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						int i = inc.intValue() + 1;
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						inc = new Integer( i );
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					}
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					// Write out the incremented integer (or 0 if the file does not exist)
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					OutputStream os = new FileOutputStream(fname);
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					ObjectOutputStream oos = new ObjectOutputStream(os);
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					oos.writeObject( inc );
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					oos.flush();
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					/*
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					 * Print out the incremented Integer as the namespace output
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					 * in java.util.Properties format.
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					 */
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					out.println( "namespace=" + inc + "\n" );
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				}
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			} else {
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				throw new Exception("The specified password is incorrect");
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			}
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		} else {
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			throw new Exception("The specified username is incorrect.");
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		}
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	} else {
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		throw new Exception("The specified authority URL is incorrect.");
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	}
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} catch (Exception e) { 
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	/*
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	 * Print out the error in java.util.Properties format.
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	 */
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	out.println( "error=" + e.getMessage() + "\n" );
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} 
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%>
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