/*
* The contents of this file are subject to the Mozilla Public License
* Version 1.1 (the "License"); you may not use this file except in
* compliance with the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS"
* basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
* the License for the specific language governing rights and limitations
* under the License.
*
* The Original Code is the Kowari Metadata Store.
*
* The Initial Developer of the Original Code is Plugged In Software Pty
* Ltd (http://www.pisoftware.com, mailto:info@pisoftware.com). Portions
* created by Plugged In Software Pty Ltd are Copyright (C) 2001,2002
* Plugged In Software Pty Ltd. All Rights Reserved.
*
* Contributor(s): N/A.
*
* [NOTE: The text of this Exhibit A may differ slightly from the text
* of the notices in the Source Code files of the Original Code. You
* should use the text of this Exhibit A rather than the text found in the
* Original Code Source Code for Your Modifications.]
*
*/
package org.mulgara.server.rmi;
// Java 2 standard packages
import java.rmi.*;
// Third party packages
import org.apache.log4j.*;
import org.mulgara.query.Answer;
import org.mulgara.query.ArrayAnswer;
import org.mulgara.query.TuplesException;
import org.mulgara.query.Variable;
import org.mulgara.util.Rmi;
/**
* Remote ITQL answer. An answer is a set of solutions, where a solution is a
* mapping of {@link Variable}s to {@link org.mulgara.query.Value}s.
*
* @author <a href="http://staff.pisoftware.com/raboczi">Simon Raboczi</a>
*
* @created 2001-07-31
*
* @version $Revision: 1.11 $
*
* @modified $Date: 2005/01/28 00:29:22 $
*
* @maintenanceAuthor $Author: newmana $
*
* @company <A href="mailto:info@PIsoftware.com">Plugged In Software</A>
*
* @copyright © 2001-2003 <A href="http://www.PIsoftware.com/">Plugged In
* Software Pty Ltd</A>
*
* @licence <a href="{@docRoot}/../../LICENCE">Mozilla Public License v1.1</a>
*/
public class AnswerWrapperRemoteAnswer extends Rmi implements RemoteAnswer, Cloneable {
/** logger */
private static final Logger logger = Logger.getLogger(AnswerWrapperRemoteAnswer.class.getName());
/**
* Allow newer compiled version of the stub to operate when changes
* have not occurred with the class.
* NOTE : update this serialVersionUID when a method or a public member is
* deleted.
*/
static final long serialVersionUID = -1887399686697126359L;
/**
* The wrapped instance.
*/
protected final Answer answer;
/**
* Wraps a new answer for paging of results.
*
* @param answer the instance to wrap
* @throws IllegalArgumentException if <var>answer</var> is <code>null</code>
*/
public AnswerWrapperRemoteAnswer(Answer answer) throws RemoteException {
// Validate "answer" parameter
if (answer == null) {
throw new IllegalArgumentException("Null \"answer\" parameter");
}
// Initialize wrapped field
this.answer = answer;
}
/**
* Reset the instance to iterate from the beginning.
*
* Needs to be followed by a call to {@link #next} before reading can start.
* Synchronized to prevent a prefetch thread from asking for a page while this
* is still in the process of executing.
*
* @throws TuplesException EXCEPTION TO DO
* @throws RemoteException EXCEPTION TO DO
*/
public synchronized AnswerPage beforeFirstAndInitPage() throws
TuplesException, RemoteException {
try {
answer.beforeFirst();
AnswerPage result = nextPage();
return result;
}
catch (TuplesException et) {
logger.error("TuplesException thrown", et);
throw et;
}
catch (RemoteException er) {
logger.error("RemoteException thrown", er);
throw er;
}
catch (Throwable t) {
logger.error("Throwable thrown", t);
throw new TuplesException("Throwable thrown", t);
}
}
/**
* Return the object at the given index.
* TODO: This should not be called now due to paging. Check.
*
* @param column PARAMETER TO DO
* @return the value at the given index
* @throws TuplesException EXCEPTION TO DO
* @throws RemoteException EXCEPTION TO DO
*/
public Object getObject(int column) throws TuplesException, RemoteException {
return optimiseObject(answer.getObject(column));
}
/**
* Return the object at the given column name.
* TODO: This should not be called now due to paging. Check.
*
* @param columnName the index of the object to retrieve
* @return the value at the given index
* @throws SQLException on failure
* @throws TuplesException EXCEPTION TO DO
* @throws RemoteException EXCEPTION TO DO
*/
public Object getObject(String columnName) throws TuplesException,
RemoteException {
return optimiseObject(answer.getObject(columnName));
}
/**
* Checks an object type, and if an Answer then converts it into a suitable form for the network.
* TODO: This should not be called now due to paging. Check.
*
* @param obj The object to check and possibly convert.
* @return An object optimised for network transport.
*/
private Object optimiseObject(Object obj) throws TuplesException,
RemoteException {
if (obj instanceof Answer) {
// Standard answers are not serializable, so either instantiate it into a serializable object
// or wrap in a remote reference
Answer ans = (Answer) obj;
if (ans.getRowExpectedCount() <= MARSHALL_SIZE_LIMIT) {
obj = new ArrayAnswer(ans); // return a serialised answer
ans.close();
}
else {
obj = new AnswerWrapperRemoteAnswer(ans); // return a remote reference to the answer
}
}
return obj;
}
/**
* @return the number of columns
*/
public int getNumberOfVariables() throws RemoteException {
return answer.getNumberOfVariables();
}
/**
* The variables bound and their default collation order. The array returned
* by this method should be treated as if its contents were immutable, even
* though Java won't enforce this. If the elements of the array are modified,
* there may be side effects on the past and future clones of the tuples it
* was obtained from.
*
* @return the {@link Variable}s bound within this answer.
* @throws RemoteException EXCEPTION TO DO
*/
public Variable[] getVariables() throws RemoteException {
return answer.getVariables();
}
/**
* Tests whether this is a unit-valued answer. A unit answer appended to
* something yields the unit answer. A unit answer joined to something yields
* the same something. Notionally, the unit answer has zero columns and one
* row.
*
* @return The Unconstrained value
* @throws TuplesException EXCEPTION TO DO
* @throws RemoteException EXCEPTION TO DO
*/
public boolean isUnconstrained() throws TuplesException, RemoteException {
return answer.isUnconstrained();
}
/**
* Advance to the next term in the solution.
*
* @return <code>false<code> if there was no further term to advance to.
* @throws TuplesException EXCEPTION TO DO
* @throws RemoteException EXCEPTION TO DO
*/
public boolean next() throws TuplesException, RemoteException {
return answer.next();
}
/**
* Advance to the next page in the solution. This advances the answer by one page.
* Synchronized to prevent a prefetch thread from asking for a page while this
* is still in the process of executing.
*
* @return The new page, or <code>null</code> if there is no data left in the answer.
* @throws TuplesException Iterating through the answer caused a problem.
* @throws RemoteException Required for RMI interfaces.
*/
public synchronized AnswerPage nextPage() throws TuplesException,
RemoteException {
try {
AnswerPageImpl page = new AnswerPageImpl(answer);
return (page.getPageSize() == 0) ? null : page;
}
catch (TuplesException et) {
logger.warn("TuplesException thrown in nextPage", et);
throw et;
}
catch (Throwable t) {
logger.warn("Throwable thrown in nextPage", t);
throw new TuplesException("Error in nextPage", t);
}
}
/**
* Accessor for the binding of a given variable within the current product
* term (row).
*
* @param column PARAMETER TO DO
* @return the bound value, or {@link org.mulgara.store.tuples.Tuples#UNBOUND}
* if there is no binding within the current product term (row)
* @throws TuplesException if there is no current row (before first or after
* last) or if <var>variable</var> isn't an element of {@link
* #getVariables}
* @throws RemoteException EXCEPTION TO DO
*/
public int getColumnIndex(Variable column) throws TuplesException,
RemoteException {
return answer.getColumnIndex(column);
}
/**
* This method returns the number of rows which this instance contains.
*
* @return the number of rows that this instance contains.
* @throws TuplesException EXCEPTION TO DO
* @throws RemoteException EXCEPTION TO DO
*/
public long getRowCount() throws TuplesException, RemoteException {
return answer.getRowCount();
}
public long getRowUpperBound() throws TuplesException, RemoteException {
return answer.getRowUpperBound();
}
public long getRowExpectedCount() throws TuplesException, RemoteException {
return answer.getRowExpectedCount();
}
public int getRowCardinality() throws TuplesException {
return answer.getRowCardinality();
}
public boolean isEmpty() throws TuplesException, RemoteException {
return answer.isEmpty();
}
/**
* Free resources associated with this instance.
*
* @throws RemoteException EXCEPTION TO DO
*/
public void close() throws TuplesException, RemoteException {
answer.close();
try {
unexportObject(this, false);
} catch (NoSuchObjectException e) {
// doesn't matter if this object was not exported, but that shouldn't happen
logger.warn("Remote object to be closed was never exported", e);
}
}
/**
* Returns a copy of this object.
*
* @return Object
*/
public Object clone() {
//copy the answer too
Answer answerClone = (Answer)this.answer.clone();
//reset the original Answer
try {
answerClone.beforeFirst();
return new AnswerWrapperRemoteAnswer(answerClone);
}
catch (TuplesException tuplesException) {
throw new RuntimeException(tuplesException);
}
catch (RemoteException remoteException) {
throw new RuntimeException(remoteException);
}
}
/**
* Returns a copy of this object for a remote client
*
* @throws RemoteException is the server fails to clone
* @return <var>RemoteAnswer</var>
*/
public RemoteAnswer remoteClone() throws RemoteException {
return (RemoteAnswer)this.clone();
}
}