/*
* ome.model.internal.GraphHolder
*
* Copyright 2006 University of Dundee. All rights reserved.
* Use is subject to license terms supplied in LICENSE.txt
*/
package ome.model.internal;
import ome.conditions.SecurityViolation;
import ome.model.IObject;
/**
* holds information regarding the graph to which an {@link ome.model.IObject}
* belongs.
*
* {@link GraphHolder#hasToken()}, {@link GraphHolder#tokenMatches(Token)},
* and {@link GraphHolder#setToken(Token, Token)} are final so that subclasses
* cannot intercept tokens.
*
* @author Josh Moore <a
* href="mailto:josh.moore@gmx.de">josh.moore@gmx.de</a>
* @version 3.0
* @since 3.0
* @author josh
*/
public final class GraphHolder {
private IObject replacement;
/**
* a replacement is a <em>managed</em> entity instance which has the same
* primary key as this instance. Storing this value here allows for several
* optimizations.
*
* @return entity
*/
public IObject getReplacement() {
return replacement;
}
/**
* used mostly by {@code ome.api.IUpdate}. Improper use of this method may
* cause erratic behavior.
*
* @param replacement
*/
public void setReplacement(IObject replacement) {
this.replacement = replacement;
}
private Token token;
/**
* tests if this {@link GraphHolder} contains a {@link Token} reference.
*/
public final boolean hasToken() {
return this.token != null;
}
/**
* check the {@link Token} for the {@link IObject} represented by this
* {@link GraphHolder}. This can be seen to approximate "ownership" of this
* Object within the JVM.
*
* @return true only if the two instances are identical.
*/
public final boolean tokenMatches(Token token) {
return this.token == token;
}
/**
* set the {@link Token} for this {@link GraphHolder} but only if you posses
* the current {@link Token}. The first call to
* {@link #setToken(Token, Token)} will succeed when {@link #token} is null.
*
* @param previousToken
* @param newToken
*/
public final void setToken(Token previousToken, Token newToken) {
if (token == null || previousToken == token) {
this.token = newToken;
}
else {
throw new SecurityViolation("Tokens do not match.");
}
}
}