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package oracle.toplink.essentials.internal.sessions;
import oracle.toplink.essentials.exceptions.*;
import oracle.toplink.essentials.threetier.*;
import oracle.toplink.essentials.internal.identitymaps.IdentityMapManager;
import oracle.toplink.essentials.queryframework.*;
import oracle.toplink.essentials.internal.sessions.AbstractSession;
import oracle.toplink.essentials.internal.sessions.AbstractRecord;
/**
* Provides isolation support by allowing a client session
* to have a local cache of the subset of the classes.
* This can be used to avoid caching frequently changing data,
* or for security or VPD purposes.
*/
public class IsolatedClientSession extends oracle.toplink.essentials.threetier.ClientSession {
public IsolatedClientSession(ServerSession parent, ConnectionPolicy connectionPolicy) {
super(parent, connectionPolicy);
}
/**
* INTERNAL:
* Set up the IdentityMapManager. This method allows subclasses of Session to override
* the default IdentityMapManager functionality.
*/
public void initializeIdentityMapAccessor() {
this.identityMapAccessor = new IsolatedClientSessionIdentityMapAccessor(this, new IdentityMapManager(this));
}
/**
* INTERNAL:
* Helper method to calculate whether to execute this query locally or send
* it to the server session.
*/
protected boolean shouldExecuteLocally(DatabaseQuery query) {
if (isIsolatedQuery(query)) {
return true;
}
return isInTransaction();
}
/**
* INTERNAL: Answers if this query is an isolated query and must be
* executed locally.
*/
protected boolean isIsolatedQuery(DatabaseQuery query) {
query.checkDescriptor(this);
if (query.isDataModifyQuery() || ((query.getDescriptor() != null) && query.getDescriptor().isIsolated())) {
// For CR#4334 if in transaction stay on client session.
// That way client's write accessor will be used for all queries.
// This is to preserve transaction isolation levels.
// also if this is an isolated class and we are in an isolated session
//load locally.
return true;
}
return false;
}
/**
* INTERNAL:
* Gets the next link in the chain of sessions followed by a query's check
* early return, the chain of sessions with identity maps all the way up to
* the root session.
* <p>
* Used for session broker which delegates to registered sessions, or UnitOfWork
* which checks parent identity map also.
* @param canReturnSelf true when method calls itself. If the path
* starting at <code>this</code> is acceptable. Sometimes true if want to
* move to the first valid session, i.e. executing on ClientSession when really
* should be on ServerSession.
* @param terminalOnly return the session we will execute the call on, not
* the next step towards it.
* @return this if there is no next link in the chain
*/
public AbstractSession getParentIdentityMapSession(DatabaseQuery query, boolean canReturnSelf, boolean terminalOnly) {
if ((query != null) && isIsolatedQuery(query)) {
return this;
} else {
return getParent().getParentIdentityMapSession(query, canReturnSelf, terminalOnly);
}
}
/**
* INTERNAL:
* Gets the session which this query will be executed on.
* Generally will be called immediately before the call is translated,
* which is immediately before session.executeCall.
* <p>
* Since the execution session also knows the correct datasource platform
* to execute on, it is often used in the mappings where the platform is
* needed for type conversion, or where calls are translated.
* <p>
* Is also the session with the accessor. Will return a ClientSession if
* it is in transaction and has a write connection.
* @return a session with a live accessor
* @param query may store session name or reference class for brokers case
*/
public AbstractSession getExecutionSession(DatabaseQuery query) {
if (shouldExecuteLocally(query)) {
return this;
} else {
return getParent().getExecutionSession(query);
}
}
/**
* INTERNAL:
* Isolated sessions must forward call execution to its parent, unless in a transaction.
* This is required as isolated sessions are always the execution session for isolated classes.
*/
public Object executeCall(Call call, AbstractRecord translationRow, DatabaseQuery query) throws DatabaseException {
if (isInTransaction()) {
return super.executeCall(call, translationRow, query);
}
return getParent().executeCall(call, translationRow, query);
}
}