== QContext
include::../variables.adoc[]

The class `QContext` contains a collection of thread-local variables, to define the current context of the QQQ code that is currently running.
For example, what `QInstance` (meta-data container) is being used, what `QSession` (user attributes) is active, etc.

Most of the time, main-line application code does not need to worry about setting up the `QContext` - although unit-test code can is a common exception to that rule.
This is because all of QQQ's entry-points into execution (e.g., web context handlers, CLI startup methods, schedulers, and multi-threaded executors) take care of initializing the context.

It is more common though, for application code to need to get data from the context, such as the current session or any piece of meta-data from the QInstance.
The methods to access data from the `QContext` are fairly straightforward:

=== Examples
==== Get a QTableMetaData from the active QInstance
[source,java]
----
QTableMeataData myTable = QContext.getQInstance().getTable("myTable");
for(QFieldMeataData field : myTable.getFields().values())
{
   // ...
}
----

==== Get a security key value for the current user session
[source,java]
----
QSession           session   = QContext.getQSession();
List<Serializable> clientIds = session.getSecurityKeyValues("clientId");
----

