In any filter, you can always depend on the following objects being defined.
Invocation context (context)
This is the context in which a filter gets invoked. Any variables or functions you define in this context will be thrown away once the filter returns.
packet: the packet or token being filtered. The exact nature of this packet depends on the filter's circumstances. You can always get the type of the packet using the packetType property.
filterContext: see below
threadContext: see below
connectionContext: see below
projectContext: see below
Filter context (context.filterContext)
This context is shared by all invocations of the filter.
There may be one or more variable defined in this context with a name that starts with an underscore. These are internal variables and should not be used.
You can define additional variables to store data that would be useful to subsequent invocations of this filter.
Connection context (context.connectionContext)
This context is shared by all logic invoked during the lifetime of the connection from the database client.
userIP: the IP address of the client, e.g. /126.96.36.199 or /2600:1701:6920:69a0:17:986a:da7a:c12a
userName: the name of the database user. When using SQL Server authentication, this is usually a simple name, e.g. jdoe. When using Windows authentication, the user name is typically prefixed by the domain name, e.g. MYDOMAIN\jdoe
lastSQL: the last SQL to be executed on this connection, either as a SQL command, or as a parameter to sp_executesql.
Project context (context.projectContext)
This context is as close as you can get to "global" variables. It is shared by all filters within a project.
Thread context (context.threadContext)
This is a special context that is only shared by invocations of various filters that happen to be on the same Java thread. Anything stored in this context is thrown away when the thread is terminated, which can happen at any time between filter invocations. This context can be useful when dealing with non-thread-safe objects.