Session System Examples

Creating a Session

    A session is like a bucket which follows the user through their experience with your web application. Objects placed into the session are stored on the server. Before a session starts following a user, it must be created. Below is an example of a session being created in the demo site:

Examples from demo Site:

Storing Object In the Session

    Objects are stored in the session by name, and can be retrieved later.  Here's some examples of objects being stored in a session from the demo site:
Examples from demo Site:

Custom Serialization

    Although any object can be stored in a session, only serializable objects can be safely stored. The the event the servlet is asked to terminate by the servlet environment, such as in a server shutdown, the SessionManager will save all existing sessions on disk. When the servlet is restarted, these sessions are revived and put back in memory.  Only objects which are serializable can survive this process, because by the definition of Serializable, they can be stored on disk. This may mean creating custom serialization methods for certain objects stored in a session. For example, a JDBC connection cannot normally be serialized.  This is because a JDBC connection has an active network socket.  However with custom serialization, a JDBC connection or other normally non-serializable objects can survive serialization. There is a special interface for use with objects which are serialized in a Session.  If an object implements the ContainsManagerTracker interface, when it is deserialized a pointer to the ManagerTracker will be passed in through the setMT method.
    The secret to writing custom serialization code is to think, "What data do I need to write to disk to recreate this object?".  As you can see in the SerializableJDBCConnection object in the apollo code, it's pretty much the same variables passed into the constructor.  

Examples from Apollo Core Code:
SerializableJDBCConnection - Custom serialization of an arbitrary JDBC Connection