The SessionIdGenerator Component

Table of Contents

Introduction

The SessionIdGenerator element represents the session id generator that will be used to create session ids used by web application HTTP sessions.

A SessionIdGenerator element MAY be nested inside a Manager component. If it is not included, a default SessionIdGenerator configuration will be created automatically, which is sufficient for most requirements, — see Standard SessionIdGenerator Implementation below for the details of this configuration.

Attributes

Common Attributes

All implementations of SessionIdGenerator support the following attributes:

Attribute Description
className

Java class name of the implementation to use. This class must implement the org.apache.catalina.SessionIdGenerator interface. If not specified, the standard value (defined below) will be used.

jvmRoute

A routing identifier for this Tomcat instance. It will be added to the session id to allow for stateless stickyness routing by load balancers. The details on how the jvmRoute will be included in the id are implementation dependent. See Standard Implementation for the default behavior.

NOTE - The value for this property is inherited automatically from the jvmRoute attribute of the Engine element.

sessionIdLength

The length of session ids created by this SessionIdGenerator. The details on how the sessionIdLength influences the session id length are implementation dependent. See Standard Implementation for the default behavior.

Standard Implementation

Tomcat provides a standard implementations of SessionIdGenerator for use.

Standard SessionIdGenerator Implementation

The standard implementation of SessionIdGenerator is org.apache.catalina.util.StandardSessionIdGenerator. It supports the following attributes:

Attribute Description
jvmRoute

A routing identifier for this Tomcat instance. It will be added to the end of the session id separated by a ".".

sessionIdLength

The length of session ids created by this SessionIdGenerator. More precisely the session id length is twice the value of sessionIdLength plus the length of the trailing jvmRoute if given. The factor 2 is because the session id is constructed using sessionIdLength random bytes, each byte being encoded in two hex characters in the actual id. The default value is 16.