Session Servlet Example

Internal

• HTTP Session
• Servlet Session Tracking API

Overview

A simple servlet that can be deployed within a JEE container and used to test continuity, load balancing, failover, session stickiness, session replication, etc. It has been tested to work with WildFly/EAP and with Tomcat. It was written to avoid container-specific dependencies. Its only dependencies are slf4j for logging and the Servlet API.

Source Code

https://github.com/NovaOrdis/novaordis-session-servlet

Build

mvn clean package

Deploy

Copy ./target/session-servlet.war into the deployment directory of the application server.

Usage

Authentication

The default build produces a servlet that does NOT require authentication.

If you want authentication, do this (JBoss 5 procedure, may need to be updated for WildFly):

1. Un-comment web.xml section starting with <security-constraint> and ending with </security-role>.

2. Replace "admin" with a valid role. The replacement must be done in both places where <role-name> is mentioned. For example, if deployed on JBoss 5, pick up an appropriate role from $JBOSS_HOME/server/$JBOSS_PROFILE/conf/props/jmx-console-roles.properties.

3. Enable <security-domain> in jboss-web.xml and make sure it points to the correct one on the server.

HTTP Session Support

The servlet will NOT establish a HTTP session by default.

If you wish it to establish a session, call the /establish-session URL:

http://localhost:8080/session-servlet/establish-session

This will create a HTTP session and send the Set-Cookie JSESSIONID back to browser. If /establish-session is called repeatedly on an already established session, the application will warn, but otherwise nothing else will happen; enable-session is idempotent.

To get more information about the current session, use:

http://localhost:8080/session-servlet/describe-session

To invalidate the current session, use:

http://localhost:8080/session-servlet/invalidate-session

To write a String attribute into the session use:

http://localhost:8080/session-servlet/write/<attribute-name>/<attribute-value>

To read the value corresponding to previously written String attribute:

http://localhost:8080/session-servlet/read/<attribute-name>

To get the names of all attributes stored into the session, use:

http://localhost:8080/session-servlet/attributes

Note that the attribute count is displayed as part of the describe-session command output.

Application Type

The session servlet application allows for experiments with an application type, represented by the ApplicationType class. The ApplicationType can be modified into a backward compatible new version, incompatible new version, etc.

To write a String into ApplicationType instance, that will be in turn written into the session, use:

http://localhost:8080/session-servlet/write/apptype/<string-value>

To read the String value from the ApplicationType instance maintained by the session:

http://localhost:8080/session-servlet/read/apptype

Enable HTTP Session Replication

The application allows for experiments with distributable sessions. To enable session replication:

1. Uncomment the <distributable> configuration element in src/main/webapp/WEB-INF/web.xml. For more details on web.xml, see:

web.xml

2. Uncomment the <replication-config> section in src/main/webapp/WEB-INF/jboss-web.xml and configure the cache name, replication trigger and replication granularity. For more details about configuring WildFly session replication see:

HTTP Session Replication - WildFly-Specific Configuration

For more details on jboss-web.xml see:

jboss-web.xml

Root Context

You can change the root context as follows:

On JBoss

Simply deploy the WAR under the desired name or change the root context in jboss-web.xml. For more details on how to do that see jboss-web.xml root context.

On Tomcat

Simply deploy the WAR under the desired name.