So, you (believe) you've configured the agent to protect your application URLs as part of your SSO implementation.
You attempt this by accessing the application URL and you're 302 re-directed to the forgeRock OpenAM login screen (so far so good).
When you initiate the OpenAM instance within a tomcat container, you'll see within the catalina log file the initial error 'SEVERE: Begin event threw error' error followed by 'java.lang.ExceptionInInitializerError error'
This is certainly a weird one though I managed to work it out. The error string value states that the agent deployment was 'Unable to get Application SSO Token'
When deploying the agent within your local environment or deploying from eclipse, you'll likely come across the
'java.lang.ClassNotFoundException: com.sun.identity.agents.filter.AmAgentFilter' error when compiling or deploying to a particular server.
When compiling the agent within the web server, I would receive the following error, 'java.lang.RuntimeException: Failed to get configuration file:OpenSSOAgentBootstrap.properties'
I discovered the reason why this occurred though I flattened the web application and resolved the issue. That solution however may not be the viable solution for most individuals.
When integrating with the OpenAM and an application, I would receive a syntax error when trying to populate the application with the filter as part of the web.xml population. You can see the display-name error when working with the eclipse IDE.