How to access web.xml init parameters from java code?

You can get it using externalContext getInitParameter method.

For example, if you have:

<context-param>
 <param-name>connectionString</param-name>
 <param-value>jdbc:oracle:thin:scott/tiger@cartman:1521:O901DB</param-value>
</context-param>

You can access this connection string with: \

FacesContext fc = FacesContext.getCurrentInstance();
String connection = fc.getExternalContext().getInitParameter("connectionString");