Monthly Archives: July 2012

If you have an AuditListener for your EclipseLink entities, you may have a problem to get the name of the current user at this level. You could use the InitialContext.lookup("java:comp/EJBContext") method, but it fails on my application. Another way is to use a servlet filter.

Define a filter class within your web.xml:

	<filter>
		<filter-name>PrincipalServletFilter</filter-name>
		<filter-class>de.uni_leipzig.smo.acltest.server.filter.PrincipalServletFilter</filter-class>
	</filter>

	<filter-mapping>
		<filter-name>PrincipalServletFilter</filter-name>
		<url-pattern>/*</url-pattern>
	</filter-mapping>

Implement a singleton enum, which stores a ThreadLocal variable to hold the current principal object.

public enum PrincipalSingleton {
	INSTANCE;

	private ThreadLocal<Principal> principal = new ThreadLocal<Principal>();

	public Principal get() {
		return principal.get();
	}

	public void set(Principal user) {
		this.principal.set(user);
	}
}

Set the current principal within the filter.

public class PrincipalServletFilter
	implements Filter {

	@Override
	public void destroy() {
	}

	@Override
	public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
		throws IOException, ServletException {
		PrincipalSingleton.INSTANCE.set(((HttpServletRequest) request).getUserPrincipal());
		chain.doFilter(request, response);
	}

	@Override
	public void init(FilterConfig config)
		throws ServletException {
	}
}

And finally use the principal within your audit class.

	private Principal getPrincipal() {
		return PrincipalSingleton.INSTANCE.get();
	}