Getting KeyCloakContext From ServletRequest

When REST APIs are protected with keycloak authentication, we might need to get user realm in the backend to get some user information.

In the ServletRequestFilter implementation,

public class ApplicationFilter implements Filter {

private Base64 decoder = new Base64(true);

        @Inject

ServletRequestHolder requestHolder;

@Override

public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain)

throws IOException, ServletException {

try {

checkAuthentication(req);

....

//TODO

}

/**

* Get the logged in user info from the request.

* 

* @param request

*/

private void checkAuthentication(ServletRequest request) {

HttpServletRequest httpServletRequest = (HttpServletRequest) request;

KeycloakSecurityContext kContext = (KeycloakSecurityContext) httpServletRequest

.getAttribute(KeycloakSecurityContext.class.getName());

String bearerToken;

if (kContext != null) {

bearerToken = kContext.getTokenString();

String[] jwtToken = bearerToken.split("\\.");

byte[] decodedClaims = decoder.decode(jwtToken[1]);

JSONObject jsonObj = new JSONObject(new String(decodedClaims));

.....

//TODO

}