KeycloakBearerTokenInterceptor.java

import org.jboss.errai.enterprise.client.jaxrs.api.interceptor.RestCallContext;
import org.jboss.errai.enterprise.client.jaxrs.api.interceptor.RestClientInterceptor;

public class KeycloakBearerTokenInterceptor implements RestClientInterceptor {

    @Override
    public void aroundInvoke(RestCallContext context) {
        String bearerToken = getBearerToken();
        context.getRequestBuilder().setHeader("Authorization", bearerToken);

        context.proceed();
    }

    public static native String getBearerToken() /*-{
        //$wnd.keycloak.updateToken(10);
        return "Bearer " + $wnd.keycloak.token;
    }-*/;
}