Multi Tenancy

Multi Tenancy, in our context, means that a single target application (WAR) can be secured with multiple Keycloak realms. The realms can be located one the same Keycloak instance or on different instances.

In practice, this means that the application needs to have multiple keycloak.json adapter configuration files.

You could have multiple instances of your WAR with different adapter configuration files deployed to different context-paths. However, this may be inconvenient and you may also want to select the realm based on something else than context-path.

Keycloak makes it possible to have a custom config resolver so you can choose what adapter config is used for each request.

To achieve this first you need to create an implementation of org.keycloak.adapters.KeycloakConfigResolver. For example:

package example;

import org.keycloak.adapters.KeycloakConfigResolver;
import org.keycloak.adapters.KeycloakDeployment;
import org.keycloak.adapters.KeycloakDeploymentBuilder;

public class PathBasedKeycloakConfigResolver implements KeycloakConfigResolver {

    public KeycloakDeployment resolve(OIDCHttpFacade.Request request) {
        if (path.startsWith("alternative")) {
            KeycloakDeployment deployment = cache.get(realm);
            if (null == deployment) {
                InputStream is = getClass().getResourceAsStream("/tenant1-keycloak.json");
        } else {
            InputStream is = getClass().getResourceAsStream("/default-keycloak.json");


You also need to configure which KeycloakConfigResolver implementation to use with the keycloak.config.resolver context-param in your web.xml: