SYNCOPE-1758 Avoid CAS servlet reinitialization in WA

wa/starter/src/main/java/org/apache/syncope/wa/starter/config/WAContext.java

@@ -43,6 +43,7 @@
 import org.apache.syncope.wa.starter.actuate.SyncopeWAInfoContributor;
 import org.apache.syncope.wa.starter.audit.WAAuditTrailManager;
 import org.apache.syncope.wa.starter.consent.WAConsentRepository;
+import org.apache.syncope.wa.starter.events.WACasConfigurationEventListener;
 import org.apache.syncope.wa.starter.events.WAEventRepository;
 import org.apache.syncope.wa.starter.gauth.WAGoogleMfaAuthCredentialRepository;
 import org.apache.syncope.wa.starter.gauth.WAGoogleMfaAuthTokenRepository;
@@ -76,6 +77,7 @@
 import org.apereo.cas.authentication.support.password.PasswordEncoderUtils;
 import org.apereo.cas.authentication.surrogate.SurrogateAuthenticationService;
 import org.apereo.cas.configuration.CasConfigurationProperties;
+import org.apereo.cas.configuration.CasConfigurationPropertiesEnvironmentManager;
 import org.apereo.cas.configuration.model.support.mfa.gauth.LdapGoogleAuthenticatorMultifactorProperties;
 import org.apereo.cas.configuration.model.support.pm.PasswordManagementProperties;
 import org.apereo.cas.configuration.support.JpaBeans;
@@ -94,6 +96,7 @@
 import org.apereo.cas.services.ServiceRegistryListener;
 import org.apereo.cas.support.events.CasEventRepository;
 import org.apereo.cas.support.events.CasEventRepositoryFilter;
+import org.apereo.cas.support.events.listener.CasConfigurationEventListener;
 import org.apereo.cas.support.pac4j.authentication.clients.DelegatedClientFactoryCustomizer;
 import org.apereo.cas.support.pac4j.authentication.handler.support.DelegatedClientAuthenticationHandler;
 import org.apereo.cas.support.saml.idp.metadata.generator.SamlIdPMetadataGenerator;
@@ -115,11 +118,14 @@
 import org.springframework.beans.factory.annotation.Qualifier;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
+import org.springframework.boot.context.properties.ConfigurationPropertiesBindingPostProcessor;
 import org.springframework.cloud.context.config.annotation.RefreshScope;
+import org.springframework.cloud.context.refresh.ContextRefresher;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Lazy;
 import org.springframework.context.annotation.ScopedProxyMode;
 import org.springframework.jdbc.datasource.DataSourceTransactionManager;
 import org.springframework.security.core.userdetails.User;
@@ -142,6 +148,20 @@ private static String version(final ConfigurableApplicationContext ctx) {
         return ctx.getEnvironment().getProperty("version");
     }
 
+    @ConditionalOnMissingBean(name = "casConfigurationEventListener")
+    @RefreshScope(proxyMode = ScopedProxyMode.DEFAULT)
+    @Bean
+    @Lazy(false)
+    public CasConfigurationEventListener casConfigurationEventListener(
+            @Qualifier("configurationPropertiesEnvironmentManager")
+            final CasConfigurationPropertiesEnvironmentManager manager,
+            final ConfigurationPropertiesBindingPostProcessor binder,
+            final ContextRefresher contextRefresher,
+            final ConfigurableApplicationContext applicationContext) {
+
+        return new WACasConfigurationEventListener(manager, binder, contextRefresher, applicationContext);
+    }
+
     @ConditionalOnMissingBean
     @Bean
     public OpenAPI casSwaggerOpenApi(final ConfigurableApplicationContext ctx) {

wa/starter/src/main/java/org/apache/syncope/wa/starter/events/WACasConfigurationEventListener.java

@@ -0,0 +1,106 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.syncope.wa.starter.events;
+
+import java.util.ArrayList;
+import java.util.Objects;
+import java.util.Set;
+import org.apache.commons.lang3.ObjectUtils;
+import org.apereo.cas.config.CasConfigurationModifiedEvent;
+import org.apereo.cas.configuration.CasConfigurationPropertiesEnvironmentManager;
+import org.apereo.cas.support.events.listener.CasConfigurationEventListener;
+import org.apereo.cas.util.function.FunctionUtils;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.boot.context.properties.ConfigurationPropertiesBindingPostProcessor;
+import org.springframework.cloud.context.environment.EnvironmentChangeEvent;
+import org.springframework.cloud.context.refresh.ContextRefresher;
+import org.springframework.cloud.context.scope.refresh.RefreshScopeRefreshedEvent;
+import org.springframework.context.ApplicationContext;
+
+/**
+ * CAS configuration listener variant that avoids manually re-initializing web servlets without ServletConfig.
+ */
+public class WACasConfigurationEventListener implements CasConfigurationEventListener {
+
+    protected static final Logger LOG = LoggerFactory.getLogger(WACasConfigurationEventListener.class);
+
+    private final CasConfigurationPropertiesEnvironmentManager configurationPropertiesEnvironmentManager;
+
+    private final ConfigurationPropertiesBindingPostProcessor binder;
+
+    private final ContextRefresher contextRefresher;
+
+    private final ApplicationContext applicationContext;
+
+    public WACasConfigurationEventListener(
+            final CasConfigurationPropertiesEnvironmentManager configurationPropertiesEnvironmentManager,
+            final ConfigurationPropertiesBindingPostProcessor binder,
+            final ContextRefresher contextRefresher,
+            final ApplicationContext applicationContext) {
+
+        this.configurationPropertiesEnvironmentManager = configurationPropertiesEnvironmentManager;
+        this.binder = binder;
+        this.contextRefresher = contextRefresher;
+        this.applicationContext = applicationContext;
+    }
+
+    @Override
+    public void onRefreshScopeRefreshed(final RefreshScopeRefreshedEvent event) {
+        LOG.info("Refreshing application context beans eagerly...");
+        initializeBeansEagerly();
+    }
+
+    @Override
+    public void onEnvironmentChangedEvent(final EnvironmentChangeEvent event) {
+        LOG.trace("Received event [{}]", event);
+        rebind();
+    }
+
+    @Override
+    public void handleConfigurationModifiedEvent(final CasConfigurationModifiedEvent event) {
+        if (event.isEligibleForContextRefresh()) {
+            LOG.info("Received event [{}]. Refreshing CAS configuration...", event);
+            final Set<String> keys = contextRefresher.refresh();
+            LOG.info("Refreshed the following settings: [{}].", keys);
+            rebind();
+            LOG.info("CAS finished rebinding configuration with new settings [{}]",
+                    ObjectUtils.getIfNull(keys, new ArrayList<>()));
+        }
+    }
+
+    private void initializeBeansEagerly() {
+        FunctionUtils.doAndHandle(unused -> {
+            for (final String beanName : applicationContext.getBeanDefinitionNames()) {
+                Objects.requireNonNull(applicationContext.getBean(beanName).getClass());
+            }
+        });
+    }
+
+    private void rebind() {
+        LOG.info("Refreshing CAS configuration. Stand by...");
+        final Object ctx = FunctionUtils.doIfNotNull(configurationPropertiesEnvironmentManager,
+                () -> configurationPropertiesEnvironmentManager.rebindCasConfigurationProperties(applicationContext),
+                () -> CasConfigurationPropertiesEnvironmentManager.rebindCasConfigurationProperties(
+                        binder, applicationContext)).
+                get();
+        Objects.requireNonNull(ctx);
+        initializeBeansEagerly();
+    }
+}

wa/starter/src/test/java/org/apache/syncope/wa/starter/events/WACasConfigurationEventListenerTest.java

@@ -0,0 +1,51 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.syncope.wa.starter.events;
+
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.cloud.context.scope.refresh.RefreshScopeRefreshedEvent;
+import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.web.servlet.DispatcherServlet;
+
+public class WACasConfigurationEventListenerTest {
+
+    @Test
+    public void refreshDoesNotInitializeDispatcherServlet() {
+        final ConfigurableApplicationContext applicationContext = mock(ConfigurableApplicationContext.class);
+        final DispatcherServlet dispatcherServlet = new DispatcherServlet();
+        when(applicationContext.getBeanDefinitionNames()).thenReturn(new String[] { "dispatcherServlet" });
+        when(applicationContext.getBean("dispatcherServlet")).thenReturn(dispatcherServlet);
+        when(applicationContext.containsBean("dispatcherServlet")).thenReturn(true);
+        when(applicationContext.getBean(DispatcherServlet.class)).thenReturn(dispatcherServlet);
+
+        final WACasConfigurationEventListener listener =
+                new WACasConfigurationEventListener(null, null, null, applicationContext);
+        assertDoesNotThrow(() -> listener.onRefreshScopeRefreshed(new RefreshScopeRefreshedEvent()));
+
+        verify(applicationContext).getBean("dispatcherServlet");
+        verify(applicationContext, never()).containsBean("dispatcherServlet");
+        verify(applicationContext, never()).getBean(DispatcherServlet.class);
+    }
+}