Add availability conditions for discovery clients

Introduce composed conditional annotations for blocking and reactive discovery availability and update auto-configs to use them. Adds ConditionalOnBlockingDiscoveryAvailable and ConditionalOnReactiveDiscoveryAvailable to encapsulate ConditionalOnClass + ConditionalOnDiscoveryEnabled + the respective blocking/reactive enablement checks, replaces repetitive annotations in DiscoveryClientAutoConfiguration and ReactiveDiscoveryClientAutoConfiguration, and adds REACTIVE_DISCOVERY_CLIENT_CLASS_NAME constant to DiscoveryClientConstants.

Author: mercyblitz

microsphere-spring-cloud-commons/src/main/java/io/microsphere/spring/cloud/client/discovery/autoconfigure/DiscoveryClientAutoConfiguration.java

@@ -18,6 +18,7 @@
 
 import io.microsphere.annotation.ConfigurationProperty;
 import io.microsphere.spring.cloud.client.discovery.UnionDiscoveryClient;
+import io.microsphere.spring.cloud.client.discovery.condition.ConditionalOnBlockingDiscoveryAvailable;
 import org.springframework.boot.autoconfigure.AutoConfigureBefore;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
@@ -42,11 +43,7 @@
  * @since 1.0.0
  */
 @Configuration(proxyBeanMethods = false)
-@ConditionalOnClass(name = {
-        DISCOVERY_CLIENT_CLASS_NAME
-})
-@ConditionalOnDiscoveryEnabled
-@ConditionalOnBlockingDiscoveryEnabled
+@ConditionalOnBlockingDiscoveryAvailable
 @AutoConfigureBefore(name = {
         COMMONS_CLIENT_AUTO_CONFIGURATION_CLASS_NAME
 })

microsphere-spring-cloud-commons/src/main/java/io/microsphere/spring/cloud/client/discovery/autoconfigure/ReactiveDiscoveryClientAutoConfiguration.java

@@ -18,6 +18,7 @@
 package io.microsphere.spring.cloud.client.discovery.autoconfigure;
 
 import io.microsphere.spring.cloud.client.discovery.ReactiveDiscoveryClientAdapter;
+import io.microsphere.spring.cloud.client.discovery.condition.ConditionalOnReactiveDiscoveryAvailable;
 import org.springframework.boot.autoconfigure.AutoConfigureAfter;
 import org.springframework.boot.autoconfigure.AutoConfigureBefore;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
@@ -43,11 +44,7 @@
  * @since 1.0.0
  */
 @Configuration(proxyBeanMethods = false)
-@ConditionalOnClass(name = {
-        DISCOVERY_CLIENT_CLASS_NAME
-})
-@ConditionalOnDiscoveryEnabled
-@ConditionalOnReactiveDiscoveryEnabled
+@ConditionalOnReactiveDiscoveryAvailable
 @AutoConfigureBefore(name = {
         REACTIVE_COMMONS_CLIENT_AUTO_CONFIGURATION_CLASS_NAME
 })

microsphere-spring-cloud-commons/src/main/java/io/microsphere/spring/cloud/client/discovery/condition/ConditionalOnBlockingDiscoveryAvailable.java

@@ -0,0 +1,70 @@
+/*
+ * 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 io.microsphere.spring.cloud.client.discovery.condition;
+
+import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
+import org.springframework.cloud.client.ConditionalOnBlockingDiscoveryEnabled;
+import org.springframework.cloud.client.ConditionalOnDiscoveryEnabled;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.Inherited;
+import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
+
+import static io.microsphere.spring.cloud.client.discovery.constants.DiscoveryClientConstants.DISCOVERY_CLIENT_CLASS_NAME;
+import static java.lang.annotation.ElementType.METHOD;
+import static java.lang.annotation.ElementType.TYPE;
+import static java.lang.annotation.RetentionPolicy.RUNTIME;
+
+/**
+ * A condition that checks if Blocking Spring Cloud Discovery is available.
+ * <p>
+ * This annotation combines {@link ConditionalOnClass} (checking for the presence of {@code DiscoveryClient}),
+ * {@link ConditionalOnDiscoveryEnabled}, and {@link ConditionalOnBlockingDiscoveryEnabled} to ensure that
+ * the discovery client is both present in the classpath and enabled for blocking operations.
+ *
+ * <h3>Example Usage:</h3>
+ * <pre>{@code
+ * @Configuration
+ * @ConditionalOnDiscoveryAvailable
+ * public class DiscoveryClientConfiguration {
+ *
+ *     @Bean
+ *     public MyService myService(DiscoveryClient discoveryClient) {
+ *         return new MyService(discoveryClient);
+ *     }
+ * }
+ * }</pre>
+ *
+ * @author <a href="mailto:mercyblitz@gmail.com">Mercy</a>
+ * @see ConditionalOnDiscoveryEnabled
+ * @see ConditionalOnBlockingDiscoveryEnabled
+ * @see ConditionalOnClass
+ * @since 1.0.0
+ */
+@Target({TYPE, METHOD})
+@Retention(RUNTIME)
+@Documented
+@Inherited
+@ConditionalOnClass(name = {
+        DISCOVERY_CLIENT_CLASS_NAME
+})
+@ConditionalOnDiscoveryEnabled
+@ConditionalOnBlockingDiscoveryEnabled
+public @interface ConditionalOnBlockingDiscoveryAvailable {
+}

microsphere-spring-cloud-commons/src/main/java/io/microsphere/spring/cloud/client/discovery/condition/ConditionalOnReactiveDiscoveryAvailable.java

@@ -0,0 +1,70 @@
+/*
+ * 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 io.microsphere.spring.cloud.client.discovery.condition;
+
+import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
+import org.springframework.cloud.client.ConditionalOnDiscoveryEnabled;
+import org.springframework.cloud.client.ConditionalOnReactiveDiscoveryEnabled;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.Inherited;
+import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
+
+import static io.microsphere.spring.cloud.client.discovery.constants.DiscoveryClientConstants.REACTIVE_DISCOVERY_CLIENT_CLASS_NAME;
+import static java.lang.annotation.ElementType.METHOD;
+import static java.lang.annotation.ElementType.TYPE;
+import static java.lang.annotation.RetentionPolicy.RUNTIME;
+
+/**
+ * {@link ConditionalOnReactiveDiscoveryEnabled} and {@link ConditionalOnClass} for Reactive Discovery Client.
+ * <p>
+ * This annotation can be used to conditionally enable a bean or configuration only when:
+ * <ul>
+ *     <li>The Spring Cloud Discovery is enabled ({@link ConditionalOnDiscoveryEnabled}).</li>
+ *     <li>The Reactive Discovery is explicitly enabled ({@link ConditionalOnReactiveDiscoveryEnabled}).</li>
+ *     <li>The Reactive Discovery Client class is present on the classpath.</li>
+ * </ul>
+ *
+ * <h3>Example Usage:</h3>
+ * <pre>{@code
+ * @Configuration
+ * public class ReactiveDiscoveryConfig {
+ *
+ *     @Bean
+ *     @ConditionalOnReactiveDiscoveryAvailable
+ *     public MyReactiveService myReactiveService(ReactiveDiscoveryClient client) {
+ *         return new MyReactiveService(client);
+ *     }
+ * }
+ * }</pre>
+ *
+ * @author <a href="mailto:mercyblitz@gmail.com">Mercy</a>
+ * @since 1.0.0
+ */
+@Target({TYPE, METHOD})
+@Retention(RUNTIME)
+@Documented
+@Inherited
+@ConditionalOnClass(name = {
+        REACTIVE_DISCOVERY_CLIENT_CLASS_NAME
+})
+@ConditionalOnDiscoveryEnabled
+@ConditionalOnReactiveDiscoveryEnabled
+public @interface ConditionalOnReactiveDiscoveryAvailable {
+}

microsphere-spring-cloud-commons/src/main/java/io/microsphere/spring/cloud/client/discovery/constants/DiscoveryClientConstants.java

@@ -19,6 +19,7 @@
 import org.springframework.cloud.client.CommonsClientAutoConfiguration;
 import org.springframework.cloud.client.ReactiveCommonsClientAutoConfiguration;
 import org.springframework.cloud.client.discovery.DiscoveryClient;
+import org.springframework.cloud.client.discovery.ReactiveDiscoveryClient;
 import org.springframework.cloud.client.discovery.composite.CompositeDiscoveryClient;
 import org.springframework.cloud.client.discovery.composite.reactive.ReactiveCompositeDiscoveryClientAutoConfiguration;
 import org.springframework.cloud.client.discovery.simple.reactive.SimpleReactiveDiscoveryClientAutoConfiguration;
@@ -38,6 +39,13 @@ public interface DiscoveryClientConstants {
      */
     String DISCOVERY_CLIENT_CLASS_NAME = "org.springframework.cloud.client.discovery.DiscoveryClient";
 
+    /**
+     * The class name of {@link ReactiveDiscoveryClient}
+     *
+     * @see org.springframework.cloud.client.discovery.ReactiveDiscoveryClient
+     */
+    String REACTIVE_DISCOVERY_CLIENT_CLASS_NAME = "org.springframework.cloud.client.discovery.ReactiveDiscoveryClient";
+
     /**
      * The class name of {@link CompositeDiscoveryClient}
      *