Dubbo cloud native (#4817)

* Polish #4542 : [Enhancement] Adapt the Java standard Event/Listener mechanism

* Polish #4541 : [Feature] Add local File System DynamicConfigurationFactory‘s extension

* Polish #4541 : Bugfix

* Polish #4541 : Optimization

* Polish #4541 : Add the compatibility for PollingWatchService on the some platforms

* Polish #4541 : Add delay publish without ThreadPoolExecutor

* Polish #4541 : Refactor the extension name

* Polish #4541 : Add remove ops

* Polish #4541 : Add testable constructor

* Polish #4541 : Add getConfigGroups method

* Polish #4610 : [Refactor] Refactor the bootstrap module

* Polish #4541 : Fix the nulling URL issue

* Polish #4622 : [Refactor] Refactor ConfigManager

* Polish #4622 : [Refactor] Refactor ConfigManager

* Polish #4622 : Support multiple configcenters

* Polish #4671 : ServiceNameMapping will not map the group, version and protocol

* update referenceCount log (#4683)

Add comments to support multiple shared connections

* Polish /#4687 : Remove the duplicated test code in dubbo-config-spring (#4688)

* #4685  修改代码if判断false问题 if (hasException == false)修改成if (!hasException) (#4695)

* Fixed Service annotation method parameters are not in effect (#4598)

* keep demo simple, and switch to use zookeeper as registry center (#4705)

* keep demo simple, and switch to use zookeeper as registry center

* remove comment

* @reference auto-wires the instance of generic interface #4594 (#4677)

* try to shorten maven output to make travis build pass (#4710)

* use CountDownLatch to check zk registry if establish connection (#4589)

* Minor change

* Rename the extension name of WritableMetadataService

* Polish #4759 : [Refactor] Change the signature of methods of MetadataService #4759

* Merge remote-tracking branch 'upstream/master' into dubbo-cloud-native

# Conflicts:
#	dubbo-all/pom.xml
#	dubbo-bom/pom.xml
#	dubbo-config/dubbo-config-api/src/main/java/org/apache/dubbo/config/AbstractInterfaceConfig.java
#	dubbo-config/dubbo-config-api/src/main/java/org/apache/dubbo/config/ApplicationConfig.java
#	dubbo-config/dubbo-config-api/src/main/java/org/apache/dubbo/config/ConfigCenterConfig.java
#	dubbo-config/dubbo-config-api/src/main/java/org/apache/dubbo/config/ReferenceConfig.java
#	dubbo-config/dubbo-config-api/src/main/java/org/apache/dubbo/config/RegistryConfig.java
#	dubbo-config/dubbo-config-api/src/main/java/org/apache/dubbo/config/ServiceConfig.java
#	dubbo-config/dubbo-config-api/src/test/java/org/apache/dubbo/config/ReferenceConfigTest.java
#	dubbo-configcenter/dubbo-configcenter-api/src/main/java/org/apache/dubbo/configcenter/DynamicConfiguration.java
#	dubbo-configcenter/dubbo-configcenter-api/src/test/java/org/apache/dubbo/configcenter/mock/MockDynamicConfiguration.java
#	dubbo-configcenter/dubbo-configcenter-consul/src/main/java/org/apache/dubbo/configcenter/consul/ConsulDynamicConfiguration.java
#	dubbo-configcenter/dubbo-configcenter-etcd/src/test/java/org/apache/dubbo/configcenter/support/etcd/EtcdDynamicConfigurationTest.java
#	dubbo-configcenter/dubbo-configcenter-nacos/src/main/java/org/apache/dubbo/configcenter/support/nacos/NacosDynamicConfiguration.java
#	dubbo-configcenter/dubbo-configcenter-nacos/src/test/java/org/apache/dubbo/configcenter/support/nacos/NacosDynamicConfigurationTest.java
#	dubbo-configcenter/dubbo-configcenter-zookeeper/src/main/java/org/apache/dubbo/configcenter/support/zookeeper/ZookeeperDynamicConfiguration.java
#	dubbo-metadata/dubbo-metadata-api/src/main/java/org/apache/dubbo/metadata/definition/model/MethodDefinition.java
#	dubbo-metadata/dubbo-metadata-api/src/main/java/org/apache/dubbo/metadata/report/identifier/MetadataIdentifier.java
#	dubbo-metadata/dubbo-metadata-api/src/main/java/org/apache/dubbo/metadata/report/support/AbstractMetadataReport.java
#	dubbo-metadata/dubbo-metadata-api/src/test/java/org/apache/dubbo/metadata/report/identifier/MetadataIdentifierTest.java
#	dubbo-metadata/dubbo-metadata-definition-protobuf/src/main/java/org/apache/dubbo/metadata/definition/protobuf/ProtobufTypeBuilder.java
#	dubbo-metadata/dubbo-metadata-definition-protobuf/src/test/java/org/apache/dubbo/metadata/definition/protobuf/ProtobufTypeBuilderTest.java
#	dubbo-metadata/pom.xml
#	dubbo-registry/dubbo-registry-api/src/main/java/org/apache/dubbo/registry/integration/AbstractConfiguratorListener.java
#	dubbo-registry/dubbo-registry-nacos/src/main/java/org/apache/dubbo/registry/nacos/NacosRegistry.java
#	dubbo-registry/dubbo-registry-nacos/src/main/java/org/apache/dubbo/registry/nacos/NacosRegistryFactory.java
#	dubbo-rpc/dubbo-rpc-xml/src/main/java/org/apache/dubbo/xml/rpc/protocol/xmlrpc/XmlRpcProtocol.java

* Polish #3984 : Add the implementation of Page<ServiceInstance> getInstances(String serviceName, int offset, int pageSize, boolean healthyOnly)

* Code merge

* Fix the cases

* Merge remote-tracking branch 'upstream/cloud-native' into dubbo-cloud-native

# Conflicts:
#	dubbo-bootstrap/src/test/java/org/apache/dubbo/bootstrap/DubboServiceProviderBootstrap.java
#	dubbo-metadata/dubbo-metadata-definition-protobuf/pom.xml
#	dubbo-registry/dubbo-registry-api/src/test/java/org/apache/dubbo/registry/support/ServiceOrientedRegistryTest.java
#	dubbo-registry/dubbo-registry-consul/src/main/java/org/apache/dubbo/registry/consul/ConsulServiceDiscoveryFactory.java
#	dubbo-registry/dubbo-registry-etcd3/src/main/java/org/apache/dubbo/registry/etcd/EtcdServiceDiscovery.java

* Refactor ConfigManager

* Refactor ConfigManager

* Resolve the issues on ConfigManager

* Refactor and add test-cases for ConfigManager

* Polish #4774 : [Feature] Dubbo Cloud Native - To Support in Spring

* Polish #4808 : [Feature] Add the registered/unregistered event mechanism ShutdownHook

* Polish #4807 : [Feature] Add the callback mechanism ShutdownHook #4807

* Polish #4813 : [Feature] add Prioritized implementation for ServiceInstanceCustomizer

* Polish #4815 : [Feature] Add the ServiceLoader for Dubbo's services or components

* Polish #4815 : [Feature] Add the ServiceLoader for Dubbo's services or components

dubbo-bootstrap/src/main/java/org/apache/dubbo/bootstrap/DubboBootstrap.java

@@ -20,11 +20,11 @@
 import org.apache.dubbo.common.config.Environment;
 import org.apache.dubbo.common.config.configcenter.DynamicConfiguration;
 import org.apache.dubbo.common.config.configcenter.wrapper.CompositeDynamicConfiguration;
+import org.apache.dubbo.common.context.Lifecycle;
 import org.apache.dubbo.common.extension.ExtensionLoader;
 import org.apache.dubbo.common.logger.Logger;
 import org.apache.dubbo.common.logger.LoggerFactory;
 import org.apache.dubbo.common.utils.CollectionUtils;
-import org.apache.dubbo.config.AbstractConfig;
 import org.apache.dubbo.config.ApplicationConfig;
 import org.apache.dubbo.config.ConfigCenterConfig;
 import org.apache.dubbo.config.ConsumerConfig;
@@ -38,7 +38,6 @@
 import org.apache.dubbo.config.ReferenceConfig;
 import org.apache.dubbo.config.RegistryConfig;
 import org.apache.dubbo.config.ServiceConfig;
-import org.apache.dubbo.config.builders.AbstractBuilder;
 import org.apache.dubbo.config.builders.ApplicationBuilder;
 import org.apache.dubbo.config.builders.ConsumerBuilder;
 import org.apache.dubbo.config.builders.ProtocolBuilder;
@@ -64,7 +63,6 @@
 import java.util.Collection;
 import java.util.HashMap;
 import java.util.List;
-import java.util.Map;
 import java.util.Set;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.atomic.AtomicBoolean;
@@ -90,7 +88,7 @@
  *
  * @since 2.7.4
  */
-public class DubboBootstrap {
+public class DubboBootstrap implements Lifecycle {
 
     public static final String DEFAULT_REGISTRY_ID = "REGISTRY#DEFAULT";
 
@@ -409,25 +407,26 @@ public DubboBootstrap cache(ReferenceConfigCache cache) {
     /**
      * Initialize
      */
-    public void init() {
+    public DubboBootstrap initialize() {
+        if (!isInitialized()) {
 
-        if (isInitialized()) {
-            return;
-        }
+            startConfigCenter();
 
-        startConfigCenter();
+            startMetadataReport();
 
-        startMetadataReport();
+            loadRemoteConfigs();
 
-        loadRemoteConfigs();
+            useRegistryAsConfigCenterIfNecessary();
 
-        useRegistryAsConfigCenterIfNecessary();
+            initialized = true;
 
-        initialized = true;
+            if (logger.isInfoEnabled()) {
+                logger.info(NAME + " has been initialized!");
+            }
 
-        if (logger.isInfoEnabled()) {
-            logger.info(NAME + " has been initialized!");
         }
+
+        return this;
     }
 
     private void loadRemoteConfigs() {
@@ -505,12 +504,12 @@ private Collection<ServiceDiscovery> getServiceDiscoveries() {
     /**
      * Start the bootstrap
      */
+    @Override
     public DubboBootstrap start() {
-
+        if (!isInitialized()) {
+            initialize();
+        }
         if (!isStarted()) {
-            if (!isInitialized()) {
-                init();
-            }
 
             exportServices();
 
@@ -574,32 +573,26 @@ public DubboBootstrap await() {
     /**
      * Stop the bootstrap
      */
-    public void stop() {
-
-        if (!isInitialized() || !isStarted()) {
-            return;
+    @Override
+    public DubboBootstrap stop() {
+        if (isInitialized() && isStarted()) {
+            unregisterServiceInstance();
+            unexportServices();
+            started = false;
         }
-
-        unregisterServiceInstance();
-
-        destroy();
-
-        clear();
-
-        release();
-
-        shutdown();
+        return this;
     }
 
+    @Override
     public boolean isInitialized() {
         return initialized;
     }
 
+    @Override
     public boolean isStarted() {
         return started;
     }
 
-
     /* serve for builder apis, begin */
     private ApplicationBuilder createApplicationBuilder(String name) {
         return new ApplicationBuilder().name(name);
@@ -716,11 +709,11 @@ private List<URL> exportMetadataService(ApplicationConfig applicationConfig,
     }
 
     private void exportServices() {
-        configManager.getServices().forEach(this::exportServiceConfig);
+        configManager.getServices().forEach(ServiceConfig::export);
     }
 
-    public void exportServiceConfig(ServiceConfig<?> serviceConfig) {
-        serviceConfig.export();
+    private void unexportServices() {
+        configManager.getServices().forEach(ServiceConfig::unexport);
     }
 
     private void referServices() {
@@ -803,22 +796,29 @@ private ServiceInstance initServiceInstance(String serviceName, String host, int
         return this.serviceInstance;
     }
 
-    private void destroy() {
+    public void destroy() {
 
-        destroyProtocolConfigs();
+        stop();
 
-        destroyReferenceConfigs();
+        destroyProtocols();
 
+        destroyReferences();
+
+        clear();
+
+        release();
+
+        shutdown();
     }
 
-    private void destroyProtocolConfigs() {
+    private void destroyProtocols() {
         configManager.getProtocols().forEach(ProtocolConfig::destroy);
         if (logger.isDebugEnabled()) {
             logger.debug(NAME + "'s all ProtocolConfigs have been destroyed.");
         }
     }
 
-    private void destroyReferenceConfigs() {
+    private void destroyReferences() {
         configManager.getReferences().forEach(ReferenceConfig::destroy);
         if (logger.isDebugEnabled()) {
             logger.debug(NAME + "'s all ReferenceConfigs have been destroyed.");
@@ -862,13 +862,4 @@ private void executeMutually(Runnable runnable) {
             lock.unlock();
         }
     }
-
-    private static <C extends AbstractConfig, B extends
-            AbstractBuilder> List<C> buildConfigs(Map<String, B> map) {
-        List<C> configs = new ArrayList<>();
-        map.entrySet().forEach(entry -> {
-            configs.add((C) entry.getValue().build());
-        });
-        return configs;
-    }
 }

dubbo-bootstrap/src/main/resources/META-INF/services/org.apache.dubbo.common.context.Lifecycle

@@ -0,0 +1 @@
+org.apache.dubbo.bootstrap.DubboBootstrap

dubbo-common/src/main/java/org/apache/dubbo/common/config/configcenter/wrapper/CompositeDynamicConfiguration.java

@@ -36,7 +36,9 @@ public class CompositeDynamicConfiguration implements DynamicConfiguration {
     private Set<DynamicConfiguration> configurations = new HashSet<>();
 
     public void addConfiguration(DynamicConfiguration configuration) {
-        this.configurations.add(configuration);
+        if (configuration != null) {
+            this.configurations.add(configuration);
+        }
     }
 
     @Override

dubbo-common/src/main/java/org/apache/dubbo/common/context/Lifecycle.java

@@ -0,0 +1,78 @@
+/*
+ * 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.dubbo.common.context;
+
+/**
+ * The Lifecycle of Dubbo component
+ *
+ * @since 2.7.4
+ */
+public interface Lifecycle {
+
+    /**
+     * Initialize the component before {@link #start() start}
+     *
+     * @return current {@link Lifecycle}
+     * @throws IllegalStateException
+     */
+    Lifecycle initialize() throws IllegalStateException;
+
+    /**
+     * Initialized or not
+     *
+     * @return if initialized, return <code>true</code>, or <code>false</code>
+     */
+    boolean isInitialized();
+
+    /**
+     * Start the component
+     *
+     * @return current {@link Lifecycle}
+     * @throws IllegalStateException
+     */
+    Lifecycle start() throws IllegalStateException;
+
+    /**
+     * The component is started or not
+     *
+     * @return if started, return <code>true</code>, or <code>false</code>
+     */
+    boolean isStarted();
+
+    /**
+     * Stop the component
+     *
+     * @return current {@link Lifecycle}
+     */
+    Lifecycle stop() throws IllegalStateException;
+
+    /**
+     * The component is stopped or not
+     *
+     * @return if stopped, return <code>true</code>, or <code>false</code>
+     */
+    default boolean isStopped() {
+        return !isStarted();
+    }
+
+    /**
+     * Destroy the component
+     *
+     * @throws IllegalStateException
+     */
+    void destroy() throws IllegalStateException;
+}

dubbo-common/src/main/java/org/apache/dubbo/common/lang/Prioritized.java

@@ -0,0 +1,71 @@
+/*
+ * 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.dubbo.common.lang;
+
+import java.util.Comparator;
+
+import static java.lang.Integer.compare;
+
+/**
+ * {@code Prioritized} interface can be implemented by objects that
+ * should be sorted, for example the tasks in executable queue.
+ *
+ * @since 2.7.4
+ */
+public interface Prioritized extends Comparable<Prioritized> {
+
+    /**
+     * The {@link Comparator} of {@link Prioritized}
+     */
+    Comparator<Object> COMPARATOR = (one, two) -> {
+        boolean b1 = one instanceof Prioritized;
+        boolean b2 = two instanceof Prioritized;
+        if (b1 && !b2) {        // one is Prioritized, two is not
+            return -1;
+        } else if (b2 && !b1) { // two is Prioritized, one is not
+            return 1;
+        } else if (b1 && b2) {  //  one and two both Prioritized
+            return ((Prioritized) one).compareTo((Prioritized) two);
+        } else {                // no different
+            return 0;
+        }
+    };
+
+    /**
+     * The maximum priority
+     */
+    int MAX_PRIORITY = Integer.MIN_VALUE;
+
+    /**
+     * The minimum priority
+     */
+    int MIN_PRIORITY = Integer.MAX_VALUE;
+
+    /**
+     * Get the priority
+     *
+     * @return the default is {@link #MIN_PRIORITY minimum one}
+     */
+    default int getPriority() {
+        return MIN_PRIORITY;
+    }
+
+    @Override
+    default int compareTo(Prioritized that) {
+        return compare(this.getPriority(), that.getPriority());
+    }
+}

dubbo-common/src/main/java/org/apache/dubbo/common/lang/ShutdownHookCallback.java

@@ -0,0 +1,32 @@
+/*
+ * 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.dubbo.common.lang;
+
+/**
+ * Dubbo ShutdownHook callback interface
+ *
+ * @since 2.7.4
+ */
+public interface ShutdownHookCallback extends Prioritized {
+
+    /**
+     * Callback execution
+     *
+     * @throws Throwable if met with some errors
+     */
+    void callback() throws Throwable;
+}