test: verify the process of exported provider in single registry center

1. Check if the exporter exported by RegistryProtocolListener, ServiceListener and ExporterListener
2. Check if the provider works well by Filter

dubbo-config/dubbo-config-api/src/test/java/org/apache/dubbo/integration/single/exportprovider/SingleRegistryCenterExportProviderExporterListener.java

@@ -0,0 +1,33 @@
+/*
+ * 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.integration.single.exportprovider;
+
+import org.apache.dubbo.common.constants.CommonConstants;
+import org.apache.dubbo.common.extension.Activate;
+import org.apache.dubbo.integration.AbstractRegistryCenterExporterListener;
+
+@Activate(group = CommonConstants.PROVIDER, order = 1000)
+public class SingleRegistryCenterExportProviderExporterListener extends AbstractRegistryCenterExporterListener {
+
+    /**
+     * Returns the interface of exported service.
+     */
+    @Override
+    protected Class<?> getInterface() {
+        return SingleRegistryCenterExportProviderService.class;
+    }
+}

dubbo-config/dubbo-config-api/src/test/java/org/apache/dubbo/integration/single/exportprovider/SingleRegistryCenterExportProviderFilter.java

@@ -0,0 +1,86 @@
+/*
+ * 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.integration.single.exportprovider;
+
+import org.apache.dubbo.common.constants.CommonConstants;
+import org.apache.dubbo.common.extension.Activate;
+import org.apache.dubbo.rpc.Filter;
+import org.apache.dubbo.rpc.Invocation;
+import org.apache.dubbo.rpc.Invoker;
+import org.apache.dubbo.rpc.RpcException;
+import org.apache.dubbo.rpc.Result;
+
+@Activate(group = CommonConstants.PROVIDER, order = 10000)
+public class SingleRegistryCenterExportProviderFilter implements Filter,Filter.Listener {
+
+    /**
+     * The filter is called or not
+     */
+    private boolean called = false;
+
+    /**
+     * There has error after invoked
+     */
+    private boolean error = false;
+
+    /**
+     * The returned result
+     */
+    private String response;
+    /**
+     * Always call invoker.invoke() in the implementation to hand over the request to the next filter node.
+     *
+     * @param invoker
+     * @param invocation
+     */
+    @Override
+    public Result invoke(Invoker<?> invoker, Invocation invocation) throws RpcException {
+        called = true;
+        return invoker.invoke(invocation);
+    }
+
+    @Override
+    public void onResponse(Result appResponse, Invoker<?> invoker, Invocation invocation) {
+        response = appResponse.getValue().toString();
+    }
+
+    @Override
+    public void onError(Throwable t, Invoker<?> invoker, Invocation invocation) {
+        error = true;
+    }
+
+    /**
+     * Returns if the filter has called.
+     */
+    public boolean hasCalled() {
+        return called;
+    }
+
+    /**
+     * Returns if there exists error.
+     */
+    public boolean hasError() {
+        return error;
+    }
+
+    /**
+     * Returns the response.
+     */
+    public String getResponse() {
+        return response;
+    }
+}

dubbo-config/dubbo-config-api/src/test/java/org/apache/dubbo/integration/single/exportprovider/SingleRegistryCenterExportProviderIntegrationTest.java

@@ -0,0 +1,230 @@
+/*
+ * 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.integration.single.exportprovider;
+
+import org.apache.dubbo.common.constants.CommonConstants;
+import org.apache.dubbo.common.extension.ExtensionLoader;
+import org.apache.dubbo.config.ServiceConfig;
+import org.apache.dubbo.config.ReferenceConfig;
+import org.apache.dubbo.config.ServiceListener;
+import org.apache.dubbo.config.ApplicationConfig;
+import org.apache.dubbo.config.ProtocolConfig;
+import org.apache.dubbo.config.bootstrap.DubboBootstrap;
+import org.apache.dubbo.integration.IntegrationTest;
+import org.apache.dubbo.registry.integration.RegistryProtocolListener;
+import org.apache.dubbo.registrycenter.DefaultSingleRegistryCenter;
+import org.apache.dubbo.registrycenter.SingleRegistryCenter;
+import org.apache.dubbo.rpc.ExporterListener;
+import org.apache.dubbo.rpc.Filter;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+
+import static org.apache.dubbo.rpc.Constants.SCOPE_LOCAL;
+
+/**
+ * The testcases are only for checking the core process of exporting provider.
+ */
+public class SingleRegistryCenterExportProviderIntegrationTest implements IntegrationTest {
+
+    private static final Logger logger = LoggerFactory.getLogger(SingleRegistryCenterExportProviderIntegrationTest.class);
+
+    /**
+     * Define the provider application name.
+     */
+    private static String PROVIDER_APPLICATION_NAME = "single-registry-center-for-export-provider";
+
+    /**
+     * The name for getting the specified instance, which is loaded using SPI.
+     */
+    private static String SPI_NAME = "singleConfigCenterExportProvider";
+
+    /**
+     * Define the protocol's name.
+     */
+    private static String PROTOCOL_NAME = CommonConstants.DUBBO;
+    /**
+     * Define the protocol's port.
+     */
+    private static int PROTOCOL_PORT = 20800;
+
+    /**
+     * Define the {@link ServiceConfig} instance.
+     */
+    private ServiceConfig<SingleRegistryCenterExportProviderService> serviceConfig;
+
+    /**
+     * Define a registry center.
+     */
+    private SingleRegistryCenter registryCenter;
+
+    /**
+     * Define a {@link RegistryProtocolListener} instance.
+     */
+    private SingleRegistryCenterExportProviderRegistryProtocolListener registryProtocolListener;
+
+    /**
+     * Define a {@link ExporterListener} instance.
+     */
+    private SingleRegistryCenterExportProviderExporterListener exporterListener;
+
+    /**
+     * Define a {@link Filter} instance.
+     */
+    private SingleRegistryCenterExportProviderFilter filter;
+
+    /**
+     * Define a {@link ServiceListener} instance.
+     */
+    private SingleRegistryCenterExportProviderServiceListener serviceListener;
+
+    @BeforeEach
+    public void setUp() throws Exception {
+        logger.info(getClass().getSimpleName() + " testcase is beginning...");
+        DubboBootstrap.reset();
+        registryCenter = new DefaultSingleRegistryCenter();
+        registryCenter.startup();
+        // initialize service config
+        serviceConfig = new ServiceConfig<>();
+        serviceConfig.setInterface(SingleRegistryCenterExportProviderService.class);
+        serviceConfig.setRef(new SingleRegistryCenterExportProviderServiceImpl());
+        serviceConfig.setAsync(false);
+
+        // initailize bootstrap
+        DubboBootstrap.getInstance()
+            .application(new ApplicationConfig(PROVIDER_APPLICATION_NAME))
+            .registry(registryCenter.getRegistryConfig())
+            .protocol(new ProtocolConfig(PROTOCOL_NAME, PROTOCOL_PORT))
+            .service(serviceConfig);
+    }
+
+    /**
+     * There are some checkpoints need to verify as follow:
+     * <ul>
+     *     <li>ServiceConfig is exported or not</li>
+     *     <li>SingleRegistryCenterExportProviderRegistryProtocolListener is null or not</li>
+     *     <li>There is nothing in ServiceListener or not</li>
+     *     <li>There is nothing in ExporterListener or not</li>
+     * </ul>
+     */
+    private void beforeExport() {
+        registryProtocolListener = (SingleRegistryCenterExportProviderRegistryProtocolListener) ExtensionLoader
+            .getExtensionLoader(RegistryProtocolListener.class)
+            .getExtension(SPI_NAME);
+        exporterListener = (SingleRegistryCenterExportProviderExporterListener) ExtensionLoader
+            .getExtensionLoader(ExporterListener.class)
+            .getExtension(SPI_NAME);
+        filter = (SingleRegistryCenterExportProviderFilter) ExtensionLoader
+            .getExtensionLoader(Filter.class)
+            .getExtension(SPI_NAME);
+        serviceListener = (SingleRegistryCenterExportProviderServiceListener) ExtensionLoader
+            .getExtensionLoader(ServiceListener.class)
+            .getExtension(SPI_NAME);
+        // ---------------checkpoints--------------- //
+        // ServiceConfig isn't exported
+        Assertions.assertFalse(serviceConfig.isExported());
+        // registryProtocolListener is just initialized by SPI
+        // so, all of fields are the default value.
+        Assertions.assertNotNull(registryProtocolListener);
+        Assertions.assertFalse(registryProtocolListener.isExported());
+        // There is nothing in ServiceListener
+        Assertions.assertTrue(serviceListener.getExportedServices().isEmpty());
+        // There is nothing in ExporterListener
+        Assertions.assertTrue(exporterListener.getExportedExporters().isEmpty());
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Test
+    @Override
+    public void integrate() {
+        beforeExport();
+        DubboBootstrap.getInstance().start();
+        afterExport();
+        ReferenceConfig<SingleRegistryCenterExportProviderService> referenceConfig = new ReferenceConfig<>();
+        referenceConfig.setInterface(SingleRegistryCenterExportProviderService.class);
+        referenceConfig.setBootstrap(DubboBootstrap.getInstance());
+        referenceConfig.setScope(SCOPE_LOCAL);
+        referenceConfig.get().hello(PROVIDER_APPLICATION_NAME);
+        afterInvoke();
+    }
+
+    /**
+     * There are some checkpoints need to check after exported as follow:
+     * <ul>
+     *     <li>the exporter is exported or not</li>
+     *     <li>The exported exporter are three</li>
+     *     <li>The exported service is SingleRegistryCenterExportProviderService or not</li>
+     *     <li>The SingleRegistryCenterExportProviderService is exported or not</li>
+     *     <li>The exported exporter contains SingleRegistryCenterExportProviderFilter or not</li>
+     * </ul>
+     */
+    private void afterExport() {
+        // The exporter is exported
+        Assertions.assertTrue(registryProtocolListener.isExported());
+        // The exported service is only one
+        Assertions.assertEquals(serviceListener.getExportedServices().size(), 1);
+        // The exported service is SingleRegistryCenterExportProviderService
+        Assertions.assertEquals(serviceListener.getExportedServices().get(0).getInterfaceClass(),
+            SingleRegistryCenterExportProviderService.class);
+        // The SingleRegistryCenterExportProviderService is exported
+        Assertions.assertTrue(serviceListener.getExportedServices().get(0).isExported());
+        // The exported exporter are three
+        // 1. InjvmExporter
+        // 2. DubboExporter with service-discovery-registry protocol
+        // 3. DubboExporter with registry protocol
+        Assertions.assertEquals(exporterListener.getExportedExporters().size(), 3);
+        // The exported exporter contains SingleRegistryCenterExportProviderFilter
+        Assertions.assertTrue(exporterListener.getFilters().contains(filter));
+    }
+
+    /**
+     * There are some checkpoints need to check after invoked as follow:
+     * <ul>
+     *     <li>The SingleRegistryCenterExportProviderFilter has called or not</li>
+     *     <li>The SingleRegistryCenterExportProviderFilter exists error after invoked</li>
+     *     <li>The SingleRegistryCenterExportProviderFilter's response is right or not</li>
+     * </ul>
+     */
+    private void afterInvoke() {
+        // The SingleRegistryCenterInjvmFilter has called
+        Assertions.assertTrue(filter.hasCalled());
+        // The SingleRegistryCenterInjvmFilter doesn't exist error
+        Assertions.assertFalse(filter.hasError());
+        // Check the SingleRegistryCenterInjvmFilter's response
+        Assertions.assertEquals("Hello " + PROVIDER_APPLICATION_NAME, filter.getResponse());
+    }
+
+    @AfterEach
+    public void tearDown() throws IOException {
+        DubboBootstrap.reset();
+        PROVIDER_APPLICATION_NAME = null;
+        serviceConfig = null;
+        // The exported service has been unexported
+        Assertions.assertTrue(serviceListener.getExportedServices().isEmpty());
+        logger.info(getClass().getSimpleName() + " testcase is ending...");
+        registryCenter.shutdown();
+        registryProtocolListener = null;
+        registryCenter = null;
+    }
+}