Track 2: Event Hubs Client Library (#3655)

* Adding azure-messaging-eventhubs and azure-core-amqp pom.xml.

* Adding EventHubClient, EventHubClientBuilder, EventHubConsumer, EventHubConsumerOptions, EventHubProducer, 
and EventHubProducerOptions.

* Adding configuration options for EventHubClientBuilder.

* Adding azure-core-amqp with common classes to AMQP for Exceptions, Sessions, Links, Connections, TransportTypes, etc.

* Adding authorization with CBS node and getting Event Hub metadata.

* Adding functionality for EventHubConsumer and EventHubProducer.

* Adding support for Azure Identity and TokenCredential.

* Adding a bare set of tests for Azure Event Hubs client library.

core/azure-core-amqp/README.md

@@ -0,0 +1,42 @@
+# Azure Core AMQP client library for Java
+
+Azure Core AMQP client library is a collection of classes common to the AMQP protocol. It help developers create their
+own AMQP client library that abstracts from the underlying transport library's implementation.
+
+## Getting started
+
+### Prerequisites
+
+- Java Development Kit (JDK) with version 8 or above
+
+### Adding the package to your product
+
+```xml
+<dependency>
+    <groupId>com.azure</groupId>
+    <artifactId>azure-core-amqp</artifactId>
+    <version>1.0.0-SNAPSHOT</version>
+</dependency>
+```
+
+## Key concepts
+
+The concepts for AMQP are well documented in [OASIS Advanced Messaging Queuing Protocol (AMQP) Version
+1.0](http://docs.oasis-open.org/amqp/core/v1.0/os/amqp-core-overview-v1.0-os.html).
+
+## Examples
+
+## Troubleshooting
+
+## Next steps
+
+## Contributing
+
+If you would like to become an active contributor to this project please follow the instructions provided in [Microsoft
+Azure Projects Contribution Guidelines](http://azure.github.io/guidelines.html).
+
+1. Fork it
+1. Create your feature branch (`git checkout -b my-new-feature`)
+1. Commit your changes (`git commit -am 'Add some feature'`)
+1. Push to the branch (`git push origin my-new-feature`)
+1. Create new Pull Request

core/azure-core-amqp/pom.xml

@@ -0,0 +1,78 @@
+<!--
+  ~ Copyright (c) Microsoft Corporation. All rights reserved.
+  ~ Licensed under the MIT License.
+  -->
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+  <parent>
+    <groupId>com.azure</groupId>
+    <artifactId>azure-core-parent</artifactId>
+    <version>1.0.0-SNAPSHOT</version>
+    <relativePath>../pom.xml</relativePath>
+  </parent>
+
+  <groupId>com.azure</groupId>
+  <artifactId>azure-core-amqp</artifactId>
+  <version>1.0.0-SNAPSHOT</version>
+  <packaging>jar</packaging>
+
+  <name>Microsoft Azure Java Core AMQP Library</name>
+  <description>This package contains core types for Azure Java AMQP clients.</description>
+  <url>https://github.com/Azure/azure-sdk-for-java</url>
+
+  <licenses>
+    <license>
+      <name>The MIT License (MIT)</name>
+      <url>http://opensource.org/licenses/MIT</url>
+      <distribution>repo</distribution>
+    </license>
+  </licenses>
+
+  <distributionManagement>
+    <site>
+      <id>azure-java-build-docs</id>
+      <url>${site.url}/site/${project.artifactId}</url>
+    </site>
+  </distributionManagement>
+
+  <scm>
+    <url>scm:git:https://github.com/Azure/azure-sdk-for-java</url>
+  </scm>
+
+  <properties>
+    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    <legal><![CDATA[[INFO] Any downloads listed may be third party software.  Microsoft grants you no rights for third party software.]]></legal>
+  </properties>
+
+  <developers>
+    <developer>
+      <id>microsoft</id>
+      <name>Microsoft</name>
+    </developer>
+  </developers>
+
+  <dependencies>
+    <dependency>
+      <groupId>com.azure</groupId>
+      <artifactId>azure-core</artifactId>
+    </dependency>
+
+    <dependency>
+      <groupId>io.projectreactor</groupId>
+      <artifactId>reactor-test</artifactId>
+      <scope>test</scope>
+    </dependency>
+
+    <dependency>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>org.slf4j</groupId>
+      <artifactId>slf4j-simple</artifactId>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
+</project>

core/azure-core-amqp/src/main/java/com/azure/core/amqp/AmqpConnection.java

@@ -0,0 +1,65 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+package com.azure.core.amqp;
+
+import reactor.core.publisher.Mono;
+
+import java.io.Closeable;
+import java.util.Map;
+
+/**
+ * Represents a TCP connection between the client and a service that uses the AMQP protocol.
+ */
+public interface AmqpConnection extends EndpointStateNotifier, Closeable {
+    /**
+     * Gets the connection identifier.
+     *
+     * @return The connection identifier.
+     */
+    String getIdentifier();
+
+    /**
+     * Gets the host for the AMQP connection.
+     *
+     * @return The host for the AMQP connection.
+     */
+    String getHost();
+
+    /**
+     * Gets the maximum frame size for the connection.
+     *
+     * @return The maximum frame size for the connection.
+     */
+    int getMaxFrameSize();
+
+    /**
+     * Gets the connection properties.
+     *
+     * @return Properties associated with this connection.
+     */
+    Map<String, Object> getConnectionProperties();
+
+    /**
+     * Gets the claims-based security (CBS) node that authorizes access to resources.
+     *
+     * @return Provider that authorizes access to AMQP resources.
+     */
+    Mono<CBSNode> getCBSNode();
+
+    /**
+     * Creates a new session with the given session name.
+     *
+     * @param sessionName Name of the session.
+     * @return The AMQP session that was created.
+     */
+    Mono<AmqpSession> createSession(String sessionName);
+
+    /**
+     * Removes a session with the {@code sessionName} from the AMQP connection.
+     *
+     * @param sessionName Name of the session to remove.
+     * @return {@code true} if a session with the name was removed; {@code false} otherwise.
+     */
+    boolean removeSession(String sessionName);
+}

core/azure-core-amqp/src/main/java/com/azure/core/amqp/AmqpEndpointState.java

@@ -0,0 +1,22 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+package com.azure.core.amqp;
+
+/**
+ * Represents a state for a connection, session, or link.
+ */
+public enum AmqpEndpointState {
+    /**
+     * The endpoint has not been initialized.
+     */
+    UNINITIALIZED,
+    /**
+     * The endpoint is active.
+     */
+    ACTIVE,
+    /**
+     * The endpoint is closed.
+     */
+    CLOSED
+}

core/azure-core-amqp/src/main/java/com/azure/core/amqp/AmqpExceptionHandler.java

@@ -0,0 +1,37 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+package com.azure.core.amqp;
+
+import com.azure.core.util.logging.ClientLogger;
+
+/**
+ * Handles exceptions generated by AMQP connections, sessions, and/or links.
+ */
+public abstract class AmqpExceptionHandler {
+    private final ClientLogger logger = new ClientLogger(AmqpExceptionHandler.class);
+
+    /**
+     * Creates a new instance of the exception handler.
+     */
+    protected AmqpExceptionHandler() {
+    }
+
+    /**
+     * Notifies the exception handler of an exception.
+     *
+     * @param exception The exception that caused the connection error.
+     */
+    public void onConnectionError(Throwable exception) {
+        logger.asWarning().log("Connection exception encountered: " + exception.toString(), exception);
+    }
+
+    /**
+     * Notifies the exception handler that a shutdown signal occurred.
+     *
+     * @param shutdownSignal The shutdown signal that was received.
+     */
+    public void onConnectionShutdown(AmqpShutdownSignal shutdownSignal) {
+        logger.asInfo().log("Shutdown received: {}", shutdownSignal);
+    }
+}

core/azure-core-amqp/src/main/java/com/azure/core/amqp/AmqpLink.java

@@ -0,0 +1,25 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+package com.azure.core.amqp;
+
+import java.io.Closeable;
+
+/**
+ * Represents a unidirectional AMQP link.
+ */
+public interface AmqpLink extends EndpointStateNotifier, Closeable {
+    /**
+     * Gets the name of the link.
+     *
+     * @return The name of the link.
+     */
+    String getLinkName();
+
+    /**
+     * The remote endpoint path this link is connected to.
+     *
+     * @return The remote endpoint path this link is connected to.
+     */
+    String getEntityPath();
+}

core/azure-core-amqp/src/main/java/com/azure/core/amqp/AmqpSession.java

@@ -0,0 +1,58 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+package com.azure.core.amqp;
+
+import reactor.core.publisher.Mono;
+
+import java.io.Closeable;
+import java.time.Duration;
+
+/**
+ * An AMQP session representing bidirectional communication that supports multiple {@link AmqpLink AMQP links}.
+ */
+public interface AmqpSession extends EndpointStateNotifier, Closeable {
+    /**
+     * Gets the name for this AMQP session.
+     *
+     * @return The name for the AMQP session.
+     */
+    String getSessionName();
+
+    /**
+     * Gets the operation timeout for starting the AMQP session.
+     *
+     * @return The timeout for starting the AMQP session.
+     */
+    Duration getOperationTimeout();
+
+    /**
+     * Creates a new AMQP link that publishes events to the message broker.
+     *
+     * @param linkName Name of the link.
+     * @param entityPath The entity path this link connects to when producing events.
+     * @param timeout Timeout required for creating and opening AMQP link.
+     * @param retry The retry policy to use when sending messages.
+     * @return A newly created AMQP link.
+     */
+    Mono<AmqpLink> createProducer(String linkName, String entityPath, Duration timeout, Retry retry);
+
+    /**
+     * Creates a new AMQP link that consumes events from the message broker.
+     *
+     * @param linkName Name of the link.
+     * @param entityPath The entity path this link connects to, so that it may read events from the message broker.
+     * @param timeout Timeout required for creating and opening an AMQP link.
+     * @param retry The retry policy to use when consuming messages.
+     * @return A newly created AMQP link.
+     */
+    Mono<AmqpLink> createConsumer(String linkName, String entityPath, Duration timeout, Retry retry);
+
+    /**
+     * Removes an {@link AmqpLink} with the given {@code linkName}.
+     *
+     * @param linkName Name of the link to remove.
+     * @return {@code true} if the link was removed; {@code false} otherwise.
+     */
+    boolean removeLink(String linkName);
+}

core/azure-core-amqp/src/main/java/com/azure/core/amqp/AmqpShutdownSignal.java

@@ -0,0 +1,56 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+package com.azure.core.amqp;
+
+import java.util.Locale;
+
+/**
+ * Represents a signal that caused the AMQP connection to shutdown.
+ */
+public class AmqpShutdownSignal {
+    private final boolean isTransient;
+    private final boolean isInitiatedByClient;
+    private final String message;
+
+    /**
+     * Creates a new instance of the AmqpShutdownSignal.
+     *
+     * @param isTransient Whether the shutdown signal can be retried or not.
+     * @param isInitiatedByClient {@code true} if the shutdown was initiated by the client; {@code false} otherwise.
+     * @param message Message associated with the shutdown.
+     */
+    public AmqpShutdownSignal(boolean isTransient, boolean isInitiatedByClient, String message) {
+        this.isTransient = isTransient;
+        this.isInitiatedByClient = isInitiatedByClient;
+        this.message = message;
+    }
+
+    /**
+     * Gets whether or not this shutdown signal is transient or if it can be restarted.
+     *
+     * @return {@code true} if the shutdown signal is transient and the connection, session, or link can be recreated.
+     *         {@code false} otherwise.
+     */
+    public boolean isTransient() {
+        return isTransient;
+    }
+
+    /**
+     * Gets whether or not this shutdown signal was initiated by the client.
+     *
+     * @return {@code true} if the shutdown signal was initiated by the client, {@code false} if the shutdown signal
+     *         occurred in the underlying AMQP layer or from the AMQP message broker.
+     */
+    public boolean isInitiatedByClient() {
+        return isInitiatedByClient;
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public String toString() {
+        return String.format(Locale.US, "%s, isTransient[%s], initiatedByClient[%s]", message, isTransient, isInitiatedByClient);
+    }
+}