Java support for DefaultAzureCredential in Service Bus (#3)

* Java support for DefaultAzureCredential in Service Bus

* Moving to a different namespace

java/com/jongallant/azure/identity/extensions/DefaultAzureServiceBusCredential.java

@@ -0,0 +1,36 @@
+package com.jongallant.azure.identity.extensions;
+
+import com.azure.core.credential.TokenRequestContext;
+import com.azure.identity.DefaultAzureCredential;
+import com.azure.identity.DefaultAzureCredentialBuilder;
+import reactor.core.publisher.Mono;
+
+import java.time.Instant;
+import java.util.concurrent.CompletableFuture;
+
+public class DefaultAzureServiceBusCredential extends TokenProvider {
+
+    private final DefaultAzureCredential defaultAzureCredential;
+
+    public DefaultAzureServiceBusCredential() {
+        this(new DefaultAzureCredentialBuilder().build());
+    }
+
+    public DefaultAzureServiceBusCredential(DefaultAzureCredential defaultAzureCredential) {
+        this.defaultAzureCredential = defaultAzureCredential;
+    }
+
+    @Override
+    public CompletableFuture<SecurityToken> getSecurityTokenAsync(String audience) {
+
+        String scope = "https://servicebus.azure.net/.default";
+        TokenRequestContext tokenRequestContext = new TokenRequestContext()
+            .addScopes(scope);
+
+        return defaultAzureCredential
+            .getToken(tokenRequestContext)
+            .flatMap(accessToken -> Mono.just(new SecurityToken(SecurityTokenType.JWT, audience, accessToken.getToken(),
+                Instant.now(), accessToken.getExpiresAt().toInstant()))).toFuture();
+    }
+
+}

java/com/jongallant/azure/identity/extensions/DefaultAzureServiceBusCredentialTest.java

@@ -0,0 +1,19 @@
+package com.jongallant.azure.identity.extensions;
+
+import com.azure.identity.DefaultAzureCredential;
+import com.azure.identity.DefaultAzureCredentialBuilder;
+import com.microsoft.azure.servicebus.primitives.ServiceBusException;
+import com.microsoft.azure.servicebus.security.DefaultAzureServiceBusCredential;
+import org.junit.Test;
+
+public class DefaultAzureServiceBusCredentialTest {
+
+    @Test
+    public void testDefaultCredential() throws ServiceBusException, InterruptedException {
+        DefaultAzureCredential defaultAzureCredential = new DefaultAzureCredentialBuilder().build();
+        TopicClient topicClient = new TopicClient("jongsb2", "srnagartopic",
+            new ClientSettings(new DefaultAzureServiceBusCredential()));
+
+        topicClient.send(new Message("hello"));
+    }
+}