Update as per the commend in PR.

Summary -
1. Updated README.md
2. SigV4AuthProvider.java to removed dependency on command lang3 , use getDefaultRegion(), changed getDefaultRegion() to return chain.getRegion().

Author: akshayar

README.md

@@ -8,7 +8,7 @@ This package implements an authentication plugin for the open-source Datastax Ja
 
 The plugin depends on the AWS SDK for Java. It uses `AWSCredentialsProvider` to obtain credentials. Because the IAuthenticator interface operates at the level of `InetSocketAddress`, you must specify the service endpoint to use for the connection.
 You can provide the Region in the constructor programmatically, via the `AWS_REGION` environment variable, or via the `aws.region` system property.
-You can also provide the IAM role, with which you want to connect with KeySpaces, in the constructor programmatically, via advanced.auth-provider.aws-role property in the conf file.
+You can also provide an IAM role to assume for access to KeySpaces, programmatically or via the configuration file.
 
 The full documentation for the plugin is available at
 https://docs.aws.amazon.com/keyspaces/latest/devguide/programmatic.credentials.html#programmatic.credentials.SigV4_KEYSPACES.
@@ -57,22 +57,19 @@ One of the constructors for `software.aws.mcs.auth.SigV4AuthProvider` takes a `S
 
 ### Configuration
 
-Set the Region explicitly in your `advanced.auth-provider.class` configuration (see example below), by specifying the `advanced.auth-provider.aws-region` property.
+Set the Region explicitly in your `advanced.auth-provider` configuration (see example below), by specifying the `advanced.auth-provider.aws-region` property.
 
 ## Assume IAM Role Configuration
 
-You must configure the AWS Region that the plugin will use when authenticating using mechanism mentioned above. 
-You can also specify IAM Role (including cross-account IAM role) configuraiton using one of the 2 methods: 
-* Constructor
-* Configuration
+You can specify an IAM role to assume for access to KeySpaces using either the constructor or the driver configuration file
 
 ### Constructor
 
-One of the constructors for `software.aws.mcs.auth.SigV4AuthProvider` takes two String , first represening the region and second one representing IAM role ARN. 
+One of the constructors for `software.aws.mcs.auth.SigV4AuthProvider` takes two Strings , the first representing the region and the second representing the ARN of the IAM role to assume. 
 
 ### Configuration
 
-Set the IAM Role explicitly in your `advanced.auth-provider.class` configuration (see example below), by specifying the `advanced.auth-provider.aws-role` property.
+Set the IAM Role explicitly in your `advanced.auth-provider` configuration (see example below), by specifying the `advanced.auth-provider.aws-role` property.
 
 ## Add the Authentication Plugin to the Application
 
@@ -155,7 +152,7 @@ The following is an example of this config without explicit role to be assumed.
     }
 ```
 
-Dollowing is an example of this config with explicit role to be assumed.
+The following is an example of this config with an explicit role to be assumed.
 
 ``` text
     datastax-java-driver {

src/main/java/software/aws/mcs/auth/SigV4AuthProvider.java

@@ -47,7 +47,6 @@
 import com.datastax.oss.driver.api.core.config.DriverOption;
 import com.datastax.oss.driver.api.core.context.DriverContext;
 import com.datastax.oss.driver.api.core.metadata.EndPoint;
-import org.apache.commons.lang3.StringUtils;
 import software.amazon.awssdk.auth.credentials.AwsCredentials;
 import software.amazon.awssdk.auth.credentials.AwsCredentialsProvider;
 import software.amazon.awssdk.auth.credentials.AwsSessionCredentials;
@@ -169,9 +168,7 @@ public SigV4AuthProvider(@NotNull AwsCredentialsProvider credentialsProvider, fi
         this.credentialsProvider = credentialsProvider;
 
         if (region == null) {
-            DefaultAwsRegionProviderChain chain = new DefaultAwsRegionProviderChain();
-            Region defaultRegion = chain.getRegion();
-            this.signingRegion = defaultRegion.toString().toLowerCase();
+            this.signingRegion = getDefaultRegion();
         } else {
             this.signingRegion = region.toLowerCase();
         }
@@ -398,7 +395,12 @@ static int indexOf(byte[] target, byte[] pattern) {
      */
     private static StsAssumeRoleCredentialsProvider createSTSRoleCredentialProvider(String roleArn,
                                                                      String stsRegion) {
-        final String roleName= StringUtils.substringAfterLast(roleArn,"/");
+        //Get role name from ARN
+        String[] arnParts = roleArn.split("/");
+        if(arnParts.length < 2){
+            throw new IllegalArgumentException("Invalid role ARN");
+        }
+        String roleName = arnParts[arnParts.length - 1];
         final String sessionName="keyspaces-session-"+roleName+System.currentTimeMillis();
         StsClient stsClient = StsClient.builder()
                 .region(Region.of(stsRegion))
@@ -419,6 +421,6 @@ private static StsAssumeRoleCredentialsProvider createSTSRoleCredentialProvider(
      */
     private static String getDefaultRegion() {
         DefaultAwsRegionProviderChain chain = new DefaultAwsRegionProviderChain();
-        return Optional.ofNullable(chain.getRegion()).orElse(Region.US_EAST_1).toString();
+        return chain.getRegion().toString().toLowerCase();
     }
 }

src/test/java/software/aws/mcs/auth/TestSigV4AssumeRoleConfig.java

@@ -0,0 +1,73 @@
+package software.aws.mcs.auth;
+
+/*-
+ * #%L
+ * AWS SigV4 Auth Java Driver 4.x Plugin
+ * %%
+ * Copyright (C) 2020-2021 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * %%
+ * Licensed 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.
+ * #L%
+ */
+
+import com.datastax.oss.driver.api.core.CqlSession;
+import com.datastax.oss.driver.api.core.config.DriverConfigLoader;
+import com.datastax.oss.driver.api.core.cql.ResultSet;
+import com.datastax.oss.driver.api.core.cql.Row;
+import org.junit.platform.commons.util.StringUtils;
+
+import java.io.File;
+import java.net.InetSocketAddress;
+import java.net.URL;
+import java.util.ArrayList;
+import java.util.Optional;
+
+public class TestSigV4AssumeRoleConfig {
+    static String KEYSPACES_DEFAULT_CONF="keyspaces-reference-norole.conf";
+    /**
+     * Before executing this test, ensure that KeySpaces tables are created.
+     * Refer ddl.cql and dml.cql to create and populate tables.
+     * @param args
+     * @throws Exception
+     */
+    public static void main(String[] args) throws Exception {
+        String keySpacesConf=KEYSPACES_DEFAULT_CONF;
+        if(args.length>1){
+            keySpacesConf=args[0];
+            System.out.println("Using key spaces config file: "+keySpacesConf);
+            keySpacesConf=Optional.of(keySpacesConf).filter(StringUtils::isBlank).orElse(KEYSPACES_DEFAULT_CONF);
+        }
+
+        URL url = TestSigV4AssumeRoleConfig.class.getClassLoader().getResource(keySpacesConf);
+
+        File file = new File(url.toURI());
+        // The CqlSession object is the main entry point of the driver.
+        // It holds the known state of the actual Cassandra cluster (notably the Metadata).
+        // This class is thread-safe, you should create a single instance (per target Cassandra cluster), and share
+        // it throughout your application.
+        try (CqlSession session = CqlSession.builder()
+                .withConfigLoader(DriverConfigLoader.fromFile(file))
+             .build()) {
+
+            // We use execute to send a query to Cassandra. This returns a ResultSet, which is essentially a collection
+            // of Row objects.
+            ResultSet rs = session.execute("select * from testkeyspace.testconf");
+            //  Extract the first row (which is the only one in this case).
+            Row row = rs.one();
+
+            // Extract the value of the first (and only) column from the row.
+            String releaseVersion = row.getString("category");
+            System.out.printf("Cassandra version is: %s%n", releaseVersion);
+        }
+    }
+}

src/test/java/software/aws/mcs/auth/TestSigV4Config.java

@@ -55,7 +55,7 @@ public static void main(String[] args) throws Exception {
         //By default the reference.conf is loaded by the driver which contains all defaults.
         //You can override this by providing reference.conf on the classpath
         //to isolate test you can load conf with a custom name
-        URL url = TestSigV4Config.class.getClassLoader().getResource("keyspaces-reference-norole.conf");
+        URL url = TestSigV4Config.class.getClassLoader().getResource("keyspaces-reference.conf");
 
         File file = new File(url.toURI());
         // The CqlSession object is the main entry point of the driver.
@@ -64,16 +64,18 @@ public static void main(String[] args) throws Exception {
         // it throughout your application.
         try (CqlSession session = CqlSession.builder()
                 .withConfigLoader(DriverConfigLoader.fromFile(file))
-             .build()) {
+                .addContactPoints(contactPoints)
+                .withLocalDatacenter("us-west-2")
+                .build()) {
 
             // We use execute to send a query to Cassandra. This returns a ResultSet, which is essentially a collection
             // of Row objects.
-            ResultSet rs = session.execute("select * from testkeyspace.testconf");
+            ResultSet rs = session.execute("select release_version from system.local");
             //  Extract the first row (which is the only one in this case).
             Row row = rs.one();
 
             // Extract the value of the first (and only) column from the row.
-            String releaseVersion = row.getString("category");
+            String releaseVersion = row.getString("release_version");
             System.out.printf("Cassandra version is: %s%n", releaseVersion);
         }
     }