feat: add iam authn example for mysql (GoogleCloudPlatform#7485)

Author: shubha-rajan

cloud-sql/mysql/servlet/src/main/java/com/example/cloudsql/ConnectionPoolContextListener.java

@@ -49,6 +49,8 @@ public void contextInitialized(ServletContextEvent event) {
     if (pool == null) {
       if (System.getenv("INSTANCE_HOST") != null) {
         pool = TcpConnectionPoolFactory.createConnectionPool();
+      } else if (System.getenv("DB_IAM_USER") != null) {
+        pool = ConnectorIamAuthnConnectionPoolFactory.createConnectionPool();
       } else {
         pool = ConnectorConnectionPoolFactory.createConnectionPool();
       }

cloud-sql/mysql/servlet/src/main/java/com/example/cloudsql/ConnectorIamAuthnConnectionPoolFactory.java

@@ -0,0 +1,73 @@
+/*
+ * Copyright 2022 Google LLC
+ *
+ * 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.
+ */
+
+package com.example.cloudsql;
+
+// [START cloud_sql_mysql_servlet_auto_iam_authn]
+import com.zaxxer.hikari.HikariConfig;
+import com.zaxxer.hikari.HikariDataSource;
+import javax.sql.DataSource;
+
+public class ConnectorIamAuthnConnectionPoolFactory extends ConnectionPoolFactory {
+
+  // Note: Saving credentials in environment variables is convenient, but not
+  // secure - consider a more secure solution such as
+  // Cloud Secret Manager (https://cloud.google.com/secret-manager) to help
+  // keep secrets safe.
+  private static final String INSTANCE_CONNECTION_NAME =
+      System.getenv("INSTANCE_CONNECTION_NAME");
+  private static final String INSTANCE_UNIX_SOCKET = System.getenv("INSTANCE_UNIX_SOCKET");
+  private static final String DB_IAM_USER = System.getenv("DB_IAM_USER");
+  private static final String DB_NAME = System.getenv("DB_NAME");
+
+
+  public static DataSource createConnectionPool() {
+    // The configuration object specifies behaviors for the connection pool.
+    HikariConfig config = new HikariConfig();
+
+    // The following URL is equivalent to setting the config options below:
+    // jdbc:mysql:///<DB_NAME>?cloudSqlInstance=<INSTANCE_CONNECTION_NAME>&
+    // socketFactory=com.google.cloud.sql.mysql.SocketFactory&user=<DB_USER>&password=<DB_PASS>
+    // See the link below for more info on building a JDBC URL for the Cloud SQL JDBC Socket Factory
+    // https://github.com/GoogleCloudPlatform/cloud-sql-jdbc-socket-factory#creating-the-jdbc-url
+
+    // Configure which instance and what database user to connect with.
+    config.setJdbcUrl(String.format("jdbc:mysql:///%s", DB_NAME));
+
+    config.addDataSourceProperty("socketFactory", "com.google.cloud.sql.mysql.SocketFactory");
+    config.addDataSourceProperty("cloudSqlInstance", INSTANCE_CONNECTION_NAME);
+
+    // If connecting using automatic database authentication, follow the instructions for
+    // connecting using the connector, but set the DB_IAM_USER value to an IAM user or
+    // service account that has been given access to the database.
+    // See https://cloud.google.com/sql/docs/postgres/iam-logins for more details.
+    config.addDataSourceProperty("enableIamAuth", "true");
+    config.addDataSourceProperty("user", DB_IAM_USER);
+    // Explicitly set sslmode to disable to prevent driver from hanging.
+    // The Java Connector will handle SSL so it is unneccesary to enable it at the driver level.
+    config.addDataSourceProperty("sslmode", "disable");
+
+
+    // ... Specify additional connection properties here.
+    // [START_EXCLUDE]
+    configureConnectionPool(config);
+    // [END_EXCLUDE]
+
+    // Initialize the connection pool using the configuration object.
+    return new HikariDataSource(config);
+  }
+}
+// [END cloud_sql_mysql_servlet_auto_iam_authn]