SQL connections using Java™ APIs

package com.adobe.aem.wknd.examples.core.connections.impl;

import com.adobe.aem.wknd.examples.core.connections.ExternalService;
import org.osgi.service.component.annotations.Activate;
import org.osgi.service.component.annotations.Component;
import org.osgi.service.metatype.annotations.AttributeDefinition;
import org.osgi.service.metatype.annotations.AttributeType;
import org.osgi.service.metatype.annotations.Designate;
import org.osgi.service.metatype.annotations.ObjectClassDefinition;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.sql.*;

@Component
@Designate(ocd = MySqlExternalServiceImpl.Config.class)
public class MySqlExternalServiceImpl implements ExternalService {
    private static final Logger log = LoggerFactory.getLogger(MySqlExternalServiceImpl.class);

    // Get the proxy host using the AEM_PROXY_HOST Java environment variable provided by AEM as a Cloud Service
    private static final String PROXY_HOST = System.getenv().getOrDefault("AEM_PROXY_HOST", "proxy.tunnel");

    // Use the port mapped to the external MySQL service in the Cloud Manager API call
    private static final int PORT_FORWARDS_PORT_ORIG = 30001;

    private Config config;

    @Override
    public boolean isAccessible() {
        log.debug("MySQL connection URL: [ {} ]", getConnectionUrl(config));

        // Establish a connection with the external MySQL service
        // This MySQL connection URL is created in getConnection(..) which will use the AEM_PROXY_HOST is it exists, and the proxied port.
        try (Connection connection = DriverManager.getConnection(getConnectionUrl(config), config.username(), config.password())) {
            // Validate the connection
            connection.isValid(1000);

            // Close the connection, since this is just a simple connectivity check
            connection.close();

            // Return true if AEM could reach the external SQL service
            return true;
        } catch (SQLException e) {
            log.error("Unable to establish an connection with MySQL service using connection URL  [ {} ]", getConnectionUrl(config), e);
        }

        return false;
    }

    /**
     * Create a connection string to the MySQL using the AEM-provided AEM_PROXY_HOST and portForwards.portOrg port
     * defined in the Cloud Manager API mapping.
     *
     * @param config OSGi configuration object
     * @return the MySQL connection URI
     */
    private String getConnectionUrl(Config config) {
        return String.format("jdbc:mysql://%s:%d/wknd-examples", PROXY_HOST, PORT_FORWARDS_PORT_ORIG);
    }

    @Activate
    protected void activate(Config config) throws ClassNotFoundException, SQLException {
        this.config = config;

        // Load the required MySQL Driver class required for Java to make the connection
        // The OSGi bundle that contains this driver is deployed via the project's all project
        DriverManager.registerDriver(new com.mysql.jdbc.Driver());
    }

    @ObjectClassDefinition
    @interface Config {
        @AttributeDefinition(type = AttributeType.STRING)
        String username();

        @AttributeDefinition(type = AttributeType.STRING)
        String password();
    }
}