@SuppressWarnings("serial")
public class CloudSqlServlet extends HttpServlet {

  @Override
  public void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException,
      ServletException {
    String path = req.getRequestURI();
    if (path.startsWith("/favicon.ico")) {
      return; // ignore the request for favicon.ico
    }
    // store only the first two octets of a users ip address
    String userIp = req.getRemoteAddr();
    InetAddress address = InetAddress.getByName(userIp);
    if (address instanceof Inet6Address) {
      // nest indexOf calls to find the second occurrence of a character in a string
      // an alternative is to use Apache Commons Lang: StringUtils.ordinalIndexOf()
      userIp = userIp.substring(0, userIp.indexOf(":", userIp.indexOf(":") + 1)) + ":*:*:*:*:*:*";
    } else if (address instanceof Inet4Address) {
      userIp = userIp.substring(0, userIp.indexOf(".", userIp.indexOf(".") + 1)) + ".*.*";
    }

    final String createTableSql = "CREATE TABLE IF NOT EXISTS visits ( visit_id INT NOT NULL "
        + "AUTO_INCREMENT, user_ip VARCHAR(46) NOT NULL, nombre VARCHAR(46) NOT NULL)";
    final String selectSql = "SELECT * from visits;";
    PrintWriter out = resp.getWriter();
    resp.setContentType("text/plain");
    String url;
    if (System.getProperty("com.google.appengine.runtime.version").startsWith("Google App Engine/")) {
      // Check the System properties to determine if we are running on appengine or not
      // Google App Engine sets a few system properties that will reliably be present on a remote
      // instance.
      url = System.getProperty("ae-cloudsql.local-database-url");
      try {
          System.out.println("Entra en appengine cloud");
        // Load the class that provides the new "jdbc:google:mysql://" prefix.
        Class.forName("com.mysql.jdbc.GoogleDriver");
      } catch (ClassNotFoundException e) {
        throw new ServletException("Error loading Google JDBC Driver", e);
      }
    } else {
         System.out.println("NO entra en appengine cloud");
      // Set the url with the local MySQL database connection url when running locally
      url = System.getProperty("ae-cloudsql.local-database-url");
    }
    try (Connection conn = DriverManager.getConnection(url)){

      try (ResultSet rs = conn.prepareStatement(selectSql).executeQuery()) {
        out.print("Datos:");
        while (rs.next()) {
          String savedIp = rs.getString("user_ip");
          String name = rs.getString("nombre");
          out.print("IP: " + name + " Nombre: " + savedIp);
        }
      }
    } catch (SQLException e) {
      throw new ServletException("SQL error", e);
    }
  }
}

<?xml version="1.0" encoding="utf-8"?>
<appengine-web-app xmlns="http://appengine.google.com/ns/1.0">
  <application>myApp</application>
  <version>1</version>


  <threadsafe>true</threadsafe>
  <use-google-connector-j>true</use-google-connector-j>

  <!-- Configure java.util.logging -->
  <system-properties>
    <property name="java.util.logging.config.file" value="WEB-INF/logging.properties"/>
  </system-properties>

  <system-properties>
    <property name="ae-cloudsql.cloudsql-database-url" value="jdbc:google:mysql://project-id-4811673067964427457:europe-west1:con-bd-myApp/BD-myApp?user=root;password=root"/>
    <property name="ae-cloudsql.local-database-url" value="jdbc:mysql://104.155.83.62/BD-myApp?user=root;password=root"/>
  </system-properties>


  <!--
    HTTP Sessions are disabled by default. To enable HTTP sessions specify:

      <sessions-enabled>true</sessions-enabled>

    It's possible to reduce request latency by configuring your application to
    asynchronously write HTTP session data to the datastore:

      <async-session-persistence enabled="true" />

    With this feature enabled, there is a very small chance your app will see
    stale session data. For details, see
    http://code.google.com/appengine/docs/java/config/appconfig.html#Enabling_Sessions
  -->

</appengine-web-app>

<dependency> <!-- Local -->
  <groupId>mysql</groupId>
  <artifactId>mysql-connector-java</artifactId>
  <version>5.1.40</version>  <!-- v5.x.x is Java 7, v6.x.x is Java 8 -->
</dependency>
<dependency> <!-- Cloud Sql -->
  <groupId>com.google.cloud.sql</groupId>
  <artifactId>mysql-socket-factory</artifactId>
  <version>1.0.2</version>
</dependency>