java.lang.NullPointerException connecting to Cloud SQL

Question

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.*;

public class ConnectionManager {
    private static String URL  = "jdbc:google:mysql://your-project-id:your-instance-name/database";
    private static String DRIVER = "com.mysql.jdbc.GoogleDriver";
    private static String USERNAME = "root";
    private static String PASSWORD = "test";
    private static Connection CON = null;

    public static Connection getConnection() {
        try {
            Class.forName(DRIVER);
            try {
                CON = DriverManager.getConnection(URL, USERNAME, PASSWORD);
            } catch (SQLException se) {
                //Handle errors for JDBC
                se.printStackTrace();
            }
        } catch (Exception ex) {
            //Handle errors for Class.forName
            ex.printStackTrace();
        }

        //return a connection object
        return CON;
    }

}

I created the above class to connect to my Cloud SQL instance in Android Studio but the above class is returning a NULL which in turn hurts the rest of my code:

conn = ConnectionManager.getConnection();
stmt = conn.createStatement();
String sql;
sql = "INSERT into messages (message) VALUES('Hello World')";
ResultSet rs = stmt.executeQuery(sql);

I'm not sure though why I cam getting this error:

Caused by: java.lang.NullPointerException: Attempt to invoke interface method 'java.sql.Statement java.sql.Connection.createStatement()' on a null object reference

Am I missing some imports or something?

Answer 1

com.mysql.jdbc.GoogleDriver

Only works if your app is running in AppEngine,and remember to enable the connector in appengine. If not just use com.mysql.jdbc.Driver.

The guide is very simple: https://cloud.google.com/appengine/docs/java/cloud-sql/#enable_connector_j

Answer 2

Found something interesting here: cloud.google.com/sql/docs/external

So you are able to connect with a normal MySQL Connector and without App Engine. You get the jar-file here: http://dev.mysql.com/downloads/connector/j/

To solve 1:

Authorize the IP or range of IPs from which you will be connecting

you need to get your ip. If you on a normal dsl you may get a dynamic ip, so you have to change this often in admin console of Cloud SQL.

Answer 3

This might be a cause of one of two things:

1) Missing permission. Try to add these in the Manifest,

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.access_wifi_state" />

2) Add "jtds-1.3.1.jar" file to app/lib forlder