android postgresql数据库连接错误

Question

i try to connect my android app with my postgresql Databse but it doesn't get a connection the dr iver is running but the connection is not working.

Here is the java code:

private void initDatabase() {

    try {

        Class.forName("org.postgresql.Driver");

    } catch (ClassNotFoundException e) {

        return;

    }

    Connection connection = null;
    String url = "jdbc:postgresql://10.0.2.2/Seminarkurs";

    try {

        connection = DriverManager.getConnection(url , "postgres", "postgres");
        Toast.makeText(getApplicationContext(), "Connection successful!", Toast.LENGTH_LONG).show();

        connection.close();

    } catch (SQLException e) {

        Toast.makeText(getApplicationContext(), "Connection Failed! Check output console", Toast.LENGTH_LONG).show();
        e.printStackTrace();
        return;

    }

}

and here is the logcat:

01-16 14:40:17.192    8044-8053/com.example.damian.schulkalender E/System﹕ Uncaught exception thrown by finalizer
01-16 14:40:17.192    8044-8053/com.example.damian.schulkalender E/System﹕ java.lang.NullPointerException
            at org.postgresql.jdbc2.AbstractJdbc2Connection.close(AbstractJdbc2Connection.java:677)
            at org.postgresql.jdbc2.AbstractJdbc2Connection.finalize(AbstractJdbc2Connection.java:1036)
            at java.lang.Daemons$FinalizerDaemon.doFinalize(Daemons.java:187)
            at java.lang.Daemons$FinalizerDaemon.run(Daemons.java:170)
            at java.lang.Thread.run(Thread.java:841)

Answer 1

I'm sure that this isn't what you want to hear, but it's really not a reasonable thing to do to try to connect directly to a server-side database from a mobile device. I see this question here several times a week, and I'm really not sure why.

The preferred way to do this is to create a server-side application that provides data to your mobile app via an HTTP connection (eg a REST Api).

That said, it looks like your attempt to create the connection is failing. You may get more info by replacing your e.printStackTrace() in your exception handler to the use of the Android logger, so that you can see the error in logcat.