A problem connecting to a MySQL DB using JDBC

Question

Here's how I'm trying to connect:

try {
   Class.forName("com.mysql.jdbc.Driver").newInstance();
   } catch (Exception e) {
      throw new DbConnectionException();
   }
   try {
      connection = DriverManager.getConnection(url,username,password);
   } catch (SQLException e) {
      e.printStackTrace();
      throw new DbConnectionException();
   }

I'm 100% sure that the url, username, password strings are correct. I've already connected successfully using an external tool (MySQL query browser). This is the error I receive:

com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception:

** BEGIN NESTED EXCEPTION **

java.net.SocketException MESSAGE: java.net.ConnectException: Connection refused

...

Is MySQL server running? Is the port unblocked from the firewall? — Buhake Sindi
– Buhake Sindi, Commented Dec 20, 2010 at 21:13

Buhake Sindi · Accepted Answer · 2010-12-20 21:31:41Z

7

Possibly a url issue. If your code is pointing to MySQL localhost, try changing localhost to 127.0.0.1 on your url.

E.g.:

jdbc:mysql://localhost:3306/MY_DB

to

jdbc:mysql://127.0.0.1:3306/MY_DB

And see if this works.

answered Dec 20, 2010 at 21:31

Buhake Sindi

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1 Comment

snakile Over a year ago

Indeed a url issue. Turns out I had another piece of code which was trying to connect to another DB and it caused the problem. Sorry for being 100% sure on something wrong.

hvgotcodes · Accepted Answer · 2010-12-20 21:11:20Z

1

did you run the mysql browser from the same machine where the code is running? What I am getting at is the permissions in mysql can be host-specific, and depending on how you set them up you might not be able to connect from the machine where the code is running.

Also, you might want to double check the url, name, pword again, perhaps with log statements or a debugger to make sure there are no typos, trailing whitespaces, etc...

answered Dec 20, 2010 at 21:11

hvgotcodes

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Comments

jzd · Accepted Answer · 2010-12-20 21:11:35Z

1

Double check the format of your url. It should start with "jdbc:mysql:". Make sure you are using a current version for the driver as well.

answered Dec 20, 2010 at 21:11

jzd

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1 Comment

snakile Over a year ago

Indeed a url issue. Turns out I had another piece of code which was trying to connect to another DB and it caused the problem. Sorry for being 100% sure on something wrong.

Michael Wiles · Accepted Answer · 2010-12-20 21:39:17Z

0

Check that you can connect to the database from the mysql admin tool, that will drive out whether your mysql is running and that the port is open.

answered Dec 20, 2010 at 21:39

Michael Wiles

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Comments

DimaSan · Accepted Answer · 2016-12-07 13:45:43Z

0

In my case the problem was that I was using a connection from emulator to localhost.

If you use emulator to localhost don't use localhost value in connection String but use 10.0.2.2 instead:

jdbc:mysql://10.0.2.2:3306/MY_DB

Hope this helps.

edited Dec 7, 2016 at 13:45

DimaSan

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answered Dec 7, 2016 at 13:27

Gerrlt

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