Empty connection Mysql
posted 2 years ago
Hi,
I try to connect with a DDBB which is remote, I am using the next code:
In the DAO file I have this code:
Then an specific file for the DB:
In the Tomcat Log I get this message:
I looks that the driver is invalid in my case
Any idea?
I try to connect with a DDBB which is remote, I am using the next code:
In the DAO file I have this code:
Then an specific file for the DB:
In the Tomcat Log I get this message:
I looks that the driver is invalid in my case
Any idea?
Dave Tolls
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Posts: 2551
27
posted 2 years ago
Print out the full stack trace.
Without that you won't know what the exception was.
I can guess (possibly a ClassNotFoundException), but it would be just that, a guess.
Without that you won't know what the exception was.
I can guess (possibly a ClassNotFoundException), but it would be just that, a guess.
Dave Tolls
Ranch Hand
Posts: 2551
27
posted 2 years ago
That's an ancient version of the connector.
Not sure if there was any change in the URL between that and the current version 5.
Why aren't you simply doing ex.printStackTrace() in that catch block? It would be simpler.
That gives you the full information, including the exception name.
That exception you are showing is caused by you returning null from your getConnection() call. You need to handle a failure to connect, even if it's simply to exit with an error.
Not sure if there was any change in the URL between that and the current version 5.
Why aren't you simply doing ex.printStackTrace() in that catch block? It would be simpler.
That gives you the full information, including the exception name.
That exception you are showing is caused by you returning null from your getConnection() call. You need to handle a failure to connect, even if it's simply to exit with an error.
posted 2 years ago
I changed to System.out.println("Database.getConnection() Error -->" );
ex.printStackTrace();
I get the same error.
Which driver/ jar should I use?
Regards
ex.printStackTrace();
I get the same error.
Which driver/ jar should I use?
Regards
posted 2 years ago
You should be using the latest driver which can be downloaded at http://dev.mysql.com/downloads/connector/j/
Also which java version are you using? Java 6 or later utilizes JDBC4 hence the line
is optional, but for backward compatibility you may want to keep it in.
Also which java version are you using? Java 6 or later utilizes JDBC4 hence the line
is optional, but for backward compatibility you may want to keep it in.
K. Tsang OCPJP7 OCMJEA6
posted 2 years ago
Run the installer.
I have no idea where it might have put the jar, though. Send the puppy looking for "mysql-connector" or something like that.
You could always download the OS-independent archive and pull the jar out of that file, though.
I have no idea where it might have put the jar, though. Send the puppy looking for "mysql-connector" or something like that.
You could always download the OS-independent archive and pull the jar out of that file, though.
An IDE is no substitute for an Intelligent Developer.
Dave Tolls
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Posts: 2551
27
posted 2 years ago
Well, you would get the same error, since you return null, but you should also get a stack trace earlier which explains the root cause of the problem.
Isaac Ferguson wrote:I changed to System.out.println("Database.getConnection() Error -->" );
ex.printStackTrace();
I get the same error.
Regards
Well, you would get the same error, since you return null, but you should also get a stack trace earlier which explains the root cause of the problem.
Dave Tolls
Ranch Hand
Posts: 2551
27
posted 2 years ago
java.sql.SQLException: Communication link failure: java.io.IOException
It can't talk to the db for some reason.
(Also you should edit that lot as only the exception is needed. The rest is causing a scrolling issue on the page.)
It can't talk to the db for some reason.
(Also you should edit that lot as only the exception is needed. The rest is causing a scrolling issue on the page.)
Dave Tolls
Ranch Hand
Posts: 2551
27
Dave Tolls
Ranch Hand
Posts: 2551
27
Dave Tolls
Ranch Hand
Posts: 2551
27
Dave Tolls
Ranch Hand
Posts: 2551
27
posted 2 years ago
Yes.
A nice simple one that gets a connection and maybe does a simple query.
No, SQL Developer.
It's a tool for working with databases.
Isaac Ferguson wrote:Sorry I dont get it
Do you mean an app which run without a server?
Yes.
A nice simple one that gets a connection and maybe does a simple query.
Isaac Ferguson wrote:
Do you mean changing the DB?
No, SQL Developer.
It's a tool for working with databases.
posted 2 years ago
I tried both things:
It launches de same error:
This is the code:
try {
Class.forName("com.mysql.jdbc.Driver");
// Connection con = DriverManager.getConnection("jdbc:mysql://domain-name:2082/dbNAme","name","pass");
Connection con = DriverManager.getConnection("jdbc:mysql://IP:2082/dbNAme","name","pass");
return con;
}
catch(Exception ex) {
System.out.println("Database.getConnection() Error -->" );
ex.printStackTrace();
return null;
}
}
Any more idea?
It launches de same error:
This is the code:
try {
Class.forName("com.mysql.jdbc.Driver");
// Connection con = DriverManager.getConnection("jdbc:mysql://domain-name:2082/dbNAme","name","pass");
Connection con = DriverManager.getConnection("jdbc:mysql://IP:2082/dbNAme","name","pass");
return con;
}
catch(Exception ex) {
System.out.println("Database.getConnection() Error -->" );
ex.printStackTrace();
return null;
}
}
Any more idea?
Dave Tolls
Ranch Hand
Posts: 2551
27
posted 2 years ago
So, SQL Developer failed to connect?
And the full exception (and stack trace) you get from the standalone test program?
And the full exception (and stack trace) you get from the standalone test program?
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