Tomcat Mysql JDBC connection diagnosis

Tomcat Mysql JDBC connection diagnosis

In case of your web application is unable to connect to the Mysql database, chec the following:

1. Is your Web.xml (/var/lib/tomcat6/webapps/<..>) refering to the correct IP or host name refering to Mysql server, with correct username/password
2. MySql server is enabled with network access (/etc/mysql/my.cnf) and bind address as 0.0.0.0.
3. check "mysql-connector-java-5.1.18-bin.jar" (version may vary) in path: "/usr/share/java".

• If not available you can download the latest version from http://dev.mysql.com/downloads/connector/j/

• /usr/share/tomcat6/lib shall have a softlink pointing to mysql-connector-java-5.1.18-bin.jar - 
• command for softlink: ln -s /usr/share/java/mysql-connector-java-5.1.18-bin.jar mysql.jar - run this command inside /usr/share/tomcat6/lib
• when you restart the tomcat server, check the catalina.out, does it showing any errors (/var/lib/tomcat6/logs/catalina.out)

NOTE: No CLASSPATH setting is required. It can be empty.
 
4. check from mysql database side- the username/password you are using to login has GRANT permission.

5.  check from the mysql server side- the mysql port (3306- default) is opened.