error communication link failure db database JDBC : Support

Reason: There are various reasons due to which a "communication link failure" exception can occur.

Some of the reasons are listed below:

Any network connectivity issues.
The IP address or hostname in the JDBC URL is wrong.
Hostname in JDBC URL is not recognized by the local DNS server.
Port number is missing or wrong in JDBC URL.
The database server is down.
The database server does not accept TCP/IP connections.
The database server has run out of connections.
Something in between Java and DB is blocking connections, e.g. a firewall or proxy.
A non-compatible version of the JDBC driver is used.
An incorrect JDBC driver from a vendor.

Solution:

Here's a compilation of a list of solutions below, one of the following solutions can help to resolve the issue:

Verify and test the connection with ping.
Refresh DNS or use an IP address in JDBC URL instead.
Verify if mysqld is started without the --skip-networking option.
Restart the database service.
If you are using a custom code/script, then check how you are closing the database connection. If required, kindly fix your code.
Disable firewall and/or configure firewall/proxy to allow/forward the port.
Try a different version of JDBC driver.
Try a JDBC driver from another vendor.
changing "bind-address" attribute

Uncomment "bind-address" attribute or change it to one of the following IPs:
bind-address="127.0.0.1"
or,
bind-address="0.0.0.0"

If there is a "skip-networking" line in your MySQL config file, make it comment by adding "#" sign at the beginning of that line.

increase "wait_timeout", "interactive_timeout", "connect_timeout" values in mysql db setting file my.ini

Add these lines to the MySQL config file:
wait_timeout = number (wait_timeout=2814400)
interactive_timeout = number
connect_timeout = number

This could be avoided by using one of two approaches:

In a connection string, use 127.0.0.1 instead of localhost to avoid localhost being translated to :::1
Run java with the option -Djava.net.preferIPv4Stack=true to force java to use IPv4 instead of IPv6. On Linux, this could also be achieved by adding an entry in /etc/profile or /home/username/.bashrc file:

export _JAVA_OPTIONS="-Djava.net.preferIPv4Stack=true"

Append this code to your connection string at the end:

&autoReconnect=true&failOverReadOnly=false&maxReconnects=10

Notes:

For the solutions that you need to change the MySQL settings, you can refer to the following files:

Linux: /etc/mysql/my.cnf or /etc/my.cnf (depending on the Linux distribution and MySQL package used)
Windows: C:**ProgramData**\MySQL\MySQL Server 5.6\my.ini (Notice it's ProgramData, not Program Files)

References:

For further read, please refer to these articles:

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