[java] Cannot create PoolableConnectionFactory

What is the problem? Can't connect to database?

   org.apache.commons.dbcp.SQLNestedException: Cannot create PoolableConnectionFactory (
            Communications link failure 
    The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.)

In my case the solution was to remove the attribute

validationQuery="select 1"

from the (Derby DB) resource tag.

This happens because firewall blocks the database connection.

Disable the firewall and then try running the program again. It worked for me... :D

The problem could be due to too many users accessing the db at the same time. Either increase number of users that can concurrently access the db or kick out existing users (or apps). Use "Show processlist;" in the host DB to check connected users;

I came across another reason, catalina.policy file, could prohibit accessing specific IP/PORT

This is a network problem. Check out your database connectivity. Either your database connection link, username and password is wrong or your database server is stopped.

I changed the driver version in pom.xml and helped me

<dependency>
    <groupId>org.postgresql</groupId>
    <artifactId>postgresql</artifactId>
    <version>42.2.2</version>
</dependency>

I had a similar error. Changing the JDBC URL to use 127.0.0.1 instead of localhost helped.

Also had tried changing entries in catalina.policy file but that did not help. The entry I changed was for - java.net.SocketPermission

Go to my.ini file at the below path in windows C:\ProgramData\MySQL\MySQL Server 8.0\my.ini

and comment the below line

#bind-address=127.0.0.1

Then restart the MySQL server and connect.

Then you would be able to connect to MySQL from other IP address/machine.

I had the same problem with localhost in the source URL. I resolved with 127.0.0.1 instead of localhost.

I encounter same problem when I setup tomcat and mysql server on VirtualBox VM using chef.

in this case, I think true problem is VirtualBox seems to assign non-localhost address to eth0 like

[vagrant@localhost webapps]$ /sbin/ifconfig
eth0      Link encap:Ethernet  HWaddr 08:00:27:60:FC:47
      inet addr:10.0.2.15  Bcast:10.0.2.255  Mask:255.255.255.0

then auto-detection feature of chef's recipe using 10.0.2.15 as mysql server bind address.

so specify bind address for node params of chef's recipe solve problem in my case. I hope this information helps people using chef with vagrant.

{
  "name" : "db",
  "default_attributes" : {
   "mysql" : {
    "bind_address" : "localhost"
    ...
   }

try

jdbc:sqlserver://hostname:port;databaseName=TEST

It worked for me after adding colon before port number instead of a comma

This is the actual cause of the problem:

Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

You have a database communication link problem. Make sure that your application have network access to your database (and the firewall isn't blocking ports to your database).

If you use apache tomcat 8.0 version, instead of it, use tomcat 7.0 I had tried localhost to 127.0.0.1 and power off firewall but not working, but use tomcat 7.0 and now working

This specific issue may arise in localhost also. We cannot rule out this is because network issue or internet connectivity issue. This issue will come even though all the database connection properties are correct.

I have faced the same issue when i have used host name. Instead use ip address. It will get resolved.

Here it was caused by avast antivirus. You can disable the avast firewall and let only windows firewall active.