com.mysql.jdbc.CommunicationsException

[Kunal Lakhani]

I am using mysql database with a Hibernate application. Sometimes it works , but sometime, it throws following exception

DEBUG - opening JDBC connection
DEBUG - opening new JDBC connection
DEBUG - Cannot open connection [???]
com.mysql.jdbc.CommunicationsException:
Communications link failure due to underlying exception:
** BEGIN NESTED EXCEPTION **
java.net.ConnectException
MESSAGE: Connection refused: connect
STACKTRACE:
java.net.ConnectException: Connection refused: connect
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)
at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)
at java.net.Socket.connect(Socket.java:519)
at java.net.Socket.connect(Socket.java:469)
at java.net.Socket.<init>(Socket.java:366)
at java.net.Socket.<init>(Socket.java:209)
.....
** END NESTED EXCEPTION **
Last packet sent to the server was 1 ms ago.
at com.mysql.jdbc.Connection.createNewIO(Connection.java:2847)
at com.mysql.jdbc.Connection.<init>(Connection.java:1555)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285)
at java.sql.DriverManager.getConnection(DriverManager.java:582)
at java.sql.DriverManager.getConnection(DriverManager.java:154)
at org.hibernate.connection.DriverManagerConnection-
.....
at org.hibernate.jdbc.ConnectionManager.openConnection
at org.hibernate.jdbc.ConnectionManager.getConnection
at org.hibernate.jdbc.JDBCContext.connection(JDBCContext.java:142)
at org.hibernate.transaction.JDBCTransaction.begin(JDBCTransaction.java:85)
at org.hibernate.impl.SessionImpl.beginTransaction(SessionImpl.java:1354)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
WARN - SQL Error: 0, SQLState: 08S01
ERROR - Communications link failure due to underlying exception:
** BEGIN NESTED EXCEPTION **

What is the reason behind this?

[lavnish lalchandani]

strange sometimes work , sometimes doesnt ??

few questions for you

are you facing a similar issue when trying to to connect to the DataBase using a query browser ? ( like sql developer for oracle or Toad ?? ) if yes its sporadic some network error

if NOT , try to change your connection properties server name with ip address etc (ex : localhost with the ip address i,e 127.0.0.1 or computer name)

[Kunal Lakhani]

Thanks for your reply
When i login through console or phpadmin, it opens successfully

I need to change the connection properties in my hibernate cfg.xml?

[lavnish lalchandani]

yes, try changing the server name to ip address ( or vice versa )
also, does PHPAdmin always works ??

[Kunal Lakhani]

Yes, phpmyadmin always works

This is the change i have done
<property name="connection.url">jdbc:mysql://127.0.0.1:3306/smartlife</property>

But it gives the same exception

Is my url correct?

[lavnish lalchandani]

possibly last thing i can think of is
* may be a firewall issue
* may be you can try changing the port of MySQL ( as of now you are using default 3306)

[Kunal Lakhani]

Thanks for your reply lavnish lalchandani
Trying changing the port

[Kunal Lakhani]

Sorry for late response, but, now, i have found out, when this error occurs.
I am using mysql as the db.

Here is my hibernate.cfg.xml

<property name="dialect">org.hibernate.dialect.MySQLDialect</property>
<property name="connection.url">jdbc:mysql://localhost:3306/smarts</property>
<property name="connection.username">root</property>
<property name="connection.password"></property>
<property name="connection.driver_class">com.mysql.jdbc.Driver</property>
<property name="myeclipse.connection.profile">smart</property>
<property name="current_session_context_class">thread</property>

My database name is "smart". Now, when i open the mysql console, it asks for password, which by default is null. I press enter, and then use this command. "use smarts"
It gets me to smarts db.

The problem is that, when i have started all services of "WAMPSERVER", (regardless of mysql console) the error never occurs. Only when there is no WAMPSERVER working, the error occurs.
Also, when i type "127.0.0.1" in browser, it opens the WampServer. Same is the case when i type "localhost" in the browser and press enter. Is that something i need to notice?
Should i go for separate ,mysql installation?
What is the problem, and how can i solve it?