Q: With MySQL, I got java.lang.StackOverflowError.

A: There is a bug in MySql's jdbc driver, version 3.0.7,
   it has an infinite loop problem:

   java.lang.StackOverflowError
	at java.net.SocketOutputStream.socketWrite0(Native Method)
	at java.net.SocketOutputStream.socketWrite(SocketOutputStream.java:92)
	at java.net.SocketOutputStream.write(SocketOutputStream.java:136)
	at java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:69)
	at java.io.BufferedOutputStream.flush(BufferedOutputStream.java:127)
	at com.mysql.jdbc.MysqlIO.send(MysqlIO.java:1478)
	at com.mysql.jdbc.MysqlIO.send(MysqlIO.java:1405)
	at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:879)
	at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:945)
	at com.mysql.jdbc.MysqlIO.sqlQuery(MysqlIO.java:917)
	at com.mysql.jdbc.Connection.execSQL(Connection.java:1841)
	at com.mysql.jdbc.Connection.execSQL(Connection.java:1787)
	at com.mysql.jdbc.Connection.execSQL(Connection.java:1768)
	at com.mysql.jdbc.Connection.rollbackNoChecks(Connection.java:1369)
	at com.mysql.jdbc.Connection.rollback(Connection.java:1356)
	at com.mysql.jdbc.Connection.close(Connection.java:1028)
	at com.mysql.jdbc.Connection.cleanup(Connection.java:2050)
	at com.mysql.jdbc.Connection.execSQL(Connection.java:1853)
	at com.mysql.jdbc.Connection.execSQL(Connection.java:1787)
	at com.mysql.jdbc.Connection.execSQL(Connection.java:1768)
	at com.mysql.jdbc.Connection.rollbackNoChecks(Connection.java:1369)

This bug was fixed in mysql jdbc driver version 3.0.8: mysql-connector-java-3.0.8-stable-bin.jar
Make sure there is no version 3.0.7 jar in your app server's classpath.