An error about the database connection: Communications link failure

The last packet sent successfully to the server was 0 milliseconds ago. The driver has no received any packets from the server.

It is easy to see that the database is out of the question and see if it is a path error in the Db.properties file

Db.properties in each database connection database:

SQL Server connecting to a database

Driverclassname=com.microsoft.jdbc.sqlserver.sqlserverdriver

Url=jdbc:microsoft:sqlserver://127.0.0.1:1433;databasename=mytestdb

Username=robinliu

Password=robinliu

InitialSize =2

maxactive=2

maxwait=2000

MYSQL connecting to a database

Driverclassname=com.mysql.jdbc.driver

Url=jdbc:mysql://localhost:3306/test

Username=root

Password=mysql

Initialsize=4

Maxactive =10

SQL Server 2005 connecting to a database

Driverclassname=com.microsoft.sqlserver.jdbc.sqlserverdriver

Url=jdbc:sqlserver://127.0.0.1:1433;databasename=stuinfo

Username=sa

password=1234

InitialSize =2

maxactive=100

maxwait=2000

Oracle Database connecting to a database

Database.database=oracle

Database.driverclassname = Oracle.jdbc.driver.OracleDriver

Database.password = Sinple

Database.show_sql = True

Database.url = jdbc\:oracle\:thin\: @localhost \:1521\:sinple

Database.username = Sinple

An error about the database connection: Communications link failure