java.sql.SQLException: Io exception: The Network Adapter could not establish the connection

This exception can be caused by many problems such as wrong URL, wrong username/password, or the database server is not reachable from your computer. However, if you can access the database with sqlplus or other tools and checked the username/password carefully, it is most likely caused by using a wrong URL.

The basic structure of database URL is like this.

      jdbc:<vendor>:<driver type>@<database host ip address>:<port>:<database SID>

For example, an Oracle database URL could look like this: jdbc:oracle:thin:@11.08.0.123:1521:orcl

The database SID can be retrieved with the following query.

      select sys_context('userenv','instance_name') from dual;

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