java - Docker - Connect Apache Tomcat web server to MySQL server -

i trying connect web server runs in apache tomcat container mysql database runs container. in order using linking mechanism docker.

docker run -it --name ${container_name} --link db:db -p 8080:8080 -d tomcat 

after running container can see containers linked , environment variables exposed properly.

in order connect web application running in tomcat container database, using following configuration file:

<context>   <resource     name="jdbc/mydb"     type="javax.sql.datasource"     auth="container"     username="user"     password="password"     driverclassname="com.mysql.jdbc.driver"     url="jdbc:mysql://${db_port_3306_tcp_addr}:${db_port_3306_tcp_port}/epcis?autoreconnect=true">   </resource> </context> 

now problem can't establish connection database because environment variables exposed docker not recognized @ tomcat environment.

there way make these environment variables exposed docker visible apache tomcat environment?

could use dns declaration db , hard code reference? think /etc/hosts file updated db , it's ip address when --link it. could:

<context>   <resource     name="jdbc/mydb"     type="javax.sql.datasource"     auth="container"     username="user"     password="password"     driverclassname="com.mysql.jdbc.driver"     url="jdbc:mysql:db:3306/epcis?autoreconnect=true">   </resource> </context> 

another technique use skydns , registrator, ip , port in dns srv record.

i don't remember tomcat should have access variables. sure tomcat evaluates url definition before using it?