Compose: pass variable to tomcat context

Open Source Projects Compose
1

I have the following problem:

I want to define an environment variable into my docker-compose.yml file as follow:

services:
  nginx:
    image: nginx:1.13
    container_name: nginx
    restart: always
    ports: 
        - "80:80"
        - "9090:9090"
    volumes: 
        - ./nginx/conf.d:/etc/nginx/conf.d
        - ./nginx/html:/usr/share/nginx/html

  webapp:
    build: WebApp
    container_name: webapp
    environment:
      - WEBAPPDB=jdbc:mysql://192.168.101.129:3306/webapp?useUnicode=true&characterEncoding=UTF-8&characterSetResults=UTF-8
    expose: 
        - "8080"
    depends_on:
        - nginx
version: '2'

the webapp application is deployed using tomcat. I would like to use the variable WEBAPPDB into the context.xml file in the following way:

<Resource
        auth="Container"
        driverClassName="com.mysql.jdbc.Driver"
        type="javax.sql.DataSource"

        initialSize="0"
        maxActive="10"
        maxIdle="5"
        maxWait="5000"
        minIdle="0"
        timeBetweenEvictionRunsMillis="34000"
        minEvictableIdleTimeMillis="55000"

        testOnBorrow="true"
        testWhileIdle="true"
        testOnReturn="false"
        validationQuery="SELECT 1 FROM dual"
        validationInterval="30000"
        removeAbandoned="true"
        removeAbandonedTimeout="10"

        name="jdbc/webapp"
        username="username"
        password="password"
        url="${WEBAPPDB}"
    />

How can I do this? thanks for you help.