Clash Royale CLAN TAG#URR8PPP

docker-compose: passing variable to tomcat context

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.

2 Answers
2

According to the documentation Tomcat Configuration Reference

Tomcat configuration files are formatted as schemaless XML; elements
and attributes are case-sensitive. Apache Ant-style variable
substitution is supported; a system property with the name propname
may be used in a configuration file using the syntax $propname. All
system properties are available including those set using the -D
syntax, those automatically made available by the JVM and those
configured in the $CATALINA_BASE/conf/catalina.properties file.

In order to make it work the WEBAPPDB variable in context.xml should be available as a system property. You can set the system properties in several ways (see Tomcat 7 - where do I set 'system properties'?
). In your case you could set the environment variable JAVA_OPTS in the docker-compose file:

WEBAPPDB

context.xml

JAVA_OPTS

docker-compose

environment:
- JAVA_OPTS=-DWEBAPPDB=jdbc:mysql://192.168.101.129:3306/webapp?useUnicode=true&characterEncoding=UTF-8&characterSetResults=UTF-8


Working in this way:

docker-compose.yml:

services:
webapp:
build: webapp
container_name: webapp
environment:
- JAVA_OPTS= -Ddb.url=192.168.101.129 -Ddb.port=3306 -Ddb.username=test -Ddb.password=test


Dockerfile:

FROM bp91/ubuntu16.04-tomcat7-java8

COPY webapps /tmp/webapps/

ADD tomcat/bin /opt/tomcat/bin/

RUN chmod 775 /opt/tomcat/bin/catalina.sh

RUN chown root:root /opt/tomcat/bin/catalina.sh

RUN cp -r /tmp/webapps/* /opt/tomcat/webapps/

ENV JAVA_OPTS ""

EXPOSE 8282

CMD sh /opt/tomcat/bin/catalina.sh $JAVA_OPTS && touch /opt/tomcat/logs/webapp.log && tail -f /opt/tomcat/logs/webapp.log


server.xml:

<GlobalNamingResources>
<Resource
auth="Container"
driverClassName="com.mysql.jdbc.Driver"
type="javax.sql.DataSource"
global="jdbc/webapp"

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="$db.username"
password="$db.password"
url="jdbc:mysql://$db.url:$db.port/webapp?useUnicode=true&amp;characterEncoding=UTF-8&amp;characterSetResults=UTF-8"
</GlobalNamingResources>


By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.