How can I configure my tomcat application using server.xml?

Question

I've got a webapp that is deployed in Tomcat.

The webapp uses a db.properties file to resolve dataSource bean properties in applicationContext.xml :

<context:property-placeholder location="file:${catalina.home}/conf/db.properties"/>

In this example db.properties file is placed in common /conf/ directory of the Tomcat.

And I want to place it not in common /conf/ , but in a separate subdirectory, like /conf/myapp/ , and myapp should be configured not in application sources, but in Tomcat settings, like server.xml .

I need it to deploy two copies of this webapp, but they should work with different databases.

How can I do this?

UPDATE

Here's my service block from server.xml

<Service name="train">
    <Connector port="8888" protocol="HTTP/1.1" connectionTimeout="20000" compression="on" compressionMinSize="2048" noCompressionUserAgents="gozilla, traviata" compressableMimeType="text/html,text/xml,text/plain,text/css,text/javascript,text/json,application/x-javascript,application/javascript,application/json"/>
    <Engine name="trainings" defaultHost="localhost">
        <Host name="localhost" appBase="webapps">
            <Context docBase="trs" path="" />              
            <Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs/train/int" prefix="access_log." suffix=".txt" pattern="%h %l %u %t &quot;%r&quot; %s %b" />
        </Host>
    </Engine>
</Service>

Answer 1

1. place <context:property-placeholder/> in applicationContext.xml
2. <Environment name="db.host" value="localhost" type="java.lang.String" override="false"/> in server.xml in Context section
3. just use ${db.host} in the application.