Adding external resources to class-path in Tomcat 8

Question

I have a Tomcat application which needs to reference some properties files that are external to the app. Generally these are stored on a local machine at a specific place like C:\PROJECT_NAME\conf\.

In Tomcat 7 this was achievable by placing a context.xml file inside of /META-INF/ which used a VirtualWebappLoader to essentially add this location to the application classpath as follows:

<Context>
    <Loader className="org.apache.catalina.loader.VirtualWebappLoader"
        virtualClasspath="/PROJECT_NAME/conf"
        searchVirtualFirst="true" />
</Context>

How do I achieve this same thing in Tomcat 8?

Michael Landes · Accepted Answer · 2014-04-18T16:01:46.603

39

There is a section about this in the Tomcat 8 migration guide which will direct you to use a resources configuration

In particular, you will be creating a WebResourceRoot object which contains the following text in its description.

VirtualWebappLoader - Replaced by Pre- and Post-Resources mapped to WEB-INF/lib and WEB-INF/classes

Your new context.xml will look something like the following:

<Context>
    <Resources className="org.apache.catalina.webresources.StandardRoot">
        <PreResources className="org.apache.catalina.webresources.DirResourceSet"
            base="C:\\PROJECT_NAME\\conf"
            internalPath="/"
            webAppMount="/WEB-INF/classes" />
    </Resources>
</Context>

edited Apr 18 '14 at 16:01

answered Apr 18 '14 at 10:48

Michael Landes

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2

I was adding in an external directory of `jar` files which I didnt want to be in the webapps lib driectory. I had to use `webAppMount="/WEB-INF/lib"` in order to get it to work. Also you can use variables in the xml such as `${catalina.base}`. – ug_ Aug 21 '15 at 11:06
Hello, Michael, I was linked here, because my post https://stackoverflow.com/q/47817600/1224441 was closed because of duplicate. But I can't figure out how to solve my problem with your reply and the links that you gave. Could you enlighten me if you have some time? Thanks. – Dec 14 '17 at 17:59

dutoitns · Answer 2 · 2016-07-23T20:33:25.890

Just another example:

Please note the comments inside and note that I used PostResources and not PreResources so that I can override classes in my current project if I'm not happy with my "util" implementation. I'm not actually sure if JarResource is treated as a "PostResource" or "PreResource" but overriding static content and classes works.

    <!--
         https://tomcat.apache.org/tomcat-8.0-doc/config/resources.html
         http://stackoverflow.com/questions/23143697/adding-external-resources-to-class-path-in-tomcat-8
         http://stackoverflow.com/questions/34515852/tomcat-7-application-migration-to-tomcat-8
         http://mikusa.blogspot.co.za/2014/07/tips-on-migrating-to-tomat-8-resources.html
    -->
    <Context path="/MY_PROJECT" docBase="/MY_PROJECT">
        <Resources className="org.apache.catalina.webresources.StandardRoot">
            <!-- Post-load the static content from my util project -->
            <PostResources className="org.apache.catalina.webresources.DirResourceSet"
                    base="/workspace/MY_UTIL_PROJECT/WebContent"
                    webAppMount="/">
            </PostResources>
            <!-- Post-load the classes from my util project -->
            <PostResources className="org.apache.catalina.webresources.DirResourceSet"
                    base="/workspace/MY_UTIL_PROJECT/WebContent/WEB-INF/classes"
                    webAppMount="/WEB-INF/classes">
            </PostResources>
            <!-- Load the JARs contained within my util project -->
            <JarResources className="org.apache.catalina.webresources.DirResourceSet"
                    base="/workspace/MY_UTIL_PROJECT/WebContent/WEB-INF/lib"
                    webAppMount="/WEB-INF/lib">
            </JarResources>
        </Resources>
    </Context>

score -1 · Answer 3 · answered Aug 30 '18 at 11:59

Just copy the property files into the Tomcat lib folder.

Or enhance conf/catalina.properties:common.loader

with a folder for the property files as described here:

How to add external resources (properties file) on to the classpath so that war can read?

Adding external resources to class-path in Tomcat 8

3 Answers3

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