<?xml version="1.0" encoding="UTF-8"?>
<Context  path="/mo"  >
   
    <Resources className="org.apache.catalina.webresources.StandardRoot">
        <PostResources className="org.apache.catalina.webresources.DirResourceSet"
                       base="c:\Catalina\mo\full"
                       webAppMount="/dataFiles" />
    </Resources>
  
</Context>

<?xml version="1.0" encoding="UTF-8"?>
<Context  path="/mo"  >
   
    <Resources className="org.apache.catalina.webresources.StandardRoot">
        <PostResources className="org.apache.catalina.webresources.DirResourceSet"
                       base="c:\Catalina\mo\full"
                       webAppMount="/dataFiles" />
<!--        
        <PostResources className="org.apache.catalina.webresources.DirResourceSet"
                       base="/user/local" 
                       webAppMount="/dataFiles1" internalPath="/" />
-->
    </Resources>
  
</Context>

Tomcat tomcat = new Tomcat();
        tomcat.setPort(8080);
        String webappDirLocation = "/C:\\Catalina\\conf\\Catalina\\localhost";
        StandardContext ctx = (StandardContext) tomcat.addWebapp(webappDirLocation, "mo");

        WebResourceRoot resources = new StandardRoot(ctx);
        resources.addPreResources(new DirResourceSet(resources, "/dataFiles", "c:\\Catalina\\mo\\full", "/"));
        ctx.setResources(resources);

Attribute	Description
base	
Identifies where the resources to be used are located. This attribute is required by the org.apache.catalina.WebResourceSet
implementations provided by Tomcat and should specify the absolute path to the file,  directory  or JAR where the resources are located.
 Custom implementations may not require it. 

org.apache.catalina.webresources.DirResourceSet