custom variable (java)

is there any way to define my own variable? similar to %BASE_URL% and %BASE_DIR%

currently I implement IBasePathBuilder to set the BASE_URL and BASE_DIR to the users specific folder.. but I also wanted to add a new type for shared images/files.. so I was hoping to be able to define my own variable SHARED_URL and SHARED_DIR.. so I could do

<type name="Images">
    <url>%BASE_URL%images/</url>
    <directory>%BASE_DIR%images</directory>
    <maxSize>0</maxSize>
    <allowedExtensions>bmp,gif,jpeg,jpg,png</allowedExtensions>
    <deniedExtensions></deniedExtensions>
</type>
<type name="Shared Images">
    <url>%SHARED_URL%images/</url>
    <directory>%SHARED_DIR%images</directory>
    <maxSize>0</maxSize>
    <allowedExtensions>bmp,gif,jpeg,jpg,png</allowedExtensions>
    <deniedExtensions></deniedExtensions>
</type>

and in case someone is going to suggest just hard coding the path to the SHARED_URL and SHARED_DIR.. I will explain my directory structure

./company/user1/images
./company/user2/images
./company/shared/images

currently the IBasePathBuilder implementation sets the BASE_DIR to ./company/user1/

what would be really nice is to be able to define %company% and %user%.. then I could simply do

<type name="Images">
    <url>%BASE_URL%%company%/%user%/images/</url>
    <directory>%BASE_DIR%%company%/%user%/images/</directory>
    <maxSize>0</maxSize>
    <allowedExtensions>bmp,gif,jpeg,jpg,png</allowedExtensions>
    <deniedExtensions></deniedExtensions>
</type>
<type name="Shared Images">
    <url>%BASE_URL%%company%/shared/images/</url>
    <directory>%BASE_DIR%%company%/shared/images/</directory>
    <maxSize>0</maxSize>
    <allowedExtensions>bmp,gif,jpeg,jpg,png</allowedExtensions>
    <deniedExtensions></deniedExtensions>
</type>

and then I could do away with the IBasePathBuilder implementation