public Decorator getDecorator(HttpServletRequest request,
    Page page) 
{
        String thisPath = request.getServletPath();
        // getServletPath() returns null unless the mapping corresponds to a servlet
        if (thisPath == null) {
            String requestURI = request.getRequestURI();
            if (request.getPathInfo() != null) {
                // strip the pathInfo from the requestURI
                thisPath = requestURI.substring(0, requestURI.indexOf(request.getPathInfo()));
            }
            else {
                thisPath = requestURI;
            }
        }
        String name = null;
        try {
            name = configLoader.getMappedName(thisPath);
        }
        catch (ServletException e) {
            e.printStackTrace();
        }
        Decorator result = getNamedDecorator(request, name);
        return result == null ? super.getDecorator(request, page) : result;
}

Retrieve com.opensymphony.module.sitemesh.Decorator based on 'pattern' tag.

 public Decorator getNamedDecorator(HttpServletRequest request,
    String name) 
{
        Decorator result = null;
        try {
            result = configLoader.getDecoratorByName(name);
        }
        catch (ServletException e) {
            e.printStackTrace();
        }
        if (result == null || (result.getRole() != null && !request.isUserInRole(result.getRole()))) {
            // if the result is null or the user is not in the role
            return super.getNamedDecorator(request, name);
        }
        else {
            return result;
        }
}

Retrieve Decorator named in 'name' attribute. Checks the role if specified.

 public  void init(Config config,
    Properties properties,
    DecoratorMapper parent) throws InstantiationException 
{
           
        super.init(config, properties, parent);
        try {
            String fileName = properties.getProperty("config", "/WEB-INF/decorators.xml");
            configLoader = new ConfigLoader(fileName, config);
        }
        catch (Exception e) {
            throw new InstantiationException(e.toString());
        }
}

Create new ConfigLoader using '/WEB-INF/decorators.xml' file.