code: public static String getWorkplaceExplorerLink(final CmsObject cms, final String explorerRootPath) {
  
          // split the root site:
          StringBuffer siteRoot = new StringBuffer();
          StringBuffer path = new StringBuffer('/');
          Scanner scanner = new Scanner(explorerRootPath);
          scanner.useDelimiter("/");
          int count = 0;
          while (scanner.hasNext()) {
              if (count < 2) {
                  siteRoot.append('/').append(scanner.next());
              } else {
                  if (count == 2) {
                      path.append('/');
                  }
                  path.append(scanner.next());
                  path.append('/');
              }
              count++;
          }
          String targetSiteRoot = siteRoot.toString();
          String targetVfsFolder = path.toString();
          // build the link
          StringBuilder link2Source = new StringBuilder();
          link2Source.append("/system/workplace/views/workplace.jsp?");
          link2Source.append(CmsWorkplace.PARAM_WP_EXPLORER_RESOURCE);
          link2Source.append("=");
          link2Source.append(targetVfsFolder);
          link2Source.append("&");
          link2Source.append(CmsFrameset.PARAM_WP_VIEW);
          link2Source.append("=");
          link2Source.append(
              OpenCms.getLinkManager().substituteLinkForUnknownTarget(
                  cms,
                  "/system/workplace/views/explorer/explorer_fs.jsp"));
          link2Source.append("&");
          link2Source.append(CmsWorkplace.PARAM_WP_SITE);
          link2Source.append("=");
          link2Source.append(targetSiteRoot);
  
          String result = link2Source.toString();
          result = OpenCms.getLinkManager().substituteLinkForUnknownTarget(cms, result);
          return result;
      }
docs: Creates a link for the OpenCms workplace that will reload the whole workplace, switch to the explorer view, the
  site of the given explorerRootPath and show the folder given in the explorerRootPath.
  <p>
  
  @param cms
  the cms object
  
  @param explorerRootPath
  a root relative folder link (has to end with '/').
  
  @return a link for the OpenCms workplace that will reload the whole workplace, switch to the explorer view, the
  site of the given explorerRootPath and show the folder given in the explorerRootPath.