Adding the filter to your application

Import the FreeHEP Web Utils as described here. To add the filter to your web application, add the following lines to WEB-INF/web.xml in your application:

  <filter>
    <filter-name>NotAvailableFilter</filter-name>
    <filter-class>org.freehep.webutil.filter.NotAvailableFilter</filter-class>
  </filter>
  <filter-mapping>
    <filter-name>NotAvailableFilter</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>

Enabling the filter

When first installed the filter is disabled. It is possible to enable it throught a simple form that comes with the filter. The default location of this form is at the relative path /admin/available in your application's URL. The location of the filter's form can be modified via the filter's properties.

The state of the filter is controlled via the Disable Application checkbox and clicking on the Apply button. The enabled/disabled state of the filter is stored in the system preferences so that it will be preserved when stopping/starting the application.

Bypassing the filter

By pressing the Bypass button on the above form the filter will be bypassed for the current session. Multiple sessions can bypass the filter simultaneously. To stop bypassing the filter press the Stop Bypass button.

Filter redirection

When the filter is enabled, any requests from sessions that are not bypassed are redirected to a different page. The default redirection page displays the following message

where the second line is the reason for the unavailability of the application that can be entered in the filter's form above.

The redirection page can be changed via the filter's properties.

Reason

In the filter's form it is possible to specify the reason for the unavailability of the application. This reason can be set to have a default value in the filter's properties. Once provided the reason is saved in the variable nonAvailableReason at the session scope. This way it can be used in a redirection JSP page.

Password protection

By default the filter's form page is not password protected. There are two ways to protect the form:

  <security-constraint>
    <web-resource-collection>
      <web-resource-name> 
        Protected Site 
      </web-resource-name>
      <!-- This is the location of the filter's form -->
      <url-pattern> /admin/available </url-pattern>
      <!-- If you list http methods, 
            only those methods are protected -->
      <http-method> DELETE </http-method>
      <http-method> GET </http-method>
      <http-method> POST </http-method>
      <http-method> PUT </http-method>
    </web-resource-collection>
    <auth-constraint>
      <!-- Roles that have access -->
      <role-name>manager</role-name>
    </auth-constraint>
  </security-constraint>
  <login-config>
    <auth-method> BASIC </auth-method>
    <realm-name>Please enter administrator password</realm-name>
  </login-config>
  <!-- Define security roles -->
  <security-role>
    <role-name>manager</role-name>
  </security-role>

Properties

The following properties can be set in WEB-INF/classes/freehepWebapp.properties :