Package org.apache.felix.webconsole.servlet

Class AbstractServlet

  • All Implemented Interfaces:
    jakarta.servlet.Servlet, jakarta.servlet.ServletConfig, Serializable
    public abstract class AbstractServlet
extends jakarta.servlet.http.HttpServlet
    This class can be used as a base class for a web console plugin. The plugin (servlet) needs to be registered as a servlet service with at least the label property.

    Extending this servlet is one way of providing a plugin. The other is to simply direclty implement the servlet interface. In both cases requests to resources with a path of "LABEL/res/*" are automatically handled.

    For html (content) requests, the web console automatically renders the header, footer and navigation.

    Support for Jakarta servlets requires that the Jakarta Servlet API and the Apache Felix Http Wrappers are available in the runtime.

    If you are upgrading from AbstractWebConsolePlugin there are some changes to be aware of:

    • Resources are detected via the getResource(String) method.
    • Regardless of the http method, if the corresponding doXXX method does not create a response, the renderContent(HttpServletRequest, HttpServletResponse) method is invoked.
    • If a doXXX method other than doGet wants to create a response, it must not call doGet or renderContent directly. It rather just does not create any response and returns. In this case the web console will invoke the renderContent method afterwards.
    See Also:
    ServletConstants.PLUGIN_LABEL, ServletConstants.PLUGIN_TITLE, ServletConstants.PLUGIN_CATEGORY, ServletConstants.PLUGIN_CSS_REFERENCES, Serialized Form

    • Constructor Summary

      Constructors 
      Constructor Description
      AbstractServlet()  

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      protected void doGet​(jakarta.servlet.http.HttpServletRequest request, jakarta.servlet.http.HttpServletResponse response)
      Handle get requests.
      protected URL getResource​(String path)
      Called to identify resources.
      protected RequestVariableResolver getVariableResolver​(jakarta.servlet.http.HttpServletRequest request)  
      protected String readTemplateFile​(String templateFile)
      Reads the templateFile as a resource through the class loader of this class converting the binary data into a string using UTF-8 encoding.
      void renderContent​(jakarta.servlet.http.HttpServletRequest request, jakarta.servlet.http.HttpServletResponse response)
      This method is used to render the main contents of the plugin
      static void setNoCache​(jakarta.servlet.http.HttpServletResponse response)
      Sets response headers to force the client to not cache the response sent back.
      protected void spoolResource​(jakarta.servlet.http.HttpServletRequest request, jakarta.servlet.http.HttpServletResponse response)
      If the request addresses a resource , this method serves it and returns true.

      • Methods inherited from class jakarta.servlet.http.HttpServlet

        doDelete, doHead, doOptions, doPost, doPut, doTrace, getLastModified, service, service

      • Methods inherited from class jakarta.servlet.GenericServlet

        destroy, getInitParameter, getInitParameterNames, getServletConfig, getServletContext, getServletInfo, getServletName, init, init, log, log

    • Constructor Detail

      • AbstractServlet

        public AbstractServlet()

    • Method Detail

      • getResource

        protected URL getResource​(String path)
        Called to identify resources. By default, if the path starts with "/res/" this is treated as a resource and the URL to the resource is tried to be loaded via the class loader.
        Parameters:
        path - the path
        Returns:
        the URL of the resource or null if not found.

      • doGet

        protected void doGet​(jakarta.servlet.http.HttpServletRequest request,
                     jakarta.servlet.http.HttpServletResponse response)
              throws jakarta.servlet.ServletException,
                     IOException
        Handle get requests. This method can be used to return resources, like JSON responses etc. If the plugin is serving a resource, this method call HttpServletResponse.setStatus(int). This method is also allowed to send a redirect or an error. If none of the three applies, the webconsole will call renderContent(HttpServletRequest, HttpServletResponse)
        Overrides:
        doGet in class jakarta.servlet.http.HttpServlet
        Throws:
        jakarta.servlet.ServletException
        IOException

      • renderContent

        public void renderContent​(jakarta.servlet.http.HttpServletRequest request,
                          jakarta.servlet.http.HttpServletResponse response)
                   throws jakarta.servlet.ServletException,
                          IOException
        This method is used to render the main contents of the plugin
        Parameters:
        request - The request
        response - The response
        Throws:
        jakarta.servlet.ServletException - If an error occurs
        IOException - If writing the response fails

      • spoolResource

        protected final void spoolResource​(jakarta.servlet.http.HttpServletRequest request,
                                   jakarta.servlet.http.HttpServletResponse response)
                            throws IOException
        If the request addresses a resource , this method serves it and returns true. Otherwise false is returned.

        If true is returned, the request is considered complete and request processing terminates. Otherwise request processing continues with normal plugin rendering.

        Parameters:
        request - The request object
        response - The response object
        Throws:
        IOException - If an error occurs accessing or spooling the resource.

      • readTemplateFile

        protected final String readTemplateFile​(String templateFile)
                                 throws IOException
        Reads the templateFile as a resource through the class loader of this class converting the binary data into a string using UTF-8 encoding.
        Parameters:
        templateFile - The absolute path to the template file to read.
        Returns:
        The contents of the template file as a string
        Throws:
        NullPointerException - if templateFile is null
        FileNotFoundException - If template file cannot be found
        IOException - On any other error reading the template file

      • getVariableResolver

        protected RequestVariableResolver getVariableResolver​(jakarta.servlet.http.HttpServletRequest request)

      • setNoCache

        public static final void setNoCache​(jakarta.servlet.http.HttpServletResponse response)
        Sets response headers to force the client to not cache the response sent back. This method must be called before the response is committed otherwise it will have no effect.

        This method sets the Cache-Control, Expires, and Pragma headers.

        Parameters:
        response - The response for which to set the cache prevention