Package org.apache.sling.api.servlets

Class SlingSafeMethodsServlet

  • All Implemented Interfaces:
    java.io.Serializable, javax.servlet.Servlet, javax.servlet.ServletConfig
    Direct Known Subclasses:
    SlingAllMethodsServlet
    public class SlingSafeMethodsServlet
extends javax.servlet.GenericServlet
    Helper base class for read-only Servlets used in Sling. This base class is actually just a better implementation of the Servlet API HttpServlet class which accounts for extensibility. So extensions of this class have great control over what methods to overwrite.

    If any of the default HTTP methods is to be implemented just overwrite the respective doXXX method. If additional methods should be supported implement appropriate doXXX methods and overwrite the mayService(SlingHttpServletRequest, SlingHttpServletResponse) method to dispatch to the doXXX methods as appropriate and overwrite the getAllowedRequestMethods(Map) to add the new method names.

    Please note, that this base class is intended for applications where data is only read. As such, this servlet by itself does not support the POST, PUT and DELETE methods. Extensions of this class should either overwrite any of the doXXX methods of this class or add support for other read-only methods only. Applications wishing to support data modification should rather use or extend the SlingAllMethodsServlet which also contains support for the POST, PUT and DELETE methods. This latter class should also be overwritten to add support for HTTP methods modifying data.

    Implementors note: The methods in this class are all declared to throw the exceptions according to the intentions of the Servlet API rather than throwing their Sling RuntimeException counter parts. This is done to ease the integration with traditional servlets.

    See Also:
    SlingAllMethodsServlet, Serialized Form

    • Constructor Detail

      • SlingSafeMethodsServlet

        public SlingSafeMethodsServlet()

    • Method Detail

      • doGet

        protected void doGet​(@NotNull
                     @NotNull SlingHttpServletRequest request,
                     @NotNull
                     @NotNull SlingHttpServletResponse response)
              throws javax.servlet.ServletException,
                     java.io.IOException
        Called by the mayService(SlingHttpServletRequest, SlingHttpServletResponse) method to handle an HTTP GET request.

        This default implementation reports back to the client that the method is not supported.

        Implementations of this class should overwrite this method with their implementation for the HTTP GET method support.

        Parameters:
        request - The HTTP request
        response - The HTTP response
        Throws:
        javax.servlet.ServletException - Not thrown by this implementation.
        java.io.IOException - If the error status cannot be reported back to the client.

      • doOptions

        protected void doOptions​(@NotNull
                         @NotNull SlingHttpServletRequest request,
                         @NotNull
                         @NotNull SlingHttpServletResponse response)
                  throws javax.servlet.ServletException,
                         java.io.IOException
        Handles the OPTIONS method by setting the HTTP Allow header on the response depending on the methods declared in this class.

        Extensions of this class should generally not overwrite this method but rather the getAllowedRequestMethods(Map) method. This method gathers all declared public and protected methods for the concrete class (upto but not including this class) and calls the getAllowedRequestMethods(Map) method with the methods gathered. The returned value is then used as the value of the Allow header set.

        Parameters:
        request - The HTTP request object. Not used.
        response - The HTTP response object on which the header is set.
        Throws:
        javax.servlet.ServletException - Not thrown by this implementation.
        java.io.IOException - Not thrown by this implementation.

      • doTrace

        protected void doTrace​(@NotNull
                       @NotNull SlingHttpServletRequest request,
                       @NotNull
                       @NotNull SlingHttpServletResponse response)
                throws javax.servlet.ServletException,
                       java.io.IOException
        Handles the TRACE method by just returning the list of all header values in the response body.

        Extensions of this class do not generally need to overwrite this method as it contains all there is to be done to the TRACE method.

        Parameters:
        request - The HTTP request whose headers are returned.
        response - The HTTP response into which the request headers are written.
        Throws:
        javax.servlet.ServletException - Not thrown by this implementation.
        java.io.IOException - May be thrown if there is an problem sending back the request headers in the response stream.

      • doGeneric

        protected void doGeneric​(@NotNull
                         @NotNull SlingHttpServletRequest request,
                         @NotNull
                         @NotNull SlingHttpServletResponse response)
                  throws javax.servlet.ServletException,
                         java.io.IOException
        Called by the service(SlingHttpServletRequest, SlingHttpServletResponse) method to handle a request for an HTTP method, which is not known and handled by this class or its extension.

        This default implementation reports back to the client that the method is not supported.

        This method should be overwritten with great care. It is better to overwrite the mayService(SlingHttpServletRequest, SlingHttpServletResponse) method and add support for any extension HTTP methods through an additional doXXX method.

        Parameters:
        request - The HTTP request
        response - The HTTP response
        Throws:
        javax.servlet.ServletException - Not thrown by this implementation.
        java.io.IOException - If the error status cannot be reported back to the client.

      • mayService

        protected boolean mayService​(@NotNull
                             @NotNull SlingHttpServletRequest request,
                             @NotNull
                             @NotNull SlingHttpServletResponse response)
                      throws javax.servlet.ServletException,
                             java.io.IOException
        Tries to handle the request by calling a Java method implemented for the respective HTTP request method.

        This base class implentation dispatches the HEAD, GET, OPTIONS and TRACE to the respective doXXX methods and returns true if any of these methods is requested. Otherwise false is just returned.

        Implementations of this class may overwrite this method but should first call this base implementation and in case false is returned add handling for any other method and of course return whether the requested method was known or not.

        Parameters:
        request - The HTTP request
        response - The HTTP response
        Returns:
        true if the requested method (request.getMethod()) is known. Otherwise false is returned.
        Throws:
        javax.servlet.ServletException - Forwarded from any of the dispatched methods
        java.io.IOException - Forwarded from any of the dispatched methods

      • handleMethodNotImplemented

        protected void handleMethodNotImplemented​(@NotNull
                                          @NotNull SlingHttpServletRequest request,
                                          @NotNull
                                          @NotNull SlingHttpServletResponse response)
                                   throws java.io.IOException
        Helper method which causes an appropriate HTTP response to be sent for an unhandled HTTP request method. In case of HTTP/1.1 a 405 status code (Method Not Allowed) is returned, otherwise a 400 status (Bad Request) is returned.
        Parameters:
        request - The HTTP request from which the method and protocol values are extracted to build the appropriate message.
        response - The HTTP response to which the error status is sent.
        Throws:
        java.io.IOException - Thrown if the status cannot be sent to the client.

      • getServletInfo

        @NotNull
public @NotNull java.lang.String getServletInfo()
        Returns the simple class name of this servlet class. Extensions of this class may overwrite to return more specific information.
        Specified by:
        getServletInfo in interface javax.servlet.Servlet
        Overrides:
        getServletInfo in class javax.servlet.GenericServlet

      • getAllowedRequestMethods

        protected java.lang.StringBuffer getAllowedRequestMethods​(java.util.Map<java.lang.String,​java.lang.reflect.Method> declaredMethods)
        Helper method called by doOptions(SlingHttpServletRequest, SlingHttpServletResponse) to calculate the value of the Allow header sent as the response to the HTTP OPTIONS request.

        This base class implementation checks whether any doXXX methods exist for GET and HEAD and returns the list of methods supported found. The list returned always includes the HTTP OPTIONS and TRACE methods.

        Implementations of this class may overwrite this method check for more methods supported by the extension (generally the same list as used in the mayService(SlingHttpServletRequest, SlingHttpServletResponse) method). This base class implementation should always be called to make sure the default HTTP methods are included in the list.

        Parameters:
        declaredMethods - The public and protected methods declared in the extension of this class.
        Returns:
        A StringBuffer containing the list of HTTP methods supported.