* all internal references, and preparing the PageContext for potential
     * reuse by a later invocation of initialize(). This method is typically
     * called from JspFactory.releasePageContext().
     * </p>
     *
     * <p> subclasses shall envelope this method </p>
     *
     */

    abstract public void release();

    /**
     * register the name and object specified with page scope semantics
     * 
     * @throws NullPointerException if the name or object is null
     */

    abstract public void setAttribute(String name, Object attribute);

    /**
     * register the name and object specified with appropriate scope semantics
     * 
     * @param name the name of the attribute to set
     * @param o    the object to associate with the name
     * @param scope the scope with which to associate the name/object
     * 
     * @throws NullPointerException if the name or object is null
     * @throws IllegalArgumentException if the scope is invalid
     *
     */

    abstract public void setAttribute(String name, Object o, int scope);

    /**
     * <p>return the object associated with the name in the page scope or null </p>
     *
     * @param name the name of the attribute to get
     * 
     * @throws NullPointerException if the name is null
     * @throws IllegalArgumentException if the scope is invalid
     */

    abstract public Object getAttribute(String name);

    /**
     * <p>return the object associated with the name in the specifed scope or null </p>
     *
     * @param name the name of the attribute to set
     * @param scope the scope with which to associate the name/object
     * 
     * @throws NullPointerException if the name is null
     * @throws IllegalArgumentException if the scope is invalid
     */

    abstract public Object getAttribute(String name, int scope);

    /**
     * <p>
     * Searches for the named attribute in page, request, session (if valid),
     * and application scope(s) in order and returns the value associated or
     * null.
     * </p>
     *
     * @return the value associated or null
     */

    abstract public Object findAttribute(String name);

    /**
     * remove the object reference associated with the specified name
     */

    abstract public void removeAttribute(String name);

    /**
     * remove the object reference associated with the specified name
     */

    abstract public void removeAttribute(String name, int scope);

    /**
     * @return the scope of the object associated with the name specified or 0
     */

    abstract public int getAttributesScope(String name);

    /**
     * @return an enumeration of names (java.lang.String) of all the attributes the specified scope
     */


    abstract public Enumeration getAttributeNamesInScope(int scope);

    /**
     * @return the current JspWriter stream being used for client response
     */

    abstract public JspWriter getOut();

    /**
     * @return the HttpSession for this PageContext or null
     */

    abstract public HttpSession getSession();

    /**
     * @return the Page implementation class instance (Servlet)  associated with this PageContext
     */

    abstract public Object getPage();


    /**
     * @return The ServletRequest for this PageContext
     */

    abstract public ServletRequest getRequest();

    /**
     * @return the ServletResponse for this PageContext
     */

    abstract public ServletResponse getResponse();

    /**
     * @return any exception passed to this as an errorpage
     */

    abstract public Exception getException();

    /**
     * @return the ServletConfig for this PageContext
     */

    abstract public ServletConfig getServletConfig();

    /**
     * @return the ServletContext for this PageContext
     */

    abstract public ServletContext getServletContext();

    /**
     * <p>
     * This method is used to re-direct, or "forward" the current ServletRequest and ServletResponse to another active component in the application.
     * </p>
     * <p>
     * If the <I> relativeUrlPath </I> begins with a "/" then the URL specified
     * is calculated relative to the DOCROOT of the <code> ServletContext </code>
     * for this JSP. If the path does not begin with a "/" then the URL 
     * specified is calculated relative to the URL of the request that was
     * mapped to the calling JSP.
     * </p>
     * <p>
     * It is only valid to call this method from a <code> Thread </code>
     * executing within a <code> _jspService(...) </code> method of a JSP.
     * </p>
     * <p>
     * Once this method has been called successfully, it is illegal for the
     * calling <code> Thread </code> to attempt to modify the <code>
     * ServletResponse </code> object.  Any such attempt to do so, shall result
     * in undefined behavior. Typically, callers immediately return from 
     * <code> _jspService(...) </code> after calling this method.
     * </p>
     *
     * @param relativeUrlPath specifies the relative URL path to the target resource as described above
     *
     * @throws ServletException
     * @throws IOException
     *
     * @throws IllegalArgumentException if target resource URL is unresolvable
     * @throws IllegalStateException if <code> ServletResponse </code> is not in a state where a forward can be performed
     * @throws SecurityException if target resource cannot be accessed by caller
     */

    abstract public void forward(String relativeUrlPath) throws ServletException, IOException;

    /**
     * <p>
     * Causes the resource specified to be processed as part of the current
     * ServletRequest and ServletResponse being processed by the calling Thread.
     * The output of the target resources processing of the request is written
     * directly to the ServletResponse output stream.
     * </p>
     * <p>
     * The current JspWriter "out" for this JSP is flushed as a side-effect
     * of this call, prior to processing the include.
     * </p>
     * <p>
     * If the <I> relativeUrlPath </I> begins with a "/" then the URL specified
     * is calculated relative to the DOCROOT of the <code> ServletContext </code>
     * for this JSP. If the path does not begin with a "/" then the URL 
     * specified is calculated relative to the URL of the request that was
     * mapped to the calling JSP.
     * </p>
     * <p>
     * It is only valid to call this method from a <code> Thread </code>
     * executing within a <code> _jspService(...) </code> method of a JSP.
     * </p>
     *
     * @param relativeUrlPath specifies the relative URL path to the target resource to be included
     *
     * @throws ServletException
     * @throws IOException
     *
     * @throws IllegalArgumentException if the target resource URL is unresolvable
     * @throws SecurityException if target resource cannot be accessed by caller
     *
     */

    abstract public void include(String relativeUrlPath) throws ServletException, IOException;

    /**
     * <p>
     * This method is intended to process an unhandled "page" level exception
     * by redirecting the exception to either the specified error page for this
     * JSP, or if none was specified, to perform some implementation dependent
     * action.
     * </p>
     * <p>
     * A JSP implementation class shall typically clean up any local state
     * prior to invoking this and will return immediately thereafter. It is
     * illegal to generate any output to the client, or to modify any 
     * ServletResponse state after invoking this call.
     * </p>
     *
     * @param e the exception to be handled
     *
     * @throws ServletException
     * @throws IOException
     *
     * @throws NullPointerException if the exception is null
     * @throws SecurityException if target resource cannot be accessed by caller
     */

    abstract public void handlePageException(Exception e) throws ServletException, IOException;

    /**
     * Return a new BodyContent object, save the current "out" JspWriter,
     * and update the value of the "out" attribute in the page scope
     * attribute namespace of the PageContext
     *
     * @return the new BodyContent
     */

    public BodyContent pushBody() {
        return null; // XXX to implement
    }
         

    /**
     * Return the previous JspWriter "out" saved by the matching
     * pushBody(), and update the value of the "out" attribute in
     * the page scope attribute namespace of the PageConxtext
     *
     * @return the saved JspWriter.
     */

    public JspWriter popBody() {
        return null; // XXX to implement
    }
    
}