pagecontext.java

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    /**
     * The current value of the request object (a ServletRequest).
     *
     * @return The ServletRequest for this PageContext
     */

    abstract public ServletRequest getRequest();

    /**
     * The current value of the response object (a ServletResponse).
     *
     * @return the ServletResponse for this PageContext
     */

    abstract public ServletResponse getResponse();

    /**
     * The current value of the exception object (an Exception).
     *
     * @return any exception passed to this as an errorpage
     */

    abstract public Exception getException();

    /**
     * The ServletConfig instance.
     *
     * @return the ServletConfig for this PageContext
     */

    abstract public ServletConfig getServletConfig();

    /**
     * The ServletContext instance.
     * 
     * @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 IllegalStateException if <code> ServletResponse </code> is not 
     *     in a state where a forward can be performed
     * @throws ServletException if the page that was forwarded to throws
     *     a ServletException
     * @throws IOException if an I/O error occurred while forwarding
     */

    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 if the page that was forwarded to throws
     *     a ServletException
     * @throws IOException if an I/O error occurred while forwarding
     */
    abstract public void include(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 current JspWriter returned by a call to getOut().
     * </p>
     * <p>
     * If flush is true, The current JspWriter "out" for this JSP 
     * is flushed as a side-effect of this call, prior to processing 
     * the include.  Otherwise, the JspWriter "out" is not flushed.
     * </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
     * @param flush True if the JspWriter is to be flushed before the include,
     *     or false if not.
     *
     * @throws ServletException if the page that was forwarded to throws
     *     a ServletException
     * @throws IOException if an I/O error occurred while forwarding
     * @since 2.0
     */
    abstract public void include(String relativeUrlPath, boolean flush) 
	throws ServletException, IOException;

    /**
     * <p>
     * This method is intended to process an unhandled 'page' level
     * exception by forwarding the exception to the specified
     * error page for this JSP.  If forwarding is not possible (for
     * example because the response has already been committed), an
     * implementation dependent mechanism should be used to invoke
     * the error page (e.g. "including" the error page instead).
     *
     * <p>
     * If no error page is defined in the page, the exception should
     * be rethrown so that the standard servlet error handling
     * takes over.
     *
     * <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>
     * This method is kept for backwards compatiblity reasons.  Newly
     * generated code should use PageContext.handlePageException(Throwable).
     *
     * @param e the exception to be handled
     *
     * @throws ServletException if an error occurs while invoking the error page
     * @throws IOException if an I/O error occurred while invoking the error
     *     page
     * @throws NullPointerException if the exception is null
     *
     * @see #handlePageException(Throwable)
     */

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

    /**
     * <p>
     * This method is intended to process an unhandled 'page' level
     * exception by forwarding the exception to the specified
     * error page for this JSP.  If forwarding is not possible (for
     * example because the response has already been committed), an
     * implementation dependent mechanism should be used to invoke
     * the error page (e.g. "including" the error page instead).
     *
     * <p>
     * If no error page is defined in the page, the exception should
     * be rethrown so that the standard servlet error handling
     * takes over.
     *
     * <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>
     * 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.
     *
     * @param t the throwable to be handled
     *
     * @throws ServletException if an error occurs while invoking the error page
     * @throws IOException if an I/O error occurred while invoking the error
     *     page
     * @throws NullPointerException if the exception is null
     *
     * @see #handlePageException(Exception)
     */

    abstract public void handlePageException(Throwable t) 
        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
    }
         

    /**
     * Provides convenient access to error information.
     *
     * @return an ErrorData instance containing information about the 
     * error, as obtained from the request attributes, as per the 
     * Servlet specification.  If this is not an error page (that is,
     * if the isErrorPage attribute of the page directive is not set
     * to "true"), the information is meaningless.
     *
     * @since 2.0
     */
    public ErrorData getErrorData() {
	return new ErrorData( 
	    (Throwable)getRequest().getAttribute( "javax.servlet.error.exception" ),
	    ((Integer)getRequest().getAttribute( 
		"javax.servlet.error.status_code" )).intValue(),
	    (String)getRequest().getAttribute( "javax.servlet.error.request_uri" ),
	    (String)getRequest().getAttribute( "javax.servlet.error.servlet_name" ) );
    }
    
}