pi3pagecontext.java

mini http server,可以集成嵌入到程序中,实现简单的web功能

     * and application scope(s) in order and returns the value associated or
     * null.
     * </p>
     *
     * @return the value associated or null
     */

    public Object findAttribute(String name) {
		Object o = attr.get(name);
		if (o != null) return o;
		
		o = req.getAttribute(name);
		if (o != null) return o;

		o = (getSession() != null) ? getSession().getValue(name) : null;
		if (o != null) return o;
		
		return getServletContext().getAttribute(name);
	};




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

    public void removeAttribute(String name) {
		attr.remove(name);
	};




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

    public void removeAttribute(String name, int scope) {
		switch (scope) {
			case 1 /* PAGE_SCOPE */ :
				attr.remove(name); break;

			case 2 /* REQUEST_SCOPE */ :
				((Pi3HttpServletRequest)req).removeAttribute(name); break;

			case 3 /* SESSION_SCOPE */ :
				if (getSession() != null) getSession().removeValue(name); break;

			case 4 /* APPLICATION_SCOPE */ :
				getServletContext().removeAttribute(name); break;

			default: throw new IllegalArgumentException("Invalid scope.");
		};
	};




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

    public int getAttributesScope(String name) {
		if (attr.get(name) != null) return PageContext.PAGE_SCOPE;
		if (req.getAttribute(name) != null) return PageContext.REQUEST_SCOPE;
		if ((getSession() != null) && (getSession().getValue(name) != null)) return PageContext.SESSION_SCOPE;
		if (getServletContext().getAttribute(name) != null) return PageContext.APPLICATION_SCOPE;
		return 0;
	};




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

    public Enumeration getAttributeNamesInScope(int scope) {
		switch (scope) {
			case 1 /* PAGE_SCOPE */ :
				return attr.keys();

			case 2 /* REQUEST_SCOPE */ :
				return ((Pi3HttpServletRequest)req).getAttributeNames();

			case 3 /* SESSION_SCOPE */ :

				/* This is what you can do with Servlet API 2.1 */
/*				if (getSession() != null) {
					String [] names = getSession().getValueNames();
					Vector v = new Vector();
					for (int i = 0; i < Array.getLength(names);) v.add(names[i++]);
					return v.elements();
				} else {
					return new Vector().elements();
				};
*/
				if (getSession() != null) {
					return ((Pi3HttpSession)getSession()).getPi3ValueNames();
				} else {
					return new Vector().elements();
				};

			case 4 /* APPLICATION_SCOPE */ :
				return getServletContext().getAttributeNames();

			default: throw new IllegalArgumentException("Invalid scope.");
		};
	};




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

    public JspWriter getOut() { return out; }




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

    public HttpSession getSession() { 
	    return nSess ? ((HttpServletRequest)req).getSession(true) : null;
	}




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

    public Object getPage() { return srl; }




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

    public ServletRequest getRequest() { return req; } 




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

    public ServletResponse getResponse() { return res; }




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

    public Exception getException() {
		return (Exception)getRequest().getAttribute("javax.servlet.jsp.jspException");
	};




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

    public ServletConfig getServletConfig() { return srl.getServletConfig(); };




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

    public ServletContext getServletContext() { return srl.getServletConfig().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
     */

    public void forward(String relativeUrlPath) throws ServletException, IOException {
		RequestDispatcher dsp = getServletContext().getRequestDispatcher(relativeUrlPath);
		if (dsp != null) {
			dsp.forward(req, res);
		} else {
			throw new IllegalArgumentException("Target resource URL is unresolvable.");
		};
	};




    /**
     * <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
     *
     */

    public void include(String relativeUrlPath) throws ServletException, IOException {
		RequestDispatcher dsp = getServletContext().getRequestDispatcher(relativeUrlPath);
		if (dsp != null) {
			dsp.include(req, res);
		} else {
			throw new IllegalArgumentException("Target resource URL is unresolvable.");
		};
	};




    /**
     * <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
     */

    public void handlePageException(Exception e) throws ServletException, IOException {
		
		if (errPage != null) forward(errPage); 
	};
}