pi3pagecontext.java

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

/*____________________________________________________________________________*\
 *

 Copyright (c) 1997-2003 John Roy, Holger Zimmermann. All rights reserved.

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 *____________________________________________________________________________*|
 *
 * $Source: /cvsroot/pi3web/Pi3Web_200/Source/Servlet/org/pi3/jsp/core/Pi3PageContext.java,v $
 * $Date: 2003/05/13 18:42:20 $
 *
 Description:
	Implementation of jsp API PageContext interface.

\*____________________________________________________________________________*/
 
package org.pi3.jsp.core;

import java.io.IOException;
import java.lang.IllegalArgumentException;
import java.lang.reflect.Array;

import java.util.Enumeration;
import java.util.Hashtable;
import java.util.Vector;

import javax.servlet.Servlet;
import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.RequestDispatcher;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.PageContext;

import org.pi3.servlet.core.Pi3HttpServletRequest;
import org.pi3.servlet.core.Pi3HttpSession;

/**
 * <p>
 * A PageContext instance provides access to all the namespaces associated with
 * a JSP page, provides access to several page attributes, as well as a layer above the
 * implementation details.
 * <p>
 * An instance of an implementation dependent subclass of this abstract base
 * class is created by a JSP implementation class at the begining of it's
 * <code> _jspService() </code> method via an implementation default 
 * <code> JspFactory </code>, as follows:
 *</p>
 *<p>
 *<p>
 *<code>
 *<pre>
 * public class foo implements Servlet {
 *
 * // ...
 *
 *public void _jspService(HttpServletRequest request,
 *			HttpServletResponse response)
 *       throws IOException, ServletException {
 *
 *    JspFactory  factory     = JspFactory.getDefaultFactory();
 *    PageContext pageContext = factory.getPageContext(
					this,
					request,
					response,
					null,  // errorPageURL
					false, // needsSession
					JspWriter.DEFAULT_BUFFER,
					true   // autoFlush
			        );
 *
 *    // initialize implicit variables for scripting env ...
 *
 *    HttpSession session = pageContext.getSession();
 *    JspWriter   out     = pageContext.getOut();
 *    Object      page    = this;
 *
 *    try {
 *        // body of translated JSP here ...
 *    } catch (Exception e) {
 *        out.clear();
 *        pageContext.handlePageException(e);
 *    } finally {
 *        out.close();
 *	  factory.releasePageContext(pageContext);
 *    }
 *}
 *</pre>
 * </code>
 * </p>
 * <p>
 * The <code> PageContext </code> class is an abstract class, designed to be
 * extended to provide implementation dependent implementations thereof, by
 * conformant JSP engine runtime environments. A PageContext instance is 
 * obtained by a JSP implementation class by calling the JspFactory.getPageContext() method, and is released by calling JspFactory.releasePageContext().
 * </p>
 * <p>
 * The PageContext provides a number of facilities to the page/component author and
 * page implementor, including:
 * <td>
 * <li>a single API to manage the various scoped namespaces
 * <li>a number of convenience API's to access various public objects
 * <li>a mechanism to obtain the JspWriter for output
 * <li>a mechanism to manage session usage by the page
 * <li>a mechanism to expose page directive attributes to the scripting environment
 * <li>mechanisms to forward or include the current request to other active components in the application
 * <li>a mechanism to handle errorpage exception processing
 * </td>
 * </p>
 *
 */

public class Pi3PageContext extends PageContext {

    private Servlet srl;
	private ServletRequest req;
	private ServletResponse res;
	private String errPage;
	private boolean nSess = true;
	private JspWriter out;
	private Hashtable attr = new Hashtable();

    /**
     * <p>
     * The initialize method is called to initialize an uninitialized PageContext
     * so that it may be used by a JSP Implementation class to service an
     * incoming request and response wihtin it's _jspService() method.
     * </p>
     * <p>
     * This method is typically called from JspFactory.getPageContext() in
     * order to initialize state.
     * </p>
     *
     * @param servlet The Servlet that is associated with this PageContext
     * @param request The currently pending request for this Servlet
     * @param response The currently pending response for this Servlet
     * @param errorPageURL The value of the errorpage attribute from the page directive or null
     * @param needsSession The value of the session attribute from the page directive
     * @param bufferSize The value of the buffer attribute from the page directive
     * @param autoFlush The value of the autoflush attribute from the page directive
     *
     * @throws IOException during creation of JspWriter
     * @throws IllegalStateException if out not correctly initialized
     */
 
    public void initialize(Servlet servlet, ServletRequest request, ServletResponse response, String errorPageURL, boolean needsSession, int bufferSize, boolean autoFlush)  throws IOException, IllegalStateException, IllegalArgumentException {
        srl = servlet;
		req = request;
		res = response;
		errPage = errorPageURL;
		nSess = needsSession;
		out =  new Pi3JspWriter(res.getOutputStream(), bufferSize, autoFlush);
	}

    /**
     * <p>
     * This method shall "reset" the internal state of a PageContext, releasing
     * 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>
     *
     */

    public void release() {
        srl = null;
		req = null;
		res = null;
		errPage = null;
		nSess = true;
		out = null;
		attr = null;
	}




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

    public void setAttribute(String name, Object attribute) {
		attr.put(name, 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
     *
     */

    public void setAttribute(String name, Object o, int scope) {
		switch (scope) {
			case 1 /* PAGE_SCOPE */ :
				attr.put(name, o); break;

			case 2 /* REQUEST_SCOPE */ :
				req.setAttribute(name, o); break;

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

			case 4 /* APPLICATION_SCOPE */ :
				getServletContext().setAttribute(name, o); break;

			default: throw new IllegalArgumentException("Invalid 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
     */

    public Object getAttribute(String name) {
		return attr.get(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
     */

    public Object getAttribute(String name, int scope) {
		switch (scope) {
			case 1 /* PAGE_SCOPE */ :
				return attr.get(name);

			case 2 /* REQUEST_SCOPE */ :
				return req.getAttribute(name);

			case 3 /* SESSION_SCOPE */ :
				return (getSession() != null) ?	getSession().getValue(name) : null;

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

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




    /**
     * <p>
     * Searches for the named attribute in page, request, session (if valid),