pagecontextimpl.java

业界著名的tomcat服务器的最新6.0的源代码。

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.jasper.runtime;

import java.io.IOException;
import java.io.Writer;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;
import java.util.Enumeration;
import java.util.HashMap;

import javax.el.ELContext;
import javax.el.ExpressionFactory;
import javax.el.ValueExpression;
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.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspFactory;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.el.ELException;
import javax.servlet.jsp.el.ExpressionEvaluator;
import javax.servlet.jsp.el.VariableResolver;
import javax.servlet.jsp.tagext.BodyContent;

import org.apache.jasper.Constants;
import org.apache.jasper.compiler.Localizer;
import org.apache.jasper.el.ELContextImpl;
import org.apache.jasper.el.ExpressionEvaluatorImpl;
import org.apache.jasper.el.FunctionMapperImpl;
import org.apache.jasper.el.VariableResolverImpl;
import org.apache.jasper.security.SecurityUtil;
import org.apache.jasper.util.Enumerator;
import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;

/**
 * Implementation of the PageContext class from the JSP spec. Also doubles as a
 * VariableResolver for the EL.
 * 
 * @author Anil K. Vijendran
 * @author Larry Cable
 * @author Hans Bergsten
 * @author Pierre Delisle
 * @author Mark Roth
 * @author Jan Luehe
 * @author Jacob Hookom
 */
public class PageContextImpl extends PageContext {

	// Logger
	private static Log log = LogFactory.getLog(PageContextImpl.class);

	private BodyContentImpl[] outs;

	private int depth;

	// per-servlet state
	private Servlet servlet;

	private ServletConfig config;

	private ServletContext context;

	private JspApplicationContextImpl applicationContext;

	private String errorPageURL;

	// page-scope attributes
	private transient HashMap<String, Object> attributes;

	// per-request state
	private transient ServletRequest request;

	private transient ServletResponse response;

	private transient HttpSession session;
	
	private transient ELContextImpl elContext;

	private boolean isIncluded;
	
	
	// initial output stream
	private transient JspWriter out;

	private transient JspWriterImpl baseOut;

	/*
	 * Constructor.
	 */
	PageContextImpl() {
		this.outs = new BodyContentImpl[0];
		this.attributes = new HashMap<String, Object>(16);
		this.depth = -1;
	}

	public void initialize(Servlet servlet, ServletRequest request,
			ServletResponse response, String errorPageURL,
			boolean needsSession, int bufferSize, boolean autoFlush)
			throws IOException {

		_initialize(servlet, request, response, errorPageURL, needsSession,
				bufferSize, autoFlush);
	}

	private void _initialize(Servlet servlet, ServletRequest request,
			ServletResponse response, String errorPageURL,
			boolean needsSession, int bufferSize, boolean autoFlush)
			throws IOException {

		// initialize state
		this.servlet = servlet;
		this.config = servlet.getServletConfig();
		this.context = config.getServletContext();
		this.errorPageURL = errorPageURL;
		this.request = request;
		this.response = response;
		
		// initialize application context
		this.applicationContext = JspApplicationContextImpl.getInstance(context);

		// Setup session (if required)
		if (request instanceof HttpServletRequest && needsSession)
			this.session = ((HttpServletRequest) request).getSession();
		if (needsSession && session == null)
			throw new IllegalStateException(
					"Page needs a session and none is available");

		// initialize the initial out ...
		depth = -1;
		if (this.baseOut == null) {
			this.baseOut = new JspWriterImpl(response, bufferSize, autoFlush);
		} else {
			this.baseOut.init(response, bufferSize, autoFlush);
		}
		this.out = baseOut;

		// register names/values as per spec
		setAttribute(OUT, this.out);
		setAttribute(REQUEST, request);
		setAttribute(RESPONSE, response);

		if (session != null)
			setAttribute(SESSION, session);

		setAttribute(PAGE, servlet);
		setAttribute(CONFIG, config);
		setAttribute(PAGECONTEXT, this);
		setAttribute(APPLICATION, context);

		isIncluded = request.getAttribute("javax.servlet.include.servlet_path") != null;
	}

	public void release() {
		out = baseOut;
		try {
			if (isIncluded) {
				((JspWriterImpl) out).flushBuffer();
				// push it into the including jspWriter
			} else {
				// Old code:
				// out.flush();
				// Do not flush the buffer even if we're not included (i.e.
				// we are the main page. The servlet will flush it and close
				// the stream.
				((JspWriterImpl) out).flushBuffer();
			}
		} catch (IOException ex) {
            IllegalStateException ise = new IllegalStateException(Localizer.getMessage("jsp.error.flush"), ex);
            throw ise;
		} finally {
		    servlet = null;
		    config = null;
		    context = null;
		    applicationContext = null;
		    elContext = null;
		    errorPageURL = null;
		    request = null;
		    response = null;
		    depth = -1;
		    baseOut.recycle();
		    session = null;
		    attributes.clear();
        }
	}

	public Object getAttribute(final String name) {

		if (name == null) {
			throw new NullPointerException(Localizer
					.getMessage("jsp.error.attribute.null_name"));
		}

		if (SecurityUtil.isPackageProtectionEnabled()) {
			return AccessController.doPrivileged(new PrivilegedAction() {
				public Object run() {
					return doGetAttribute(name);
				}
			});
		} else {
			return doGetAttribute(name);
		}

	}

	private Object doGetAttribute(String name) {
		return attributes.get(name);
	}

	public Object getAttribute(final String name, final int scope) {

		if (name == null) {
			throw new NullPointerException(Localizer
					.getMessage("jsp.error.attribute.null_name"));
		}

		if (SecurityUtil.isPackageProtectionEnabled()) {
			return AccessController.doPrivileged(new PrivilegedAction() {
				public Object run() {
					return doGetAttribute(name, scope);
				}
			});
		} else {
			return doGetAttribute(name, scope);
		}

	}

	private Object doGetAttribute(String name, int scope) {
		switch (scope) {
		case PAGE_SCOPE:
			return attributes.get(name);

		case REQUEST_SCOPE:
			return request.getAttribute(name);

		case SESSION_SCOPE:
			if (session == null) {
				throw new IllegalStateException(Localizer
						.getMessage("jsp.error.page.noSession"));
			}
			return session.getAttribute(name);

		case APPLICATION_SCOPE:
			return context.getAttribute(name);

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

	public void setAttribute(final String name, final Object attribute) {

		if (name == null) {
			throw new NullPointerException(Localizer
					.getMessage("jsp.error.attribute.null_name"));
		}

		if (SecurityUtil.isPackageProtectionEnabled()) {
			AccessController.doPrivileged(new PrivilegedAction() {
				public Object run() {
					doSetAttribute(name, attribute);
					return null;
				}
			});
		} else {
			doSetAttribute(name, attribute);
		}
	}

	private void doSetAttribute(String name, Object attribute) {
		if (attribute != null) {
			attributes.put(name, attribute);
		} else {
			removeAttribute(name, PAGE_SCOPE);
		}
	}

	public void setAttribute(final String name, final Object o, final int scope) {

		if (name == null) {
			throw new NullPointerException(Localizer
					.getMessage("jsp.error.attribute.null_name"));
		}

		if (SecurityUtil.isPackageProtectionEnabled()) {
			AccessController.doPrivileged(new PrivilegedAction() {
				public Object run() {
					doSetAttribute(name, o, scope);
					return null;
				}
			});
		} else {
			doSetAttribute(name, o, scope);
		}

	}

	private void doSetAttribute(String name, Object o, int scope) {
		if (o != null) {
			switch (scope) {
			case PAGE_SCOPE:
				attributes.put(name, o);
				break;

			case REQUEST_SCOPE:
				request.setAttribute(name, o);
				break;

			case SESSION_SCOPE:
				if (session == null) {
					throw new IllegalStateException(Localizer
							.getMessage("jsp.error.page.noSession"));
				}
				session.setAttribute(name, o);
				break;

			case APPLICATION_SCOPE:
				context.setAttribute(name, o);
				break;

			default:
				throw new IllegalArgumentException("Invalid scope");
			}
		} else {
			removeAttribute(name, scope);
		}
	}

	public void removeAttribute(final String name, final int scope) {

		if (name == null) {
			throw new NullPointerException(Localizer
					.getMessage("jsp.error.attribute.null_name"));
		}
		if (SecurityUtil.isPackageProtectionEnabled()) {
			AccessController.doPrivileged(new PrivilegedAction() {
				public Object run() {
					doRemoveAttribute(name, scope);
					return null;
				}
			});
		} else {
			doRemoveAttribute(name, scope);
		}
	}

	private void doRemoveAttribute(String name, int scope) {
		switch (scope) {
		case PAGE_SCOPE:
			attributes.remove(name);
			break;

		case REQUEST_SCOPE:
			request.removeAttribute(name);
			break;

		case SESSION_SCOPE:
			if (session == null) {
				throw new IllegalStateException(Localizer
						.getMessage("jsp.error.page.noSession"));
			}
			session.removeAttribute(name);
			break;

		case APPLICATION_SCOPE:
			context.removeAttribute(name);
			break;

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

	public int getAttributesScope(final String name) {

		if (name == null) {
			throw new NullPointerException(Localizer
					.getMessage("jsp.error.attribute.null_name"));
		}

		if (SecurityUtil.isPackageProtectionEnabled()) {
			return ((Integer) AccessController
					.doPrivileged(new PrivilegedAction() {
						public Object run() {
							return new Integer(doGetAttributeScope(name));
						}
					})).intValue();
		} else {
			return doGetAttributeScope(name);
		}
	}

	private int doGetAttributeScope(String name) {
		if (attributes.get(name) != null)
			return PAGE_SCOPE;

		if (request.getAttribute(name) != null)
			return REQUEST_SCOPE;

		if (session != null) {
			if (session.getAttribute(name) != null)
				return SESSION_SCOPE;
		}

		if (context.getAttribute(name) != null)
			return APPLICATION_SCOPE;

		return 0;
	}

	public Object findAttribute(final String name) {
		if (SecurityUtil.isPackageProtectionEnabled()) {
			return AccessController.doPrivileged(new PrivilegedAction() {
				public Object run() {
					if (name == null) {
						throw new NullPointerException(Localizer
								.getMessage("jsp.error.attribute.null_name"));
					}

					return doFindAttribute(name);
				}
			});
		} else {
			if (name == null) {
				throw new NullPointerException(Localizer
						.getMessage("jsp.error.attribute.null_name"));
			}

			return doFindAttribute(name);
		}
	}

	private Object doFindAttribute(String name) {

		Object o = attributes.get(name);
		if (o != null)
			return o;

		o = request.getAttribute(name);
		if (o != null)
			return o;

		if (session != null) {
			o = session.getAttribute(name);
			if (o != null)
				return o;
		}