Java tutorial
/* * $Header: /home/cvs/jakarta-tomcat-jasper/jasper2/src/share/org/apache/jasper/runtime/JspContextWrapper.java,v 1.20 2003/09/02 21:39:59 remm Exp $ * $Revision: 1.20 $ * $Date: 2003/09/02 21:39:59 $ * * ==================================================================== * * The Apache Software License, Version 1.1 * * Copyright (c) 1999 The Apache Software Foundation. All rights * reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in * the documentation and/or other materials provided with the * distribution. * * 3. The end-user documentation included with the redistribution, if * any, must include the following acknowlegement: * "This product includes software developed by the * Apache Software Foundation (http://www.apache.org/)." * Alternately, this acknowlegement may appear in the software itself, * if and wherever such third-party acknowlegements normally appear. * * 4. The names "The Jakarta Project", "Tomcat", and "Apache Software * Foundation" must not be used to endorse or promote products derived * from this software without prior written permission. For written * permission, please contact apache@apache.org. * * 5. Products derived from this software may not be called "Apache" * nor may "Apache" appear in their names without prior written * permission of the Apache Group. * * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * ==================================================================== * * This software consists of voluntary contributions made by many * individuals on behalf of the Apache Software Foundation. For more * information on the Apache Software Foundation, please see * <http://www.apache.org/>. * */ package org.apache.jasper.runtime; import java.io.IOException; import java.io.Writer; import java.util.ArrayList; import java.util.Enumeration; import java.util.Hashtable; import java.util.Iterator; import java.util.Map; 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.HttpSession; import javax.servlet.jsp.JspContext; 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 javax.servlet.jsp.tagext.VariableInfo; import org.apache.commons.el.VariableResolverImpl; import org.apache.jasper.compiler.Localizer; /** * Implementation of a JSP Context Wrapper. * * The JSP Context Wrapper is a JspContext created and maintained by a tag * handler implementation. It wraps the Invoking JSP Context, that is, the * JspContext instance passed to the tag handler by the invoking page via * setJspContext(). * * @author Kin-man Chung * @author Jan Luehe */ public class JspContextWrapper extends PageContext implements VariableResolver { // Invoking JSP context private PageContext invokingJspCtxt; private transient Hashtable pageAttributes; // ArrayList of NESTED scripting variables private ArrayList nestedVars; // ArrayList of AT_BEGIN scripting variables private ArrayList atBeginVars; // ArrayList of AT_END scripting variables private ArrayList atEndVars; private Map aliases; private Hashtable originalNestedVars; /** * The variable resolver, for evaluating EL expressions. */ private VariableResolverImpl variableResolver = new VariableResolverImpl(this); public JspContextWrapper(JspContext jspContext, ArrayList nestedVars, ArrayList atBeginVars, ArrayList atEndVars, Map aliases) { this.invokingJspCtxt = (PageContext) jspContext; this.nestedVars = nestedVars; this.atBeginVars = atBeginVars; this.atEndVars = atEndVars; this.pageAttributes = new Hashtable(16); this.aliases = aliases; if (nestedVars != null) { this.originalNestedVars = new Hashtable(nestedVars.size()); } syncBeginTagFile(); } public void initialize(Servlet servlet, ServletRequest request, ServletResponse response, String errorPageURL, boolean needsSession, int bufferSize, boolean autoFlush) throws IOException, IllegalStateException, IllegalArgumentException { } public Object getAttribute(String name) { if (name == null) { throw new NullPointerException(Localizer.getMessage("jsp.error.attribute.null_name")); } return pageAttributes.get(name); } public Object getAttribute(String name, int scope) { if (name == null) { throw new NullPointerException(Localizer.getMessage("jsp.error.attribute.null_name")); } if (scope == PAGE_SCOPE) { return pageAttributes.get(name); } return invokingJspCtxt.getAttribute(name, scope); } public void setAttribute(String name, Object value) { if (name == null) { throw new NullPointerException(Localizer.getMessage("jsp.error.attribute.null_name")); } if (value != null) { pageAttributes.put(name, value); } else { removeAttribute(name, PAGE_SCOPE); } } public void setAttribute(String name, Object value, int scope) { if (name == null) { throw new NullPointerException(Localizer.getMessage("jsp.error.attribute.null_name")); } if (scope == PAGE_SCOPE) { if (value != null) { pageAttributes.put(name, value); } else { removeAttribute(name, PAGE_SCOPE); } } else { invokingJspCtxt.setAttribute(name, value, scope); } } public Object findAttribute(String name) { if (name == null) { throw new NullPointerException(Localizer.getMessage("jsp.error.attribute.null_name")); } Object o = pageAttributes.get(name); if (o == null) { o = invokingJspCtxt.getAttribute(name, REQUEST_SCOPE); if (o == null) { if (getSession() != null) { o = invokingJspCtxt.getAttribute(name, SESSION_SCOPE); } if (o == null) { o = invokingJspCtxt.getAttribute(name, APPLICATION_SCOPE); } } } return o; } public void removeAttribute(String name) { if (name == null) { throw new NullPointerException(Localizer.getMessage("jsp.error.attribute.null_name")); } pageAttributes.remove(name); invokingJspCtxt.removeAttribute(name, REQUEST_SCOPE); if (getSession() != null) { invokingJspCtxt.removeAttribute(name, SESSION_SCOPE); } invokingJspCtxt.removeAttribute(name, APPLICATION_SCOPE); } public void removeAttribute(String name, int scope) { if (name == null) { throw new NullPointerException(Localizer.getMessage("jsp.error.attribute.null_name")); } if (scope == PAGE_SCOPE) { pageAttributes.remove(name); } else { invokingJspCtxt.removeAttribute(name, scope); } } public int getAttributesScope(String name) { if (name == null) { throw new NullPointerException(Localizer.getMessage("jsp.error.attribute.null_name")); } if (pageAttributes.get(name) != null) { return PAGE_SCOPE; } else { return invokingJspCtxt.getAttributesScope(name); } } public Enumeration getAttributeNamesInScope(int scope) { if (scope == PAGE_SCOPE) { return pageAttributes.keys(); } return invokingJspCtxt.getAttributeNamesInScope(scope); } public void release() { invokingJspCtxt.release(); } public JspWriter getOut() { return invokingJspCtxt.getOut(); } public HttpSession getSession() { return invokingJspCtxt.getSession(); } public Object getPage() { return invokingJspCtxt.getPage(); } public ServletRequest getRequest() { return invokingJspCtxt.getRequest(); } public ServletResponse getResponse() { return invokingJspCtxt.getResponse(); } public Exception getException() { return invokingJspCtxt.getException(); } public ServletConfig getServletConfig() { return invokingJspCtxt.getServletConfig(); } public ServletContext getServletContext() { return invokingJspCtxt.getServletContext(); } public void forward(String relativeUrlPath) throws ServletException, IOException { invokingJspCtxt.forward(relativeUrlPath); } public void include(String relativeUrlPath) throws ServletException, IOException { invokingJspCtxt.include(relativeUrlPath); } public void include(String relativeUrlPath, boolean flush) throws ServletException, IOException { include(relativeUrlPath, false); // XXX } public VariableResolver getVariableResolver() { return this; } public BodyContent pushBody() { return invokingJspCtxt.pushBody(); } public JspWriter pushBody(Writer writer) { return invokingJspCtxt.pushBody(writer); } public JspWriter popBody() { return invokingJspCtxt.popBody(); } public ExpressionEvaluator getExpressionEvaluator() { return invokingJspCtxt.getExpressionEvaluator(); } public void handlePageException(Exception ex) throws IOException, ServletException { // Should never be called since handleException() called with a // Throwable in the generated servlet. handlePageException((Throwable) ex); } public void handlePageException(Throwable t) throws IOException, ServletException { invokingJspCtxt.handlePageException(t); } /** * VariableResolver interface */ public Object resolveVariable(String pName) throws ELException { return variableResolver.resolveVariable(pName); } /** * Synchronize variables at begin of tag file */ public void syncBeginTagFile() { saveNestedVariables(); } /** * Synchronize variables before fragment invokation */ public void syncBeforeInvoke() { copyTagToPageScope(VariableInfo.NESTED); copyTagToPageScope(VariableInfo.AT_BEGIN); } /** * Synchronize variables at end of tag file */ public void syncEndTagFile() { copyTagToPageScope(VariableInfo.AT_BEGIN); copyTagToPageScope(VariableInfo.AT_END); restoreNestedVariables(); } /** * Copies the variables of the given scope from the virtual page scope of * this JSP context wrapper to the page scope of the invoking JSP context. * * @param scope variable scope (one of NESTED, AT_BEGIN, or AT_END) */ private void copyTagToPageScope(int scope) { Iterator iter = null; switch (scope) { case VariableInfo.NESTED: if (nestedVars != null) { iter = nestedVars.iterator(); } break; case VariableInfo.AT_BEGIN: if (atBeginVars != null) { iter = atBeginVars.iterator(); } break; case VariableInfo.AT_END: if (atEndVars != null) { iter = atEndVars.iterator(); } break; } while ((iter != null) && iter.hasNext()) { String varName = (String) iter.next(); Object obj = getAttribute(varName); varName = findAlias(varName); if (obj != null) { invokingJspCtxt.setAttribute(varName, obj); } else { invokingJspCtxt.removeAttribute(varName, PAGE_SCOPE); } } } /** * Saves the values of any NESTED variables that are present in * the invoking JSP context, so they can later be restored. */ private void saveNestedVariables() { if (nestedVars != null) { Iterator iter = nestedVars.iterator(); while (iter.hasNext()) { String varName = (String) iter.next(); varName = findAlias(varName); Object obj = invokingJspCtxt.getAttribute(varName); if (obj != null) { originalNestedVars.put(varName, obj); } } } } /** * Restores the values of any NESTED variables in the invoking JSP * context. */ private void restoreNestedVariables() { if (nestedVars != null) { Iterator iter = nestedVars.iterator(); while (iter.hasNext()) { String varName = (String) iter.next(); varName = findAlias(varName); Object obj = originalNestedVars.get(varName); if (obj != null) { invokingJspCtxt.setAttribute(varName, obj); } else { invokingJspCtxt.removeAttribute(varName, PAGE_SCOPE); } } } } /** * Checks to see if the given variable name is used as an alias, and if so, * returns the variable name for which it is used as an alias. * * @param varName The variable name to check * @return The variable name for which varName is used as an alias, or * varName if it is not being used as an alias */ private String findAlias(String varName) { if (aliases == null) return varName; String alias = (String) aliases.get(varName); if (alias == null) { return varName; } return alias; } }