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Tomcat example source code file (JspContextWrapper.java)

This example Tomcat source code file (JspContextWrapper.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Tomcat tags/keywords

arraylist, hashmap, http, io, ioexception, iterator, jsp, jspwriter, nullpointerexception, nullpointerexception, object, object, page_scope, page_scope, request, servlet, servletexception, string, string, util

The Tomcat JspContextWrapper.java source code

/*
 * 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.util.ArrayList;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

import javax.el.ELContext;
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.jasper.compiler.Localizer;
import org.apache.jasper.util.Enumerator;

/**
 * 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
 * @author Jacob Hookom
 */
public class JspContextWrapper extends PageContext implements VariableResolver {

	// Invoking JSP context
	private PageContext invokingJspCtxt;

	private transient HashMap<String, Object> 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 HashMap<String, Object> originalNestedVars;

	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 HashMap<String, Object>(16);
		this.aliases = aliases;

		if (nestedVars != null) {
			this.originalNestedVars = new HashMap<String, Object>(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<String> getAttributeNamesInScope(int scope) {
		if (scope == PAGE_SCOPE) {
			return new Enumerator(pageAttributes.keySet().iterator());
		}

		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 {
		ELContext ctx = this.getELContext();
		return ctx.getELResolver().getValue(ctx, null, 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;
	}

	//private ELContextImpl elContext;

	public ELContext getELContext() {
        // instead decorate!!!
        
        return this.invokingJspCtxt.getELContext();
        
        /*
		if (this.elContext != null) {
			JspFactory jspFact = JspFactory.getDefaultFactory();
			ServletContext servletContext = this.getServletContext();
			JspApplicationContextImpl jspCtx = (JspApplicationContextImpl) jspFact
					.getJspApplicationContext(servletContext);
			this.elContext = jspCtx.createELContext(this);
		}
		return this.elContext;
        */
	}
}

Other Tomcat examples (source code examples)

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