Java tutorial
/* * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER. * * Copyright (c) 1997-2010 Oracle and/or its affiliates. All rights reserved. * * The contents of this file are subject to the terms of either the GNU * General Public License Version 2 only ("GPL") or the Common Development * and Distribution License("CDDL") (collectively, the "License"). You * may not use this file except in compliance with the License. You can * obtain a copy of the License at * https://glassfish.dev.java.net/public/CDDL+GPL_1_1.html * or packager/legal/LICENSE.txt. See the License for the specific * language governing permissions and limitations under the License. * * When distributing the software, include this License Header Notice in each * file and include the License file at packager/legal/LICENSE.txt. * * GPL Classpath Exception: * Oracle designates this particular file as subject to the "Classpath" * exception as provided by Oracle in the GPL Version 2 section of the License * file that accompanied this code. * * Modifications: * If applicable, add the following below the License Header, with the fields * enclosed by brackets [] replaced by your own identifying information: * "Portions Copyright [year] [name of copyright owner]" * * Contributor(s): * If you wish your version of this file to be governed by only the CDDL or * only the GPL Version 2, indicate your decision by adding "[Contributor] * elects to include this software in this distribution under the [CDDL or GPL * Version 2] license." If you don't indicate a single choice of license, a * recipient has the option to distribute your version of this file under * either the CDDL, the GPL Version 2 or to extend the choice of license to * its licensees as provided above. However, if you add GPL Version 2 code * and therefore, elected the GPL Version 2 license, then the option applies * only if the new code is made subject to such option by the copyright * holder. * * * This file incorporates work covered by the following copyright and * permission notice: * * Copyright 2004 The Apache Software Foundation * * Licensed 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 javax.servlet.jsp; import javax.el.ELResolver; import javax.el.ExpressionFactory; import javax.el.ELContextListener; /** * Stores application-scoped information relevant to JSP containers. * * <p>The JSP container must create a single instance of * <code>JspApplicationContext</code> for each * <code>ServletContext</code> instance.</p> * * <p>An instance of <code>JspApplicationContext</code> is obtained by * invoking the static {@link JspFactory#getJspApplicationContext} method, * passing the <code>ServletContext</code> of the corresponding web * application.</p> * * <p>The <code>JspApplicationContext</code> provides the following services * to JSP applications: * <ul> * <li>Allows registration of <code>ELResolver</code>s, which are used to * resolve variables in EL expressions contained in JSP pages and * tag files.</li> * <li>Provides an instance of <code>ExpressionFactory</code> for those * applications or frameworks that need to perform programmatic * evaluation of EL expressions instead of allowing the JSP * container to do it for them.</li> * <li>Allows the attachment of <code>ELContextListener</code> instances * for notification whenever a new <code>ELContext</code> is created. * This is necessary when an application wishes to make custom * context objects available to their pluggable * <code>ELResolver</code>s.</li> * </ul> * </p> * * @see javax.servlet.ServletContext * @see JspFactory * @see javax.el.ELResolver * @see javax.el.ExpressionFactory * @see javax.el.ELContextListener * @since JSP 2.1 */ public interface JspApplicationContext { /** * Adds an <code>ELResolver</code> to affect the way EL variables * and properties are resolved for EL expressions appearing in JSP pages * and tag files. * * <p>For example, in the EL expression ${employee.lastName}, an * <code>ELResolver</code> determines what object "employee" * references and how to find its "lastName" property.</p> * * <p>When evaluating an expression, the JSP container will consult a * set of standard resolvers as well as any resolvers registered via * this method. The set of resolvers are consulted in the following * order: * <ul> * <li>{@link javax.servlet.jsp.el.ImplicitObjectELResolver}</li> * <li><code>ELResolver</code>s registered via this method, in the * order in which they are registered.</li> * <li>{@link javax.el.MapELResolver}</li> * <li>{@link javax.el.ListELResolver}</li> * <li>{@link javax.el.ArrayELResolver}</li> * <li>{@link javax.el.BeanELResolver}</li> * <li>{@link javax.servlet.jsp.el.ScopedAttributeELResolver}</li> * </ul></p> * * <p>It is illegal to register an <code>ELResolver</code> after the * application has received any request from the client. If an * attempt is made to register an <code>ELResolver</code> after that time, * an <code>IllegalStateException</code> is thrown.</p> * This restriction is * in place to allow the JSP container to optimize for the common * case where no additional <code>ELResolver</code>s are in the chain, * aside from the standard ones. It is permissible to add * <code>ELResolver</code>s before or after initialization to * a <code>CompositeELResolver</code> that is already in the chain.</p> * * <p>It is not possible to remove an <code>ELResolver</code> registered * with this method, once it has been registered.</p> * * @param resolver The new <code>ELResolver</code> * @throws IllegalStateException if an attempt is made to * call this method after all <code>ServletContextListener</code>s * have had their <code>contextInitialized</code> methods invoked. */ public void addELResolver(ELResolver resolver); /** * Returns a factory used to create <code>ValueExpression</code>s and * <code>MethodExpression</code>s so that EL expressions can be * parsed and evaluated. * * @return A concrete implementation of the * an <code>ExpressionFactory</code>. */ public ExpressionFactory getExpressionFactory(); /** * Registers a <code>ELContextListener</code>s so that context objects * can be added whenever a new <code>ELContext</code> is created. * * <p>At a minimum, the <code>ELContext</code> objects created will * contain a reference to the <code>JspContext</code> for this request, * which is added by the JSP container. * This is sufficient for all the * default <code>ELResolver</code>s listed in {@link #addELResolver}. * Note that <code>JspContext.class</code> is used as the key to ELContext.putContext() * for the <code>JspContext</code> object reference.</p> * * <p>This method is generally used by frameworks and applications that * register their own <code>ELResolver</code> that needs context other * than <code>JspContext</code>. The listener will typically add the * necessary context to the <code>ELContext</code> provided in the * event object. Registering a listener that adds context allows the * <code>ELResolver</code>s in the stack to access the context they * need when they do a resolution.</p> * * @param listener The listener to be notified when a new * <code>ELContext</code> is created. */ public void addELContextListener(ELContextListener listener); }