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. 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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.tagext; import javax.servlet.jsp.*; /** * The IterationTag interface extends Tag by defining one additional * method that controls the reevaluation of its body. * * <p> A tag handler that implements IterationTag is treated as one that * implements Tag regarding the doStartTag() and doEndTag() methods. * IterationTag provides a new method: <code>doAfterBody()</code>. * * <p> The doAfterBody() method is invoked after every body evaluation * to control whether the body will be reevaluated or not. If doAfterBody() * returns IterationTag.EVAL_BODY_AGAIN, then the body will be reevaluated. * If doAfterBody() returns Tag.SKIP_BODY, then the body will be skipped * and doEndTag() will be evaluated instead. * * <p><B>Properties</B> * There are no new properties in addition to those in Tag. * * <p><B>Methods</B> * There is one new methods: doAfterBody(). * * <p><B>Lifecycle</B> * * <p> Lifecycle details are described by the transition diagram * below. Exceptions that are thrown during the computation of * doStartTag(), BODY and doAfterBody() interrupt the execution * sequence and are propagated up the stack, unless the tag handler * implements the TryCatchFinally interface; see that interface for * details. * * <p> * <IMG src="doc-files/IterationTagProtocol.gif" * alt="Lifecycle Details Transition Diagram for IterationTag"/> * * <p><B>Empty and Non-Empty Action</B> * <p> If the TagLibraryDescriptor file indicates that the action must * always have an empty element body, by a <body-content> entry of * "empty", then the doStartTag() method must return SKIP_BODY. * * <p>Note that which methods are invoked after the doStartTag() depends on * both the return value and on if the custom action element is empty * or not in the JSP page, not on how it's declared in the TLD. * * <p> * If SKIP_BODY is returned the body is not evaluated, and then doEndTag() * is invoked. * * <p> * If EVAL_BODY_INCLUDE is returned, and the custom action element is not * empty, the body is evaluated and "passed through" to the current out, * then doAfterBody() is invoked and, after zero or more iterations, * doEndTag() is invoked. */ public interface IterationTag extends Tag { /** * Request the reevaluation of some body. * Returned from doAfterBody. * * For compatibility with JSP 1.1, the value is carefully selected * to be the same as the, now deprecated, BodyTag.EVAL_BODY_TAG, * */ public final static int EVAL_BODY_AGAIN = 2; /** * Process body (re)evaluation. This method is invoked by the * JSP Page implementation object after every evaluation of * the body into the BodyEvaluation object. The method is * not invoked if there is no body evaluation. * * <p> * If doAfterBody returns EVAL_BODY_AGAIN, a new evaluation of the * body will happen (followed by another invocation of doAfterBody). * If doAfterBody returns SKIP_BODY, no more body evaluations will occur, * and the doEndTag method will be invoked. * * <p> * If this tag handler implements BodyTag and doAfterBody returns * SKIP_BODY, the value of out will be restored using the popBody * method in pageContext prior to invoking doEndTag. * * <p> * The method re-invocations may be lead to different actions because * there might have been some changes to shared state, or because * of external computation. * * <p> * The JSP container will resynchronize the values of any AT_BEGIN and * NESTED variables (defined by the associated TagExtraInfo or TLD) after * the invocation of doAfterBody(). * * @return whether additional evaluations of the body are desired * @throws JspException if an error occurred while processing this tag */ int doAfterBody() throws JspException; }