| /* |
| * 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; |
| } |