jakarta.servlet.jsp.tagext.IterationTag Maven / Gradle / Ivy
/*
* Copyright (c) 1997, 2020 Oracle and/or its affiliates and others.
* All rights reserved.
* 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 jakarta.servlet.jsp.tagext;
import jakarta.servlet.jsp.JspException;
/**
* The IterationTag interface extends Tag by defining one additional method that controls the reevaluation of its body.
*
*
* A tag handler that implements IterationTag is treated as one that implements Tag regarding the doStartTag() and
* doEndTag() methods. IterationTag provides a new method: doAfterBody()
.
*
*
* 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.
*
*
* Properties There are no new properties in addition to those in Tag.
*
*
* Methods There is one new methods: doAfterBody().
*
*
* Lifecycle
*
*
* 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.
*
*
*
*
*
* Empty and Non-Empty Action
*
* 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.
*
*
* 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.
*
*
* If SKIP_BODY is returned the body is not evaluated, and then doEndTag() is invoked.
*
*
* 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.
*
*
* 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.
*
*
* 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.
*
*
* 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.
*
*
* 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;
}