javax.servlet.jsp.tagext.IterationTag Maven / Gradle / Ivy
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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.
*
* 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;
}