Interface IterationTag

All Superinterfaces:
JspTag, Tag
All Known Subinterfaces:
All Known Implementing Classes:
BodyTagSupport, TagSupport

public interface IterationTag extends Tag
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 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.

Lifecycle Details Transition Diagram for IterationTag

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.