Package org.apache.taglibs.standard.tag.common.core

Class ForEachSupport

java.lang.Object

javax.servlet.jsp.tagext.TagSupport

javax.servlet.jsp.jstl.core.LoopTagSupport

org.apache.taglibs.standard.tag.common.core.ForEachSupport

All Implemented Interfaces:

java.io.Serializable, LoopTag, javax.servlet.jsp.tagext.IterationTag, javax.servlet.jsp.tagext.JspTag, javax.servlet.jsp.tagext.Tag, javax.servlet.jsp.tagext.TryCatchFinally

Direct Known Subclasses:

ForEachTag, ForEachTag

public abstract class ForEachSupport
extends LoopTagSupport

Support for tag handlers for <forEach>, the core iteration tag in JSTL 1.0. This class extends LoopTagSupport and provides ForEach-specific functionality. The rtexprvalue library and the expression-evaluating library each have handlers that extend this class.

Localized here is the logic for handling the veritable smorgasbord of types supported by <forEach>, including arrays, Collections, and others. To see how the actual iteration is controlled, review the javax.servlet.jsp.jstl.core.LoopTagSupport class instead.

See Also:

LoopTagSupport, Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
private static class	ForEachSupport.ArrayIterator	Iterator over an array, including arrays of primitive types.
private static class	ForEachSupport.DeferredIterator
private static class	ForEachSupport.EnumerationIterator	Iterator over an Enumeration.
private static class	ForEachSupport.IndexedDeferredIterator
private static class	ForEachSupport.IteratedDeferredIterator
private static class	ForEachSupport.ReadOnlyIterator
private static class	ForEachSupport.ToEndIterator	Iterator that simply counts up to 'end.' Unlike the previous implementation this does not attempt to pre-allocate an array containing all values from 0 to 'end' as that can result in excessive memory allocation for large values of 'end.' LoopTagSupport calls next() 'begin' times in order to discard the initial values, In order to maintain this contract, this implementation always starts at 0.

Field Summary

Fields

Modifier and Type	Field	Description
protected java.util.Iterator	items
protected java.lang.Object	rawItems

Fields inherited from class javax.servlet.jsp.jstl.core.LoopTagSupport

begin, beginSpecified, deferredExpression, end, endSpecified, itemId, statusId, step, stepSpecified

Fields inherited from class javax.servlet.jsp.tagext.TagSupport

id, pageContext

Fields inherited from interface javax.servlet.jsp.tagext.IterationTag

EVAL_BODY_AGAIN

Fields inherited from interface javax.servlet.jsp.tagext.Tag

EVAL_BODY_INCLUDE, EVAL_PAGE, SKIP_BODY, SKIP_PAGE

Constructor Summary

Constructors

Constructor	Description
ForEachSupport()

Method Summary

Modifier and Type	Method	Description
protected boolean	hasNext()	Returns information concerning the availability of more items over which to iterate.
private boolean	isIndexed(java.lang.Object o)
protected java.lang.Object	next()	Returns the next object over which the tag should iterate.
protected void	prepare()	Prepares for a single tag invocation.
void	release()	Releases any resources this LoopTagSupport may have (or inherit).
private java.util.Iterator	toIterator(java.lang.Object rawItems)

Methods inherited from class javax.servlet.jsp.jstl.core.LoopTagSupport

doAfterBody, doCatch, doFinally, doStartTag, getCurrent, getDelims, getLoopStatus, setVar, setVarStatus, validateBegin, validateEnd, validateStep

Methods inherited from class javax.servlet.jsp.tagext.TagSupport

doEndTag, findAncestorWithClass, getId, getParent, getValue, getValues, removeValue, setId, setPageContext, setParent, setValue

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface javax.servlet.jsp.tagext.Tag

doEndTag, getParent, setPageContext, setParent

Field Detail

items

protected java.util.Iterator items

rawItems

protected java.lang.Object rawItems

Constructor Detail

ForEachSupport

public ForEachSupport()

Method Detail

prepare

protected void prepare()
                throws javax.servlet.jsp.JspTagException

Description copied from class: LoopTagSupport

Prepares for a single tag invocation. Specifically, allows subclasses to prepare for calls to hasNext() and next(). Subclasses can assume that prepare() will be called once for each invocation of doStartTag() in the superclass.

Specified by:

prepare in class LoopTagSupport

Throws:

javax.servlet.jsp.JspTagException

toIterator

private java.util.Iterator toIterator(java.lang.Object rawItems)
                               throws javax.servlet.jsp.JspTagException

Throws:

javax.servlet.jsp.JspTagException

isIndexed

private boolean isIndexed(java.lang.Object o)

hasNext

protected boolean hasNext()
                   throws javax.servlet.jsp.JspTagException

Description copied from class: LoopTagSupport

Returns information concerning the availability of more items over which to iterate. This method must be provided by concrete subclasses of LoopTagSupport to assist the iterative logic provided by the supporting base class.

See next for more information about the purpose and expectations behind this tag.

Specified by:

hasNext in class LoopTagSupport

Returns:

true if there is at least one more item to iterate over, false otherwise

Throws:

javax.servlet.jsp.JspTagException

See Also:

LoopTagSupport.next()

next

protected java.lang.Object next()
                         throws javax.servlet.jsp.JspTagException

Description copied from class: LoopTagSupport

Returns the next object over which the tag should iterate. This method must be provided by concrete subclasses of LoopTagSupport to inform the base logic about what objects it should iterate over.

It is expected that this method will generally be backed by an Iterator, but this will not always be the case. In particular, if retrieving the next object raises the possibility of an exception being thrown, this method allows that exception to propagate back to the JSP container as a JspTagException; a standalone Iterator would not be able to do this. (This explains why LoopTagSupport does not simply call for an Iterator from its subtags.)

Specified by:

next in class LoopTagSupport

Returns:

the java.lang.Object to use in the next round of iteration

Throws:

javax.servlet.jsp.JspTagException - for other, unexpected exceptions

release

public void release()

Description copied from class: LoopTagSupport

Releases any resources this LoopTagSupport may have (or inherit).

Specified by:

release in interface javax.servlet.jsp.tagext.Tag

Overrides:

release in class LoopTagSupport