Class 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, 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
    • 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