http://jsp.totalroute.net Blog about JavaServer Page Tue, 13 Mar 2007 03:01:50 +0000 http://backend.userland.com/rss092 en Generalized iterating tags protected void clearProperties() { elements = null; c super.clearProperties(); } } class IteratorIterationSupport implements IterationSupport { d Iterator i = null; IteratorIterationSupport(Iterator i) { this.i = i; } public boolean ... http://jsp.totalroute.net/2007/03/13/generalized-iterating-tags-protected-void-clearproperties-elements/ CHAPTER 10 Iterating with tags D Override if you have additional attributes in the specialized tag (you probably do). E Override if you have additional service state in the specialized tag. Listing 10.5 shows that the general structure of IterationTagSupport is very ... http://jsp.totalroute.net/2007/03/13/generalized-iterating-tags-user-probably-disconnected-2/ Generalized iterating tags // User probably disconnected ... // Log and throw a JspTagException } if(elementsList.hasNext()) { exportVariables(); return EVAL_BODY_TAG; } return SKIP_BODY; } protected abstract void fetchIterationSupport() b throws JspException; ... http://jsp.totalroute.net/2007/03/13/generalized-iterating-tags-user-probably-disconnected/ Generalized iterating tags Listing 10.4 Source code for the generic iteration interface package book.iteration; import javax.servlet.jsp.JspException; public interface IterationSupport { public boolean hasNext() throws JspException; public Object getNext() throws JspException; } Why do we need another iteration/enumeration interface, as Java already ... http://jsp.totalroute.net/2007/03/12/generalized-iterating-tags-listing-104-source-code-for/ CHAPTER 10 Iterating with tags is custom built to handle a particular iterator type and a particular type of object in that iterator. Export a different set of JSP variables. Whenever IterationTagSupport wants to export its iterator value, it should ... http://jsp.totalroute.net/2007/03/12/generalized-iterating-tags-listing-104-source-code-for-2/ CHAPTER 10 Iterating with tags elements="1,2,3,4"> The selected item is < %= item %> Now when we execute our JSP, SimpleForeachTag will repeat its body four times (one for each string in elements ); first ... http://jsp.totalroute.net/2007/03/12/iterating-with-tags-101-to-export-the-values-2/ Iterating with tags 101 to export the values of the iterator, we ll create a TagExtraInfo class for it that will inform the runtime of this. We ll call this class ForeachTagExtraInfo. Its implementation is in listing 10.2 wherein you see that it merely notifies the JSP ... http://jsp.totalroute.net/2007/03/12/iterating-with-tags-101-to-export-the-values/ CHAPTER 10 Iterating with tags E Breaks the string list into a Java list. F Writes the results of this iteration back to the user and clears the body buffer. G If we have more elements in the list, exports a new iterator value and ... http://jsp.totalroute.net/2007/03/12/iterating-with-tags-101-protected-void-parseelements-2/ Iterating with tags 101 } protected void parseElements() throws JspException { List l = new LinkedList(); StringTokenizer st = new StringTokenizer(elements, ","); e while(st.hasMoreTokens()) { l.add(st.nextToken()); } elementsList = ... http://jsp.totalroute.net/2007/03/12/iterating-with-tags-101-protected-void-parseelements/ CHAPTER 10 Iterating with tags The selected item is < %= item %> Executing the above JSP fragment generates the following content: The selected item is 1 The selected item is 2 The selected item is 3 ... http://jsp.totalroute.net/2007/03/11/iterating-with-tags-101-to-further-illustrate-how-2/