package foo;
import java.io.IOException;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.TagSupport;

/**
MyClassicTag.java
Clasic Tag Handler by Sandeep Desai (http://www.thedesai.net/sandeep)

Pre JSP 2.0 style Tag Handlers

Tag instance maybe reused

interface JspTag

interface SimpleTag extends JspTag

interface Tag extends JspTag
  void setPageContext(PageContext)
  void setParent(Tag)
  Tag getParent()
  int doStartTag() throws JspException // SKIP_BODY, EVAL_BODY_INCLUDE
  int doEndTag() throws JspException // SKIP_PAGE, EVAL_PAGE
  void release()
 
interface IterationTag extends Tag
  int doAfterBody() throws JspException // SKIP_BODY, EVAL_BODY_AGAIN
 
interface BodyTag extends IterationTag
  void doInitBody()
  void setBodyContent(BodyContent)
 
class TagSupport implements IterationTag, Serializable
   PageContext pageContext
   static findAncestorWithClass(String name , Class)
 
class BodyTagSupport extends TagSupport implements BodyTag

Extend either TagSupport or BodyTagSupport

Classic tags lifecycle
1) Load class
2) Instantiate class with no arg constructor (container may reuse instances)
3) Call the setPageContext(PageContext)
4) If nested tag call setParent(Tag)
5) If tag has attributes call attribute setters
6) call doStartTag()
7) if tag is not declared empty in DD and tag has body
   and doStartTag() returns EVAL_BODY_INCLUDE
   then body is executed
8) if body content evaluated call doAfterBody()
9) call doEndTag()

Classic lifecycle with TagSupport
  int status = doStartTag(); // default is SKIP_BODY
  if (status == SKIP_BODY)
     doEndTag();
  if (status == EVAL_BODY_INCLUDE && !empty body) {
     do {
       evaluate body;
       status = doAfterBody();
     } while (status != SKIP_BODY);
   }
   status = doEndTag();
   if (status == EVAL_PAGE)
      evaluate rest of page;
   if (status == SKIP_PAGE)
      skip rest of page;

Classic lifecycle with BodyTagSupport
 
  int status = doStartTag(); // default is EVAL_BODY_BUFFERED
  if (status == SKIP_BODY)
     doEndTag();
  if (status == EVAL_BODY_BUFFERED && !empty body) {
     setBodyContent();
     doInitBody();
  }
  if (status == EVAL_BODY_INCLUDE && !empty body) {
     do {
       evaluate body;
       status = doAfterBody();
     } while (status != SKIP_BODY);
   }
   status = doEndTag();
    if (status == EVAL_PAGE)
       evaluate rest of page;
    if (status == SKIP_PAGE)
       skip rest of page;

*/

 
public class MyClassicTag extends TagSupport  {
  public MyClassicTag() {
    System.out.println("^^^^ MyClassicTag()");
  }
 
  // unlike Simple Tag does not throw IOException
  public int doStartTag() throws JspException {
    System.out.println("^^^^ doStartTag");
    JspWriter out = pageContext.getOut();
    try {
      out.println("MyClassicTag doStartTag() called");
      out.flush();
    } catch (IOException e) {
      throw new JspException(e);
    }
    if (showCars == null)
        return SKIP_BODY; // Don't evaluate body if one
    else {
      index = 0; // initialize here as we container may reuse instance
      // we need to duplicate this code here and in do AfterBody
      // as the body is processed between doStartTag and doAfterBody
      pageContext.setAttribute("car", cars[index]);
      ++index;
      return EVAL_BODY_INCLUDE; //
    }
  }
 
  public int doAfterBody() throws JspException {
    if (index < cars.length) {
      pageContext.setAttribute("car", cars[index]);
      ++index;
      return EVAL_BODY_AGAIN; // container will write body and call doAfterBody
    }
    else return SKIP_BODY;
  }
 
  public int doEndTag() throws JspException {
    System.out.println("^^^ doEndTag");
    JspWriter out = pageContext.getOut();
    try {
      out.println("MyClassicTag doEndTag() called");
      out.flush();
    } catch (IOException e) {
      throw new JspException(e);
    }
    return EVAL_PAGE; // evaluate rest page
                      // SKIP_PAGE like SkipPageException will not evaluate rest of page
  }
 
  public void release() { } // clean up tag
 
  public void showCars(String showCars) {
    this.showCars = showCars;
  }
 
  private String showCars;
  private String[] cars = {"Honda Accord", "Toyota Camry" };
  private int index = 0;
}