Reviews : Java Books :
Professional Java Server Programming J2EE Edition : Chapter 12

Title: Professional Java Server Programming J2EE Edition ISBN: 1861004656 US Price: $ 64.99 Canadian Price: C$ 97.95 UK Price: £ 46.99 Publication Date: September 2000 Pages: 1633 © Wrox Press Limited, US and UK.

// Populate the data store. In a real application, this data would
// be sourced from a database or another part of the application.
public NameTag() {
  infoHash.put("Rod", new PersonalInfo("Australian", "London"));
  infoHash.put("Isabelle", new PersonalInfo("French", "Gabon"));
  infoHash.put("Bob", new PersonalInfo("Australian", "Sydney"));
}
public int doStartTag() throws JspTagException {
  String nationality = "Unknown";
  String city = "Unknown";

  // Test whether this tag has an ancestor of the required type,
  // which we can use to obtain a name to lookup.
  // Note that using the findAncestorWithClass static method is more
  // flexible than using getParent(). getParent() will fail if
  // one or more tags separate this tag from the desired tag in
  // the runtime hierarchy of tag handlers.
  NameContext nameContextAncestor = (NameContext)
	TagSupport.findAncestorWithClass(this, NameContext.class);
		
  // The exception thrown here will be handled by 
  //the JSP engine as normal.
  // This will normally mean redirection to an error page.
  if (nameContextAncestor == null) {
	throw new JspTagException
	("NameTag must only be used within a NameContext tag");
}

  // If we get here, we have a valid ancestor from which 
  // we can obtain a context.
  String name = nameContextAncestor.getName();
  PersonalInfo pi = (PersonalInfo) infoHash.get(name);
 if (pi != null) {
	nationality = pi.getNationality();
	city = pi.getCity();
  }
  pageContext.setAttribute("nationality", nationality);
  pageContext.setAttribute("city", city);
  return EVAL_BODY_INCLUDE;
}


// Inner class containing additional data retrieved for each name
private class PersonalInfo {
  private String nationality;
  private String city;

  public PersonalInfo(String nationality, String city) {
	this.nationality = nationality;
	this.city = city;
  }

  public String getNationality() {
	return nationality;
  }

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