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Display Current Date using JSP Custom(user define) Tag
Posted on: June 28, 2010 at 12:00 AM
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In this section, we will discuss about how to display current date & time using custom(user define) tag.

Display Current Date using JSP Custom(user define) Tag

In this section, we will discuss about how to display current date & time using  custom(user define) tag.

JSP Custom Tags :
  • Provide a mechanism to a Web programmer to reuse and encapsulate complex recurring code in a JSP application.

  •  Provide simplicity and reusability of Java code.

  • Enable you to perform various functions, such as:

  1. Accessing all implicit variables of a JSP page, such as request, response, in, and out.

  2.  Modifying the response generated by a calling JSP page.

  3. Initializing and instantiating a JavaBean component.
Types of Custom Tags

The various types of custom tags that you can develop in JSP are :

  • Empty tags: Refer to the custom tags that do not have any attribute or body. The following code snippet shows an empty custom tag:

  <td:welcome />

  • Tags with attributes: Refer to custom tags for which you can define attributes to customize the behavior of the custom tag. The following code snippet shows a custom tag with an attribute color:

  <td: welcome color=?blue?></td:welcome>

  •  Tags with a body: Refer to the custom tag within which you can define nested custom tags, scripting elements, actions, HTML text,   and JSP directives. The following code snippet shows a custom tag that contains a JSP scripting element as its body:

 <td: welcome>

 <%=today_date%>

 </td:welcome>

  •  Nested tags: Refer to the set of custom tags in which one custom tag encloses one or more custom tags. The following code snippet shows a nested custom tag:

 <td1:ifTag condition ?<%=eval>? >

     <td2:valueTrue>

       The expression evaluates to true

     </td2:valueTrue>

 </td1:ifTag>

Development of Custom Tag :

To develop a custom tag, you need to perform following steps:

  •  Develop a tag handler or class file(.java)

  • Develop the Tag Library Descriptor (TLD) file

  •  Include the Tag Library in a JSP page

  • Deploy the application

EXAMPLE :

In this Example, Current date & time will display using custom tag.

Tag Handler File :  Build a class that implements the javax.servlet.jsp.tagext  tag interface as follows. Compile it and place it under the web-inf/classes directory (in the appropriate package structure). 

ShowDateTag.java
package foo;

import java.io.*;

import javax.servlet.jsp.*;
import javax.servlet.jsp.tagext.*;

public class ShowDateTag implements Tag {
  
  private PageContext pageContext;
  private Tag parent;
  
  public int doStartTag() throws JspException {
    return SKIP_BODY;
  }
  
  public int doEndTag() throws JspException {
    try {
      pageContext.getOut().write("" new java.util.Date());
    catch (IOException ioe) {
      throw new JspException(ioe.getMessage());
    }
    
    return EVAL_PAGE;
  }
  
  public void release() {
  }
  
  public void setPageContext(PageContext page) {
    this.pageContext = page;
  }
  
  public void setParent(Tag tag) {
    this.parent = tag;
  }
  
  public Tag getParent() {
    return this.parent;
  }
  
}

Tag Library Descriptor (TLD) file :  Now we need to describe the tag, so create a file called "taglib.tld" and place it under the web-inf directory.

<taglib>
<tlibversion>1.0</tlibversion>
<jspversion>1.1</jspversion>
<shortname>myTag</shortname>
<uri>http://www.roseindia.net/taglib</uri>
<info>My own tag library</info>

<tag>
<name>showDate</name>
<tagclass>foo.ShowDateTag</tagclass>
<info>Show the current date</info>
</tag>

</taglib>

JSP file :

<html>

<head><title>Date tag example</title></head>

<body>
<h1><font color="red">TIME IS NOW:
<br>
<%@ taglib uri="http://www.roseindia.net/taglib" prefix="myTag" %>

<myTag:showDate/>
</font></h1>
</body>
</html>

Deployment of application (OUTPUT) :

Download Source Code

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Posted on: June 28, 2010

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