Display Current Date using JSP Custom(user define) Tag

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Display Current Date using JSP Custom(user define) Tag
Posted on: June 28, 2010 at 12:00 AM

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:

Accessing all implicit variables of a JSP page, such as request, response, in, and out.
Modifying the response generated by a calling JSP page.
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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