JSP - Tag Files

Tag Files were introduced in JSP 2.0. A Tag File is a JSP page or document designed to be used as a custom tag. The main advantage is simplicity — you can build custom tags using JSP syntax instead of writing Java classes.

Key characteristics:

• Saved with .tag extension
• Placed in /WEB-INF/tags folder
• No TLD file required (when placed in the standard location)
• Tag files are internally converted to Simple Tag Handlers by the web container
• Limited processing power — not suitable for complex business logic

3 steps to create and use a tag file:

1. Write a JSP page and save it with .tag extension
2. Place it in /WEB-INF/tags folder
3. Use taglib directive with tagdir attribute in your JSP

Project structure:

tagFileA/
├── test.jsp
└── WEB-INF/
    └── tags/
        └── mytag.tag

test.jsp:

<%@ taglib prefix="mine" tagdir="/WEB-INF/tags" %>
<h1>This is Tag File Demo Example</h1>
<mine:mytag />
<mine:mytag />

mytag.tag:

<h1>Hello....This is from the tag file</h1>

Output:

This is Tag File Demo Example
Hello....This is from the tag file
Hello....This is from the tag file

Use the attribute directive to declare attributes for tag files:

<%@ attribute name="title" required="true" rtexprvalue="true" %>

Demo — Tag file with attribute:

<%@ taglib prefix="mine" tagdir="/WEB-INF/tags" %>
<h1>Tag File with Attributes Example</h1>
<mine:mytag title="kabali" />

mytag.tag:

<%@ attribute name="title" required="true" rtexprvalue="true" %>
<h1>Hello....${title} is big flop but business is good 600Cr..</h1>

Tag file invocation can contain a body, but scripting elements are not allowed in the body.

Declaring body content:

<%@ tag body-content="tagdependent" %>

Allowed values: empty, tagdependent, scriptless. Default is scriptless.

To access the tag body inside the tag file, use <jsp:doBody/>.

Demo — Tag file with body:

<%@ taglib prefix="mine" tagdir="/WEB-INF/tags" %>

<mine:header color="red">
  This is Body of tag file
</mine:header>

header.tag:

<%@ attribute name="color" required="true" rtexprvalue="true" %>
<%@ tag body-content="tagdependent" %>
<h1> Hello....This is from the tag file<br>
  <font color="${color}"> <jsp:doBody/></font>
</h1>

The web container searches for tag files in these locations:

1. Directly or indirectly in /WEB-INF/tags folder
2. Directly or indirectly in /META-INF/tags folder present in a JAR file under /WEB-INF/lib

Directory structure example:

webapps1/
└── WEB-INF/
    ├── tags/
    │   └── MyTags/
    └── lib/
        └── MyJar.jar
            └── META-INF/
                ├── MyTld.tld
                └── tags/
                    └── MyTags/

Note: When deploying tag files in a JAR, you must write a TLD file.

To deploy tag files inside a JAR file:

Step 1 — Create the JAR structure:

durga/
├── META-INF/
│   └── MyTld.tld
└── tags/
    └── MyTags.tag

Step 2 — Create the JAR:

jar -cvf durga.jar META-INF tags

Step 3 — Place JAR in WEB-INF/lib

Step 4 — TLD file must reference the tag file path:

<taglib version="2.1">
  <tlib-version>1.2</tlib-version>

  <tag-file>
    <name>mytagfile</name>
    <path>/META-INF/tags/mytag.tag</path>
  </tag-file>

</taglib>

Usage in JSP:

<%@ taglib prefix="mine" uri="/WEB-INF/MyTld.tld" %>
<mine:mytagfile />

It is not recommended to use scripting elements in JSP. You can disable them globally using web.xml:

<web-app>
  <jsp-config>
    <jsp-property-group>
      <url-pattern>*.jsp</url-pattern>
      <scripting-invalid>true</scripting-invalid>
    </jsp-property-group>
  </jsp-config>
</web-app>

Once scripting is invalidated, any use of scripting elements in JSP causes a translation time error.

Similarly, you can disable the Expression Language globally:

<web-app>
  <jsp-config>
    <jsp-property-group>
      <url-pattern>*.jsp</url-pattern>
      <el-ignored>true</el-ignored>
    </jsp-property-group>
  </jsp-config>
</web-app>

JSP pages have 9 implicit objects automatically available: