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Use and share a class in JSP pages Tag(s): Servlet/JSP


I have a class 
public class Hello {
  public String say() {
    return "Hello";
  }
}
and I need to use it in many JSP pages using 
<%= say() %>

They are many to achieve that goal :

  • Create a Java class with the method in it, compile it, and deploy the resulting .class file(s) in your webapp's WEB-INF/class directory. 
    <%
Hello h = new Hello();
out.print(h.say());
%>

  • Create a JAR file containing the .class file(s) and deploy the resulting JAR file via your webapp's WEB-INF/lib directory. 
    <%
Hello h = new Hello();
out.print(h.say());
%>

  • Create a tag library for it, deploy it via the webapp's WEB-INF/tld directory.

    TAG source code 

    package test;

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

public class HelloTag extends TagSupport  {
  public int doStartTag() throws JspException
  {
    try {
      pageContext.getOut().println("Hello");
    } catch (IOException e) {
    }

    return SKIP_BODY;
  }
}
    the resulting class should go in the WEB-INF/class directory.

    TLD configuration (in the WEB-INF/tlds as hello.tld) 

    <taglib>
  <tag>
    <name>hello</name>
    <tagclass>test.HelloTag</tagclass>
  </tag>
</taglib>
    and to use the tag 
    <%@ taglib prefix="ht" uri="WEB-INF/tlds/hello.tld" %>
...
<ht:hello/>

  • Create the desired method at the top of the page and copy it from page to page 
    <%!
    public static String say() {
      return "Hello";
    }
%>

  • Create an "include file" (say hello.inc), place the method noted above in it, and include it at the top of each JSP page 
    <%@ include file="hello.inc" %>
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