Create a JSP called "template.jsp"
Use the JSTL import tag:
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<body>
<c:import url="/WEB-INF/jsps/${content}.jsp"/>
</body>
</html>
Run all your requests through a servlet.
Always include a "content" request attribute when you forward requests to the template.jsp.
The content attribute should be the name of the JSP to be embedded in your template.