FreeMarker

Description #

FreeMarker is a powerful Java-based templating engine used to generate dynamic HTML, configuration files, source code, and more, primarily in Java web applications.

History #

FreeMarker was created in 2000 by Jonathan Revusky and later maintained by the Apache Software Foundation. It was designed to separate logic from presentation in Java-based MVC architectures and became a core part of frameworks like Spring MVC.

Hello World Code #

<h1>${message}</h1>

With context:

Map<String, Object> data = new HashMap<>();
data.put("message", "Hello, World!");

How to Run #

Option 1: Online
Use a FreeMarker preview tool:
https://try.freemarker.apache.org/

Option 2: Local
Add to a Java project:

<dependency>
  <groupId>org.freemarker</groupId>
  <artifactId>freemarker</artifactId>
  <version>2.3.31</version>
</dependency>

Render in Java:

Template template = cfg.getTemplate("hello.ftl");
template.process(data, new OutputStreamWriter(System.out));

Key Concepts #

• Syntax: ${} for expressions, <#...> for logic
• Template files use .ftl extension
• Used in Java frameworks like Spring, Struts, Spark
• Supports conditionals, loops, macros, includes
• Data model passed as a Map or POJO
• Safe HTML escaping options
• Can generate any text format (HTML, XML, etc.)
• Extensible via directives and custom methods
• Fast performance with precompiled templates
• Apache-licensed and widely supported

Try It Online #

https://try.freemarker.apache.org

Fun Facts #

• The “Free” in FreeMarker refers to freedom, not price—though it is both.
• Used by many CMS platforms and Java web servers to render user-customizable views.
• The syntax is similar to Velocity but more robust and easier to extend.

Resources #

Official site
Docs or tutorial
GitHub or interpreter
Community or learning resources