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How to use Google closure compiler with Jawr

The goal of this tutorial is to explain how to use with Jawr.
This feature is available since the version 3.5 of Jawr.

How it works ?

Since the version 3.5, Jawr provides by default a postprocessor to compress your JS bundles with Google Closure Compiler.
The google closure compiler postprocessor is a global postprocessor, which means that it will be launched at the end of the bundling process.  This google closure compiler postprocessor is defined as a global postprocessor, because in advance mode, the compiler will check the JS functions to remove the dead code.

The default compilation level is WHITESPACE_ONLY.
Here is the list of available level :


The default warning level is VERBOSE.

You can pass arguments to the closure compiler using the prefix jawr.js.closure.

For instance, you can pass the boolean “third_party” argument using jawr.js.closure.third_party in the jawr properties file. The full list of arguments are define in, so you can check it at the following link

There are 2 arguments which are not allowed because they are managed by Jawr :

  • js
  • module

To exclude a bundle from the closure processing, you can use the following property jawr.js.closure.bundles.excluded, whose the value is a comma separated list of the bundles to exclude.

        # Use Google closure as global postprocessor


Set up Jawr in your project

Please check the quickstart tutorial for the instruction about Jawr installation in your project.

Configure instances of the Jawr Servlet

You must configure Jawr to use at least the JS servlet.

Jawr configuration file

We will follow the following example :

        # Use Google closure as global postprocessor

Create a test JS file

Write a test JS file named /js/sample01.js and add the following content:

 * Hello function
 * Add two variables
function hello(name){

        alert("hello "+name); 

window['hello'] = hello;

Write a test JS file named /js/sample02.js and add the following content:

 * Add function
 * Returns the addition of the two parameter
function add(c1, c2){

        return c1 + c2; 

Write a test JSP page and add the following content:

<%@ taglib uri="" prefix="jawr" %>
<%@ page contentType="text/html;charset=UTF-8" %>
        <jawr:script src="/js/sample.js" />
        <button type="button" onclick="hello('world!')">Click Me!</button>

Deploy your application to a server and open the JSP you created. You will notice that the add function has been removed from the generated bundle as it is considered as not used.