Run a JNLP
Run a JWS/JNLP application in the browser
This quickstart tutorial will take you step by step on how to run your JNLP app (also known as Java Web Start application) in the browser with CheerpJ.
You will need:
- The application
- An HTML file where your Java app will be wrapped.
- A simple HTTP server to test your webpage locally.
.jnlp file contains the specifics of how to launch your Java application. The usual pipeline starts when this file is triggered from a website so it is passed to the user’s local JNLP client which downloads the application
.jar files and further resources. Finally, the app is executed with the local JRE installation. With CheerpJ it is possible to run this application in the browser sandbox, no Java installation required.
.jnlp file might look something like the example below. There are three essential elements you need to find:
.jarfiles specified under the
<resources>element, usually indicated with a
- Your application type. Look for an
- You may need the
codebaseURL given by
2. Create a project directory
Once you have identified where the
<nativelib> tags are in your JNLP, you can simply download these JARs by copying and pasting their URLs in the browser’s navigation bar. If these URLs are relative then build the full URL by appending the
codebase URL and the
Please create a directory for your project and place the JARs you just downloaded inside this folder, remember to keep the same directory structure as shown in your
Once you moved the JARs it should look like this:
3. Create a basic HTML file
3.1 Identify your application type
A JNLP app can be a standalone application or an applet. This is easy to spot on your
.jnlp file with the tags
We will create a basic HTML file where the CheerpJ runtime will be integrated and the java application displayed. Create this file in the root of the project folder. The way the app is loaded might differ if the application is a standalone app or an applet. The following steps will specify how the HTML will look like for each case.
3.2 If your application is a standalone app
Take a close look at content of
<application-desc> and keep the following at hand:
- The application class name: You can find it at the
main-classattribute. This attribute may not be there if the class name is included in the manifest.
- The application arguments: If any arguments are required, you will find these with the
NoteIf you do not find any of the elements listed above, this means you do not need them to run your application.
Example of an HTML file for an app where the class name is included in the manifest:
Alternatively, if the class name is in the
.jnlp file but not in the manifest, then replace
Any application arguments must be passed to
/app/prefix is a virtual filesystem mount point that references the root of the web server this page is loaded from.
3.2 If your application is an applet
Take a close look to the
<applet-desc> tag on your
.jnlp and keep the following at hand:
Any applet tag parameters:
- The applet class name: You can find it at the main-class attribute.
- The applet ideal size: defined at
- Applet parameters: found as
<applet-desc>if your applet requires it.
documentBase: If you retrieve this URL, you will obtain an HTML file where the applet is wrapped. You can use it, or create your own HTML like the example below. If you use the
documentBaseHTML file, remember to add the scripts where the CheerpJ runtime is integrated and called.
The HTML for an applet would look like this:
Any applet parameters should be passed as
<param> in the
<applet> tag as usual:
In case your users have a native Java plugin installed, you can replace the original HTML tag with a cheerpj- prefixed version.
<cheerpj-embed>are all supported.
4. Host your page
Your final project directory tree should look similar to:
You can now go to the project directory and serve this web page on a simple HTTP server, such as the http-server utility.
This is the end of the tutorial. To learn more about running standalone applications and applets with CheerpJ, you can visit the dedicated tutorials: