Trail: Deployment
Lesson: Deployment In-Depth
Section: Java Network Launch Protocol

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Structure of the JNLP File

This topic describes the syntax of the Java Network Launch Protocol (JNLP) file for rich Internet applications (RIAs).

The following code snippet shows a sample JNLP file for a Java Web Start application:

<?xml version="1.0" encoding="UTF-8"?>
<jnlp spec="1.0+" codebase="" href="">
    <information>
        <title>Dynamic Tree Demo</title>
        <vendor>Dynamic Team</vendor>
        <icon href="sometree-icon.jpg"/>
        <offline-allowed/>
    </information>
    <resources>
        <!-- Application Resources -->
        <j2se version="1.6+" href=
           "http://java.sun.com/products/autodl/j2se"/>
        <jar href="DynamicTreeDemo.jar"
            main="true" />

    </resources>
    <application-desc
         name="Dynamic Tree Demo Application"
         main-class="webstartComponentArch.DynamicTreeApplication"
         width="300"
         height="300">
     </application-desc>
     <update check="background"/>
</jnlp>

The following table describes the elements and attributes commonly used in JNLP files. Click the parent link to view an element's parent.

Note: This table does not include all possible contents of the JNLP file. For more information, see the Java Network Launching Protocol and API Specification Change Log.

**Commonly Used Elements and Attributes in a JNLP file**
Element	Attributes	Description	Since	Required
jnlp		The topmost xml element for a JNLP file.	1.0	Yes
	spec	Value of the attribute can be 1.0, 1.5, or 6.0, or can use wildcards such as 1.0+. It denotes the minimum version of the JNLP Specification that this JNLP file can work with.	1.0
	codebase	The base location for all relative URLs specified in `href` attributes in the JNLP file.	1.0
	href	The URL of the JNLP file itself.	1.0
	version	The version of the RIA being launched, as well as the version of the JNLP file itself.	1.0
information ^parent		Contains other elements that describe the RIA and its source.	1.0	Yes
	os	The operating system for which this information element should be considered.	1.5.0
	arch	The architecture for which this information element should be considered.	1.5.0
	platform	The platform for which this information element should be considered.	1.5.0
	locale	The locale for which this information element should be considered.	1.5.0
title ^parent		The title of the RIA.	1.0	Yes
vendor ^parent		The provider of the RIA.	1.0	Yes
homepage ^parent		The homepage of the RIA.	1.0
	href	A URL pointing to where more information about this RIA can be found.	1.0	Yes
description ^parent		A short statement describing the RIA.	1.0
	kind	An indicator as to the type of description. Legal values are one-line, short, and tooltip.	1.0
icon ^parent		An icon that can be used to identify the RIA to the user.	1.0
	href	A URL pointing to the icon file. Can be in one of the following formats: gif, jpg, png, ico.	1.0	Yes
	kind	Indicates the suggested use of the icon, can be: default, selected, disabled, rollover, splash, or shortcut.	1.0
	width	Can be used to indicate the resolution of the image.	1.0
	height	Can be used to indicate the resolution of the image.	1.0
	depth	Can be used to indicate the resolution of the image.	1.0
offline-allowed ^parent		Indicates that this RIA can operate when the client system is disconnected from the network.	1.0
shortcut ^parent		Can be used to indicate the RIA's preferences for desktop integration.	1.5.0
	online	Can be used to describe the RIA's preference for creating a shortcut to run online or offline.	1.5.0
desktop ^parent		Can be used to indicate the RIA's preference for putting a shortcut on the user's desktop.	1.5.0
menu ^parent		Can be used to indicate the RIA's preference for putting a menu item in the user's start menus.	1.5.0
	sub-menu	Can be used to indicate the RIA's preference for where to place the menu item.	1.5.0
association ^parent		Can be used to hint to the JNLP client that the RIA wants to be registered with the operating system as the primary handler of certain extensions and a certain mime-type. If this element is included, either the offline-allowed element must also be included, or the href attribute must be set for the jnlp element.	1.5.0
	extensions	A list of file extensions (separated by spaces) that the RIA requests it be registered to handle.	1.5.0
	mime-type	The mime-type that the RIA requests it be registered to handle.	1.5.0
related-content ^parent		An additional piece of related content that can be integrated with the RIA.	1.5.0
	href	A URL pointing to the related content.	1.5.0	Yes
update ^parent		The preferences for how RIA updates should be handled by the JNLP client.	1.6.0
	check	The preference for when the JNLP client should check for updates. Value can be always, timeout, or background..	1.6.0
	policy	The preference for how the JNLP client should handle a RIA update when a new version is available before the RIA is launched. Values can be always, prompt-update, or prompt-run.	1.6.0
			1.0
security ^parent		Can be used to request enhanced permissions. If this element is not included, the application is run in the security sandbox.	1.0
all-permissions ^parent		Requests that the RIA be run with all permissions.	1.0
j2ee-application-client-permissions ^parent		Requests that the RIA be run with a permission set that meets the security specifications of the J2EE application client environment.	1.0
resources ^parent		Describes all the resources that are needed for the RIA.	1.0	Yes
	os	The operating system for which the resources element should be considered.	1.0
	arch	The architecture for which the resources element should be considered.	1.0
	locale	The locales for which the resources element should be considered.
java or j2se ^parent		Versions of Java software to run the RIA with.	1.6.0 (java)
	version	Ordered list of version ranges to use.	1.0	Yes
	href	The URL denoting the supplier of this version of Java software, and from where it can be downloaded.	1.0
	java-vm-args	An additional set of standard and non-standard virtual machine arguments that the RIA would prefer the JNLP client use when launching the JRE software.	1.0
	initial-heap-size	The initial size of the Java heap.	1.0
	max-heap-size	The maximum size of the Java heap.	1.0
jar ^parent		A JAR file that is part of the RIA's classpath.	1.0	Yes
	href	The URL of the JAR file.	1.0	Yes
	version	The requested version of the JAR file. Requires using the version-based download protocol	1.0
	main	Indicates if this JAR file contains the class containing the `main` method of the RIA.	1.0
	download	Indicates that this JAR file can be downloaded lazily, or when needed.	1.0
	size	The downloadable size of the JAR file in bytes.	1.0
	part	Can be used to group resources together so that they are downloaded at the same time.	1.0
nativelib ^parent		A JAR file that contains native libraries in its root directory.	1.0
	href	The URL of the JAR file.	1.0	Yes
	version	The requested version of the JAR file. Requires using the version-based download protocol	1.0
	download	Can be used to indicate this JAR file can be downloaded lazily.	1.0
	size	The downloadable size of the JAR file in bytes.	1.0
	part	Can be used to group resources together so they will be downloaded at the same time.	1.0
extension ^parent		A pointer to an additional component-desc or installer-desc to be used with this RIA.	1.0
	href	The URL to the additional extension JNLP file.	1.0	Yes
	version	The version of the additional extension JNLP file.	1.0
	name	The name of the additional extension JNLP file	1.0
ext-download ^parent		Can be used in an extension element to denote the parts contained in a component-extension.	1.0
	ext-part	The name of a part that can be expected to be found in the extension.	1.0	Yes
	download	Can be used to indicate this extension can be downloaded eagerly or lazily.	1.0
	part	Denotes the name of a part in this JNLP file in which to include the extension.	1.0
package ^parent		Can be used to indicate to the JNLP client which packages are implemented in which JAR files.	1.0
	name	Package name contained in the JAR files of the given part.	1.0	Yes
	part	Part name containing the JAR files that include the given package name.	1.0	Yes
	recursive	Can be used to indicate that all package names, beginning with the given name, can be found in the given part.	1.0
property ^parent		Defines a system property that will be available through the `System.getProperty` and `System.getProperties` methods.	1.0
	name	Name of the system property.	1.0	Yes
	value	Value of the system property.	1.0	Yes
		Note: A JNLP file must contain one of the following: application-desc, applet-desc, component-desc, or installer-desc.	1.0	Yes
application-desc ^parent		Denotes this is the JNLP file for an application.	1.0
	main-class	The name of the class containing the `public static void main(String[])` method of the application.	1.0	Yes
argument ^parent		Each argument contains (in order) an additional argument to be passed to the `main` method.	1.0
applet-desc ^parent		Denotes this is the JNLP file for an applet.	1.0
	main-class	The name of the main applet class.	1.0	Yes
	documentbase	The document base for the applet as a URL.	1.0
	name	Name of the applet.	1.0	Yes
	width	The width of the applet in pixels.	1.0	Yes
	height	The height of the applet in pixels.	1.0	Yes
param ^parent		A set of parameters that can be passed to the applet.	1.0
	name	The name of this parameter.	1.0	Yes
	value	The value of this parameter.	1.0	Yes
component-desc ^parent		Denotes this is the JNLP file for a component extension.	1.0
installer-desc ^parent		Denotes this is the JNLP file for an installed extension.	1.0
	main-class	The name of the class containing the `public static void main(String[])` method of the installer.	1.0	Yes

Encoding JNLP Files

Java Web Start software supports encoding of JNLP files in any character encoding supported by the Java platform. For more information about character encoding in the Java platform, see the Supported Encodings Guide. To encode a JNLP file, specify an encoding in the XML prolog of that file. For example, the following line indicates that the JNLP file is encoded in UTF-16.

<?xml version="1.0" encoding="utf-16"?>

Note: The XML prolog itself must be UTF-8-encoded.

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