In computing, Java Web Start (also known as JavaWS or as javaws), a framework developed by Sun Microsystems, allows users to start application software for the Java Platform directly from the Internet using a web browser. Unlike Java applets, Web Start applications do not run inside the browser, and the sandbox in which they run need not have as many restrictions, although this can be configured. Web Start has an advantage over applets in that it overcomes many compatibility problems with browsers' Java plugins and different JVM versions. On the other hand, Web Start programs cannot communicate with the browser as easily as applets. To assist migration, users can also invoke a Java Applet as a Java Web Start application.
Web Start provides a series of classes in the javax.jnlp package which provide various services to the application. Sun designed most of these services with the aim of allowing carefully controlled access to resources (such as files and the system clipboard) while restricting the application to authorized operations.
Sun introduced version 1.0 of Web Start in March 2001.[1] Since J2SE 1.4 Web Start comes as a default part of Java Runtime Environment (JRE) and computer administrators no longer have to install it separately.
Java Network Launching Protocol
Programmers often speak of the Java Network Launching Protocol (JNLP, a closely-related concept) interchangeably with the term "Web Start". The JNLP protocol, defined with an XML schema, specifies how to launch Java Web Start applications. JNLP consists of a set of rules defining how exactly to implement the launching mechanism. JNLP files include information such as the ___location of the jar package file and the name of the main class for the application, in addition to any other parameters for the program. A properly configured browser passes JNLP files to a Java Runtime Environment (JRE) which in turn downloads the application onto the user's machine and starts executing it. The development of JNLP took place under the Java Community Process as JSR 56. It includes the original 1.0 release, the subsequent 1.5 maintenance release, and as of 2006, the pending 6.0 maintenance release. JNLP is free; developers need not pay a license fee in order to use it in programs.
Important Web Start features include the ability to automatically download and install a JRE in the case where the user does not have Java installed, and for programmers to specify which JRE version a given program needs in order to execute. The user does not have to remain connected to the Internet to execute the downloaded programs, because they execute from a locally-maintained cache. Updates of the software download from the Web are available when the user is connected to the Internet, thus easing the burden of deployment.
Any computer user can use JNLP by simply installing a JNLP client (most commonly Java Web Start). The client installation can occur automatically, so that the end users can see the client launcher downloading and installing before the Java application the first time they launch the latter.
JNLP works on a classic client-server scheme. The JNLP client reads and executes the JNLP file (an XML file) eventually contacting a JNLP Server or some web server for help. The JNLP client runs locally on the client system whereas the server (implemented by some servlet) functions only for some advanced features of the protocol.
Signed WebStart applications
By default, Java webstart applications run restricted, which means that they do not have access to some system resources such as local files. But end-users can remove these restrictions by signing their webstart applications with the jarsigner tool that comes with the JDK.
Well-known applications
- Kaijudo Portal – an online platform for playing the Duel Masters Trading Card Game in KirriCorp and Japanese formats.
- Wurm Online – a 3D Massively Multiplayer Online Fantasy Simulator.
- PoxNora – a 3/4 perspective, turn-based strategy, collectible card game
- CrossFTP – a user friendly FTP client and server
- PowerTeacher – a gradebook program for student scores as part of the larger student information system used by schools called PowerSchool.
- DataReport Tool – A Java Web Start tool developed by Caprion Proteomics for viewing, analyzing and filtering through a set of differentially expressed proteins
- Clockwiser – a free puzzle game designed to prevent your brain from melting in the witches' cauldron of the daily routine
See also
- ClickOnce - a similar system for the .Net Framework.
- Zero Install - a similar system which works for non-Java applications.
References
External links
- Sun's Java Web Start product page
- Deploying Software with JNLP and Java Web Start
- Java Web Start Architecture JNLP Specification & API Documentation
- JSR 56 (JNLP 1.0, 1.5 and 6.0)
- Startdirectory Connect and Work
- Java Web Start tutorial
- Getting Started with Java Web Start
- JNLP implementations other than Sun's reference implementation: