Java Applications and Java Web Start

1
Java Applications and Java Web Start

• By
• Lau Larsen
• Danish Meteorological Institute

2
Background1

• DMI deliver a lot of data from our hompage
• Some data are best viewed in an interactive
  environment.
• Executeables have been distributed for specific
  platforms or Java Applets have been used.

3
Problems with executeables2

• Distribution
• Installation on remote computer
• Platforms supported
• New versions

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What is Java Web Start?3

• Java Web Start is an Application deployment
  solution for the Web.
• Java Web Start is installed locally once.
• Java Web Start has an Application Manager
• Java Web Start currently runs on all Windows
  platforms, Linux and Solaris.

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What does Java Web Start do?4

• Download, run and update Java Applications from
  the Web.
• Support for offline use.
• Run Applications in a restricted environment
  (sandbox)

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How is Java Web Start used?5

• From a Web browser by clicking on a link
• From Java Web Starts Application Manager
• From desktop icons or the Start Menu on the
  Windows platform

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Application development considerations for Java
Web Start6

• An application must be delivered as a set of JAR
  files
• All resources must be stored in JAR files
• Remember the restrictions of the sandbox or get
  unrestricted access (by delivering a set of
  signed JAR files).
• Make a description of your application in a JNLP
  file.

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What is JNLP?7

• Java Network Launching Protocol
• A JNLP file is a XML document
• It describes the application and its environment.

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JNLP file contents8
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DMI (test) JWS-Application9

• Java application (userinterface)
• Communicate with old telnet-based program to
  present flight dokumentation
• Fetch chart products via http from our homepage.

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Special considerations for DMI (test)
JWS-Application10

• Use ltnativelibgt and Java Native Interface to use
  platform-dependent code.
• Use Java Web Start API PersistenceService
• Must have all permissions to print, use disk,
  have several network connections and to use
  native libraries.

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ltnativelibgt11

• We have made a Windows DLL to lookup in the
  registry database the program that is used to
  view and print pdf-files.
• This DLL can be downloaded depending of target
  platform and used via Java Native Interface (JNI)
  from the application.

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JWS API PersistanceService12

• Java Web Start provide different Services to open
  files, save files, print, download etc.
• PersistanceService is a service a bit like
  cookies in a browser.
• We have used the PersistanceService to save some
  initial information for the application to use.

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ltall-permissions/gt13

• To run an application in a unrestricted
  environment, all the jars must be signed with
  jarsigner. This means that one have to get a
  certificate from a certificate authority, such as
  VeriSign. (Can be a very big administrative task)
• If not, Java Web Start states it is highly
  recommended not to install and run this code.

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Use of DMI (test) JWS-Application14

• Short description of Java Web Start
• Link to Sun Microsystems Java Web Start download
  page
• Short description of the DMI application
• Link to start the DMI Application
• Link to userguide for the DMI application

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Security Warning15

• When asking for unrestricted access to the
  target machine Java Web Start presents this
  security warning to the user.

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Java Web Start Experience16

• In half a year we have had a Java Web Start
  application operational on our homepage.
• Only 300 companies/persons have username and
  password to run the old software and now also the
  new Java Web Start application.
• The Java Web Start application now have over 100
  users. Mostly Windows. Some (very) unexperienced
  users. (We have made no marketing to move users
  to the Java Web Start solution.)
• Only a handfull have called for help.

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Java Web Start Experience continued17

• The Java Web Start considerations are minimal
  problem for the application. (Especially if you
  ask for all permissions.)
• The JNLP file is easy to make for simple
  applications. But it is flexible and can, with
  some extra work, handle more complex applications
  as well.
• The Java Web Start installation from Sun
  Microsystems is standard and simple (especially
  on the Windows platform).

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Java Web Start ExperienceConclusion18

• Minimal considerations for the Application.
• Flexible JNLP for different applications.
• FREE distribution, installation and update of
  applications.
• Users have no problems installing Java Web Start
  or running the applications.

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DMI status19

• We have joined the NinJo-project with DWD and
  MeteoSwiss this year.
• We have had 2 softwaredevelopers on courses in
  NinJo in Germany and held internal cources for a
  dusin DMI developers.
• We have finished a requirements specification for
  a trajectory presentation layer. And will go on
  with design and implementation.

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DMI status, continued20

• We expect to move from intel Solaris to the Linux
  platform in 3 years at the latest.
• We will only use Solaris on Sparc Servers.

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DMI status, continued21

• Old lightningapplication will not run under new
  versions of Solaris and uses Mortif.
• New sensors also provide cloud to cloud
  lightning.
• New lightningapplication is in Java and will also
  be available via Java Web Start.

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DMI status, continued22

• New application to get an overview of
  precipitation from different formatted stations.
• Used in situations with prediction of extreme
  precipitation.
• Precipitationapplication is in Java and available
  (internally) via Java Web Start.