Re: Basics : JVM, JRE and Java Web Start
alex.sales@gmail.com wrote:
...
Is there a difference between JVM and JRE or is the same thing ?
They are the same thing, effectively. Though technically
a JRE might include the runtime (JVM) as well as properties
and config. files
Is there different versions of JRE, for example light version vs full
version ?
There are different microversions fo the JVM, e.g.
Java 1.6 has an 1.6.0 JVM, and also 1.6.0_01,
1.6.0_02 & 1.6.0_03. There is no 'light or heavy'
equivalent - applets get the standard JVM, but if
they (or untrusted JWS apps.) are sandboxed, the
SecurityManager of the JVM will be restricted in
what it will permit. Either desktop appications
or applets can also make use of the '-server' form
of the JVM, it is merely an option of the standard JVM
that JITs more aggressively to speed up the app.
..For example does it exist a light version which would only
allow to run applet ?
No. The applet JVM is sandboxed, but otherwise standard.
When you install IE 6, it looks like it automatically install a JRE,
is that right ?
Yes, then no, and now posibly yes for a while.
The matter of whether a real and current JVM is deployed
with IE is a long running saga.
It is safest to assume your client's PC has no JVM,
and has never heard of Java. Most will not be in that
situation (at least their PC has Java), but it is safest to
make no assumptions.
..Is that a full JRE ?
If there, Yep. (Unless you are talking of a really old
- 'Win. 98 vintage' installer that includes IE 6 and the
MSVM.)
I need to deploy a Java Web Start application on several clients.
Which is the oldest JRE that can run JWS ?
Java 1.2. java 1.4 was the first version that had
JWS co-bundled with the JRE. Java 1.5 (or 1.6,
not sure) was the first Java that could not only include
the JVM and JWS, but coax the Opera browser into
recognising the JNLP files as needing to be handed to
JWS, rather than rendered as if they were HTML.
--
Andrew Thompson
http://www.athompson.info/andrew/
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