Re: How "run under JDK" not JRE?

Lew <>
Thu, 28 May 2009 12:09:25 -0700 (PDT)
On May 28, 12:33 pm, Lee <> wrote:

I hope this isnt too much of a newbie question for this formum, but here

On my wintel machine running windows XP I had (and still have) a JRE.

I want to run the solr tutorials, which require running a particular jar

BUT according to the instructions the jar must be run under a JDK (1.5
or higher), NOT a JRE.

That is not correct. One always runs "under a JRE" - that just means
that a particular JRE is providing the JVM and other parts of the Java
runtime environment (which is what "JRE" stands for).

When the instructions say, "run under JDK 1.5 or higher" they really
mean "run under JRE 5 or higher". In a few cases, they also mean,
"include JARs in the class path that only come with the JDK, not the
standalone JRE". Even in those few cases, the running itself happens
in the JRE.

You get the JRE in one of two ways - as a standalone module, or as a
sub-module of the full JDK. In a JDK installation, say "/java/
jdk1.6.0_13/", you will find a "jre/" subdirectory. That subdirectory
contains the JRE specific to that JDK. It is exactly parallel to the
regular installation directory of a corresponding standalone JRE.

I downloaded and installed JDK 1.6.0_13 from SUN
The installation package also installs JavaFX (but I dont have a clue
about what that is or what its for)

After installation if I run
java -version

Whoops, there's java RUN TIME 1.6.0_13.

That is correct - it is always the run time that does the running.

So how do I run the jar "under the JDK"

Make sure that the JRE directory or subdirectory for the corresonding
version is in your executable path, or else put an absolute path to
the 'java' command.

The jar runs "jetty" a lightweight HTML demon on the local host. I can
tell that jetty is running but not properly because I get 404 errors
when I try the url "http://localhost:8983/solr/admin/" from my browser=


You probably left out a few configuration steps. I would have to read
the Jetty documentation to guess which ones.


Do I need to set my CLASSPATH to something interesting, or do I need
different PATH settings or what?

CLASSPATH (which you should almost never use) is like "-claspath" to
the 'java' command - it sets a class path for the JVM to use when
loading classes. You want PATH - the way to tell the OS where its
executables are. This is the same as for running any other executable
in your OS.

Are the paths supposed to be set the the "...\Java" directory or to the
...\Java\jdk1.6.0_13 directory or the \bin under it or the \lib or what?

You set the PATH to include the directory where executables reside,
just as for any executable in your OS.

Many Java environments are trained to react to the JAVA_HOME
environment variable, which would hold the directory in which the JDK
is installed, for example, "/opt/java/jdk1.6.0_13" or "D:\java
\jdk1.6.0_13". These environments will look into "$JAVA_HOME/bin/"
for executables because they're just that smart.


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