As Mandy said, jdeps can't do that. There are other tools that perform
bytecode engineering, optimization and shrinking that could assist you
in determining a useful subset of all your application's classes to feed
into jdeps for further analysis.
cheers,
dalibor topic
On 08.09.2016 00:42, Waldek Kozaczuk wrote:
My real question I am in pursuit of answering is this: is it in theory possible
to build an automated process that would use jdeps to analyze my app to build a
minimal JRE image it would run on? The latter could be done by rewriting rt.jar
in Java 8 and using jlink in Java 9.
Sent from my iPhone
On Sep 7, 2016, at 18:34, Waldek Kozaczuk <jwkozac...@gmail.com> wrote:
Thanks for your responses.
So today I did some experimentation with Java 8 jdeps to analyze how my app.jar
depends at class level on other jars and eventually individual JRE classes. I
would run following command:
jdeps -v -P -R -cp lib/* app.jar # where lib/ contains jars that app.jar
depends on to run and libs did not contain app.jar
It turns our that jdeps would find and present dependent classes in all jars irregardless if
any class in app.jar would directly or indirectly depend on it per "->"
references.
The good example of it was log4j jar where jdeps showed number of classes that
depend directly or indirectly on some java.awt.* or javax.swing.* classes. And
I am sure that this app does not requires AWT nor Swing to execute. Is it
because jdeps finds individual class dependencies by detecting reflection calls
in bytecode of log4j?
Or maybe this "greedy" behavior of jdeps is intende and I would need to build a
tool that would process its generated dependency graph starting from app.jar and that way
find the real subset of JRE it depends on? I am still thinking that jdeps would not be
able to show me classes that were called through java.lang.reflect.* constructs or
Class.forName().
Do my findings make sense?
On Wed, Sep 7, 2016 at 5:03 PM, Mandy Chung <mandy.ch...@oracle.com> wrote:
On Sep 7, 2016, at 8:07 AM, Sander Mak <sander....@luminis.eu> wrote:
On 07 Sep 2016, at 16:12, Waldek Kozaczuk <jwkozac...@gmail.com> wrote:
Will I be able to take advantage of jlink's ability to produce subset-only
image of the JRE even if I do not use new Java 9 modular jars? In other
words if my app.jar and other dependent jars are old java 8 ones and do not
have any module descriptors will jlink be able to identify only needed JRE
modules and produce minimal runtime image?
Jlink will not be able to do that for you without module descriptors, but there's an
alternative solution. First, use jdeps to find all the platform modules your
application needs. Then create an image using jlink with an --add-modules
<platform_module> argument for each of the identified platform modules. You can
then run your existing application with all application/library JARs on the classpath
on top of the resulting image.
As Sander said, jlink creates custom image from packaged modules only. You can
create a minimal runtime image and your application and other libraries can be
put on the classpath.
The open issue of adding link-time support for automatic modules is JDK-8139947
[1].
Mandy
[1] https://bugs.openjdk.java.net/browse/JDK-8130047
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