So what is a .jimage?

Alan Bateman Alan.Bateman at
Thu Oct 16 12:37:08 UTC 2014

On 16/10/2014 10:14, deven you wrote:
> Hi Alan,
> I have 2 questions about the .jimage.
> 1. Is there any tool I can use to explore .jimage like we use arch 
> tool to explore .jar file?
There's a "jimage" tool in the bin directory that is useful for 
troubleshooting, you can use this to list or expand for example. It's 
not the full range of options that you have with the "jar" tool but that 
is mostly because the jimage format is intended to be JDK-internal and 
not something that most developers will interact directly with.

> 2. I see in build/ folder, jdk and jre are parallel now which means 
> jdk dos not contain a full jre, is that correct? And it also means in 
> the further, if someone need a jre at the same time he has already had 
> a jdk, he must download a jre from Oracle's website again?
images/jdk and images/jre are the equivalent of images/j2sdk-image and 
images/j2re-image. There isn't an overlaying or separate download. Aside 
from the images not containing JAR files, the other main change is that 
the SDK image (now called "jdk") does not have a "jre" directory. 
Clearly there will be scripts and code that check for the existence of 
the jre directory and that is a compatibility hump that will need to be 
gotten over. As to why the "jre" directory should go then this is 
consequence of modules completely blurring the distinction between what 
we know today as the JRE and JDK. Going forward it should be possible to 
link arbitrary sets of modules (be they Java SE, JDK-specific, non-JDK, 
...) to create custom images. The internal "jre" directory doesn't 
really have a home in this new world.


More information about the jigsaw-dev mailing list