jkernel has been broken in JDK 7.  This was uncovered when we started the testing for 6888880.

jprt jkernel build completed successfully but I spotted the following error in the jprt log.  The build doesn't fail with this NumberFormatException which seems to be one issue.

Exec: C:\temp\jprt\P1\B\002430.mchung\source\build\windows-i586\j2sdk-image\bin\pack200 -J-mx256m --no-gzip -f C:\temp\jprt\P1\B\002430~1.MCH\source\build\windows-i586\tmp\kernel\pack.properties C:\temp\jprt\P1\B\002430.mchung\source\build\windows-i586\tmp\kernel\pack\resources_other.pack C:\temp\jprt\P1\B\002430.mchung\source\build\windows-i586\tmp\kernel\pack\resources_other.jar
Creating java_awt_min...
NeededToRun attempt=1 Exec: "C:\temp\jprt\P1\B\002430.mchung\source\build\windows-i586\tmp\kernel\j2re-image-copy\bin\java" -verbose -Dkernel.nomerge=true -Dkernel.debug=true -Dkernel.download.url=internal-resource/ -Dkernel.background.download=false -Dkernel.deploy.debug=true -classpath SplitJRE.jar;"C:/temp/jprt/P1/B/002430.mchung/source/build/windows-i586/tmp/kernel/j2re-image-copy"/lib/plugin.jar;"C:/temp/jprt/P1/B/002430.mchung/source/build/windows-i586/tmp/kernel/j2re-image-copy"/lib/deploy.jar sun.kernel.SwingMinTest in working directory: C:\temp\jprt\P1\B\002430.mchung\source\build\windows-i586\tmp\kernel
[Opened C:\temp\jprt\P1\B\002430.mchung\source\build\windows-i586\tmp\kernel\j2re-image-copy\lib\resources.jar]
[Opened C:\temp\jprt\P1\B\002430.mchung\source\build\windows-i586\tmp\kernel\j2re-image-copy\lib\rt.jar]
[Opened C:\temp\jprt\P1\B\002430.mchung\source\build\windows-i586\tmp\kernel\j2re-image-copy\lib\jsse.jar]
[Opened C:\temp\jprt\P1\B\002430.mchung\source\build\windows-i586\tmp\kernel\j2re-image-copy\lib\jce.jar]
[Opened C:\temp\jprt\P1\B\002430.mchung\source\build\windows-i586\tmp\kernel\j2re-image-copy\lib\charsets.jar]
DownloadManager startup
Log opened
Checking for requested bundles...
Entering getBootClassPathEntryForResource(sun/kernel/SwingMinTest.class)
Entering getBootClassPathEntryForResource(sun/jkernel/resource_map)
Bailing: false, false
getBootClassPathEntryForResource(sun/kernel/SwingMinTest.class) == null
Entering getBootClassPathEntryForResource(sun/kernel/SwingMinTest.class)
getBootClassPathEntryForResource(sun/kernel/SwingMinTest.class) == null
Entering getBootClassPathEntryForResource(sun/kernel/SwingMinTest.class)
getBootClassPathEntryForResource(sun/kernel/SwingMinTest.class) == null
Entering getBootClassPathEntryForResource(java/lang/Object.class)
Entering getBootClassPathEntryForResource(sun/jkernel/file_map)
Bailing: false, false
Entering getBootClassPathEntryForResource(sun/jkernel/bundle.properties)
Bailing: false, false
On-demand downloading core for resource java/lang/Object.class...
Error downloading bundle for java/lang/Object.class:
java.lang.NumberFormatException: null
	at java.lang.Integer.parseInt(Integer.java:454)
	at java.lang.Integer.valueOf(Integer.java:582)
	at sun.jkernel.Bundle.getSize(Bundle.java:319)
	at sun.jkernel.Bundle.install(Bundle.java:770)
	at sun.jkernel.Bundle.install(Bundle.java:745)
	at sun.jkernel.DownloadManager.doGetBootClassPathEntryForResource(DownloadManager.java:746)
	at sun.jkernel.DownloadManager.access$300(DownloadManager.java:43)
	at sun.jkernel.DownloadManager$4.run(DownloadManager.java:926)
	at java.security.AccessController.doPrivileged(Native Method)
	at sun.jkernel.DownloadManager.getBootClassPathEntryForResource(DownloadManager.java:923)
	at sun.jkernel.DownloadManager.getBootClassPathEntryForClass(DownloadManager.java:948)
	at sun.jkernel.DownloadManager.loadBootstrapClass(DownloadManager.java:1634)
	at sun.misc.BootClassLoaderHook.preLoadClass(BootClassLoaderHook.java:68)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:317)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:316)
	at java.lang.ClassLoader.defineClass1(Native Method)
	at java.lang.ClassLoader.defineClass(ClassLoader.java:747)
	at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:144)
	at java.net.URLClassLoader.defineClass(URLClassLoader.java:382)
	at java.net.URLClassLoader.access$100(URLClassLoader.java:75)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:294)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:288)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(URLClassLoader.java:287)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:383)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:325)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:316)
	at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:195)

getBootClassPathEntryForResource(java/lang/Object.class) == null
[Loaded sun.kernel.SwingMinTest from file:/C:/temp/jprt/P1/B/002430.mchung/source/build/windows-i586/tmp/kernel/SplitJRE.jar]
Entering getBootClassPathEntryForResource(java/lang/Throwable.class)
getBootClassPathEntryForResource(java/lang/Throwable.class) == null