registry : Java Glossary

Registry Corruption and Repair

RMI (Remote Method Invocation) Registry

Backing Up The Registry

Ordinary backup programs cannot deal with backing up or restoring the registry since it is always locked and in use. All you can do is extract the data from it and feed it back transaction by transaction with regedit. Programs like Norton Ghost can backup and restore the entire registry by running under DOS (Disk Operating System) where the registry is not used at all. Ghost is the only way I know of recovering from a fatally damaged registry. You can backup/restore sections of the registry, provided the registry as a whole is intact, with code like this (which saves the SET environment): You can spawn such regedit code with Runtime.exec. In W2K, XP, W2003, Vista, W2008, W7-32, W7-64, W8-32, W8-64, W2012, W10-32 and W10-64 it dumps the file in UTF-16LE (little endian) encoding with an FFFE BOM (Byte Order Mark). If you try to read it with an ordinary 8-bit editor it will show every second character as null.

Physical Location

• In W95, W98 and Me, the registry is contained in two hidden files in your Windows directory, called USER.DAT and SYSTEM.DAT.
• In NT, W2K, XP and W2003, the registry is stored in several hives, located in the \windows\system32\config and \Documents and Settings\{username} folders. One major chunk is called NTUSER.DAT which contain the HKEY_CURRENT_USER hive. Two other major chunks are called software and system.

Exploring The Registry

You can learn quite a bit about how the registry handles java just by searching for strings like java, JavaSoft, java.exe, javaw.exe, javaws.exe, jnlp, jar, jdk, jre, J:\Program Files\java\jdk1.8.0_131\ or 1.8.0.

You could use regedit to look at HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft to see this as a small tree of fields. If it is damaged and you don’t have a backup, you could patch it field by field, or use the text above to create phony registry section backup, convert it to the encoding your version of regedit expects and restore that and then fine tune the result.

Alternatively, if the registry is a real mess, you could uninstall all java JREs (Java Runtime Environments) and JDK (Java Development Kit) s, delete all the files for the JREs and JDK s, delete the HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft registry tree and start from scratch.

Useful Registry Locations

Note the registry is not stored purely alphabetically: HKEY_CLASSES_ROOT, HKEY_CURRENT_USER, HKEY_LOCAL_MACHINE, HKEY_USERS, HKEY_CURRENT_CONFIG.

The Auxiliary Registry App Paths

If you use tcc/TakeCommand, you can just type the name of any program in this auxiliary list with or without the .exe to invoke it. However, the default cmd.exe command processor will not do this for you. However, if you invoke the program on the with NT and W2K start ⇒ run or Vista, W2008, W7-32, W7-64, W8-32, W8-64, W2012, W10-32 and W10-64 start ⇒ all programs ⇒ accessories ⇒ run, the program will launch.

It is a good idea to prune this region of the registry of deadwood. It gets filled with references to non-existent programs during failed installs and uninstalls.

Installers are sometimes too timid/stupid to fix broken entries. I found, for example, that Opera would not launch properly when I typed Opera on the command line. I discovered a registry entry in this region was pointing it to an old version of Opera that was no longer installed. I patched the entry with regedit to point to the new name and off it went. Registry cleaners will automatically purge broken entries of this type, but they won’t repair them. Sometimes purging is enough. The next install might recreate it.

Java and the Registry

It is wise to take a snapshot of the java portion of the registry. Then when it is later inevitably damaged, you can restore it. Without such a backup you must either manually patch the registry or uninstall all your JDK s, JRE s, JWS

REM export Java region of registry
regedit /E C:\ENV\java.reg "HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft"

REM restore Java region of registry
C:\ENV\java.reg

How Java Finds its Executables

1. Java Web Start uses the registry auxiliary Apps Path technique. You will find an entry in HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths for javaws.exe pointing it to the javaws.exe it will use if you just type javaws on the command line where there is no javaws.exe on the path.
2. java.exe uses a different mechanism that uses an extra C:\Windows\System32\java.exe (which is on the path) that examines the registry to find the currently active JRE and hence the official copy of java.exe.
3. Just for variety, javac.exe just uses the plain old path to find the executable, though, of course, you are free to set up an App Paths entry manually with regedit.

Manipulating the Registry

The Preferences feature of Java uses the Windows registry to store configuration information. This does not give you general access to the registry however. I take it Sun was too cheap to buy/write some disk-based BTree code or a simple SQL engine to handle this with ordinary files that could be easily backed up and restored.

For earlier JDK ’s IBM (International Business Machines) ’s JConfig does not support registry operations because JConfig is cross platform and Windows is the only OS (Operating System) with this idiotic contraption.

Nodes in the registry can have an optional name/key for direct lookup and an optional value. For nodes with keys, accessible via direct name lookup, the associated value is called the data. For nodes without keys, only accessible as a subnodes of some other node, the associated value is called a value. Inserting a node without a key is referred to as inserting a value.

If you are developer, a more robust technique is to store your data in C:\Documents and Settings\User\Application Data\ in ordinary flat files.

You can span a copy of reg.exe or redit.exe for quick and dirty changes.

Poking The Registry With JNI (Java Native Interface)

JNIWrapper Winpack does many more native tweakings that access the registry.

Registry: Second Stupidest Idea In Computing

1. Microsoft lock in

   To make it more difficult to port Windows apps to operating systems without a registry. Microsoft wants to lock in developers.

2. Piracy

   To make it more difficult to backup and restore individual applications. You have to totally reinstall them from the master CD (Compact Disc). This discouraged piracy in the days before the CD burner. As a side effect, the registry harms legitimate users trying to restore a corrupted application or trying to move it to a different partition. To move an application to a different drive or partition, you must uninstall it, reinstall it, then manually reenter all the configuration options, if you can remember them! If a customer has lost the key for an app or misplaced the master CD, or can’t figure out which key goes with which disk, he can’t even reinstall. He has to buy a new copy of the application. Hmmm.

3. Cover Up for Incompetence

   To make it necessary to reinstall Windows every once in a while. If anything in the registry goes, novice users have little hope but to reformat the disk and start over and re-install Windows and all the applications. An ex Microsoft employee told me that Microsoft coders do this as a matter, of course, each month. The registration keys are designed to be easy to lose and hard to match with the corresponding CD. Legitimate owners of software end up rebuying unnecessary copies of the products. Registration keys have no effect on pirates; they only harm legitimate users. Branding, in contrast, would deter pirates.
   installer for more discussion

4. Intercorporate Spying and Warfare

   To make it easier to snoop on and meddle with your competitor’s configurations and file associations. In future secure computer architectures, each application will run in an airtight sandbox where it cannot snoop on or meddle with the files or programs of its competitors. The CPU (Central Processing Unit) will have a dark room where encrypted code is expanded using the CPU ’s private key. The code can be executed, but not examined by anyone. This will put an end to piracy. There will be no more need for the idiotic registry. The only central unified registry needed will be a simple list of apps and where they are. The slapdash extension association system will be replaced with a secure program association set for each file.

How could the registry be fixed. It need three major changes:

1. Separation

   The OS assigns each application a hive — a mini registry. Applications can’t look outside their hive, except read-only access to a deliberately public central hive. Only the app itself looks at its hive. Normally, not even the OS peeks inside an application hive. As a result, the registry ceases to be a performance bottleneck. It ceases to contain material irrelevant to the current purpose. It no longer requires contention to access it.

2. Placement

   The hive for an app lives in the directory for that app. If the hive becomes corrupted, only that app is harmed. If that app is backed up and restored to any other machine, partition or directory it still works. The hive has no idea where it is. Microsoft has to give up the idea of punishing legitimate application migration and restoration.

3. Robustness Through Automatic Restoration

   There is a mechanism to publish a few public facts, e.g. the mime types of files the app is willing to display, edit, print… (An app on its own cannot commandeer a MIME (Multipurpose Internet Mail Extensions) type from all other apps. It can merely get it self added to list of potential associations). This structured public information is replicated centrally. If for some reason the central registry becomes corrupt and loses these facts, the O/S can get them back by asking any hives it finds lying about. It can thus recreate the damaged central hive from the public portion of the application hives. The OS is the only entity that knows where an app is. Apps themselves don’t know where physically they are.

Books

Book referral for Windows Registry Troubleshooting

	recommend book⇒Windows Registry Troubleshooting
	by	Mike Halsey, Andrew Bettany	978-1-4842-0993-6	paperback
	birth	1970-03-27 age:48	978-1-4842-0992-9	eBook
	publisher	Apress	B00SMFP7VW	kindle
	published	2015-04-30
This is an introductory book on the registry.
Online bookstores carrying Windows Registry Troubleshooting abe books anz abe books.ca abe books.de amazon.ca amazon.de Chapters Indigo amazon.es Chapters Indigo eBooks iberlibro.com abe books.com abe books.fr amazon.com amazon.fr Barnes & Noble abe books.it Nook at Barnes & Noble amazon.it Kobo junglee.com Google play abe books.co.uk O’Reilly Safari amazon.co.uk Powells other stores
Greyed out stores probably do not have the item in stock. Try looking for it with a bookfinder.

Book referral for Microsoft Windows Registry Guide

	recommend book⇒Microsoft Windows Registry Guide
	by	Jerry Honeycutt	978-0-7356-2218-0	paperback
	publisher	Microsoft	978-0-7356-3735-1	eBook
	published	2005-09-14	B0043M58TY	kindle
Covers XP registry, but not Vista.
Online bookstores carrying Microsoft Windows Registry Guide abe books anz abe books.ca abe books.de amazon.ca amazon.de Chapters Indigo amazon.es Chapters Indigo eBooks iberlibro.com abe books.com abe books.fr amazon.com amazon.fr Barnes & Noble abe books.it Nook at Barnes & Noble amazon.it Kobo junglee.com Google play abe books.co.uk O’Reilly Safari amazon.co.uk Powells other stores
Greyed out stores probably do not have the item in stock. Try looking for it with a bookfinder.