TrueZip : Java Glossary

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TrueZip

The current version is 7.4.3 Last revised/verified: 2011-12-15. It is a Java library that lets you treat a zip file as if it were a directory. You can shuffle files around and when you are done, call umount() which creates a new zip reflecting all your changes.

TrueZip gives you complete flexibility in just how much qualification you include with each member. You can have none, full qualification, anything in between, or even include the original drive letter (which maps into a subdirectory called E: for example). It is up to you as a programmer to construct the file name of the zip entry, then pour your file/files into it. The name does not even have to bear any resemblance to the name of the file you are adding. You can’t just copy files into the root of the archive. You must first create a zip entry file with a name to contain each one. It behaves much more like a directory tree than a traditional archive.

TrueZip compresses as you add, but does not construct the final archive file until you call umount. Using the default settings, TrueZip archives take up about an extra 28% more space that WinZip using its proprietary compression algorithms. It possible to squeeze more compression out of TrueZip if you are willing to take more time.

See the timestamp gotchas about PkZip format. They plague TrueZip too. TrueZip can use other formats that may avoid these problems.

Java 7 will have built-in True-zip like features. Mark Hall is working on giving TrueZip an API (Application Programming Interface) that will be compatible. That means you can write code for Java 7 that will work on earlier JDKs.

TrueZip 7

TrueZip 7 is a rewrite of TrueZip 6 with a slightly different API.

One welcome change isde.schlichtherle.io.File has been renamedde.schlichtherle.truezip.file.TFile so that you don’t confuse it with the built-in Java File.
de.schlichtherle.io.DefaultArchiveDetector is gone, replaced byde.schlichtherle.truezip.file.TArchiveDetector .
de.schlichtherle.io.File.delete is replaced byde.schlichtherle.truezip.file.TFile.rm.
de.schlichtherle.io.File.copyTo is replaced byde.schlichtherle.truezip.file.TFile.cp_p.
There is no equivalent for the old archiveCopyFrom. You must reverse the direction and usede.schlichtherle.truezip.file.TFile.cp_p and ensure both source and destination are TFiles. Or use the static method de.schlichtherle.truezip.file.TFile.cp_p
Oddly there is a name collision withde.schlichtherle.truezip.zip.ZipOutputStream andjava.util.zip.ZipOutputStream. The author assures me it is deliberate.
Instead of sometimes returning status codes, methods consistently throw EOFExceptions.
TrueZip 7 no longer lets you have elements of your zip with drive letters. To back up to zip, you would have to create directories called C D E etc. to keep track of where the files came from.
TFile.list no longer returns any absolute entries. You are probable best to convert them to relative entries with drive letters represented by a dummy directory e.g. C:\ ⇒ C\

There are many other little changes, but they pretty easy to discover letting the compiler point out syntax errors and scanning the Javadoc.

TrueZip 6 works onJava version 1.4 or later. TrueZip 7 works onJava version 1.6 or later.

Support

TrueZip supports to following flavours of archive:

Archive Formats that TrueZip supports
Type	Canonical Suffixes	Description	Advantages	Disadvantages
ZIP	zip	ZIP file: Archive file with central directory and compressible entries	Widely supported. People can easily access the archive without TrueZip. Uses standard Java java.util.zip.Deflater to do the actual compression, which is also a disadvantage because it is not a particularly quick or strong. You can trade off time for additional compression.	Incompetent date-time stamp format. They don't understand time zones or daylight saving. They are only accurate to two seconds.
JAR	ear ❘ jar ❘ war	Java Archive: ZIP with custom directory tree layout	Fully multiplatform because of Java support.	Uses rather lame compression techniques. Same advantages and disadvantages as zip. Jar is just a flavour of zip.
ODF	odb ❘ odf ❘ odg ❘ odm ❘ odp ❘ ods ❘ odt ❘ otg ❘ oth ❘ otp ❘ ots ❘ ott	OpenDocument Format, like XML (extensible Markup Language) compressed with PkZip.	Works with OpenOffice	Not a general format
TZP	tzp ❘ zip.rae ❘ zip.raes	RAES encrypted ZIP file	AES (Advanced Encryption Standard) is serious encryption.	Needs aux BouncyCastle bcprov.jar. Does not use JCE (Java Cryptography Extension) because JCE lacks the needed random access.
SFX/EXE	exe	ZIP file with a code preamble for self extraction	If you send the archive to someone, they need no additional software at all to open it.	This driver is pretty slow. Windows only. Read-only.
TAR (Tape Archive)	tar	TAR : Uncompressed tape archive file.	Universally supported under Unix.	Needs aux ant.jar.
TAR.BZ	tbz ❘ tb2 ❘ tar.bz2	TAR file wrapped in BZIP2 compression format	More aggressive compression than ZIP.	Needs aux ant.jar.
TAR.GZ	tar.gz ❘ tgz	TAR file wrapped in GZIP compression format.	Traditional Unix archive	Not particularly aggressive compression. Needs aux ant.jar.

Sample Code for TrueZip 6

Here is a simple program to add a file to a zip and display a directory of its contents.

Sample Code for TrueZip 7

Here is a simple program to add a file to a zip and display a directory of its contents.

BackupToZip Substantial Truezip Application

Here is the source code for a more complex TrueZip program that maintains a mirror of a set of files in an archive view

Encoding Gotcha

ZIP files use IBM437, an eight bit character set to encode the filenames. Anything which is not representable in this charset gets rejected. You can change this in the File API and the ZIP API. For the File API, just do this:

Another way to do it is to create an empty zip file using ZipOutputStream with a specified encoding.

However, this will stop interoperability of the created ZIP files with older tools because support for UTF-8 has been added only fairly recently! So anybody else will probably not be able to extract these ZIP files. WinZip, however, can handle them.

If you need a better option, use the JAR file format — it supports UTF-8. The TAR file format is not an option either because it supports only US-ASCII.

ANT/Genjar

It is fairly tricky to bundle just the parts of the TrueZip jar that you need inside your own jar. Here is how

The truezip works jar contains some ant code in it. If you put that code in the ext directory, ant will stop working. Remove it from the jar first.

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