Java IO.pdf - Nguyen Dang Binh

Java I/O
pairs, one to a line. Names are separated from values by colons and whitespace, as in email
headers. For example:
Name: com/macfaq/awt/Filmstrip.class
Java-Bean: true
Last-modified: 09-07-1998
Depends-On: com/macfaq/io/StreamCopier.class
Brad: Majors
Digest-Algorithms: MD5
MD5-Digest: XD4578YEEIK9MGX54RFGT7UJUI9810
This defines an entry with the name com/macfaq/awt/Filmstrip.class. This entry has six
attributes: Java-Bean with the value true, Last-modified with the value 09-07-1998, Brad
with the value Majors, Depends-On with the value com/macfaq/io/StreamCopier.class,
and so on. Each of these has a specific meaning in a particular context. For instance, the
Java-Bean attribute with the value true means that this class is a Java Bean that can be
loaded into a visual builder tool. Digest-Algorithms gives you the types of message digests
computed from the file, and MD5-Digest gives the value of one particular digest. Most of the
attributes have an application-specific meaning. Applications reading a JAR archive that don't
understand a particular attribute should simply ignore it.
One possible manifest file for the directory shown in Figure 9.3 looks like this:
Manifest-Version: 1.0
Name: com/macfaq/awt/StreamedTextArea.class
Name: com/macfaq/io/BufferedStreamCopier.class
Name: com/macfaq/io/FileCopier.class
Name: com/macfaq/io/LittleEndianOutputStream.class
Name: com/macfaq/io/MultiOutputStream.class
Name: com/macfaq/io/NullOutputStream.class
Name: com/macfaq/io/PrintableInputStream.class
Name: com/macfaq/io/PrintableOutputStream.class
Name: com/macfaq/io/RandomInputStream.class
Name: com/macfaq/io/StreamCopier.class
Brad: Majors
Name: com/macfaq/io/TeeOutputStream.class
Riff: Raff
Name: com/macfaq/util/CommandLineArguments.class
The files in the JAR archive may be signed using a digital signature algorithm. Different
individuals may sign different files, and more than one person may sign each file. For each
file that's signed, the META-INF directory will also contain a signature file. I won't discuss
signatures in great detail here; for starters, they're very different in Java 1.1 and Java 2.
However, you should realize that signatures can be checked when a file is read from a JAR
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