Java IO.pdf - Nguyen Dang Binh

Java I/O
The Manifest class also contains methods to read a Manifest object from an input stream
and write one onto an output stream. These are mostly for Java's private use.
public void write(OutputStream out) throws IOException // Java 2
public void read(InputStream in) throws IOException // Java 2
The write() method is particularly useless, since there's no good way to create a Manifest
object and add attributes to it from within Java. [5] Most commonly, you'll simply work with
Manifest objects returned by getManifest().
Finally, the Manifest class overrides the default implementations of equals() and clone():
public boolean equals(Object o) // Java 2
public Object clone() // Java 2
9.5.8 JarInputStream
JarInputStream is a subclass of ZipInputStream that reads data from JAR archives.
public class JarInputStream extends ZipInputStream // Java 2
There are two constructors that chain the JAR input stream to an underlying input stream.
public JarInputStream(InputStream in) throws IOException // Java 2
public JarInputStream(InputStream in, boolean verify)
throws IOException // Java 2
By default, any signatures present in the JAR archive will be verified and an IOException
thrown if verification fails. However, you can turn this behavior off by passing false as the
second argument to the constructor. For example:
FileInputStream fin = new FileInputStream("javaio.jar");
JarInputStream jin = new JarInputStream(fin, false);
When the JarInputStream object is constructed, the manifest, if present, is read from the
stream and stored inside the class as a Manifest object. You do not get an opportunity to read
the manifest from the stream yourself. However, you can retrieve the Manifest object with
the getManifest() method:
public Manifest getManifest() // Java 2
Otherwise, a JAR input stream is used almost exactly like a zip input stream. You position the
stream on a particular entry in the file, then read data from it using the normal read()
methods. Any necessary inflation is performed transparently. When you've finished reading
an entry, you close it, then position the stream on the next entry. Two methods,
getNextEntry() and read(), are overridden so that verification of signatures can be
performed. A getNextJarEntry() method that returns a JarEntry instead of ZipEntry is
also available. This method can be used in place of getNextEntry(), if you like.
5
I suppose you could write a manifest file on a byte array output stream, create a byte array input stream from the output stream's byte array, then
read it back in, but that's really a kludge.
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