Java in a Nutshell, 5th Edition [Electronic resources]

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JarURLConnectionjava.net

Java 1.2

This class is a specialized URLConnection that represents a connection to a jar: URL. A jar: URL is a compound URL that includes the URL of a JAR archive and, optionally, a reference to a file or directory within the JAR archive. The jar: URL syntax uses the ! character to separate the pathname of the JAR archive from the filename within the JAR archive. Note that a jar: URL contains a subprotocol that specifies the protocol that retrieves the JAR file itself. For example:

jar:http://my.jar.com/my.jar!/ // The whole archive jar:file:/usr/java/lib/my.jar!/com/jar/ // A directory of the archive jar:ftp://ftp.jar.com/pub/my.jar!/com/jar/Jar.class // A file in the archive

To obtain a JarURLConnection, define a URL object for a jar: URL, open a connection to it with openConnection( ), and cast the returned URLConnection object to a JarURLConnection. The various methods defined by JarURLConnection allow you to read the manifest file of the JAR archive and look up attributes from that manifest for the archive as a whole or for individual entries in the archive. These methods make use of various classes from the java.util.jar package.

Figure 12-10. java.net.JarURLConnection

public abstract class

JarURLConnection extends URLConnection { // Protected Constructors protected

JarURLConnection (URL

url ) throws MalformedURLException; // Public Instance Methods public java.util.jar.Attributes

getAttributes ( ) throws java.io.IOException; public java.security.cert.Certificate[ ]

getCertificates ( ) throws java.io.IOException; public String

getEntryName ( ); public java.util.jar.JarEntry

getJarEntry ( ) throws java.io.IOException; public abstract java.util.jar.JarFile

getJarFile ( ) throws java.io.IOException; public URL

getJarFileURL ( ); public java.util.jar.Attributes

getMainAttributes ( ) throws java.io.IOException; public java.util.jar.Manifest

getManifest ( ) throws java.io.IOException; // Protected Instance Fields protected URLConnection

jarFileURLConnection ; }