JarURLConnection (Java Platform SE 8 ) (original) (raw)

A URL Connection to a Java ARchive (JAR) file or an entry in a JAR file.

The syntax of a JAR URL is:

jar:!/{entry}

for example:

jar:http://www.foo.com/bar/baz.jar!/COM/foo/Quux.class

Jar URLs should be used to refer to a JAR file or entries in a JAR file. The example above is a JAR URL which refers to a JAR entry. If the entry name is omitted, the URL refers to the whole JAR file:jar:http://www.foo.com/bar/baz.jar!/

Users should cast the generic URLConnection to a JarURLConnection when they know that the URL they created is a JAR URL, and they need JAR-specific functionality. For example:

URL url = new URL("jar:file:/home/duke/duke.jar!/"); JarURLConnection jarConnection = (JarURLConnection)url.openConnection(); Manifest manifest = jarConnection.getManifest();

JarURLConnection instances can only be used to read from JAR files. It is not possible to get a OutputStream to modify or write to the underlying JAR file using this class.

Examples:

A Jar entry

jar:http://www.foo.com/bar/baz.jar!/COM/foo/Quux.class

A Jar file

jar:http://www.foo.com/bar/baz.jar!/

A Jar directory

jar:http://www.foo.com/bar/baz.jar!/COM/foo/

!/ is referred to as the separator.

When constructing a JAR url via new URL(context, spec), the following rules apply:

• if there is no context URL and the specification passed to the URL constructor doesn't contain a separator, the URL is considered to refer to a JarFile.
• if there is a context URL, the context URL is assumed to refer to a JAR file or a Jar directory.
• if the specification begins with a '/', the Jar directory is ignored, and the spec is considered to be at the root of the Jar file.
  Examples:
  context: jar:http://www.foo.com/bar/jar.jar!/, spec:baz/entry.txt
  url:jar:http://www.foo.com/bar/jar.jar!/baz/entry.txt
  context: jar:http://www.foo.com/bar/jar.jar!/baz, spec:entry.txt
  url:jar:http://www.foo.com/bar/jar.jar!/baz/entry.txt
  context: jar:http://www.foo.com/bar/jar.jar!/baz, spec:/entry.txt
  url:jar:http://www.foo.com/bar/jar.jar!/entry.txt