JarFile

AI-generated Key Takeaways

• The JarFile class is used to read the contents of a JAR file, extending ZipFile and supporting an optional Manifest entry for metadata.

• Null arguments passed to JarFile constructors or methods result in a NullPointerException.

• Signed JAR files can be verified upon opening, but the signer's certificate is not validated; use JarEntry.getCodeSigners() for further inspection.

• JarFile provides methods for retrieving specific entries, the manifest, an input stream for entry content, and enumerating all entries.

• JarFile inherits methods from ZipFile and Object for closing the file, getting entries, comments, and other functionalities.

public class JarFile extends ZipFile

The JarFile class is used to read the contents of a jar file from any file that can be opened with java.io.RandomAccessFile. It extends the class java.util.zip.ZipFile with support for reading an optional Manifest entry. The Manifest can be used to specify meta-information about the jar file and its entries.

Unless otherwise noted, passing a null argument to a constructor or method in this class will cause a NullPointerException to be thrown. If the verify flag is on when opening a signed jar file, the content of the file is verified against its signature embedded inside the file. Please note that the verification process does not include validating the signer's certificate. A caller should inspect the return value of JarEntry.getCodeSigners() to further determine if the signature can be trusted.

See Also

• Manifest
• ZipFile
• JarEntry

Constant Summary

String

MANIFEST_NAME

The JAR manifest file name.

Inherited Constant Summary

From class java.util.zip.ZipFile

int	CENATT
int	CENATX
int	CENCOM
int	CENCRC
int	CENDSK
int	CENEXT
int	CENFLG
int	CENHDR
int	CENHOW
int	CENLEN
int	CENNAM
int	CENOFF
long	CENSIG
int	CENSIZ
int	CENTIM
int	CENVEM
int	CENVER
int	ENDCOM
int	ENDHDR
int	ENDOFF
long	ENDSIG
int	ENDSIZ
int	ENDSUB
int	ENDTOT
int	EXTCRC
int	EXTHDR
int	EXTLEN
long	EXTSIG
int	EXTSIZ
int	LOCCRC
int	LOCEXT
int	LOCFLG
int	LOCHDR
int	LOCHOW
int	LOCLEN
int	LOCNAM
long	LOCSIG
int	LOCSIZ
int	LOCTIM
int	LOCVER
int	OPEN_DELETE	Mode flag to open a zip file and mark it for deletion.
int	OPEN_READ	Mode flag to open a zip file for reading.

Public Constructor Summary

	JarFile(String name) Creates a new JarFile to read from the specified file name.
	JarFile(String name, boolean verify) Creates a new JarFile to read from the specified file name.
	JarFile(File file) Creates a new JarFile to read from the specified File object.
	JarFile(File file, boolean verify) Creates a new JarFile to read from the specified File object.
	JarFile(File file, boolean verify, int mode) Creates a new JarFile to read from the specified File object in the specified mode.

Public Method Summary

Enumeration<JarEntry>	entries() Returns an enumeration of the zip file entries.
ZipEntry	getEntry(String name) Returns the ZipEntry for the given entry name or null if not found.
synchronized InputStream	getInputStream(ZipEntry ze) Returns an input stream for reading the contents of the specified zip file entry.
JarEntry	getJarEntry(String name) Returns the JarEntry for the given entry name or null if not found.
Manifest	getManifest() Returns the jar file manifest, or null if none.
Stream<JarEntry>	stream() Return an ordered Stream over the ZIP file entries.

Inherited Method Summary

From class java.util.zip.ZipFile

void	close() Closes the ZIP file.
Enumeration<? extends ZipEntry>	entries() Returns an enumeration of the ZIP file entries.
void	finalize() Ensures that the system resources held by this ZipFile object are released when there are no more references to it.
String	getComment() Returns the zip file comment, or null if none.
ZipEntry	getEntry(String name) Returns the zip file entry for the specified name, or null if not found.
InputStream	getInputStream(ZipEntry entry) Returns an input stream for reading the contents of the specified zip file entry.
String	getName() Returns the path name of the ZIP file.
int	size() Returns the number of entries in the ZIP file.
Stream<? extends ZipEntry>	stream() Return an ordered Stream over the ZIP file entries.

From class java.lang.Object

Object	clone() Creates and returns a copy of this Object.
boolean	equals(Object obj) Compares this instance with the specified object and indicates if they are equal.
void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
final Class<?>	getClass() Returns the unique instance of Class that represents this object's class.
int	hashCode() Returns an integer hash code for this object.
final void	notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
final void	notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
String	toString() Returns a string containing a concise, human-readable description of this object.
final void	wait(long timeout, int nanos) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait(long timeout) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait() Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object.

From interface java.io.Closeable

abstract void

close() Closes this stream and releases any system resources associated with it.

From interface java.lang.AutoCloseable

abstract void

close() Closes this resource, relinquishing any underlying resources.

Constants

public static final String MANIFEST_NAME

The JAR manifest file name.

Constant Value: "META-INF/MANIFEST.MF"

Public Constructors

public JarFile (String name)

Creates a new JarFile to read from the specified file name. The JarFile will be verified if it is signed.

Parameters

name	the name of the jar file to be opened for reading

Throws

IOException	if an I/O error has occurred
SecurityException	if access to the file is denied by the SecurityManager

public JarFile (String name, boolean verify)

Creates a new JarFile to read from the specified file name.

Parameters

name	the name of the jar file to be opened for reading
verify	whether or not to verify the jar file if it is signed.

Throws

IOException	if an I/O error has occurred
SecurityException	if access to the file is denied by the SecurityManager

public JarFile (File file)

Creates a new JarFile to read from the specified File object. The JarFile will be verified if it is signed.

Parameters

file	the jar file to be opened for reading

Throws

IOException	if an I/O error has occurred
SecurityException	if access to the file is denied by the SecurityManager

public JarFile (File file, boolean verify)

Creates a new JarFile to read from the specified File object.

Parameters

file	the jar file to be opened for reading
verify	whether or not to verify the jar file if it is signed.

Throws

IOException	if an I/O error has occurred
SecurityException	if access to the file is denied by the SecurityManager.

public JarFile (File file, boolean verify, int mode)

Creates a new JarFile to read from the specified File object in the specified mode. The mode argument must be either OPEN_READ or OPEN_READ | OPEN_DELETE.

Parameters

file	the jar file to be opened for reading
verify	whether or not to verify the jar file if it is signed.
mode	the mode in which the file is to be opened

Throws

IOException	if an I/O error has occurred
IllegalArgumentException	if the mode argument is invalid
SecurityException	if access to the file is denied by the SecurityManager

Public Methods

public Enumeration<JarEntry> entries ()

Returns an enumeration of the zip file entries.

Returns

• an enumeration of the ZIP file entries

public ZipEntry getEntry (String name)

Returns the ZipEntry for the given entry name or null if not found.

Parameters

name	the jar file entry name

Returns

• the ZipEntry for the given entry name or null if not found

Throws

IllegalStateException	may be thrown if the jar file has been closed

See Also

• ZipEntry

public synchronized InputStream getInputStream (ZipEntry ze)

Returns an input stream for reading the contents of the specified zip file entry.

Parameters

ze	the zip file entry

Returns

• an input stream for reading the contents of the specified zip file entry

Throws

ZipException	if a zip file format error has occurred
IOException	if an I/O error has occurred
SecurityException	if any of the jar file entries are incorrectly signed.
IllegalStateException	may be thrown if the jar file has been closed

public JarEntry getJarEntry (String name)

Returns the JarEntry for the given entry name or null if not found.

Parameters

name	the jar file entry name

Returns

• the JarEntry for the given entry name or null if not found.

Throws

IllegalStateException	may be thrown if the jar file has been closed

See Also

• JarEntry

public Manifest getManifest ()

Returns the jar file manifest, or null if none.

Returns

• the jar file manifest, or null if none

Throws

IllegalStateException	may be thrown if the jar file has been closed
IOException	if an I/O error has occurred

public Stream<JarEntry> stream ()

Return an ordered Stream over the ZIP file entries. Entries appear in the Stream in the order they appear in the central directory of the ZIP file.

Returns

• an ordered Stream of entries in this ZIP file