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/OpenJDK 21

Class JarFile

java.lang.Object
java.util.zip.ZipFile
java.util.jar.JarFile
All Implemented Interfaces:
Closeable, AutoCloseable 
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, and support for processing multi-release jar files. The Manifest can be used to specify meta-information about the jar file and its entries.

A multi-release jar file is a jar file that contains a manifest with a main attribute named "Multi-Release", a set of "base" entries, some of which are public classes with public or protected methods that comprise the public interface of the jar file, and a set of "versioned" entries contained in subdirectories of the "META-INF/versions" directory. The versioned entries are partitioned by the major version of the Java platform. A versioned entry, with a version n, 8 < n, in the "META-INF/versions/{n}" directory overrides the base entry as well as any entry with a version number i where 8 < i < n.

By default, a JarFile for a multi-release jar file is configured to process the multi-release jar file as if it were a plain (unversioned) jar file, and as such an entry name is associated with at most one base entry. The JarFile may be configured to process a multi-release jar file by creating the JarFile with the JarFile(File, boolean, int, Runtime.Version) constructor. The Runtime.Version object sets a maximum version used when searching for versioned entries. When so configured, an entry name can correspond with at most one base entry and zero or more versioned entries. A search is required to associate the entry name with the latest versioned entry whose version is less than or equal to the maximum version (see getEntry(String)).

Class loaders that utilize JarFile to load classes from the contents of JarFile entries should construct the JarFile by invoking the JarFile(File, boolean, int, Runtime.Version) constructor with the value Runtime.version() assigned to the last argument. This assures that classes compatible with the major version of the running JVM are loaded from multi-release jar files.

If the verify flag is on when opening a signed jar file, the content of the jar entry is verified against the signature embedded inside the manifest that is associated with its path name. For a multi-release jar file, the content of a versioned entry is verfieid against its own signature and JarEntry.getCodeSigners() returns its own signers. 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.

Unless otherwise noted, passing a null argument to a constructor or method in this class will cause a NullPointerException to be thrown.

Implementation Note:
If the API can not be used to configure a JarFile (e.g. to override the configuration of a compiled application or library), two System properties are available.
  • jdk.util.jar.version can be assigned a value that is the String representation of a non-negative integer <= Runtime.version().feature(). The value is used to set the effective runtime version to something other than the default value obtained by evaluating Runtime.version().feature(). The effective runtime version is the version that the JarFile(File, boolean, int, Runtime.Version) constructor uses when the value of the last argument is JarFile.runtimeVersion().
  • jdk.util.jar.enableMultiRelease can be assigned one of the three String values true, false, or force. The value true, the default value, enables multi-release jar file processing. The value false disables multi-release jar processing, ignoring the "Multi-Release" manifest attribute, and the versioned directories in a multi-release jar file if they exist. Furthermore, the method isMultiRelease() returns false. The value force causes the JarFile to be initialized to runtime versioning after construction. It effectively does the same as this code: (new JarFile(File, boolean, int, JarFile.runtimeVersion()).
Since:
1.2
See Also:

Field Summary

Modifier and Type Field Description
static final int CENATT
Central directory (CEN) header internal file attributes field offset.
static final int CENATX
Central directory (CEN) header external file attributes field offset.
static final int CENCOM
Central directory (CEN) header comment length field offset.
static final int CENCRC
Central directory (CEN) header uncompressed file crc-32 value field offset.
static final int CENDSK
Central directory (CEN) header disk number start field offset.
static final int CENEXT
Central directory (CEN) header extra field length field offset.
static final int CENFLG
Central directory (CEN) header encrypt, decrypt flags field offset.
static final int CENHDR
Central directory (CEN) header size in bytes (including signature).
static final int CENHOW
Central directory (CEN) header compression method field offset.
static final int CENLEN
Central directory (CEN) header uncompressed size field offset.
static final int CENNAM
Central directory (CEN) header filename length field offset.
static final int CENOFF
Central directory (CEN) header LOC header offset field offset.
static final long CENSIG
Central directory (CEN) header signature.
static final int CENSIZ
Central directory (CEN) header compressed size field offset.
static final int CENTIM
Central directory (CEN) header modification time field offset.
static final int CENVEM
Central directory (CEN) header version made by field offset.
static final int CENVER
Central directory (CEN) header version needed to extract field offset.
static final int ENDCOM
End of central directory (END) header zip file comment length field offset.
static final int ENDHDR
End of central directory (END) header size in bytes (including signature).
static final int ENDOFF
End of central directory (END) header offset for the first CEN header field offset.
static final long ENDSIG
End of central directory (END) header signature.
static final int ENDSIZ
End of central directory (END) header central directory size in bytes field offset.
static final int ENDSUB
End of central directory (END) header number of entries on this disk field offset.
static final int ENDTOT
End of central directory (END) header total number of entries field offset.
static final int EXTCRC
Extra local (EXT) header uncompressed file crc-32 value field offset.
static final int EXTHDR
Extra local (EXT) header size in bytes (including signature).
static final int EXTLEN
Extra local (EXT) header uncompressed size field offset.
static final long EXTSIG
Extra local (EXT) header signature.
static final int EXTSIZ
Extra local (EXT) header compressed size field offset.
static final int LOCCRC
Local file (LOC) header uncompressed file crc-32 value field offset.
static final int LOCEXT
Local file (LOC) header extra field length field offset.
static final int LOCFLG
Local file (LOC) header general purpose bit flag field offset.
static final int LOCHDR
Local file (LOC) header size in bytes (including signature).
static final int LOCHOW
Local file (LOC) header compression method field offset.
static final int LOCLEN
Local file (LOC) header uncompressed size field offset.
static final int LOCNAM
Local file (LOC) header filename length field offset.
static final long LOCSIG
Local file (LOC) header signature.
static final int LOCSIZ
Local file (LOC) header compressed size field offset.
static final int LOCTIM
Local file (LOC) header modification time field offset.
static final int LOCVER
Local file (LOC) header version needed to extract field offset.
static final String MANIFEST_NAME
The JAR manifest file name.

Fields declared in class java.util.zip.ZipFile

OPEN_DELETE, OPEN_READ

Constructor Summary

Constructor Description
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.
JarFile(File file, boolean verify, int mode, Runtime.Version version)
Creates a new JarFile to read from the specified File object in the specified mode.
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.

Method Summary

Modifier and Type Method Description
static Runtime.Version baseVersion()
Returns the version that represents the unversioned configuration of a multi-release jar file.
Enumeration<JarEntry> entries()
Returns an enumeration of the jar file entries.
ZipEntry getEntry(String name)
Returns the ZipEntry for the given base entry name or null if not found.
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 base entry name or null if not found.
Manifest getManifest()
Returns the jar file manifest, or null if none.
final Runtime.Version getVersion()
Returns the maximum version used when searching for versioned entries.
final boolean isMultiRelease()
Indicates whether or not this jar file is a multi-release jar file.
static Runtime.Version runtimeVersion()
Returns the version that represents the effective runtime versioned configuration of a multi-release jar file.
Stream<JarEntry> stream()
Returns an ordered Stream over the jar file entries.
Stream<JarEntry> versionedStream()
Returns a Stream of the versioned jar file entries.

Methods declared in class java.util.zip.ZipFile

close, getComment, getName, size

Methods declared in class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

MANIFEST_NAME

public static final String MANIFEST_NAME
The JAR manifest file name.
See Also:

LOCSIG

static final long LOCSIG
Local file (LOC) header signature.
See Also:

EXTSIG

static final long EXTSIG
Extra local (EXT) header signature.
See Also:

CENSIG

static final long CENSIG
Central directory (CEN) header signature.
See Also:

ENDSIG

static final long ENDSIG
End of central directory (END) header signature.
See Also:

LOCHDR

static final int LOCHDR
Local file (LOC) header size in bytes (including signature).
See Also:

EXTHDR

static final int EXTHDR
Extra local (EXT) header size in bytes (including signature).
See Also:

CENHDR

static final int CENHDR
Central directory (CEN) header size in bytes (including signature).
See Also:

ENDHDR

static final int ENDHDR
End of central directory (END) header size in bytes (including signature).
See Also:

LOCVER

static final int LOCVER
Local file (LOC) header version needed to extract field offset.
See Also:

LOCFLG

static final int LOCFLG
Local file (LOC) header general purpose bit flag field offset.
See Also:

LOCHOW

static final int LOCHOW
Local file (LOC) header compression method field offset.
See Also:

LOCTIM

static final int LOCTIM
Local file (LOC) header modification time field offset.
See Also:

LOCCRC

static final int LOCCRC
Local file (LOC) header uncompressed file crc-32 value field offset.
See Also:

LOCSIZ

static final int LOCSIZ
Local file (LOC) header compressed size field offset.
See Also:

LOCLEN

static final int LOCLEN
Local file (LOC) header uncompressed size field offset.
See Also:

LOCNAM

static final int LOCNAM
Local file (LOC) header filename length field offset.
See Also:

LOCEXT

static final int LOCEXT
Local file (LOC) header extra field length field offset.
See Also:

EXTCRC

static final int EXTCRC
Extra local (EXT) header uncompressed file crc-32 value field offset.
See Also:

EXTSIZ

static final int EXTSIZ
Extra local (EXT) header compressed size field offset.
See Also:

EXTLEN

static final int EXTLEN
Extra local (EXT) header uncompressed size field offset.
See Also:

CENVEM

static final int CENVEM
Central directory (CEN) header version made by field offset.
See Also:

CENVER

static final int CENVER
Central directory (CEN) header version needed to extract field offset.
See Also:

CENFLG

static final int CENFLG
Central directory (CEN) header encrypt, decrypt flags field offset.
See Also:

CENHOW

static final int CENHOW
Central directory (CEN) header compression method field offset.
See Also:

CENTIM

static final int CENTIM
Central directory (CEN) header modification time field offset.
See Also:

CENCRC

static final int CENCRC
Central directory (CEN) header uncompressed file crc-32 value field offset.
See Also:

CENSIZ

static final int CENSIZ
Central directory (CEN) header compressed size field offset.
See Also:

CENLEN

static final int CENLEN
Central directory (CEN) header uncompressed size field offset.
See Also:

CENNAM

static final int CENNAM
Central directory (CEN) header filename length field offset.
See Also:

CENEXT

static final int CENEXT
Central directory (CEN) header extra field length field offset.
See Also:

CENCOM

static final int CENCOM
Central directory (CEN) header comment length field offset.
See Also:

CENDSK

static final int CENDSK
Central directory (CEN) header disk number start field offset.
See Also:

CENATT

static final int CENATT
Central directory (CEN) header internal file attributes field offset.
See Also:

CENATX

static final int CENATX
Central directory (CEN) header external file attributes field offset.
See Also:

CENOFF

static final int CENOFF
Central directory (CEN) header LOC header offset field offset.
See Also:

ENDSUB

static final int ENDSUB
End of central directory (END) header number of entries on this disk field offset.
See Also:

ENDTOT

static final int ENDTOT
End of central directory (END) header total number of entries field offset.
See Also:

ENDSIZ

static final int ENDSIZ
End of central directory (END) header central directory size in bytes field offset.
See Also:

ENDOFF

static final int ENDOFF
End of central directory (END) header offset for the first CEN header field offset.
See Also:

ENDCOM

static final int ENDCOM
End of central directory (END) header zip file comment length field offset.
See Also:

Constructor Details

JarFile

public JarFile(String name) throws IOException
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

JarFile

public JarFile(String name, boolean verify) throws IOException
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

JarFile

public JarFile(File file) throws IOException
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

JarFile

public JarFile(File file, boolean verify) throws IOException
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.

JarFile

public JarFile(File file, boolean verify, int mode) throws IOException
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
Since:
1.3

JarFile

public JarFile(File file, boolean verify, int mode, Runtime.Version version) throws IOException
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. The version argument, after being converted to a canonical form, is used to configure the JarFile for processing multi-release jar files.

The canonical form derived from the version parameter is Runtime.Version.parse(Integer.toString(n)) where n is Math.max(version.feature(), JarFile.baseVersion().feature()).

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
version - specifies the release version for a multi-release jar file
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
NullPointerException - if version is null
Since:
9

Method Details

baseVersion

public static Runtime.Version baseVersion()
Returns the version that represents the unversioned configuration of a multi-release jar file.
Returns:
the version that represents the unversioned configuration
Since:
9

runtimeVersion

public static Runtime.Version runtimeVersion()
Returns the version that represents the effective runtime versioned configuration of a multi-release jar file.

By default the feature version number of the returned Version will be equal to the feature version number of Runtime.version(). However, if the jdk.util.jar.version property is set, the returned Version is derived from that property and feature version numbers may not be equal.

Returns:
the version that represents the runtime versioned configuration
Since:
9

getVersion

public final Runtime.Version getVersion()
Returns the maximum version used when searching for versioned entries.

If this JarFile is not a multi-release jar file or is not configured to be processed as such, then the version returned will be the same as that returned from baseVersion().

Returns:
the maximum version
Since:
9

isMultiRelease

public final boolean isMultiRelease()
Indicates whether or not this jar file is a multi-release jar file.
Returns:
true if this JarFile is a multi-release jar file
Since:
9

getManifest

public Manifest getManifest() throws IOException
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

getJarEntry

public JarEntry getJarEntry(String name)
Returns the JarEntry for the given base entry name or null if not found.

If this JarFile is a multi-release jar file and is configured to be processed as such, then a search is performed to find and return a JarEntry that is the latest versioned entry associated with the given entry name. The returned JarEntry is the versioned entry corresponding to the given base entry name prefixed with the string "META-INF/versions/{n}/", for the largest value of n for which an entry exists. If such a versioned entry does not exist, then the JarEntry for the base entry is returned, otherwise null is returned if no entries are found. The initial value for the version n is the maximum version as returned by the method getVersion().

Implementation Requirements:
This implementation invokes getEntry(String).
Parameters:
name - the jar file entry name
Returns:
the JarEntry for the given entry name, or the versioned entry name, or null if not found
Throws:
IllegalStateException - may be thrown if the jar file has been closed
See Also:

getEntry

public ZipEntry getEntry(String name)
Returns the ZipEntry for the given base entry name or null if not found.

If this JarFile is a multi-release jar file and is configured to be processed as such, then a search is performed to find and return a ZipEntry that is the latest versioned entry associated with the given entry name. The returned ZipEntry is the versioned entry corresponding to the given base entry name prefixed with the string "META-INF/versions/{n}/", for the largest value of n for which an entry exists. If such a versioned entry does not exist, then the ZipEntry for the base entry is returned, otherwise null is returned if no entries are found. The initial value for the version n is the maximum version as returned by the method getVersion().

Overrides:
getEntry in class ZipFile
Implementation Requirements:
This implementation may return a versioned entry for the requested name even if there is not a corresponding base entry. This can occur if there is a private or package-private versioned entry that matches. If a subclass overrides this method, assure that the override method invokes super.getEntry(name) to obtain all versioned entries.
Parameters:
name - the jar file entry name
Returns:
the ZipEntry for the given entry name or the versioned entry name or null if not found
Throws:
IllegalStateException - may be thrown if the jar file has been closed
See Also:

entries

public Enumeration<JarEntry> entries()
Returns an enumeration of the jar file entries.
Overrides:
entries in class ZipFile
Returns:
an enumeration of the jar file entries
Throws:
IllegalStateException - may be thrown if the jar file has been closed

stream

public Stream<JarEntry> stream()
Returns an ordered Stream over the jar file entries. Entries appear in the Stream in the order they appear in the central directory of the jar file.
Overrides:
stream in class ZipFile
Returns:
an ordered Stream of entries in this jar file
Throws:
IllegalStateException - if the jar file has been closed
Since:
1.8

versionedStream

public Stream<JarEntry> versionedStream()
Returns a Stream of the versioned jar file entries.

If this JarFile is a multi-release jar file and is configured to be processed as such, then an entry in the stream is the latest versioned entry associated with the corresponding base entry name. The maximum version of the latest versioned entry is the version returned by getVersion(). The returned stream may include an entry that only exists as a versioned entry. If the jar file is not a multi-release jar file or the JarFile is not configured for processing a multi-release jar file, this method returns the same stream that stream() returns.

Returns:
stream of versioned entries
Since:
10

getInputStream

public InputStream getInputStream(ZipEntry ze) throws IOException
Returns an input stream for reading the contents of the specified zip file entry.
Overrides:
getInputStream in class ZipFile
API Note:
The InputStream returned by this method can wrap an InflaterInputStream, whose read(byte[], int, int) method can modify any element of the output buffer.
Parameters:
ze - the zip file entry
Returns:
an input stream for reading the contents of the specified zip file entry or null if the zip file entry does not exist within the jar file
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

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Documentation extracted from Debian's OpenJDK Development Kit package.
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https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/util/jar/JarFile.html