Module java.base

Package java.util.jar

Class JarInputStream

java.lang.Object

java.io.InputStream

java.io.FilterInputStream

java.util.zip.InflaterInputStream

java.util.zip.ZipInputStream

java.util.jar.JarInputStream

All Implemented Interfaces:

Closeable, AutoCloseable

public class JarInputStream
extends ZipInputStream

The JarInputStream class, which extends ZipInputStream, is used to read the contents of a JAR file from an input stream. It provides support for reading an optional Manifest entry. The Manifest can be used to store meta-information about the JAR file and its entries.

Accessing the Manifest

The getManifest method is used to return the Manifest from the entry META-INF/MANIFEST.MF when it is the first entry in the stream (or the second entry if the first entry in the stream is META-INF/ and the second entry is META-INF/MANIFEST.MF).

The getNextJarEntry() and getNextEntry() methods are used to read JAR file entries from the stream. These methods skip over the Manifest (META-INF/MANIFEST.MF) when it is at the beginning of the stream. In other words, these methods do not return an entry for the Manifest when the Manifest is the first entry in the stream. If the first entry is META-INF/ and the second entry is the Manifest then both are skipped over by these methods. Whether these methods skip over the Manifest when it appears later in the stream is not specified.

Signed JAR Files

A JarInputStream verifies the signatures of entries in a Signed JAR file when:

• The Manifest is the first entry in the stream (or the second entry if the first entry in the stream is META-INF/ and the second entry is META-INF/MANIFEST.MF).
• All signature-related entries immediately follow the Manifest

Once the JarEntry has been completely verified, which is done by reading until the end of the entry's input stream, JarEntry.getCertificates() may be called to obtain the certificates for this entry and JarEntry.getCodeSigners() may be called to obtain the signers.

It is important to 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.

API Note:

If a JarEntry is modified after the JAR file is signed, a SecurityException will be thrown when the entry is read.

Since:

1.2

See Also:

• Manifest
• ZipInputStream

Field Summary

Fields

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.

Fields declared in class java.util.zip.InflaterInputStream

buf, inf, len

Fields declared in class java.io.FilterInputStream

in

Constructor Summary

Constructors

Constructor	Description
JarInputStream(InputStream in)	Creates a new JarInputStream and reads the optional manifest.
JarInputStream(InputStream in, boolean verify)	Creates a new JarInputStream and reads the optional manifest.

Method Summary

Modifier and Type	Method	Description
protected ZipEntry	createZipEntry(String name)	Creates a new JarEntry (ZipEntry) for the specified JAR file entry name.
Manifest	getManifest()	Returns the Manifest for this JAR file when it is the first entry in the stream (or the second entry if the first entry in the stream is META-INF/ and the second entry is META-INF/MANIFEST.MF), or null otherwise.
ZipEntry	getNextEntry()	Reads the next ZIP file entry and positions the stream at the beginning of the entry data.
JarEntry	getNextJarEntry()	Reads the next JAR file entry and positions the stream at the beginning of the entry data.
int	read(byte[] b, int off, int len)	Reads from the current JAR entry into an array of bytes, returning the number of inflated bytes.

Methods declared in class java.util.zip.ZipInputStream

available, close, closeEntry, read, readAllBytes, readNBytes, readNBytes, skip, skipNBytes, transferTo

Methods declared in class java.util.zip.InflaterInputStream

fill, mark, markSupported, reset

Methods declared in class java.io.FilterInputStream

read

Methods declared in class java.io.InputStream

nullInputStream

Methods declared in class java.lang.Object

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

Field Details

LOCSIG

static final long LOCSIG

Local file (LOC) header signature.

See Also:

• Constant Field Values

EXTSIG

static final long EXTSIG

Extra local (EXT) header signature.

See Also:

• Constant Field Values

CENSIG

static final long CENSIG

Central directory (CEN) header signature.

See Also:

• Constant Field Values

ENDSIG

static final long ENDSIG

End of central directory (END) header signature.

See Also:

• Constant Field Values

LOCHDR

static final int LOCHDR

Local file (LOC) header size in bytes (including signature).

See Also:

• Constant Field Values

EXTHDR

static final int EXTHDR

Extra local (EXT) header size in bytes (including signature).

See Also:

• Constant Field Values

CENHDR

static final int CENHDR

Central directory (CEN) header size in bytes (including signature).

See Also:

• Constant Field Values

ENDHDR

static final int ENDHDR

End of central directory (END) header size in bytes (including signature).

See Also:

• Constant Field Values

LOCVER

static final int LOCVER

Local file (LOC) header version needed to extract field offset.

See Also:

• Constant Field Values

LOCFLG

static final int LOCFLG

Local file (LOC) header general purpose bit flag field offset.

See Also:

• Constant Field Values

LOCHOW

static final int LOCHOW

Local file (LOC) header compression method field offset.

See Also:

• Constant Field Values

LOCTIM

static final int LOCTIM

Local file (LOC) header modification time field offset.

See Also:

• Constant Field Values

LOCCRC

static final int LOCCRC

Local file (LOC) header uncompressed file crc-32 value field offset.

See Also:

• Constant Field Values

LOCSIZ

static final int LOCSIZ

Local file (LOC) header compressed size field offset.

See Also:

• Constant Field Values

LOCLEN

static final int LOCLEN

Local file (LOC) header uncompressed size field offset.

See Also:

• Constant Field Values

LOCNAM

static final int LOCNAM

Local file (LOC) header filename length field offset.

See Also:

• Constant Field Values

LOCEXT

static final int LOCEXT

Local file (LOC) header extra field length field offset.

See Also:

• Constant Field Values

EXTCRC

static final int EXTCRC

Extra local (EXT) header uncompressed file crc-32 value field offset.

See Also:

• Constant Field Values

EXTSIZ

static final int EXTSIZ

Extra local (EXT) header compressed size field offset.

See Also:

• Constant Field Values

EXTLEN

static final int EXTLEN

Extra local (EXT) header uncompressed size field offset.

See Also:

• Constant Field Values

CENVEM

static final int CENVEM

Central directory (CEN) header version made by field offset.

See Also:

• Constant Field Values

CENVER

static final int CENVER

Central directory (CEN) header version needed to extract field offset.

See Also:

• Constant Field Values

CENFLG

static final int CENFLG

Central directory (CEN) header encrypt, decrypt flags field offset.

See Also:

• Constant Field Values

CENHOW

static final int CENHOW

Central directory (CEN) header compression method field offset.

See Also:

• Constant Field Values

CENTIM

static final int CENTIM

Central directory (CEN) header modification time field offset.

See Also:

• Constant Field Values

CENCRC

static final int CENCRC

Central directory (CEN) header uncompressed file crc-32 value field offset.

See Also:

• Constant Field Values

CENSIZ

static final int CENSIZ

Central directory (CEN) header compressed size field offset.

See Also:

• Constant Field Values

CENLEN

static final int CENLEN

Central directory (CEN) header uncompressed size field offset.

See Also:

• Constant Field Values

CENNAM

static final int CENNAM

Central directory (CEN) header filename length field offset.

See Also:

• Constant Field Values

CENEXT

static final int CENEXT

Central directory (CEN) header extra field length field offset.

See Also:

• Constant Field Values

CENCOM

static final int CENCOM

Central directory (CEN) header comment length field offset.

See Also:

• Constant Field Values

CENDSK

static final int CENDSK

Central directory (CEN) header disk number start field offset.

See Also:

• Constant Field Values

CENATT

static final int CENATT

Central directory (CEN) header internal file attributes field offset.

See Also:

• Constant Field Values

CENATX

static final int CENATX

Central directory (CEN) header external file attributes field offset.

See Also:

• Constant Field Values

CENOFF

static final int CENOFF

Central directory (CEN) header LOC header offset field offset.

See Also:

• Constant Field Values

ENDSUB

static final int ENDSUB

End of central directory (END) header number of entries on this disk field offset.

See Also:

• Constant Field Values

ENDTOT

static final int ENDTOT

End of central directory (END) header total number of entries field offset.

See Also:

• Constant Field Values

ENDSIZ

static final int ENDSIZ

End of central directory (END) header central directory size in bytes field offset.

See Also:

• Constant Field Values

ENDOFF

static final int ENDOFF

End of central directory (END) header offset for the first CEN header field offset.

See Also:

• Constant Field Values

ENDCOM

static final int ENDCOM

End of central directory (END) header zip file comment length field offset.

See Also:

• Constant Field Values

Constructor Details

JarInputStream

public JarInputStream(InputStream in)
               throws IOException

Creates a new JarInputStream and reads the optional manifest. If a manifest is present, also attempts to verify the signatures if the JarInputStream is signed.

Parameters:

in - the actual input stream

Throws:

IOException - if an I/O error has occurred

JarInputStream

public JarInputStream(InputStream in,
 boolean verify)
               throws IOException

Creates a new JarInputStream and reads the optional manifest. If a manifest is present and verify is true, also attempts to verify the signatures if the JarInputStream is signed.

Parameters:

in - the actual input stream

verify - whether or not to verify the JarInputStream if it is signed.

Throws:

IOException - if an I/O error has occurred

Method Details

getManifest

public Manifest getManifest()

Returns the Manifest for this JAR file when it is the first entry in the stream (or the second entry if the first entry in the stream is META-INF/ and the second entry is META-INF/MANIFEST.MF), or null otherwise.

Returns:

the Manifest for this JAR file, or null otherwise.

getNextEntry

public ZipEntry getNextEntry()
                      throws IOException

Reads the next ZIP file entry and positions the stream at the beginning of the entry data. If verification has been enabled, any invalid signature detected while positioning the stream for the next entry will result in an exception.

Overrides:

getNextEntry in class ZipInputStream

Returns:

the next ZIP file entry, or null if there are no more entries

Throws:

ZipException - if a ZIP file error has occurred

IOException - if an I/O error has occurred

SecurityException - if any of the jar file entries are incorrectly signed.

getNextJarEntry

public JarEntry getNextJarEntry()
                         throws IOException

Reads the next JAR file entry and positions the stream at the beginning of the entry data. If verification has been enabled, any invalid signature detected while positioning the stream for the next entry will result in an exception.

Returns:

the next JAR file entry, or null if there are no more entries

Throws:

ZipException - if a ZIP file error has occurred

IOException - if an I/O error has occurred

SecurityException - if any of the jar file entries are incorrectly signed.

read

public int read(byte[] b,
 int off,
 int len)
         throws IOException

Reads from the current JAR entry into an array of bytes, returning the number of inflated bytes. If len is not zero, the method blocks until some input is available; otherwise, no bytes are read and 0 is returned.

If the current entry is compressed and this method returns a nonzero integer n then buf[off] through buf[off+n-1] contain the uncompressed data. The content of elements buf[off+n] through buf[off+len-1] is undefined, contrary to the specification of the InputStream superclass, so an implementation is free to modify these elements during the inflate operation. If this method returns -1 or throws an exception then the content of buf[off] through buf[off+len -1] is undefined.

If verification has been enabled, any invalid signature on the current entry will be reported at some point before the end of the entry is reached.

Overrides:

read in class ZipInputStream

Parameters:

b - the buffer into which the data is read

off - the start offset in the destination array b

len - the maximum number of bytes to read

Returns:

the actual number of bytes read, or -1 if the end of the entry is reached

Throws:

NullPointerException - If b is null.

IndexOutOfBoundsException - If off is negative, len is negative, or len is greater than b.length - off

ZipException - if a ZIP file error has occurred

IOException - if an I/O error has occurred

SecurityException - if any of the jar file entries are incorrectly signed.

See Also:

• FilterInputStream.in

createZipEntry

protected ZipEntry createZipEntry(String name)

Creates a new JarEntry (ZipEntry) for the specified JAR file entry name. The manifest attributes of the specified JAR file entry name will be copied to the new JarEntry.

Overrides:

createZipEntry in class ZipInputStream

Parameters:

name - the name of the JAR/ZIP file entry

Returns:

the JarEntry object just created