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:

  • 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:

    • 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

    • 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:

    • 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