All Implemented Interfaces:
Closeable, AutoCloseable

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

    static final int

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

    static final int

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

    static final int

    Central directory (CEN) header comment length field offset.

    static final int

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

    static final int

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

    static final int

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

    static final int

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

    static final int

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

    static final int

    Central directory (CEN) header compression method field offset.

    static final int

    Central directory (CEN) header uncompressed size field offset.

    static final int

    Central directory (CEN) header filename length field offset.

    static final int

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

    static final long

    Central directory (CEN) header signature.

    static final int

    Central directory (CEN) header compressed size field offset.

    static final int

    Central directory (CEN) header modification time field offset.

    static final int

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

    static final int

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

    static final int

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

    static final int

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

    static final int

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

    static final long

    End of central directory (END) header signature.

    static final int

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

    static final int

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

    static final int

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

    static final int

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

    static final int

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

    static final int

    Extra local (EXT) header uncompressed size field offset.

    static final long

    Extra local (EXT) header signature.

    static final int

    Extra local (EXT) header compressed size field offset.

    static final int

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

    static final int

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

    static final int

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

    static final int

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

    static final int

    Local file (LOC) header compression method field offset.

    static final int

    Local file (LOC) header uncompressed size field offset.

    static final int

    Local file (LOC) header filename length field offset.

    static final long

    Local file (LOC) header signature.

    static final int

    Local file (LOC) header compressed size field offset.

    static final int

    Local file (LOC) header modification time field offset.

    static final int

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

  • Constructor Summary

    Constructors

    Creates a new JarInputStream and reads the optional manifest.

    Creates a new JarInputStream and reads the optional manifest.

  • Method Summary

    Creates a new JarEntry (ZipEntry) for the specified JAR file entry name.

    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.

    Reads the next ZIP file entry and positions the stream at the beginning of the entry data.

    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.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.

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    • LOCTIM

      static final int LOCTIM

      Local file (LOC) header modification time field offset.

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    • LOCCRC

      static final int LOCCRC

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

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    • 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.

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    • 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.

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    • 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.

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    • 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.

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    • 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

      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

      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

      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

      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

      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

      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