javax.crypto

Class CipherOutputStream

  1. java.lang.Object
  2. extended byjava.io.OutputStream
  3. extended byjava.io.FilterOutputStream
  4. extended byjavax.crypto.CipherOutputStream
All implemented interfaces:
java.io.Closeable, java.io.Flushable

  1. public class CipherOutputStream
  2. extends java.io.FilterOutputStream
A CipherOutputStream is composed of an OutputStream and a Cipher so that write() methods first process the data before writing them out to the underlying OutputStream. The cipher must be fully initialized before being used by a CipherOutputStream.

For example, if the cipher is initialized for encryption, the CipherOutputStream will attempt to encrypt data before writing out the encrypted data.

This class adheres strictly to the semantics, especially the failure semantics, of its ancestor classes java.io.OutputStream and java.io.FilterOutputStream. This class has exactly those methods specified in its ancestor classes, and overrides them all. Moreover, this class catches all exceptions that are not thrown by its ancestor classes.

It is crucial for a programmer using this class not to use methods that are not defined or overriden in this class (such as a new method or constructor that is later added to one of the super classes), because the design and implementation of those methods are unlikely to have considered security impact with regard to CipherOutputStream.

Since:
1.4
Version:
1.24, 01/06/04
Author:
Li Gong
See Also:
OutputStream, FilterOutputStream, Cipher, CipherInputStream

Field Summary

Fields inherited from class java.io.FilterOutputStream
out

Constructor Summary

Modifier Constructor and Description
  1. protected
CipherOutputStream(java.io.OutputStream os)
Constructs a CipherOutputStream from an OutputStream without specifying a Cipher.
  1. (package private)
CipherOutputStream(java.io.OutputStream os,Cipher c)
Constructs a CipherOutputStream from an OutputStream and a Cipher.

Method Summary

Modifier and Type Method and Description
  1. void
close()
Closes this output stream and releases any system resources associated with this stream.
  1. void
flush()
Flushes this output stream by forcing any buffered output bytes that have already been processed by the encapsulated cipher object to be written out.
  1. void
write(byte[] b)
Writes b.length bytes from the specified byte array to this output stream.
  1. void
write(byte[] b,int off,int len)
Writes len bytes from the specified byte array starting at offset off to this output stream.
  1. void
write(int b)
Writes the specified byte to this output stream.
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

CipherOutputStream

  1. public CipherOutputStream(java.io.OutputStream os,
  2. Cipher c)
Constructs a CipherOutputStream from an OutputStream and a Cipher.
Note: if the specified output stream or cipher is null, a NullPointerException may be thrown later when they are used.
Parameters:
os - the OutputStream object
c - an initialized Cipher object

CipherOutputStream

  1. protected CipherOutputStream(java.io.OutputStream os)
Constructs a CipherOutputStream from an OutputStream without specifying a Cipher. This has the effect of constructing a CipherOutputStream using a NullCipher.
Note: if the specified output stream is null, a NullPointerException may be thrown later when it is used.
Parameters:
os - the OutputStream object

Method Detail

write

  1. public void write(int b)
  2. throws java.io.IOException
Writes the specified byte to this output stream.
Overrides:
write in class java.io.FilterOutputStream
Parameters:
b - the byte.
Throws:
java.io.IOException - if an I/O error occurs.
Since:
JCE1.2

write

  1. public void write(byte[] b)
  2. throws java.io.IOException
Writes b.length bytes from the specified byte array to this output stream.

The write method of CipherOutputStream calls the write method of three arguments with the three arguments b, 0, and b.length.

Overrides:
write in class java.io.FilterOutputStream
Parameters:
b - the data.
Throws:
java.lang.NullPointerException - if b is null.
java.io.IOException - if an I/O error occurs.
Since:
JCE1.2
See Also:

write

  1. public void write(byte[] b,
  2. int off,
  3. int len)
  4. throws java.io.IOException
Writes len bytes from the specified byte array starting at offset off to this output stream.
Overrides:
write in class java.io.FilterOutputStream
Parameters:
b - the data.
off - the start offset in the data.
len - the number of bytes to write.
Throws:
java.io.IOException - if an I/O error occurs.
Since:
JCE1.2

flush

  1. public void flush()
  2. throws java.io.IOException
Flushes this output stream by forcing any buffered output bytes that have already been processed by the encapsulated cipher object to be written out.

Any bytes buffered by the encapsulated cipher and waiting to be processed by it will not be written out. For example, if the encapsulated cipher is a block cipher, and the total number of bytes written using one of the write methods is less than the cipher's block size, no bytes will be written out.

Specified by:
flush in interface java.io.Flushable
Overrides:
flush in class java.io.FilterOutputStream
Throws:
java.io.IOException - if an I/O error occurs.
Since:
JCE1.2

close

  1. public void close()
  2. throws java.io.IOException
Closes this output stream and releases any system resources associated with this stream.

This method invokes the doFinal method of the encapsulated cipher object, which causes any bytes buffered by the encapsulated cipher to be processed. The result is written out by calling the flush method of this output stream.

This method resets the encapsulated cipher object to its initial state and calls the close method of the underlying output stream.

Specified by:
close in interface java.io.Closeable
Overrides:
close in class java.io.FilterOutputStream
Throws:
java.io.IOException - if an I/O error occurs.
Since:
JCE1.2