Module java.base
Package javax.crypto

## Class CipherOutputStream

- java.lang.Object
- - java.io.OutputStream
  - - java.io.FilterOutputStream
    - - javax.crypto.CipherOutputStream

- All Implemented Interfaces:
    `Closeable`, `Flushable`, `AutoCloseable`

      public class CipherOutputStream
      extends 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. In particular, this class catches BadPaddingException and other exceptions thrown by failed integrity checks during decryption. These exceptions are not re-thrown, so the client will not be informed that integrity checks failed. Because of this behavior, this class may not be suitable for use with decryption in an authenticated mode of operation (e.g. GCM) if the application requires explicit notification when authentication fails. Such an application can use the Cipher API directly as an alternative to using this class.

  It is crucial for a programmer using this class not to use methods that are not defined or overridden 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
  See Also:
    `OutputStream`, `FilterOutputStream`, `Cipher`, `CipherInputStream`

- - ### Field Summary

    - ### Fields declared in class java.io.FilterOutputStream

      `out`

  - ### Constructor Summary

    Constructors
    Modifier | Constructor | Description
    --- | --- | ---
    `protected` | `CipherOutputStream​(OutputStream os)` | Constructs a CipherOutputStream from an OutputStream without specifying a Cipher.
    `` | `CipherOutputStream​(OutputStream os, Cipher c)` | Constructs a CipherOutputStream from an OutputStream and a Cipher.

  - ### Method Summary

    Modifier and Type | Method | Description
    --- | --- | ---
    `void` | `close()` | Closes this output stream and releases any system resources associated with this stream.
    `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.
    `void` | `write​(byte[] b)` | Writes `b.length` bytes from the specified byte array to this output stream.
    `void` | `write​(byte[] b, int off, int len)` | Writes `len` bytes from the specified byte array starting at offset `off` to this output stream.
    `void` | `write​(int b)` | Writes the specified byte to this output stream.

    - ### Methods declared in class java.io.OutputStream

      `nullOutputStream`

    - ### Methods declared in class java.lang.Object

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

- - ### Constructor Detail

    - #### CipherOutputStream

          public CipherOutputStream​(OutputStream os,
                                    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

          protected CipherOutputStream​(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

          public void write​(int b)
                     throws IOException

      Writes the specified byte to this output stream.
      Overrides:
        `write` in class `FilterOutputStream`
      Parameters:
        `b` - the `byte`.
      Throws:
        `IOException` - if an I/O error occurs.

    - #### write

          public void write​(byte[] b)
                     throws 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 `FilterOutputStream`
      Parameters:
        `b` - the data.
      Throws:
        `NullPointerException` - if `b` is null.
        `IOException` - if an I/O error occurs.
      See Also:
        `write(byte[], int, int)`

    - #### write

          public void write​(byte[] b,
                            int off,
                            int len)
                     throws IOException

      Writes `len` bytes from the specified byte array starting at offset `off` to this output stream.
      Overrides:
        `write` in class `FilterOutputStream`
      Parameters:
        `b` - the data.
        `off` - the start offset in the data.
        `len` - the number of bytes to write.
      Throws:
        `IOException` - if an I/O error occurs.
      See Also:
        `FilterOutputStream.write(int)`

    - #### flush

          public void flush()
                     throws 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 `Flushable`
      Overrides:
        `flush` in class `FilterOutputStream`
      Throws:
        `IOException` - if an I/O error occurs.
      See Also:
        `FilterOutputStream.out`

    - #### close

          public void close()
                     throws 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 `AutoCloseable`
      Specified by:
        `close` in interface `Closeable`
      Overrides:
        `close` in class `FilterOutputStream`
      Throws:
        `IOException` - if an I/O error occurs.
      See Also:
        `FilterOutputStream.flush()`, `FilterOutputStream.out`