Package java.io

Class ObjectOutputStream

java.lang.Object
java.io.OutputStream
java.io.ObjectOutputStream
All Implemented Interfaces:
Closeable, DataOutput, Flushable, ObjectOutput, ObjectStreamConstants, AutoCloseable
public class ObjectOutputStream
extends OutputStream
implements ObjectOutput, ObjectStreamConstants
A specialized OutputStream that is able to write (serialize) Java objects as well as primitive data types (int, byte, char etc.). The data can later be loaded using an ObjectInputStream.
See Also:
ObjectInputStream, ObjectOutput, Serializable, Externalizable

  • Constructor Details

    • ObjectOutputStream

      protected ObjectOutputStream() throws IOException
      Constructs a new ObjectOutputStream. This default constructor can be used by subclasses that do not want to use the public constructor if it allocates unneeded data.
      Throws:
      IOException - if an error occurs when creating this stream.

    • ObjectOutputStream

      public ObjectOutputStream​(OutputStream output) throws IOException
      Constructs a new ObjectOutputStream that writes to the OutputStream output.
      Parameters:
      output - the non-null OutputStream to filter writes on.
      Throws:
      IOException - if an error occurs while writing the object stream header

  • Method Details

    • annotateClass

      protected void annotateClass​(Class<?> aClass) throws IOException
      Writes optional information for class aClass to the output stream. This optional data can be read when deserializing the class descriptor (ObjectStreamClass) for this class from an input stream. By default, no extra data is saved.
      Parameters:
      aClass - the class to annotate.
      Throws:
      IOException - if an error occurs while writing to the target stream.
      See Also:
      ObjectInputStream.resolveClass(ObjectStreamClass)

    • annotateProxyClass

      protected void annotateProxyClass​(Class<?> aClass) throws IOException
      Writes optional information for a proxy class to the target stream. This optional data can be read when deserializing the proxy class from an input stream. By default, no extra data is saved.
      Parameters:
      aClass - the proxy class to annotate.
      Throws:
      IOException - if an error occurs while writing to the target stream.
      See Also:
      ObjectInputStream.resolveProxyClass(String[])

    • close

      public void close() throws IOException
      Closes this stream. Any buffered data is flushed. This implementation closes the target stream.
      Specified by:
      close in interface AutoCloseable
      Specified by:
      close in interface Closeable
      Specified by:
      close in interface ObjectOutput
      Overrides:
      close in class OutputStream
      Throws:
      IOException - if an error occurs while closing this stream.

    • defaultWriteObject

      public void defaultWriteObject() throws IOException
      Default method to write objects to this stream. Serializable fields defined in the object's class and superclasses are written to the output stream.
      Throws:
      IOException - if an error occurs while writing to the target stream.
      NotActiveException - if this method is not called from writeObject().
      See Also:
      ObjectInputStream.defaultReadObject()

    • drain

      protected void drain() throws IOException
      Writes buffered data to the target stream. This is similar to flush but the flush is not propagated to the target stream.
      Throws:
      IOException - if an error occurs while writing to the target stream.

    • enableReplaceObject

      protected boolean enableReplaceObject​(boolean enable)
      Enables object replacement for this stream. By default this is not enabled. Only trusted subclasses (loaded with system class loader) are allowed to change this status.
      Parameters:
      enable - true to enable object replacement; false to disable it.
      Returns:
      the previous setting.
      See Also:
      replaceObject(java.lang.Object), ObjectInputStream.enableResolveObject(boolean)

    • flush

      public void flush() throws IOException
      Writes buffered data to the target stream and calls the flush method of the target stream.
      Specified by:
      flush in interface Flushable
      Specified by:
      flush in interface ObjectOutput
      Overrides:
      flush in class OutputStream
      Throws:
      IOException - if an error occurs while writing to or flushing the output stream.

    • putFields

      public ObjectOutputStream.PutField putFields() throws IOException
      Gets this stream's PutField object. This object provides access to the persistent fields that are eventually written to the output stream. It is used to transfer the values from the fields of the object that is currently being written to the persistent fields.
      Returns:
      the PutField object from which persistent fields can be accessed by name.
      Throws:
      IOException - if an I/O error occurs.
      NotActiveException - if this method is not called from writeObject().
      See Also:
      ObjectInputStream.defaultReadObject()

    • replaceObject

      protected Object replaceObject​(Object object) throws IOException
      Allows trusted subclasses to substitute the specified original object with a new object. Object substitution has to be activated first with calling enableReplaceObject(true). This implementation just returns object.
      Parameters:
      object - the original object for which a replacement may be defined.
      Returns:
      the replacement object for object.
      Throws:
      IOException - if any I/O error occurs while creating the replacement object.
      See Also:
      enableReplaceObject(boolean), ObjectInputStream.enableResolveObject(boolean), ObjectInputStream.resolveObject(java.lang.Object)

    • reset

      public void reset() throws IOException
      Resets the state of this stream. A marker is written to the stream, so that the corresponding input stream will also perform a reset at the same point. Objects previously written are no longer remembered, so they will be written again (instead of a cyclical reference) if found in the object graph.
      Throws:
      IOException - if reset() is called during the serialization of an object.

    • useProtocolVersion

      public void useProtocolVersion​(int version) throws IOException
      Sets the specified protocol version to be used by this stream.
      Parameters:
      version - the protocol version to be used. Use a PROTOCOL_VERSION_x constant from java.io.ObjectStreamConstants.
      Throws:
      IllegalArgumentException - if an invalid version is specified.
      IOException - if an I/O error occurs.
      See Also:
      ObjectStreamConstants.PROTOCOL_VERSION_1, ObjectStreamConstants.PROTOCOL_VERSION_2

    • write

      public void write​(byte[] buffer, int offset, int length) throws IOException
      Writes count bytes from the byte array buffer starting at offset index to the target stream. Blocks until all bytes are written.
      Specified by:
      write in interface DataOutput
      Specified by:
      write in interface ObjectOutput
      Overrides:
      write in class OutputStream
      Parameters:
      buffer - the buffer to write.
      offset - the index of the first byte in buffer to write.
      length - the number of bytes from buffer to write to the output stream.
      Throws:
      IOException - if an error occurs while writing to the target stream.

    • write

      public void write​(int value) throws IOException
      Writes a single byte to the target stream. Only the least significant byte of the integer value is written to the stream. Blocks until the byte is actually written.
      Specified by:
      write in interface DataOutput
      Specified by:
      write in interface ObjectOutput
      Specified by:
      write in class OutputStream
      Parameters:
      value - the byte to write.
      Throws:
      IOException - if an error occurs while writing to the target stream.
      See Also:
      DataInput.readByte()

    • writeBoolean

      public void writeBoolean​(boolean value) throws IOException
      Writes a boolean to the target stream.
      Specified by:
      writeBoolean in interface DataOutput
      Parameters:
      value - the boolean value to write to the target stream.
      Throws:
      IOException - if an error occurs while writing to the target stream.
      See Also:
      DataInput.readBoolean()

    • writeByte

      public void writeByte​(int value) throws IOException
      Writes a byte (8 bit) to the target stream.
      Specified by:
      writeByte in interface DataOutput
      Parameters:
      value - the byte to write to the target stream.
      Throws:
      IOException - if an error occurs while writing to the target stream.
      See Also:
      DataInput.readByte(), DataInput.readUnsignedByte()

    • writeBytes

      public void writeBytes​(String value) throws IOException
      Writes the string value as a sequence of bytes to the target stream. Only the least significant byte of each character in the string is written.
      Specified by:
      writeBytes in interface DataOutput
      Parameters:
      value - the string to write to the target stream.
      Throws:
      IOException - if an error occurs while writing to the target stream.

    • writeChar

      public void writeChar​(int value) throws IOException
      Writes a character (16 bit) to the target stream.
      Specified by:
      writeChar in interface DataOutput
      Parameters:
      value - the character to write to the target stream.
      Throws:
      IOException - if an error occurs while writing to the target stream.
      See Also:
      DataInput.readChar()

    • writeChars

      public void writeChars​(String value) throws IOException
      Writes the string value as a sequence of characters to the target stream.
      Specified by:
      writeChars in interface DataOutput
      Parameters:
      value - the string to write to the target stream.
      Throws:
      IOException - if an error occurs while writing to the target stream.
      See Also:
      DataInput.readChar()

    • writeDouble

      public void writeDouble​(double value) throws IOException
      Writes a double (64 bit) to the target stream.
      Specified by:
      writeDouble in interface DataOutput
      Parameters:
      value - the double to write to the target stream.
      Throws:
      IOException - if an error occurs while writing to the target stream.
      See Also:
      DataInput.readDouble()

    • writeFields

      public void writeFields() throws IOException
      Writes the fields of the object currently being written to the target stream. The field values are buffered in the currently active PutField object, which can be accessed by calling putFields().
      Throws:
      IOException - if an error occurs while writing to the target stream.
      NotActiveException - if there are no fields to write to the target stream.
      See Also:
      putFields()

    • writeFloat

      public void writeFloat​(float value) throws IOException
      Writes a float (32 bit) to the target stream.
      Specified by:
      writeFloat in interface DataOutput
      Parameters:
      value - the float to write to the target stream.
      Throws:
      IOException - if an error occurs while writing to the target stream.
      See Also:
      DataInput.readFloat()

    • writeInt

      public void writeInt​(int value) throws IOException
      Writes an integer (32 bit) to the target stream.
      Specified by:
      writeInt in interface DataOutput
      Parameters:
      value - the integer to write to the target stream.
      Throws:
      IOException - if an error occurs while writing to the target stream.
      See Also:
      DataInput.readInt()

    • writeLong

      public void writeLong​(long value) throws IOException
      Writes a long (64 bit) to the target stream.
      Specified by:
      writeLong in interface DataOutput
      Parameters:
      value - the long to write to the target stream.
      Throws:
      IOException - if an error occurs while writing to the target stream.
      See Also:
      DataInput.readLong()

    • writeClassDescriptor

      protected void writeClassDescriptor​(ObjectStreamClass classDesc) throws IOException
      Writes a class descriptor to the target stream.
      Parameters:
      classDesc - the class descriptor to write to the target stream.
      Throws:
      IOException - if an error occurs while writing to the target stream.

    • writeObject

      public final void writeObject​(Object object) throws IOException
      Writes an object to the target stream.
      Specified by:
      writeObject in interface ObjectOutput
      Parameters:
      object - the object to write to the target stream.
      Throws:
      IOException - if an error occurs while writing to the target stream.
      See Also:
      ObjectInputStream.readObject()

    • writeUnshared

      public void writeUnshared​(Object object) throws IOException
      Writes an unshared object to the target stream. This method is identical to writeObject, except that it always writes a new object to the stream versus the use of back-referencing for identical objects by writeObject.
      Parameters:
      object - the object to write to the target stream.
      Throws:
      IOException - if an error occurs while writing to the target stream.
      See Also:
      ObjectInputStream.readUnshared()

    • writeObjectOverride

      protected void writeObjectOverride​(Object object) throws IOException
      Method to be overridden by subclasses to write object to the target stream.
      Parameters:
      object - the object to write to the target stream.
      Throws:
      IOException - if an error occurs while writing to the target stream.

    • writeShort

      public void writeShort​(int value) throws IOException
      Writes a short (16 bit) to the target stream.
      Specified by:
      writeShort in interface DataOutput
      Parameters:
      value - the short to write to the target stream.
      Throws:
      IOException - if an error occurs while writing to the target stream.
      See Also:
      DataInput.readShort(), DataInput.readUnsignedShort()

    • writeStreamHeader

      protected void writeStreamHeader() throws IOException
      Writes the ObjectOutputStream header to the target stream.
      Throws:
      IOException - if an error occurs while writing to the target stream.

    • writeUTF

      public void writeUTF​(String value) throws IOException
      Writes a string encoded with modified UTF-8 to the target stream.
      Specified by:
      writeUTF in interface DataOutput
      Parameters:
      value - the string to write to the target stream.
      Throws:
      IOException - if an error occurs while writing to the target stream.
      See Also:
      DataInput.readUTF()