ObjectInputStream

ObjectInputStream

java.io

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Java 1.1

closeable

ObjectInputStream deserializes objects, arrays, and other values from a stream that was previously created with an ObjectOutputStream . The readObject( ) method deserializes objects and arrays (which should then be cast to the appropriate type); various other methods read primitive data values from the stream. Note that only objects that implement the Serializable or Externalizable interface can be serialized and deserialized.

A class may implement its own private readObject(ObjectInputStream) method to customize the way it is deserialized. If you define such a method, there are several ObjectInputStream methods you can use to help deserialize the object. defaultReadObject( ) is the easiest . It reads the content of the object just as an ObjectInputStream would normally do. If you wrote additional data before or after the default object contents, you should read that data before or after calling defaultReadObject( ) . When working with multiple versions or implementations of a class, you may have to deserialize a set of fields that do not match the fields of your class. In this case, give your class a static field named serialPersistentFields whose value is an array of ObjectStreamField objects that describe the fields to be deserialized. If you do this, your readObject( ) method can call readFields( ) to read the specified fields from the stream and return them in a ObjectInputStream.GetField object. See ObjectStreamField and ObjectInputStream.GetField for more details. Finally, you can call registerValidation( ) from a custom readObject( ) method. This method registers an ObjectInputValidation object (typically the object being deserialized) to be notified when a complete tree of objects has been deserialized, and the original call to the readObject( ) method of the ObjectInputStream is about to return to its caller.

The remaining methods include miscellaneous stream-manipulation methods and several protected methods for use by subclasses that want to customize the deserialization behavior of ObjectInputStream .

Figure 9-36. java.io.ObjectInputStream

 public class  ObjectInputStream  extends InputStream implements ObjectInput,       ObjectStreamConstants {  // Public Constructors  public  ObjectInputStream  (InputStream  in  ) throws IOException;  // Protected Constructors   1.2  protected  ObjectInputStream  ( ) throws IOException, SecurityException;  // Nested Types   1.2  public abstract static class  GetField  ;  // Public Instance Methods  public void  defaultReadObject  ( ) throws IOException, ClassNotFoundException;  1.2  public ObjectInputStream.GetField  readFields  ( ) throws IOException,       ClassNotFoundException;  1.4  public Object  readUnshared  ( ) throws IOException, ClassNotFoundException;        public void  registerValidation  (ObjectInputValidation  obj  , int  prio  ) throws       NotActiveException, InvalidObjectException;  // Methods Implementing DataInput  public boolean  readBoolean  ( ) throws IOException;        public byte  readByte  ( ) throws IOException;        public char  readChar  ( ) throws IOException;        public double  readDouble  ( ) throws IOException;        public float  readFloat  ( ) throws IOException;        public void  readFully  (byte[ ]  buf  ) throws IOException;        public void  readFully  (byte[ ]  buf  , int  off  , int  len  ) throws IOException;        public int  readInt  ( ) throws IOException;        public long  readLong  ( ) throws IOException;        public short  readShort  ( ) throws IOException;        public int  readUnsignedByte  ( ) throws IOException;        public int  readUnsignedShort  ( ) throws IOException;        public String  readUTF  ( ) throws IOException;        public int  skipBytes  (int  len  ) throws IOException;  // Methods Implementing ObjectInput  public int  available  ( ) throws IOException;        public void  close  ( ) throws IOException;        public int  read  ( ) throws IOException;        public int  read  (byte[ ]  buf  , int  off  , int  len  ) throws IOException;        public final Object  readObject  ( ) throws IOException, ClassNotFoundException;  // Protected Instance Methods  protected boolean  enableResolveObject  (boolean  enable  ) throws SecurityException;  1.3  protected ObjectStreamClass  readClassDescriptor  ( ) throws IOException,       ClassNotFoundException;  1.2  protected Object  readObjectOverride  ( ) throws IOException,       ClassNotFoundException;  constant  protected void  readStreamHeader  ( ) throws IOException, StreamCorruptedException;        protected Class<?>  resolveClass  (ObjectStreamClass  desc  ) throws IOException,       ClassNotFoundException;        protected Object  resolveObject  (Object  obj  ) throws IOException;  1.3  protected Class<?>  resolveProxyClass  (String[ ]  interfaces  ) throws IOException,       ClassNotFoundException;  // Deprecated Public Methods   #  public String  readLine  ( ) throws IOException;  Implements:  DataInput }