Java I/O 教程（十） ObjectOutputStream和ObjectInputStream

ObjectOutputStream

ObjectOutputStream用于往输出流中写入原始类型和Java对象。

类定义

public class ObjectOutputStream
extends OutputStream
implements ObjectOutput, ObjectStreamConstants

构造函数

protected	ObjectOutputStream() Provide a way for subclasses that are completely reimplementing ObjectOutputStream to not have to allocate private data just used by this implementation of ObjectOutputStream.
	ObjectOutputStream(OutputStream out) Creates an ObjectOutputStream that writes to the specified OutputStream.

方法

protected void	annotateClass(Class<?> cl) Subclasses may implement this method to allow class data to be stored in the stream.
protected void	annotateProxyClass(Class<?> cl) Subclasses may implement this method to store custom data in the stream along with descriptors for dynamic proxy classes.
void	close() Closes the stream.
void	defaultWriteObject() Write the non-static and non-transient fields of the current class to this stream.
protected void	drain() Drain any buffered data in ObjectOutputStream.
protected boolean	enableReplaceObject(boolean enable) Enable the stream to do replacement of objects in the stream.
void	flush() Flushes the stream.
ObjectOutputStream.PutField	putFields() Retrieve the object used to buffer persistent fields to be written to the stream.
protected Object	replaceObject(Object obj) This method will allow trusted subclasses of ObjectOutputStream to substitute one object for another during serialization.
void	reset() Reset will disregard the state of any objects already written to the stream.
void	useProtocolVersion(int version) Specify stream protocol version to use when writing the stream.
void	write(byte[] buf) Writes an array of bytes.
void	write(byte[] buf, int off, int len) Writes a sub array of bytes.
void	write(int val) Writes a byte.
void	writeBoolean(boolean val) Writes a boolean.
void	writeByte(int val) Writes an 8 bit byte.
void	writeBytes(String str) Writes a String as a sequence of bytes.
void	writeChar(int val) Writes a 16 bit char.
void	writeChars(String str) Writes a String as a sequence of chars.
protected void	writeClassDescriptor(ObjectStreamClass desc) Write the specified class descriptor to the ObjectOutputStream.
void	writeDouble(double val) Writes a 64 bit double.
void	writeFields() Write the buffered fields to the stream.
void	writeFloat(float val) Writes a 32 bit float.
void	writeInt(int val) Writes a 32 bit int.
void	writeLong(long val) Writes a 64 bit long.
void	writeObject(Object obj) Write the specified object to the ObjectOutputStream.
protected void	writeObjectOverride(Object obj) Method used by subclasses to override the default writeObject method.
void	writeShort(int val) Writes a 16 bit short.
protected void	writeStreamHeader() The writeStreamHeader method is provided so subclasses can append or prepend their own header to the stream.
void	writeUnshared(Object obj) Writes an "unshared" object to the ObjectOutputStream.
void	writeUTF(String str) Primitive data write of this String in   modified UTF-8  format.

例子

FileOutputStream fos = new FileOutputStream("t.tmp");
      ObjectOutputStream oos = new ObjectOutputStream(fos);

      oos.writeInt(12345);
      oos.writeObject("Today");
      oos.writeObject(new Date());

      oos.close();

ObjectInputStream

ObjectInputStream用于从输入流读取Java对象。

类定义

public class ObjectInputStream
extends InputStream
implements ObjectInput, ObjectStreamConstants

构造函数

protected	ObjectInputStream() Provide a way for subclasses that are completely reimplementing ObjectInputStream to not have to allocate private data just used by this implementation of ObjectInputStream.
	ObjectInputStream(InputStream in) Creates an ObjectInputStream that reads from the specified InputStream.

方法

int	available() Returns the number of bytes that can be read without blocking.
void	close() Closes the input stream.
void	defaultReadObject() Read the non-static and non-transient fields of the current class from this stream.
protected boolean	enableResolveObject(boolean enable) Enable the stream to allow objects read from the stream to be replaced.
int	read() Reads a byte of data.
int	read(byte[] buf, int off, int len) Reads into an array of bytes.
boolean	readBoolean() Reads in a boolean.
byte	readByte() Reads an 8 bit byte.
char	readChar() Reads a 16 bit char.
protected ObjectStreamClass	readClassDescriptor() Read a class descriptor from the serialization stream.
double	readDouble() Reads a 64 bit double.
ObjectInputStream.GetField	readFields() Reads the persistent fields from the stream and makes them available by name.
float	readFloat() Reads a 32 bit float.
void	readFully(byte[] buf) Reads bytes, blocking until all bytes are read.
void	readFully(byte[] buf, int off, int len) Reads bytes, blocking until all bytes are read.
int	readInt() Reads a 32 bit int.
String	readLine() Deprecated.  This method does not properly convert bytes to characters. see DataInputStream for the details and alternatives.
long	readLong() Reads a 64 bit long.
Object	readObject() Read an object from the ObjectInputStream.
protected Object	readObjectOverride() This method is called by trusted subclasses of ObjectOutputStream that constructed ObjectOutputStream using the protected no-arg constructor.
short	readShort() Reads a 16 bit short.
protected void	readStreamHeader() The readStreamHeader method is provided to allow subclasses to read and verify their own stream headers.
Object	readUnshared() Reads an "unshared" object from the ObjectInputStream.
int	readUnsignedByte() Reads an unsigned 8 bit byte.
int	readUnsignedShort() Reads an unsigned 16 bit short.
String	readUTF() Reads a String in   modified UTF-8  format.
void	registerValidation(ObjectInputValidation obj, int prio) Register an object to be validated before the graph is returned.
protected Class<?>	resolveClass(ObjectStreamClass desc) Load the local class equivalent of the specified stream class description.
protected Object	resolveObject(Object obj) This method will allow trusted subclasses of ObjectInputStream to substitute one object for another during deserialization.
protected Class<?>	resolveProxyClass(String[] interfaces) Returns a proxy class that implements the interfaces named in a proxy class descriptor; subclasses may implement this method to read custom data from the stream along with the descriptors for dynamic proxy classes, allowing them to use an alternate loading mechanism for the interfaces and the proxy class.
int	skipBytes(int len) Skips bytes.

例子

FileInputStream fis = new FileInputStream("t.tmp");
      ObjectInputStream ois = new ObjectInputStream(fis);

      int i = ois.readInt();
      String today = (String) ois.readObject();
      Date date = (Date) ois.readObject();

      ois.close();

关于读取Java对象的例子，请参考文章：

Java序列化（Serializable）与反序列化详解