Java I/O 教程（十） ObjectOutputStream和ObjectInputStream

indexman發表於2018-01-10
JavaObject

ObjectOutputStream

ObjectOutputStream用於往輸出流中寫入原始型別和Java物件。

類定義

public class ObjectOutputStream
extends OutputStream
implements ObjectOutput, ObjectStreamConstants

建構函式

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用於從輸入流讀取Java物件。

類定義

public class ObjectInputStream
extends InputStream
implements ObjectInput, ObjectStreamConstants

建構函式

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();

關於讀取Java物件的例子，請參考文章：

Java序列化（Serializable）與反序列化詳解


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