JavaIO<4>--ObjectInputStream和ObjectOutputStream

ObjectInputStream 和 ObjectOutputStream 介绍

ObjectInputStream 和 ObjectOutputStream 的作用是，对基本数据和对象进行序列化操作支持。
创建“文件输出流”对应的ObjectOutputStream对象，该ObjectOutputStream对象能提供对“基本数据或对象”的持久存储；当我们需要读取这些存储的“基本数据或对象”时，可以创建“文件输入流”对应的ObjectInputStream，进而读取出这些“基本数据或对象”。
注意： 只有支持 java.io.Serializable 或 java.io.Externalizable 接口的对象才能被ObjectInputStream/ObjectOutputStream所操作！

ObjectOutputStream 函数列表

// 构造函数  
ObjectOutputStream(OutputStream output)  
// public函数  
void     close()  
void     defaultWriteObject()  
void     flush()  
ObjectOutputStream.PutField     putFields()  
void     reset()  
void     useProtocolVersion(int version)  
void     write(int value)  
void     write(byte[] buffer, int offset, int length)  
void     writeBoolean(boolean value)  
void     writeByte(int value)  
void     writeBytes(String value)  
void     writeChar(int value)  
void     writeChars(String value)  
void     writeDouble(double value)  
void     writeFields()  
void     writeFloat(float value)  
void     writeInt(int value)  
void     writeLong(long value)  
final void     writeObject(Object object)  
void     writeShort(int value)  
void     writeUTF(String value)  
void     writeUnshared(Object object) 

ObjectInputStream 函数列表

// 构造函数  
ObjectInputStream(InputStream input)  
 
int     available()  
void     close()  
void     defaultReadObject()  
int     read(byte[] buffer, int offset, int length)  
int     read()  
boolean     readBoolean()  
byte     readByte()  
char     readChar()  
double     readDouble()  
ObjectInputStream.GetField     readFields()  
float     readFloat()  
void     readFully(byte[] dst)  
void     readFully(byte[] dst, int offset, int byteCount)  
int     readInt()  
String     readLine()  
long     readLong()  
final Object     readObject()  
short     readShort()  
String     readUTF()  
Object     readUnshared()  
int     readUnsignedByte()  
int     readUnsignedShort()  
synchronized void     registerValidation(ObjectInputValidation object, int priority)  
int     skipBytes(int length)

演示程序

package org.credo.jdk.io.ObjectStreamTest;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

import org.apache.commons.lang.builder.EqualsBuilder;
import org.apache.commons.lang.builder.HashCodeBuilder;
import org.apache.commons.lang.builder.ToStringBuilder;

public class ObjectStreamTest
{

	public static void main(String[] args)
	{
		try
		{
			testWrite();
			testRead();
		} catch (IOException | ClassNotFoundException e)
		{
			e.printStackTrace();
		}
	}

	private static final String TMP_FILE = "computer.tmp";
	

	public static void testWrite() throws FileNotFoundException, IOException
	{
		ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream(TMP_FILE));
		out.writeBoolean(true);
		out.writeByte((byte) 65);
		out.writeChar('a');
		out.writeInt(20131015);
		out.writeFloat(3.14F);
		out.writeDouble(1.414D);
		// 写入HashMap对象  
        HashMap<String,String> map = new HashMap<>();  
        map.put("one", "red");  
        map.put("two", "green");  
        map.put("three", "blue");  
        out.writeObject(map);  
        // 写入自定义的Computer对象，Computer实现了Serializable接口  
        Computer computer=new Computer(1, 5666.66, "Y480");
        out.writeObject(computer);
        out.close();
	}
	
	@SuppressWarnings("rawtypes")
	public static void testRead() throws FileNotFoundException, IOException, ClassNotFoundException
	{
		ObjectInputStream in=new ObjectInputStream(new FileInputStream(TMP_FILE));
		System.out.printf("boolean:%b\n" , in.readBoolean());  
        System.out.printf("byte:%d\n" , (in.readByte()&0xff));  
        System.out.printf("char:%c\n" , in.readChar());  
        System.out.printf("int:%d\n" , in.readInt());  
        System.out.printf("float:%f\n" , in.readFloat());  
        System.out.printf("double:%f\n" , in.readDouble());
        
        // 读取HashMap对象  
        HashMap map = (HashMap) in.readObject();
        Iterator iterator=map.entrySet().iterator();
        while (iterator.hasNext())
		{
			Map.Entry mapEntry = (Map.Entry) iterator.next();
			System.out.printf("%-6s -- %s\n" , mapEntry.getKey(), mapEntry.getValue());
		}
        
        //读取Computer
        Computer computer=(Computer)in.readObject();
        System.out.println("computer: " + computer);
        in.close();
	}

}

class Computer implements Serializable
{

	private static final long serialVersionUID = -6347513352513264586L;

	private int id;
	private double price;
	private String name;
	
	public Computer(int id,double price,String name) {
		this.id=id;
		this.price=price;
		this.name=name;
	}

	public int getId()
	{
		return id;
	}

	public void setId(int id)
	{
		this.id = id;
	}

	public double getPrice()
	{
		return price;
	}

	public void setPrice(double price)
	{
		this.price = price;
	}

	public String getName()
	{
		return name;
	}

	public void setName(String name)
	{
		this.name = name;
	}

	@Override
	public int hashCode()
	{
		return HashCodeBuilder.reflectionHashCode(this);
	}

	@Override
	public boolean equals(Object obj)
	{
		return EqualsBuilder.reflectionEquals(this, obj);
	}

	@Override
	public String toString()
	{
		return ToStringBuilder.reflectionToString(this);
	}

}

输出

boolean:true
byte:65
char:a
int:20131015
float:3.140000
double:1.414000
three  -- blue
two    -- green
one    -- red
computer: org.credo.jdk.io.ObjectStreamTest.Computer@4935b92e[id=1,price=5666.66,name=Y480]