java io學習（四） ObjectInputStream 和 ObjectOutputStream

本章，我們學習ObjectInputStream 和 ObjectOutputStream

ObjectInputStream 和 ObjectOutputStream 介紹

ObjectInputStream 和 ObjectOutputStream 的作用是，對基本數據和對象進行序列化操作支持。

創建“文件輸出流”對應的ObjectOutputStream對象，該ObjectOutputStream對象能提供對“基本數據或對象”的持久存儲；當我們需要讀取這些存儲的“基本數據或對象”時，可以創建“文件輸入流”對應的ObjectInputStream，進而讀取出這些“基本數據或對象”。

注意： 只有支持 java.io.Serializable 或 java.io.Externalizable 接口的對象才能被ObjectInputStream/ObjectOutputStream所操作！

ObjectOutputStream 函數列表

// 構造函數
ObjectOutputStream(OutputStream output)
// public函數
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 函數列表

// 構造函數
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)

查看本欄目

演示程序

源碼如下(ObjectStreamTest.java)：

/**
 * ObjectInputStream 和 ObjectOutputStream 測試程序
 *
 * 注意：通過ObjectInputStream, ObjectOutputStream操作的對象，必須是實現了Serializable或Externalizable序列化接口的類的實例。
 *
 * @author skywang
 */
     
import java.io.FileInputStream;   
import java.io.FileOutputStream;   
import java.io.ObjectInputStream;   
import java.io.ObjectOutputStream;   
import java.io.Serializable;   
import java.util.Map;
import java.util.HashMap;
import java.util.Iterator;
       
public class ObjectStreamTest { 
    private static final String TMP_FILE = "box.tmp";
       
    public static void main(String[] args) {   
        testWrite();
        testRead();
    }
       
     
    /**
     * ObjectOutputStream 測試函數
     */
    private static void testWrite() {   
        try {
            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);
            // 寫入HashMap對象
            HashMap map = new HashMap();
            map.put("one", "red");
            map.put("two", "green");
            map.put("three", "blue");
            out.writeObject(map);
            // 寫入自定義的Box對象，Box實現了Serializable接口
            Box box = new Box("desk", 80, 48);
            out.writeObject(box);
     
            out.close();
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }
      
    /**
     * ObjectInputStream 測試函數
     */
    private static void testRead() {
        try {
            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());
            // 讀取HashMap對象
            HashMap map = (HashMap) in.readObject();
            Iterator iter = map.entrySet().iterator();
            while (iter.hasNext()) {
                Map.Entry entry = (Map.Entry)iter.next();
                System.out.printf("%-6s -- %s\n" , entry.getKey(), entry.getValue());
            }
            // 讀取Box對象，Box實現了Serializable接口
            Box box = (Box) in.readObject();
            System.out.println("box: " + box);
     
            in.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}
     
     
class Box implements Serializable {
    private int width;   
    private int height; 
    private String name;   
     
    public Box(String name, int width, int height) {
        this.name = name;
        this.width = width;
        this.height = height;
    }
     
    @Override
    public String toString() {
        return "["+name+": ("+width+", "+height+") ]";
    }
}

運行結果：

boolean:true
byte:65
char:a
int:20131015
float:3.140000
double:1.414000
two    -- green
one    -- red
three  -- blue
box: [desk: (80, 48) ]

來源：http://www.cnblogs.com/skywang12345/p/io_05.html