Java I/O 学习笔记(9) 对象持久化

package files;import java.io.Externalizable;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.FileOutputStream;import java.io.IOException;import java.io.ObjectInput;import java.io.ObjectInputStream;import java.io.ObjectOutput;import java.io.ObjectOutputStream;import java.io.Serializable;/** * 数据类实现Serializable接口 *  * @author QuPeng *  */class Data1 implements Serializable {private static final long serialVersionUID = 1L;private int i = 0;private transient int j = 0;public int getI() {return i;}public void setI(int i) {this.i = i;}public int getJ() {return j;}public void setJ(int j) {this.j = j;}}/** * 数据类实现Externalizable接口，必须声明无参构造函数，所有需要序列化的属性必需自己实现 *  * @author QuPeng *  */class Data2 implements Externalizable {public static int j = 0;private int i = 0;public Data2() {}public int getI() {return i;}public void setI(int i) {this.i = i;}@Overridepublic void writeExternal(ObjectOutput out) throws IOException {out.writeInt(j);out.writeInt(i);}@Overridepublic void readExternal(ObjectInput in) throws IOException,ClassNotFoundException {j = in.readInt();i = in.readInt();}}/** * 数据类实现Serializable接口，添加writeObject和readObject方法，用来持久化静态属性 *  * @author QuPeng *  */class Data3 implements Serializable {private static final long serialVersionUID = 1L;public static int j = 0;private int i = 0;public int getI() {return i;}public void setI(int i) {this.i = i;}private void writeObject(ObjectOutputStream stream) throws IOException {stream.defaultWriteObject();stream.writeInt(j);}private void readObject(ObjectInputStream stream) throws IOException,ClassNotFoundException {stream.defaultReadObject();j = stream.readInt();}}public class TestObjectStream {private static final long serialVersionUID = 1L;public static void main(String[] args) throws FileNotFoundException,IOException, ClassNotFoundException {testSerializableObject();testExternalizableObject();testSerializable2();}public static void testSerializableObject() throws FileNotFoundException,IOException, ClassNotFoundException {ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("output.txt"));Data1 d = new Data1();d.setI(99);oos.writeObject(d);oos.close();ObjectInputStream ois = new ObjectInputStream(new FileInputStream("output.txt"));Data1 dRestore = (Data1) ois.readObject();System.out.println(dRestore.getI());ois.close();}public static void testExternalizableObject() throws FileNotFoundException,IOException, ClassNotFoundException {ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("output.txt"));Data2 d = new Data2();d.setI(88);Data2.j = 99;oos.writeObject(d);oos.close();Data2.j = 77;ObjectInputStream ois = new ObjectInputStream(new FileInputStream("output.txt"));Data2 dRestore = (Data2) ois.readObject();System.out.println(Data2.j);System.out.println(dRestore.getI());ois.close();}public static void testSerializable2() throws FileNotFoundException,IOException, ClassNotFoundException {ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("output.txt"));Data3 d = new Data3();d.setI(88);Data3.j = 99;oos.writeObject(d);oos.close();Data3.j = 77;ObjectInputStream ois = new ObjectInputStream(new FileInputStream("output.txt"));Data3 dRestore = (Data3) ois.readObject();System.out.println(Data3.j);System.out.println(dRestore.getI());ois.close();}}