Serializable序列化(一)

package serializ;import java.io.BufferedInputStream;import java.io.BufferedOutputStream;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;/** * 类要实现序列化,必须实现Serializable接口 <br> * 但该接口并没有任何方法要实现 <br> * 一般序列化可以保存到字节数据或者文件 <br> * 比如为了实现对象在系统间传输 *  * @author yli *  */public class Employee implements Serializable {/** * 一旦实现Serializable接口,就应该定义默认的序列ID * 因为类可以不断升级,比如增加字段或者增加方法 * 那么老版本的类和新版本的类,如果通过序列化关联起来 * 就要求新老版本的类拥有相同的 serialVersionUID *  * @see 在JDK的bin目录,有serialver.exe程序,可以用于生成每个类的UID */private static final long serialVersionUID = 5128673904770381297L;protected String name;protected double salary;public Employee(String name, double salary) {this.name = name;this.salary = salary;}public String toString() {return String.format("{name:%s,salary:%s}", this.name, this.salary);}public Employee getEmp() {return this;}public static void main(String[] args) {String file = "src/serialize.dat";Employee emp1 = new Employee("yli", 10000d);System.out.println("==>write Employee");System.out.println(emp1);writeObject(emp1, file);System.out.println("==>read Employee");Employee emp2 = (Employee) readObject(file);System.out.println(emp2);System.out.println("============================");System.out.println(String.format("(emp1==emp2)===>%s", emp1 == emp2));// 反序列化之后两个对象不会相等// 因为反序列化回来内存地址肯定不一样,比如在另一台机器上反序列化// 地址是不可能相等的,那如果A对象被B、C对象引用// A、B、C 全部序列化了,那反序列化回来之后：B、C持有的A对象还是相等的吗?// Java的序列化机制保证了反序列化回来之后持有的A对象想的Manager m1 = new Manager("m1", 15000d);m1.setEmp(emp1);Manager m2 = new Manager("m2", 20000d);m2.setEmp(emp1);Employee[] emps1 = new Employee[]{emp1,m1,m2};System.out.println("==>write Employee[]");writeObject(emps1, file);System.out.println("==>read Employee[]");Employee[] emps2 = (Employee[]) readObject(file);// 打印结果显示m1和m2持有的emp对象是相同的// 因为在序列化每个对象时,会为这对象产生唯一的序列号Id// 比如emp1序列化成功后,产生序列Id：001// 那么m1和m2在序列化时,因为关联到同一个employee对象// 且发现emp1对象已经序列化了,则m1和m2都关联到 emp1的Id：001 上面即可// 反序列化过程也要依赖每个对象的IdSystem.out.println(String.format("(emps2[0]==emps2[1].getEmp()===>%s)", emps2[0]==emps2[1].getEmp()));System.out.println(String.format("(emps2[0]==emps2[2].getEmp()===>%s)", emps2[0]==emps2[2].getEmp()));}// 序列化对象private static void writeObject(Object obj, String file) {ObjectOutputStream oos = null;try {oos = new ObjectOutputStream(new BufferedOutputStream(new FileOutputStream(file)));oos.writeObject(obj);} catch (FileNotFoundException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();} finally {try {oos.close();} catch (IOException e) {e.printStackTrace();}}}// 反序列化private static Object readObject(String file) {ObjectInputStream ois = null;Object obj = null;try {ois = new ObjectInputStream(new BufferedInputStream(new FileInputStream(file)));obj = ois.readObject();} catch (FileNotFoundException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();} catch (ClassNotFoundException e) {e.printStackTrace();} finally {try {ois.close();} catch (IOException e) {e.printStackTrace();}}return obj;}}class Manager extends Employee {private static final long serialVersionUID = -3030759793812915423L;private Employee emp;public Manager(String name, double salary) {super(name, salary);}public Employee getEmp() {return emp;}public void setEmp(Employee emp) {this.emp = emp;}public static long getSerialversionuid() {return serialVersionUID;}}