IO-对象流

Posted 2020-09-15

对象的序列化:将对象转换为字节序列
对象的反序列化:将字节序列还原(恢复)成对象
　　序列化的优点:
　　　　1.可以将对象通过序列化保存到本地磁盘，起到方便存储的作用
　　　　2.可以通过对象序列化在网络之间进行传输，起到数据共享的作用
　　实现步骤:
　　　　前提:如果一个类要完成对象的序列化，该类必须实现Serializable接口(标示性接口)
　　　　1.将要实现对象序列化的类实现Serializable接口
　　　　2.使用对象流ObjectInputStream/ObjectOutputStream完成对象的序列化或反序列化
ObjectOutputStream类:继承了OutputStream类
　　构造函数:
　　　　ObjectOutputStream(OutputStream out) 创建写入指定 OutputStream 的 ObjectOutputStream。
　　常用方法:
　　　　writeObject(Object obj):将指定的对象写入 ObjectOutputStream。
　　　　writeXxx(Xx x):Xxx对应的是基本数据类型:写入一个 xx 值。
　　　　writeBoolean(boolean b) writeInt(int int) writeDouble(Double d)....
　　　　flush():刷新该流的缓冲。
　　　　close():关闭流。
ObjectInputStream类:继承了InputStream类
　　构造函数:
　　　　ObjectInputStream(InputStream in) 创建从指定 InputStream 读取的 ObjectInputStream。
　　常用的方法:
　　　　readObject() : 从 ObjectInputStream 读取对象。
　　　　readXxx():读取一个 xx 值。
　　　　readInt() readDouble()....
　　　　close(): 关闭输入流。

public class Student implements Serializable{
    private static final long serialVersionUID = 1L;
    private String name;
    private int age;
    private double score;
    
    public Student() {
        
    }
    
    public Student(String name, int age, double score) {
        super();
        this.name = name;
        this.age = age;
        this.score = score;
    }

    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public double getScore() {
        return score;
    }
    public void setScore(double score) {
        this.score = score;
    }
    
}

 

public class TestObjectStream {
    public static void main(String[] args) {
        Student stu = new Student("zhangsan",20,80);
        File file = new File("D:/test.obj");
        try {
            //1.对象序列化
            OutputStream ops = new FileOutputStream(file);
            ObjectOutputStream oos = new ObjectOutputStream(ops);
            oos.writeObject(stu);//将stu对象写入指定位置 (序列化)
            oos.writeDouble(3.14);//将stu对象写入指定位置 (序列化)
            oos.flush();
            //2.反序列化
            InputStream ips = new FileInputStream(file);
            ObjectInputStream ois = new ObjectInputStream(ips);
            Student stu2 = (Student)ois.readObject();
            double pi =  ois.readDouble();
            System.out.println(stu2.getName()+"---"+stu2.getAge()+"---"+stu2.getScore());
            System.out.println("pi="+pi);
            //关闭资源
            oos.close();
            ops.close();
            ois.close();
            ips.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
}

只能保存对象的非静态成员变量
不能保存任何成员方法和静态的成员变量
不保存transient成员变量
如果一个对象的成员变量是一个对象，这个对象的成员变量也会保存

public class Dept implements Serializable{
    private int deptId;
    private String deptName;
    public Dept(){
        
    }
    public Dept(int deptId,String deptName){
        this.deptId= deptId;
        this.deptName=deptName;
    }
    
    public int getDeptId() {
        return deptId;
    }
    public void setDeptId(int deptId) {
        this.deptId = deptId;
    }
    public String getDeptName() {
        return deptName;
    }
    public void setDeptName(String deptName) {
        this.deptName = deptName;
    }
    
}

public class Employee implements Serializable{
    private int empId;
    private String empName;
    private transient int empAge; //使用transient修饰的属性，该属性不能被序列化
    private Dept dept;//封装了该员工对于的部门信息
    
    
    
    public Employee() {
        
    }
    
    public Employee(int empId, String empName, int empAge, Dept dept) {
        this.empId = empId;
        this.empName = empName;
        this.empAge = empAge;
        this.dept = dept;
    }

    public int getEmpId() {
        return empId;
    }
    public void setEmpId(int empId) {
        this.empId = empId;
    }
    public String getEmpName() {
        return empName;
    }
    public void setEmpName(String empName) {
        this.empName = empName;
    }
    public int getEmpAge() {
        return empAge;
    }
    public void setEmpAge(int empAge) {
        this.empAge = empAge;
    }
    public Dept getDept() {
        return dept;
    }
    public void setDept(Dept dept) {
        this.dept = dept;
    }
    
    
    
}

public class TestObjectStream2 {
    public static void main(String[] args) {
        Dept dept = new Dept(1,"讨账部");
        Employee employee = new Employee(1,"陈浩南",28,dept);
        Employee employee2 = new Employee(2,"山鸡",27,dept);
        
        try {
            //序列化
            FileOutputStream fos = new FileOutputStream("tt.o");
            ObjectOutputStream oos = new ObjectOutputStream(fos);
            oos.writeObject(employee);
            oos.writeObject(employee2);
            //反序列化
            FileInputStream fis = new FileInputStream("tt.o");
            ObjectInputStream ois  =new ObjectInputStream(fis);
            Employee emp = (Employee)ois.readObject();
            System.out.println(emp.getEmpId()+"--"+emp.getEmpName()+"--"+emp.getEmpAge());
            Dept dept2 = emp.getDept();
            System.out.println(dept2.getDeptId()+"--"+dept2.getDeptName());
            Employee emp2 = (Employee)ois.readObject();
            System.out.println(emp2.getEmpId()+"--"+emp2.getEmpName()+"--"+emp2.getEmpAge());
            Dept dept3 = emp2.getDept();
            System.out.println(dept3.getDeptId()+"--"+dept3.getDeptName());
            
            //关闭流
            oos.close();
            fos.close();
            ois.close();
            fis.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
}

 

 

public class User implements Serializable{
    private String name;
    private int age;
    private Gender gender;
    public User(){
    }
    public User(String name, int age, Gender gender) {
        this.name = name;
        this.age = age;
        this.gender = gender;
    }
    
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public Gender getGender() {
        return gender;
    }
    public void setGender(Gender gender) {
        this.gender = gender;
    }
    @Override
    public String toString() {
        return "User [name=" + name + ", age=" + age + ", gender=" + gender + "]";
    }
}
//枚举
enum Gender{
    男,女
}

public class TestObjectStream3 {
    public static void main(String[] args) {
        List<User> list = new ArrayList<User>();
        User user1 = new User("zhangsan",30,Gender.男);
        User user2 = new User("zhangsan2",24,Gender.男);
        User user3 = new User("zhangsan3",28,Gender.男);
        list.add(user1);
        list.add(user2);
        list.add(user3);
        try {
//            序列化
            FileOutputStream fos = new FileOutputStream("D:/tt.o");
            ObjectOutputStream oos = new ObjectOutputStream(fos);
            oos.writeObject(list);
            oos.flush();
            //反序列化
            FileInputStream fis = new FileInputStream("D:/tt.o");
            ObjectInputStream ois = new ObjectInputStream(fis);
            List<User> usersList = (List)ois.readObject();
            for (User user : usersList) {
                System.out.println(user);
            }
            
            ois.close();
            fis.close();
            oos.close();
            fos.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
        
    }
}