Java序列化

在java中序列化对象需要实现一个接口，表示该对象可以被序列化

java.io.Serializable

接下来介绍一个关键字

transient

这个关键字的意思就是取反：

如果一个对象实现了Serializable接口，加上这个关键字表示这个对象不能被序列化；

如果一个对象没有实现Serializable接口，加上这个关键字表示这个对象可以被序列化，同时需要告诉虚拟机应该如何序列化，在类的内部写两个方法。

1// 注：这些方法定义时必须是私有的，因为不需要你显示调用，序列化机制会自动调用的
2private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException;
3private void writeObject(ObjectOutputStream out) throws IOException;

栗子：

完整栗子：

1package top.swimmer.tokenizer;
2
3import java.time.LocalDateTime;
4
5public class Foo {
6    private String a;
7    private LocalDateTime time;
8
9    public String getA() {
10        return a;
11    }
12
13    public void setA(String a) {
14        this.a = a;
15    }
16
17    public LocalDateTime getTime() {
18        return time;
19    }
20
21    public void setTime(LocalDateTime time) {
22        this.time = time;
23    }
24
25    public Foo() {
26        a = "Hello world!";
27        time = LocalDateTime.now();
28    }
29}
30
31
32package top.swimmer.tokenizer;
33
34import java.io.Closeable;
35import java.io.IOException;
36import java.io.ObjectInputStream;
37import java.io.ObjectOutputStream;
38import java.io.Serializable;
39import java.time.LocalDateTime;
40
41public class Too implements Serializable, Closeable {
42    private transient Foo foo; // Foo没有实现Serializable接口，但是加了transient关键字就可以被序列化了
43    private String c;
44
45    public Too() {
46        c = "Good man!";
47        foo = new Foo();
48    }
49
50    @Override
51    public void close() throws IOException {
52        System.out.println("too close");
53    }
54
55    // 要写两个方法供虚拟机调用，分别告诉虚拟机对于Foo对象如何写，如何读
56    private void writeObject(ObjectOutputStream out) throws IOException {
57        out.defaultWriteObject();
58        out.writeObject(foo.getA());
59        out.writeObject(foo.getTime());
60    }
61
62    private void readObject(ObjectInputStream input) throws IOException, ClassNotFoundException {
63        input.defaultReadObject();
64        Foo foo = new Foo();
65        foo.setA((String) input.readObject());
66        foo.setTime((LocalDateTime) input.readObject());
67        this.foo = foo;
68    }
69}
70
71
72package top.swimmer.tokenizer;
73
74import java.io.File;
75import java.io.FileInputStream;
76import java.io.FileOutputStream;
77import java.io.ObjectInputStream;
78import java.io.ObjectOutputStream;
79
80public class ObjectDemo {
81    public static void main(String[] args) throws Exception {
82        Too t = new Too();
83        File file = new File(ObjectDemo.class.getResource("/aaa.json").getFile());
84
85        ObjectOutputStream output = new ObjectOutputStream(new FileOutputStream(file));
86        output.writeObject(t);
87        ObjectInputStream input = new ObjectInputStream(new FileInputStream(file));
88        Too t1 = (Too) input.readObject();
89        System.out.println();
90    }
91}