序列化-Hessian

　　引用官网介绍：

Hessian is a dynamically-typed, binary serialization and Web Services protocol designed for object-oriented transmission.

　　Hessian 是动态类型、二进制、紧凑的，并且可跨语言移植的一种序列化框架。Hessian 协议要比 JDK、JSON 更加紧凑，性能上要比 JDK、JSON 序列化高效很多，而且生成的字节数也更小。

代码示例如下：

@Data
public class SimplePOJO implements Serializable {
    String field1;
    String field2;
    public SimplePOJO(String s1, String s2) {
        field1 = s1;
        field2 = s2;
    }
    // fastjson逆序列化时要求对象必须要有一个默认的构造函数
    public SimplePOJO(){}
}
public static void main(String[] args) throws IOException, ClassNotFoundException {
    SimplePOJO student = new SimplePOJO("16","张三");
    //把student对象转化为byte数组
    ByteArrayOutputStream bos = new ByteArrayOutputStream();
    Hessian2Output output = new Hessian2Output(bos);
    output.writeObject(student);
    output.flushBuffer();
    byte[] data = bos.toByteArray();
    bos.close();
    
    // 把字节流存入文件
    FileOutputStream fos = new FileOutputStream("C:\\Users\\user\\Desktop\\student.dat");
    fos.write(data);
    fos.close();
    // 从文件中读取字节流
    FileInputStream fis = new FileInputStream( "C:\\Users\\user\\Desktop\\student.dat");
    byte[] bytes = new byte[fis.available()];
    fis.read(bytes);
    
    // 转化为student对象
    ByteArrayInputStream bis = new ByteArrayInputStream(data);
    Hessian2Input input = new Hessian2Input(bis);
    SimplePOJO deStudent = (SimplePOJO) input.readObject();
    input.close();
    System.out.println(deStudent);
}

　　打开保存的中间文件看看：

　　可以看到有类名以及属性名和对应值

　　具体的数据-byte类型的映射可以参考官网http://hessian.caucho.com/doc/hessian-serialization.html

　　对于上述代码，其数据类型为Object类型。Object类型转换格式为（官网）：

class Car {
  String color;
  String model;
}

out.writeObject(new Car("red", "corvette"));
out.writeObject(new Car("green", "civic"));

---

C                        # object definition (#0)
  x0b example.Car        # type is example.Car
  x92                    # two fields
  x05 color              # color field name
  x05 model              # model field name

O                        # object def (long form)
  x90                    # object definition #0
  x03 red                # color field value
  x08 corvette           # model field value

x60                      # object def #0 (short form)
  x05 green              # color field value
  x05 civic              # model field value