Hessian protobuf 序列化

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mob64ca14144dde 2025-01-05 15:24:04

1 引入Hessian依赖

<!--hessian-->
    <dependency>
      <groupId>com.caucho</groupId>
      <artifactId>hessian</artifactId>
      <version>4.0.38</version>
    </dependency>

2 编写Hessian序列化，反序列化方法，定义实体类示例

public class HessianSerializerUtil {

    public static <T> byte[] serialize(T obj) {
        byte[] bytes = null;
        // 1、创建字节输出流
        ByteArrayOutputStream bos = new ByteArrayOutputStream();

        // 2、对字节数组流进行再次封装

        // step 1. 定义外部序列化工厂
        //ExtSerializerFactory extSerializerFactory = new ExtSerializerFactory();
        //extSerializerFactory.addSerializer(java.time.OffsetDateTime.class, new OffsetDateTimeRedisSerializer());
        //extSerializerFactory.addDeserializer(java.time.OffsetDateTime.class, new OffsetDateTimeRedisDeserializer());
        // step 2. 序列化工厂
        //SerializerFactory serializerFactory = new SerializerFactory();
        //serializerFactory.addFactory(extSerializerFactory);

        HessianOutput hessianOutput = new HessianOutput(bos);
        //hessianOutput.setSerializerFactory(serializerFactory);

        try {
            // 注意，obj 必须实现Serializable接口
            hessianOutput.writeObject(obj);
            bytes = bos.toByteArray();
        } catch (IOException e) {
            e.printStackTrace();
        }

        return bytes;
    }

    public static <T> T deserialize(byte[] data) {
        if (data == null) {
            return null;
        }
        // 1、将字节数组转换成字节输入流
        ByteArrayInputStream bis = new ByteArrayInputStream(data);

        // step 1. 定义外部序列化工厂
        //ExtSerializerFactory extSerializerFactory = new ExtSerializerFactory();
        //extSerializerFactory.addSerializer(java.time.OffsetDateTime.class, new OffsetDateTimeRedisSerializer());
        //extSerializerFactory.addDeserializer(java.time.OffsetDateTime.class, new OffsetDateTimeRedisDeserializer());
        // step 2. 序列化工厂
        //SerializerFactory serializerFactory = new SerializerFactory();
        //serializerFactory.addFactory(extSerializerFactory);
        HessianInput hessianInput = new HessianInput(bis);
        //hessianInput.setSerializerFactory(serializerFactory);
        Object object = null;

        try {
            object = hessianInput.readObject();
        } catch (IOException e) {
            e.printStackTrace();
        }

        return (T) object;
    }
}

package cn.micai.base.io;
 
import java.io.Serializable;
 
/**
 * 描述：
 * <p>
 *
 *     transient使用小结
 *     1.一旦变量被transient修饰，变量将不再是对象持久化的一部分，该变量内容在序列化后无法获得访问。
 *     2.transient关键字只能修饰变量，而不能修饰方法和类。注意，本地变量是不能被transient关键字修饰的。变量如果是用户自定义类变量，则该类需要实现Serializable接口。
 *     3.被transient关键字修饰的变量不再能被序列化，一个静态变量不管是否被transient修饰，均不能被序列化。
 *
 * @author: 赵新国
 * @date: 2018/6/7 12:10
 */
public class Employee implements Serializable {
 
    private static final long serialVersionUID = 1L;
    private int employeeId;
    private String employeeName;
    /**
     * 使用transient关键字，表示该字段不序列化
     */
    private transient String department;
 
    public int getEmployeeId() {
        return employeeId;
    }
    public void setEmployeeId(int employeeId) {
        this.employeeId = employeeId;
    }
    public String getEmployeeName() {
        return employeeName;
    }
    public void setEmployeeName(String employeeName) {
        this.employeeName = employeeName;
    }
    public String getDepartment() {
        return department;
    }
    public void setDepartment(String department) {
        this.department = department;
    }
 
    @Override
    public String toString() {
        return "Employee{" +
                "employeeId=" + employeeId +
                ", employeeName='" + employeeName + '\'' +
                ", department='" + department + '\'' +
                '}';
    }
}

hession 序列化的特点

1.一旦变量被transient修饰，变量将不再是对象持久化的一部分，该变量内容在序列化后无法获得访问。
2.transient关键字只能修饰变量，而不能修饰方法和类。被序列化的类需要实现Serializable接口。
3.一个静态变量不管是否被transient修饰，均不能被序列化
4 final类型变量不管是否被transient修饰，均可以被序列化。
5 Student类集成Teacher类，Teacher类中有跟Student类型相同且属性名相同的字段name,接下来看代码：

public class Person implements Serializable {
    private static final long serialVersionUID = 2l;
    private  int gender;

    public int getGender() {
        return gender;
    }

    public void setGender(int gender) {
        this.gender = gender;
    }

    @Override
    public String toString() {
        return "Person{" +
                "gender='" + gender + '\'' +
                '}';
    }
}

public class Em extends Person {

    private int gender;

    public Em() {
    }

    @Override
    public int getGender() {
        return gender;
    }

    @Override
    public void setGender(int gender) {
        this.gender = gender;
        //super.setGender(gender);
    }

    @Override
    public String toString() {
        return "Em{" +
                "gender=" + gender +
                '}';
    }
}



测试类：
   public class Set {

    public static void main(String[] args) throws Exception{

        Em person=new Em();
        person.setGender(1);


        FileOutputStream fos = new FileOutputStream("tempdata.ser");
        Hessian2Output output = new Hessian2Output(fos);
        output.writeObject(person);
        output.close();


        FileInputStream fis = new FileInputStream("tempdata.ser");
        Hessian2Input input = new Hessian2Input(fis);


        Em p = (Em) input.readObject();
        System.out.println(p);





    }
}

输出结果为：
Em{gender=0}

理论上输出的结果应该为“gender=1”,但现在为gender=0,原因如下:

hessian序列化的时候会取出对象的所有自定义属性，相同类型的属性是子类在前父类在后的顺序；
hessian在反序列化的时候，是将对象所有属性取出来，存放在一个map中 key = 属性名 value是反序列类，相同名字的会以子类为准进行反序列化；
相同名字的属性在反序列化的是时候，由于子类在父类前面，子类的属性总是会被父类的覆盖，由于java多态属性，在上述例子中父类 student.name = null。

得出结论,两种解决办法

1 使用hessian序列化时，一定要注意子类和父类不能有同名字段
2 在给子类赋值的时候，也给父类赋值。
@Override
public void setGender(int gender) {
this.gender = gender;
//super.setGender(gender);
}