dubbo序列化问题（三）子类覆盖父类字段hession反序列化获取不到

朱雀 2022-04-06 10:46 305阅读 0赞

在进行dubbo开发中遇到一个问题，当是用hession2进行序列化时，子类和父类有相同的字段时，hession2反序列化获取不到该字段数据，如下：

import java.io.Serializable;
    import java.util.Date;
    
    public class User implements Serializable{
    
    	/**
    	 * 
    	 */
    	private static final long serialVersionUID = 1L;
    	private String userId;
    	private String userName;
    	private Date addDate;
    	public String getUserId() {
    		return userId;
    	}
    	public void setUserId(String userId) {
    		this.userId = userId;
    	}
    	public String getUserName() {
    		return userName;
    	}
    	public void setUserName(String userName) {
    		this.userName = userName;
    	}
    	public Date getAddDate() {
    		return addDate;
    	}
    	public void setAddDate(Date addDate) {
    		this.addDate = addDate;
    	}
    	
    	
    }

import java.util.Date;
    
    public class ChildrenUser extends User {
    
    	/**
    	 * 
    	 */
    	private static final long serialVersionUID = 1L;
    
    	private String userId;
    	
    	private Date addDate;
    
    	public String getUserId() {
    		return userId;
    	}
    
    	public void setUserId(String userId) {
    		this.userId = userId;
    	}
    
    	public Date getAddDate() {
    		return addDate;
    	}
    
    	public void setAddDate(Date addDate) {
    		this.addDate = addDate;
    	}
    
    	@Override
    	public String toString() {
    		return "ChildrenUser [userId=" + userId + ", addDate=" + addDate + "]";
    	}
    	
    }

测试程序如下：

import java.io.ByteArrayInputStream;
    import java.io.ByteArrayOutputStream;
    import java.io.IOException;
    import java.util.Date;
    
    import com.alibaba.com.caucho.hessian.io.Hessian2Input;
    import com.alibaba.com.caucho.hessian.io.Hessian2Output;
    import com.pinganwj.clinic.api.demo.domain.ChildrenUser;
    import com.pinganwj.clinic.api.demo.domain.User;
    
    
    public class TestHessionLite1 {
    
    
    	public static void main(String[] args) throws IOException {
    		User user=new ChildrenUser();
    		user.setAddDate(new Date());
    		user.setUserId("123");
    		user.setUserName("呵呵");
    		byte[] aa=TestHessionLite1.serialize(user);
    		Object mm=TestHessionLite1.deserialize(aa);
    		System.out.println(mm.toString());
    		
    	}
    	
    	public static byte[] serialize(Object obj) throws IOException{  
    		 ByteArrayOutputStream os = new ByteArrayOutputStream(); 
    		 Hessian2Output ho = new Hessian2Output(os);  
    		 byte[] cc = null;
    		try {
    			if(obj==null) throw new NullPointerException();  
    		    ho.writeObject(obj);
    		    ho.flushBuffer();
    		    cc=os.toByteArray();  
    		} catch (Exception e) {
    			e.printStackTrace();
    		}finally{
    			ho.close();
    		}
    		return cc;  
    	    
    	} 
    	
    	public static Object deserialize(byte[] by) throws IOException{ 
    		try {
    			if(by==null) throw new NullPointerException();  
    			ByteArrayInputStream is = new ByteArrayInputStream(by);
    		    Hessian2Input hi = new Hessian2Input(is);  
    		    return hi.readObject();  
    		} catch (Exception e) {
    			e.printStackTrace();
    		}
    		return null;
    	    
    	}  
    }

运行该测试程序，输出如下

ChildrenUser [userId=null, addDate=null]

然后我再是用kryo来进行序列化，

import java.io.ByteArrayInputStream;
    import java.io.ByteArrayOutputStream;
    import java.io.IOException;
    import java.io.Serializable;
    import java.util.Date;
    
    import org.apache.commons.codec.binary.Base64;
    
    import com.esotericsoftware.kryo.Kryo;
    import com.esotericsoftware.kryo.io.Input;
    import com.esotericsoftware.kryo.io.Output;
    import com.esotericsoftware.kryo.serializers.JavaSerializer;
    import com.pinganwj.clinic.api.demo.domain.ChildrenUser;
    import com.pinganwj.clinic.api.demo.domain.User;
    
    public class TestKryo1 {
    
    	public static void main(String[] args) {
    
    		User user=new ChildrenUser();
    		user.setAddDate(new Date());
    		user.setUserId("123");
    		user.setUserName("呵呵");
    		String aa=TestKryo1.serialize(user);
    		Object mm=TestKryo1.deserialize(aa,User.class);
    		System.out.println(mm.toString());
    	}
    	private static <T extends Serializable> String serialize(T obj) {
            Kryo kryo = new Kryo();
            kryo.setReferences(false);
            kryo.register(obj.getClass(), new JavaSerializer());
     
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            Output output = new Output(baos);
            kryo.writeClassAndObject(output, obj);
            output.flush();
            output.close();
     
            byte[] b = baos.toByteArray();
            try {
                baos.flush();
                baos.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
     
            return new String(new Base64().encode(b));
        }
     
        @SuppressWarnings("unchecked")
        private static <T extends Serializable> T deserialize(String obj,
                Class<T> clazz) {
            Kryo kryo = new Kryo();
            kryo.setReferences(false);
            kryo.register(clazz, new JavaSerializer());
     
            ByteArrayInputStream bais = new ByteArrayInputStream(
                    new Base64().decode(obj));
            Input input = new Input(bais);
            return (T) kryo.readClassAndObject(input);
        }
    }

输出结果如下：

ChildrenUser [userId=123, addDate=Fri Aug 25 00:28:45 CST 2017]

输出正确。

这个是hession2的一个坑，经过查看源码Hessian2Input类中的readObjectInstance方法

他将父类的属性都读取了

![46aa6187-3b55-328e-bc56-c21c7e399abc.png][]

而每次第一次能读取到值，然后第二次读取就是null，都被覆盖了，所以输出都是null。

所以解决方案就是去掉子类中的字段或者父类中的字段，或者改用kryo等其他序列化方式。

[46aa6187-3b55-328e-bc56-c21c7e399abc.png]: /images/20220406/d84be132e50d4065a47a8dd2b8f8d1da.png