com.alibaba.com.caucho.hessian.io.HessianProtocolException: com.alibaba.com.caucho.hessian.io.ObjectDeserializer: unexpected object java.lang.String (2)

[xuyanhua]

我们使用dubbo的时候，返回的结果对象是这样的
class Result {
int code;//错误码
String message;//错误消息
T module ;//保存数据
}
但是调用时报反序列失败，报错如下：
Exception in thread "main" com.alibaba.com.caucho.hessian.io.HessianFieldException: AVX$Result.data: com.alibaba.com.caucho.hessian.io.ObjectDeserializer: unexpected object java.lang.String (2) at com.alibaba.com.caucho.hessian.io.JavaDeserializer.logDeserializeError(JavaDeserializer.java:163) at com.alibaba.com.caucho.hessian.io.JavaDeserializer$ObjectFieldDeserializer.deserialize(JavaDeserializer.java:394) at com.alibaba.com.caucho.hessian.io.JavaDeserializer.readObject(JavaDeserializer.java:269) at com.alibaba.com.caucho.hessian.io.JavaDeserializer.readObject(JavaDeserializer.java:196) at com.alibaba.com.caucho.hessian.io.SerializerFactory.readObject(SerializerFactory.java:527) at com.alibaba.com.caucho.hessian.io.Hessian2Input.readObjectInstance(Hessian2Input.java:2743) at com.alibaba.com.caucho.hessian.io.Hessian2Input.readObject(Hessian2Input.java:2683) at com.alibaba.com.caucho.hessian.io.Hessian2Input.readObject(Hessian2Input.java:2657) at AVX.deserialize(AVX.java:37) at AVX.main(AVX.java:18) Caused by: com.alibaba.com.caucho.hessian.io.HessianProtocolException: com.alibaba.com.caucho.hessian.io.ObjectDeserializer: unexpected object java.lang.String (2) at com.alibaba.com.caucho.hessian.io.AbstractDeserializer.error(AbstractDeserializer.java:101) at com.alibaba.com.caucho.hessian.io.AbstractDeserializer.readMap(AbstractDeserializer.java:90) at com.alibaba.com.caucho.hessian.io.Hessian2Input.readObject(Hessian2Input.java:2066) at com.alibaba.com.caucho.hessian.io.JavaDeserializer$ObjectFieldDeserializer.deserialize(JavaDeserializer.java:390) ... 8 more

代码如下：

`
import com.alibaba.com.caucho.hessian.io.Hessian2Input;
import com.alibaba.com.caucho.hessian.io.Hessian2Output;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.Serializable;
import java.util.HashMap;

public class AVX {
public static void main(String[] args) throws IOException, ClassNotFoundException {
HashMap<String, String> map = new HashMap<>();
map.put("2", "2");

    Result<HashMap<String, String>> test = new Result(map);
    byte[] bytes = serialize(test);

    Result<HashMap<String, String>> mm = (Result<HashMap<String, String>>) deserialize(bytes);
    System.out.println(mm);
}

public static byte[] serialize(Object obj) throws IOException {
    if (obj == null) throw new NullPointerException();

    ByteArrayOutputStream os = new ByteArrayOutputStream();
    Hessian2Output ho = new Hessian2Output(os);
    ho.writeObject(obj);
    ho.flushBuffer();
    return os.toByteArray();
}

public static Object deserialize(byte[] by) throws IOException {
    if (by == null) throw new NullPointerException();

    ByteArrayInputStream is = new ByteArrayInputStream(by);
    Hessian2Input hi = new Hessian2Input(is);
    return hi.readObject();
}

static class Result<T extends Serializable> implements Serializable {

    public Result(T data) {
        this.data = data;
    }

    private T data;

    public T getData() {
        return data;
    }

    public void setData(T data) {
        this.data = data;
    }

    @Override
    public String toString() {
        return "Result{" +
                "data=" + data +
                '}';
    }
}

}`

经过测试，如果
static class Result<T extends Serializable> implements Serializable {
改为
static class Result<T> implements Serializable {

则能正常反序列化出来。

求大神帮助 看看

[icankeep]

这个主要是因为T extends Serializable这样写之后，data字段的类型就是java.io.Serializable，在读取data字段的值的时候，就是通过readObject(in, java.io.Serializable.class)

最终就会执行到Hessian2Input#readObject(Class expectedClass, Class<?>... expectedTypes)中

  case 'H': {
      // 最终获取的是ObjectDeserializer
      Deserializer reader = findSerializerFactory().getDeserializer(expectedClass);

      boolean keyValuePair = expectedTypes != null && expectedTypes.length == 2;
      // ObjectDeserializer并没有实现readMap，所以最终调用的AbstractDeserializer#readMap，该方法最终都会抛出错误
      return reader.readMap(this
              , keyValuePair ? expectedTypes[0] : null
              , keyValuePair ? expectedTypes[1] : null);
  }

我不懂的是为啥这里是reader.readMap而不是reader.readObject，如果是readObject的话这个问题应该就不存在了

我觉得这应该是hessian2的bug

[justein]

如果不设计文件传输的场景，建议用其他的序列化方式把