java.io.InvalidClassException: ; incompatible types for field 异常追踪

java.io.InvalidClassException: <className>; incompatible types for field <fieldName> 异常追踪

异常信息

后台日志中产生了如下异常信息：

java.io.InvalidClassException: <className>; incompatible types for field <fieldName>
        at java.io.ObjectStreamClass.matchFields(ObjectStreamClass.java:2299) ~[?:1.8.0_74]
        at java.io.ObjectStreamClass.getReflector(ObjectStreamClass.java:2193) ~[?:1.8.0_74]
        at java.io.ObjectStreamClass.initNonProxy(ObjectStreamClass.java:669) ~[?:1.8.0_74]
        at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1623) ~[?:1.8.0_74]
        at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1518) ~[?:1.8.0_74]
        at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1774) ~[?:1.8.0_74]
        at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1351) ~[?:1.8.0_74]
        at java.io.ObjectInputStream.readArray(ObjectInputStream.java:1707) ~[?:1.8.0_74]
        at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1345) ~[?:1.8.0_74]
        at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:2000) ~[?:1.8.0_74]
        at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1924) ~[?:1.8.0_74]
        at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1801) ~[?:1.8.0_74]
        at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1351) ~[?:1.8.0_74]
        at java.io.ObjectInputStream.readObject(ObjectInputStream.java:371) ~[?:1.8.0_74]

涉及到OutputInputStream.readObject，因此猜测是对象反序列化时，而产生的问题。

异常来源

 private static ObjectStreamField[] matchFields(ObjectStreamField[] fields,
                                                   ObjectStreamClass localDesc)
        throws InvalidClassException{
  // ...   
        for (int j = 0; j < localFields.length; j++) {
                ObjectStreamField lf = localFields[j];
                if (f.getName().equals(lf.getName())) {
                    if ((f.isPrimitive() || lf.isPrimitive()) &&
                        f.getTypeCode() != lf.getTypeCode())
                    {
                        throw new InvalidClassException(localDesc.name,
                            "incompatible types for field " + f.getName());
                    }
                    if (lf.getField() != null) {
                        m = new ObjectStreamField(
                            lf.getField(), lf.isUnshared(), false);
                    } else {
                        m = new ObjectStreamField(
                            lf.getName(), lf.getSignature(), lf.isUnshared());
                    }
                }
            }
     // ...
 }

异常重现

import java.io.Serializable;

public class Request implements Serializable {

    private static final long serialVersionUID = 3663364724485038109L;

    public Integer status;

    public Integer addressStatus;

    // setter getter
}

序列化Request对象

public class Serialization {

    public static void main(String[] args) throws IOException, ClassNotFoundException{
        Request r1 = new Request();
        r1.setAddressStatus(100);
        r1.setStatus(200);
        Request r2 = new Request();
        r2.setAddressStatus(300);
        r2.setStatus(400);

        File file = new File("D:/MySQL/workspace/spring/resources/request.ser");

        serializable(file, r1, r2);

        Request[] rs = deserializable(file);
        for (Request request : rs)
            System.out.println(request.getAddressStatus() + " " + request.getStatus());
    }

    public static void serializable(File file, Request... requests) throws IOException {
        ObjectOutputStream stream = new ObjectOutputStream(new FileOutputStream(file));
        if (requests != null)
            stream.writeObject(requests);
        stream.close();
    }

    public static Request[] deserializable(File file) throws IOException, ClassNotFoundException {
        ObjectInputStream stream = new ObjectInputStream(new FileInputStream(file));
        Request[] requests = (Request[])stream.readObject();
        stream.close();
        return requests;
    }
}

修改Request作用域类型

import java.io.Serializable;

public class Request implements Serializable {

    private static final long serialVersionUID = 3663364724485038109L;

    public int status;

    public int addressStatus;

    // setter getter
}

反序列化对象

public class Serialization {

    public static void main(String[] args) throws IOException, ClassNotFoundException{
        Request r1 = new Request();
        r1.setAddressStatus(100);
        r1.setStatus(200);
        Request r2 = new Request();
        r2.setAddressStatus(300);
        r2.setStatus(400);

        File file = new File("D:/MySQL/workspace/spring/resources/request.ser");

        Request[] rs = deserializable(file);
        for (Request request : rs)
            System.out.println(request.getAddressStatus() + " " + request.getStatus());
    }

    public static void serializable(File file, Request... requests) throws IOException {
        ObjectOutputStream stream = new ObjectOutputStream(new FileOutputStream(file));
        if (requests != null)
            stream.writeObject(requests);
        stream.close();
    }

    public static Request[] deserializable(File file) throws IOException, ClassNotFoundException {
        ObjectInputStream stream = new ObjectInputStream(new FileInputStream(file));
        Request[] requests = (Request[])stream.readObject();
        stream.close();
        return requests;
    }
}

将会抛出如下异常

Exception in thread "main" java.io.InvalidClassException: com.spring.domain.Request; incompatible types for field addressStatus
    at java.io.ObjectStreamClass.matchFields(ObjectStreamClass.java:2399)
    at java.io.ObjectStreamClass.getReflector(ObjectStreamClass.java:2293)
    at java.io.ObjectStreamClass.initNonProxy(ObjectStreamClass.java:741)
    at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1876)
    at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1745)
    at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:2033)
    at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1567)
    at java.io.ObjectInputStream.readArray(ObjectInputStream.java:1966)
    at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1561)
    at java.io.ObjectInputStream.readObject(ObjectInputStream.java:427)
    at com.spring.domain.Serialization.deserializable(Serialization.java:38)
    at com.spring.domain.Serialization.main(Serialization.java:24)

调试分析,可知反序列化类型为int和对象的序列化类型为Integer, 因此产生异常。

总结

项目中使用了Spring httpinvoker 远程服务。客户端与服务端使用一套服务接口，而接口的具体实现是在服务端。

客户端调用远程方法时，会序列化要调用的(接口)方法和参数，发送到服务端。

服务端会根据请求反序列化还原，调用具体方法获取结果，并将结果序列化发给客户端。

客户端接收响应，将服务端结果反序列化还原。

而如果客户端与服务端代码的版本不一致，就会产生该异常。