tomcat session not serializable for spring component with @Value injection

Question

It's a rather strange problem. In Spring I've configured a bean as session.

@Component
@Scope(value="session", proxyMode=ScopedProxyMode.TARGET_CLASS)
public class UserSession implements Serializable{...}

There is an interceptor which who interact with this session.

public class UserInterceptor extends HandlerInterceptorAdapter{
    ...
    @Autowired private UserSession userSession;
    @Autowired private WebUser webUser;

    public boolean preHandle(...){
        userSession.setUserId(webUser.getUserId());
        userSession.setUserList(webUser.getUsers());
        ...
    }
...
}

The WebUser is an interface, in which depend on environment it will inject different WebUser. In profile LOCAL, in will inject LocalWebUser

@Component
@Primary
@Profile({"LOCAL"})
public class LocalWebUser implements WebUser, Serializable{
   @Autowired private transient UserManager userManager;

   @Value("${env.tester.userId}")
   private transient String userId;

   @Override
   public List<String> getUsers() {
       return this.userManager.getUsers();
   }
   ...
}

Notice that I did give make field as transient to prevent common serialization problem. However, in tomcat it throws that LocalWebUser is not serializable.

Caused by: java.io.NotSerializableException: com.company.component.web.LocalWebUser$1 at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1164) at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1518) at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1483) ....

LocalWebUser is actually not stored in session, it's just that session retrieve value from it. Why it complains about it is not serializable?

I did found out a solution that by removing @Value injection from properties, the exception went away, which confuse me even more....

Christopher Schultz Christopher Schultz · Accepted Answer · 2013-12-07T05:08:28

It's not complaining about LocalWebUser. It's complaining about LocalWebUser$1 which is an anonymous inner class within LocalWebUser. Look through the code in LocalWebUser for something like this:

Object something = new Something() { .... };

That's an anonymous inner class. If that isn't serializable and a reference to that is being leaked into an object stored in the session, then there's your problem.

tomcat session not serializable for spring component with @Value injection

2 Answers