CDI：为什么我的瞬态字段被序列化？

Question

With CDI (Weld) I implemented a producer method for a non serializable class. If the producer got serialized and the field NonSerializableObject is gone, I reinitialize a NonSerializableObject:

@SessionScoped
public class NonSerializableObjectProducer implements Serializable {

/** UUID */
private static final long serialVersionUID = -436472364723647647367L;

/** my transient non serializbale object */
private transient NonSerializableObject nonSerializableObject;

@SessionScoped
@Produces
protected NonSerializableObject produceNonSerializableObject() {
    if (nonSerializableObject == null) {
       // reinitialize object and set it
       // nonSerializableObject = ...
    }
    return nonSerializableObject;
}

I inject a NonSerializableObject like:

@SessionScoped
public class UseSerializableObject implements Serializable {

    private static final long serialVersionUID = 62378785678643784689L;

    @Inject
    private transient NonSerializableObject nonSerializableObject;

    public void doSomething() {
        nonSerializableObject.go();
    }
}

When my application server (Tomcat 7) redeploys the following exception occurs:

Sep 22, 2014 4:41:58 PM org.apache.catalina.session.StandardSession writeObject
WARNING: Cannot serialize session attribute WELD_S#5 for session 4694BB90FF1BBD8
java.io.NotSerializableException: com.MemberOfNonSerializableObject 
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1181)

So, a member variable of my NonSerializableObject gets serialized. Why? I declared everything as transient!

Answer 1

Your method:

@SessionScoped
@Produces
protected NonSerializableObject produceNonSerializableObject() {}

produces @SessionScoped object, which is not serializable. All @RequestScoped, @SessionScoped, and @ApplicationScoped beans must be Serializable.

So it would work, if you would removed @SessionScoped from the producer method.