throwing a Serializable RuntimeException in OnNext requires OnNext value to be Serializable as well

[saharh]

when throwing a runtime exception during OnNext, the exception is wrapped within OnErrorThrowable$OnNextValue, which features access to the value emitted in OnNext. this feature comes at a cost - If one would wish to serialize/deserialize the exception or any object containing that exception, one would also be required to have the type of item emitted by OnNext also implement Serializable (which could lead to whole hierarchy of objects be serializable). While the original runtime exception thrown is serializable, the OnErrorThrowable$OnNextValue which includes reference to the onnext emitted item, isn't.
This leads to java.io.NotSerializableException thrown when trying to serialize the exception:

Caused by: java.io.NotSerializableException: com.example.SomeUnserializableObject
        at java.io.ObjectOutputStream.writeNewObject(ObjectOutputStream.java:1344)
        at java.io.ObjectOutputStream.writeObjectInternal(ObjectOutputStream.java:1651)
        at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:1497)
        at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:1461)
        at java.io.ObjectOutputStream.writeFieldValues(ObjectOutputStream.java:959)
        at java.io.ObjectOutputStream.defaultWriteObject(ObjectOutputStream.java:360)
        at java.io.ObjectOutputStream.writeHierarchy(ObjectOutputStream.java:1054)
        at java.io.ObjectOutputStream.writeNewObject(ObjectOutputStream.java:1384)
        at java.io.ObjectOutputStream.writeObjectInternal(ObjectOutputStream.java:1651)
        at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:1497)
        at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:1461)
        at java.io.ObjectOutputStream.writeFieldValues(ObjectOutputStream.java:959)
        at java.io.ObjectOutputStream.defaultWriteObject(ObjectOutputStream.java:360)
        at java.lang.Throwable.writeObject(Throwable.java:436)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.io.ObjectO

I dont see any way around it other than avoiding throwing of RuntimeException during onNext, and instead move to flatmap and return Observable.error(exception).

[JakeWharton]

We can mark the value as transient in the exception.

On Thu, Sep 15, 2016 at 3:29 PM saharh notifications@github.com wrote:

when throwing a runtime exception during OnNext, the exception is wrapped
within OnErrorThrowable$OnNextValue, which features access to the value
emitted in OnNext. this feature comes at a cost - If one would wish to
serialize/deserialize the exception or any object containing that
exception, one would also be required to have the type of item emitted by
OnNext also implement Serializable (which could lead to whole hierarchy of
objects be serializable). While the original runtime exception thrown is
serializable, the OnErrorThrowable$OnNextValue which includes reference to
the onnext emitted item, isn't.
This leads to java.io.NotSerializableException thrown when trying to
serialize the exception:

                                                                     Caused by: java.io.NotSerializableException: com.example.sample.SomeUnserializableObject
                                                                        at java.io.ObjectOutputStream.writeNewObject(ObjectOutputStream.java:1344)
                                                                        at java.io.ObjectOutputStream.writeObjectInternal(ObjectOutputStream.java:1651)
                                                                        at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:1497)
                                                                        at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:1461)
                                                                        at java.io.ObjectOutputStream.writeFieldValues(ObjectOutputStream.java:959)
                                                                        at java.io.ObjectOutputStream.defaultWriteObject(ObjectOutputStream.java:360)
                                                                        at java.io.ObjectOutputStream.writeHierarchy(ObjectOutputStream.java:1054)
                                                                        at java.io.ObjectOutputStream.writeNewObject(ObjectOutputStream.java:1384)
                                                                        at java.io.ObjectOutputStream.writeObjectInternal(ObjectOutputStream.java:1651)
                                                                        at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:1497)
                                                                        at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:1461)
                                                                        at java.io.ObjectOutputStream.writeFieldValues(ObjectOutputStream.java:959)
                                                                        at java.io.ObjectOutputStream.defaultWriteObject(ObjectOutputStream.java:360)
                                                                        at java.lang.Throwable.writeObject(Throwable.java:436)
                                                                        at java.lang.reflect.Method.invoke(Native Method)
                                                                        at java.io.ObjectO

I dont see any way around it other than avoiding throwing of
RuntimeException during onNext, and instead move to flatmap and return
Observable.error(exception).

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[rzsombor]

I must ask: what's your use case where you want to serialize exceptions? Are passing them over to some other process maybe?

[saharh]

It is a rather rare use case, but i do pass a result which might include an exception between activities in android, which requires the object to be serializable

[akarnokd]

See #4841

[akarnokd]

Closing via #4841