Follow instructions in LiveReload section causes ClassCastException

[anasmi]

Steps to reproduce:

• Follow instructions at https://github.com/vaadin/bakery-app-starter-flow-spring#automatic-restart-and-live-reload
• Update anything in the code
• Restart is triggered and exception is thrown
• Page redirected to login

The full stacktrace:

java.lang.ClassCastException: java.lang.StackTraceElement cannot be cast to java.lang.String
	at java.io.ObjectInputStream.readTypeString(ObjectInputStream.java:1421) ~[na:1.8.0_91]
	at java.io.ObjectStreamClass.readNonProxy(ObjectStreamClass.java:719) ~[na:1.8.0_91]
	at java.io.ObjectInputStream.readClassDescriptor(ObjectInputStream.java:833) ~[na:1.8.0_91]
	at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1609) ~[na:1.8.0_91]
	at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1521) ~[na:1.8.0_91]
	at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1781) ~[na:1.8.0_91]
	at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1353) ~[na:1.8.0_91]
	at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:2018) ~[na:1.8.0_91]
	at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1942) ~[na:1.8.0_91]
	at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1808) ~[na:1.8.0_91]
	at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1353) ~[na:1.8.0_91]
	at java.io.ObjectInputStream.readObject(ObjectInputStream.java:373) ~[na:1.8.0_91]
	at org.apache.catalina.session.StandardSession.doReadObject(StandardSession.java:1611) ~[tomcat-embed-core-8.5.31.jar:8.5.31]
	at org.apache.catalina.session.StandardSession.readObjectData(StandardSession.java:1077) ~[tomcat-embed-core-8.5.31.jar:8.5.31]
	at org.apache.catalina.session.StandardManager.doLoad(StandardManager.java:218) ~[tomcat-embed-core-8.5.31.jar:8.5.31]
	at org.apache.catalina.session.StandardManager.load(StandardManager.java:162) ~[tomcat-embed-core-8.5.31.jar:8.5.31]
	at org.apache.catalina.session.StandardManager.startInternal(StandardManager.java:356) ~[tomcat-embed-core-8.5.31.jar:8.5.31]
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) [tomcat-embed-core-8.5.31.jar:8.5.31]
	at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5273) [tomcat-embed-core-8.5.31.jar:8.5.31]
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150) [tomcat-embed-core-8.5.31.jar:8.5.31]
	at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1421) [tomcat-embed-core-8.5.31.jar:8.5.31]
	at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1411) [tomcat-embed-core-8.5.31.jar:8.5.31]
	at java.util.concurrent.FutureTask.run(FutureTask.java:266) [na:1.8.0_91]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_91]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_91]
	at java.lang.Thread.run(Thread.java:745) [na:1.8.0_91]

[alexberazouski]

Which IDE are you using?
Are you using any DB or default in-memory storage?
Does exception occur if you do even small changes?

[anasmi]

Intellij in my case and is broken for customer on Eclipse. So should not matter.

I actually added simple System.out.printl. No changes to "working" code as per se.

Or just pressing save the file(no changes)--> it reloads automatically--> exception thrown

Default storage. Plain Bakery app + adding dependencies and configuration as mention in the documentation.
(Some sort of Serialization issue? )

[alexberazouski]

1. Exception happens for me too
2. Login issue I have as well (as far as I remember it could be a flow issue, but not sure)

Even though hotswapping itself works fine.

[alexberazouski]

We've discovered that exception happens if the change related to the view with a vaadin-grid-flow inside (basically any page except login page in bakery). So we will address this issue there

By the way, using Hotswap Agent instead of spring dev-tools resolves both of the issues.

[anasmi]

Thanks, @alexberazouski :)

[tulioag]

Upon further investigation, we discovered it is a serialization issue.

The exception is misleading and there is a bug reported for spring boot for that: spring-projects/spring-boot#9457

I created an issue in vaadin-spring, because I can partially reproduce it using the skeleton starter vaadin/spring#338

Bakery itself has some non serializable classes that would need to be handled. One of the issues is how to autowire service beans (which are singletons) back in the UI on desserialization.