SpringBoot/Tomcat fails to start when a @WebListener has a constructor with an argument

[bencalegari]

Spring Boot Version: 2.4.2

Here's an abbreviated ./gradlew bootRun log from a sample app I created to replicate the issue:

2021-01-30 18:31:03.430 DEBUG 2609 --- [           main] o.apache.catalina.core.StandardContext   : Configuring application event listeners
2021-01-30 18:31:03.430 DEBUG 2609 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       :  Configuring event listener class 'com.example.springbootlistenerbug.Listener'
2021-01-30 18:31:03.431 ERROR 2609 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Error configuring application listener of class [com.example.springbootlistenerbug.Listener]

java.lang.NoSuchMethodException: com.example.springbootlistenerbug.Listener.<init>()
	at java.base/java.lang.Class.getConstructor0(Class.java:3427) ~[na:na]
	at java.base/java.lang.Class.getConstructor(Class.java:2165) ~[na:na]
	at org.apache.catalina.core.DefaultInstanceManager.newInstance(DefaultInstanceManager.java:151) ~[tomcat-embed-core-9.0.41.jar:9.0.41]
	at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4640) ~[tomcat-embed-core-9.0.41.jar:9.0.41]
	at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5177) ~[tomcat-embed-core-9.0.41.jar:9.0.41]
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183) ~[tomcat-embed-core-9.0.41.jar:9.0.41]
	at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1384) ~[tomcat-embed-core-9.0.41.jar:9.0.41]
	at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1374) ~[tomcat-embed-core-9.0.41.jar:9.0.41]
	at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264) ~[na:na]

You can find the entirety of the log in this Github action from the repo.

We noticed this issue in our application when attempting to upgrade from 2.3.5.RELEASE to 2.4.2. In our case, the arguments passed to the class annotated with @WebListener are @Component classes, but in the example repo I was able to reproduce the error with or without that annotation. Spring starts just fine when you remove the argument to the constructor.

I configured the app to use the Spring Boot 2.5 snapshot and got the same error, for what it's worth.

[philwebb]

This is probably related to #18303

I'm a little surprised that @WebListener constructor injection worked in 2.4, it was probably by accident rather than design. @bencalegari If you change your SessionListener class so that it's annotated with @Component and not @WebListener do things work as expected? All HttpSessionListener beans in the context should be automatically added to the servlet container.

[bencalegari]

Thanks! That fixed it, both in the sample app and ours. Is there a reason why constructor injection in @WebListeners should've been avoided at the outset?

[philwebb]

Usually the lifecycle of @WebListeners is handled directly by the Servlet Containers and as such they don't know anything about Spring.

[wilkinsona]

It's a requirement of the Servlet spec that listeners, filters, and servlets must have a zero-args constructor. This applies whether they're registered via web.xml or the various annotations.