AbstractApplicationEventMulticaster throws NPE when ApplicationEvent's source is null [SPR-10945]

[spring-projects-issues]

Johannes Scharf opened SPR-10945 and commented

AbstractApplicationEventMulticaster throws a NullPointerException at line 131 if the ApplicationEvent's source is null:

protected Collection<ApplicationListener> getApplicationListeners(ApplicationEvent event) {
	Class<? extends ApplicationEvent> eventType = event.getClass();
	Class sourceType = event.getSource().getClass(); // NPE here if source is null
	ListenerCacheKey cacheKey = new ListenerCacheKey(eventType, sourceType);
	ListenerRetriever retriever = this.retrieverCache.get(cacheKey);
	if (retriever != null) {
		return retriever.getApplicationListeners();
	}
	// Rest omitted

The Event's source is null because we serialize our objects to XML by using XStream and publishing them later asynchronously by a job. Unfortunately source is declared transient in EventObject (the superclass of ApplicationEvent) and hence not serialized by XStream. Therefore after deserialization from XML source is null.

Although we could work around this by setting source (it has modifier protected) again after deserialization AbstractApplicationEventMulticaster should not blow up and handle null source of events more robust.

---

Affects: 3.2.3

Sub-tasks:

• Backport: AbstractApplicationEventMulticaster throws NPE when ApplicationEvent's source is null [SPR-11012] #15640 Backport: AbstractApplicationEventMulticaster throws NPE when ApplicationEvent's source is null

Referenced from: commits b0ff834, 1ea7f74