39 lines
1.5 KiB
Plaintext
39 lines
1.5 KiB
Plaintext
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== Why is this an issue?
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Spring provides the `@EventListener` annotation as a simpler alternative to implementing the `ApplicationListener` interface for handling events. The `@EventListener` annotation registers a method as an event handler.
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This allows to skip the implementation of the `ApplicationListener` interface, making it easier to handle events.
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The `@EventListener` annotation can only be used on methods that have at most one parameter, which should be the specific event that we want to handle.
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To listen to several types of events, use the `classes` argument of the `@EventListener` annotation.
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This rule raises an issue on all methods annotated with `@EventListener` that have more than one parameter.
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== How to fix it
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=== Code examples
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==== Noncompliant code example
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[source,java,diff-id=1,diff-type=noncompliant]
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----
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@EventListener
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void handleEvent(CustomerEvent customerEvent, ExceptionalEvent exceptionalEvent) { // Non compliant, this will cause a runtime error
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//... some event handling
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}
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----
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==== Compliant solution
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[source,java,diff-id=1,diff-type=compliant]
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----
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@EventListener(classes = {CustomerEvent.class, ExceptionalEvent.class})
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void handleEvent(ApplicationEvent event) { // Only one parameter, of the super type `ApplicationEvent`
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//... some event handling
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}
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----
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== Resources
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=== Documentation
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Spring API - https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/context/event/EventListener.html[@EventListener]
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