For add Async methods:

1. add in Application annotation: @EnableAsync
2. add for service method annotation: @Async

First – let’s go over the rules – @Async has two limitations:

• it must be applied to public methods only
• self-invocation – calling the async method from within the same class – won’t work

The reasons are simple – the method needs to be public so that it can be proxied. And self-invocation doesn’t work because it bypasses the proxy and calls the underlying method directly.

By default, Spring uses a SimpleAsyncTaskExecutor to actually run these methods asynchronously. The defaults can be overridden at two levels – at the application level or at the individual method level.

See GlobalAsyncConfig.java

Set type of executor and config. And set exception handler for Exception Async

See local config LocalAsyncConfig.java and see SimpleVoidService.java how to use

Compare time execution for multi threads and single thread in test.

When testing is very difficult to work with asynchronous methods, so we need to make the execution synchronous.

To do this:

• we used the method of creating profiles @Profile("non-async") for override global executor config /src/test/java/examples/GlobalSyncConfig.java
• for override local config bean name executor (see /src/main/java/examples/configasync/LocalAsyncConfig.java) we must create own test @SpringBootApplication class see /src/test/java/examples/TestApplication.java