#Async in Rest Controller not working - asynchronous

Question

I am developing a REST API and want to make it as an asynchronous Rest Controller,
So my Controller is below:
#RestController
#Async
public class ApiController {
List<ApiObject> apiDataList;
#RequestMapping(value="/data",produces={MediaType.APPLICATION_JSON_VALUE},method=RequestMethod.GET)
public ResponseEntity<List<ApiObject>> getData(){
List<ApiObject> apiDataList=getApiData();
return new ResponseEntity<List<ApiObject>>(apiDataList,HttpStatus.OK);
}
#ResponseBody
public List<ApiObject> getApiData(){
List<ApiObject> apiDataList3=new List<ApiObject> ();
//do the processing
return apiDataList3;
}
}
Then in the Spring boot Application class I created as
#SpringBootApplication
#EnableScheduling
#EnableCaching
#EnableAsync
public class APIApplication {
public static void main(String[] args) {
SpringApplication.run(APIApplication.class, args);
}
}
After that in the server.xml I tried to add the Nio Connector like below:
<Connector maxThreads="1000" port="8080" protocol="org.apache.coyote.http11.Http11Nioprotocol"
connectionTimeout="20000"
redirectPort="8443" />
But the Application starts but the response is empty.Any help is appreciated

Answer 1

#Async should be annotated by method (not class).
You have annotated it for class
#Async
public class ApiController {
You have to specify for methods only (where the caller of the method will not wait)
Example:
#Async
public void asyncMethodWithVoidReturnType(){
System.out.println("Execute method asynchronously. "
+ Thread.currentThread().getName());
}
Note for Executor
In spring boot it is preferable to use a bean and specify the Executor to in #Async annotation
Executor Bean
#Configuration
#EnableAsync
public class SpringAsyncConfig {
#Bean(name = "threadPoolTaskExecutor")
public Executor threadPoolTaskExecutor() {
return new ThreadPoolTaskExecutor();
}
}
Use of Executor Bean
#Async("threadPoolTaskExecutor")
public void asyncMethodWithConfiguredExecutor() {
System.out.println("Execute method with configured executor - "
+ Thread.currentThread().getName());
}
Or if you have to use xml
<task:executor id="threadPoolTaskExecutor" pool-size="5" />
<task:annotation-driven executor="threadPoolTaskExecutor"/>
For detail document you can see here