Global Exception Handling in Spring Cloud Function on AWS Lambda Platform - spring

Question

I am using spring cloud function on AWS lambda. I am trying to achieve global exception handling like Spring Boot using #ExceptionHandler annotation. But this method is not getting executed and I am getting 500 for any type of exception.
Sample code is below-
#SpringBootApplication
public class App{
public static void main( String[] args ){
SpringApplication.run(App.class, args);
}
#Bean
public Function<Message<User>, User> getUser(){
return (message)->{
User u = message.getPayload();
if(u==null){
throw new ResponseStatusException(HttpStatus.BAD_REQUEST,"No user details provided");
}
return u;
}
}
#ExceptionHandler(ResponseStatusException.class)
public APIGatewayProxyResponseEvent handleException(ResponseStatusException e){
APIGatewayProxyResponseEvent response = new APIGatewayProxyResponseEvent();
response.setStatusCode(e.getRawStatusCode());
response.setBody(e.getMessage());
return response;
}
}
I am getting 500 in response instead Bad Request. Is there any way to achieve this scenario ?

Answer 1

You can provide your custom exceptionHandler while building SpringBootLambdaContainerHandler.
public class StreamLambdaHandler implements RequestStreamHandler {
private static SpringBootLambdaContainerHandler<AwsProxyRequest, AwsProxyResponse> handler;
static {
handler = new SpringBootProxyHandlerBuilder<AwsProxyRequest>()
.defaultProxy()
.exceptionHandler(***your customer handler here***)
// other methods are skipped
.buildAndInitialize();
}
}

Answer 2

If you are using spring cloud functions no need to use SpringBootLambdaContainerHandler, what you need to do is create a custom routing function and handle the exception thrown from your lambda function and return APIGatewayProxyResponseEvent. below shows how I achieved the desired result
public class CustomRoutingFunction implements Function<Message<?>, APIGatewayProxyResponseEvent> {
private final FunctionCatalog functionCatalog;
private final FunctionProperties functionProperties;
private final MessageRoutingCallback routingCallback;
public static final String DEFAULT_ROUTE_HANDLER = "defaultMessageRoutingHandler";
public CustomRoutingFunction(FunctionCatalog functionCatalog,
FunctionProperties functionProperties,
MessageRoutingCallback routingCallback) {
this.functionCatalog = functionCatalog;
this.functionProperties = functionProperties;
this.routingCallback = routingCallback;
}
#Override
public APIGatewayProxyResponseEvent apply(Message<?> input) {
ObjectMapper mapper = new ObjectMapper();
mapper.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false);
try {
String functionDefinition = this.routingCallback.routingResult(input);
SimpleFunctionRegistry.FunctionInvocationWrapper function = functionCatalog.lookup(functionDefinition);
Object output = function.apply(input);
String payload = mapper.writeValueAsString(output);
return new APIGatewayProxyResponseEvent()
.withIsBase64Encoded(false)
.withBody(payload)
.withHeaders(Map.of(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE,
"statusCode", "200"))
.withStatusCode(200);
} catch (Exception e) {
return new APIGatewayProxyResponseEvent()
.withIsBase64Encoded(false)
.withHeaders(Map.of(HttpHeaders.CONTENT_TYPE,
MediaType.APPLICATION_JSON_VALUE,
"statusCode", String.valueOf(HttpStatus.BAD_REQUEST.value())))
.withBody(e.getMessage())
.withStatusCode(HttpStatus.BAD_REQUEST.value());
}
}
}
now you need to register your router function as a bean and pass it to spring.cloud.function.definition
#Bean
public CustomRoutingFunction customRoutingFunction(FunctionCatalog functionCatalog,
FunctionProperties functionProperties,
#Nullable MessageRoutingCallback routingCallback,
#Nullable DefaultMessageRoutingHandler defaultMessageRoutingHandler) {
if (defaultMessageRoutingHandler != null) {
FunctionRegistration functionRegistration = new FunctionRegistration(defaultMessageRoutingHandler, CustomRoutingFunction.DEFAULT_ROUTE_HANDLER);
functionRegistration.type(FunctionTypeUtils.consumerType(ResolvableType.forClassWithGenerics(Message.class, Object.class).getType()));
((FunctionRegistry) functionCatalog).register(functionRegistration);
}
return new CustomRoutingFunction(functionCatalog, functionProperties, routingCallback);
}
inside your application.yml file
spring:
cloud:
function:
definition: customRoutingFunction