How to parse and get headers property values externally in Spring Integration

Question

I need to parse and get headers property value which I send via MessagingGateway, I doubt if it has something to do with IntegrationEvaluationContext

Here is what I tried and failed miserably:

@Bean
public IntegrationFlow deleteFiles(){
    return IntegrationFlows.from("integration.channel.bulk-delete")
            .handle(Sftp.outboundGateway(sftpSessionFactory(),
            AbstractRemoteFileOutboundGateway.Command.LS,"headers[path]")
                    .options(AbstractRemoteFileOutboundGateway.Option.NAME_ONLY)
                    .filterFunction(file->{
                     //Here I'm trying to get the age value from headers
                        int age = ExpressionUtils.intExpression("headers[age]").getValue(integrationEvaluationContext.getObject(),Integer.class);
                        Instant decidedTime = Instant.now().minus(age, ChronoUnit.SECONDS);
                        return Instant.ofEpochSecond(file.getAttrs().getMTime()).isBefore(decidedTime);
                    }))
                   .get();

The error message:

org.springframework.expression.spel.SpelEvaluationException: EL1007E: Property or field 'headers' cannot be found on null 

I even tried autowiring StandardEvaluationContext and passing:

new SpelExpressionParser().parseExpression("headers[age]").getValue(standardEvaluationContext)

How can I get the EvaluationContext and pass it so that headers[] get parsed?

Answer 1

The filters don't have access to the gateway's input message; they only have access to the LsEntry.

You need to provide the age some other way, perhaps store it in a ThreadLocal.

public class AgeHolder {

     private static final ages = new ThreadLocal<Integer>;

     public static setAge(int age) {
         ages.set(age);
     }

     public static Integer getAge() {
         Integer age = ages.get();
         ages.remove();
         return age;
     }

}

Then T(AgeHolder).getAge() in the expression.

Or you can do the filtering in Spring Integration instead

    .from(Sfp...) // not NAME_ONLY
    .split
    .filter(...) // use the `headers` and `payload`
    .transform(...) -> LsEntry -> name
    .aggregate()
    ...