How to get arguments from an instance of functional interface object passed as lambda?

Question

@FunctionalInterface
public interface ServiceCaller {
    void callService();
}

//common method to execute any service call
public void executeService(ServiceCaller serviceCaller) {
    //do common things
    //i want to access dbValidationRequest/apiValidationRequest here for logging purpose
    try {
        serviceCaller.callService();
    } catch (Exception ex) {
        //do common things
        LogUtils.log(logger, ex);
    }
    //do common things
}

//my clients call this
public void validateFromDb(DbValidationRequest dbValidationRequest){
    commonUtils.executeService(()-> dbValidationService.validate(dbValidationRequest));
}

//my clients call this
public void validateFromApi(ApiValidationRequest apiValidationRequest){
    commonUtils.executeService(()-> apiValidationService.validate(apiValidationRequest));
}

This is a controller of Java Spring Application. Inside the executeService method, i pass an instance of ServiceCaller interface. I call all my service from controller using this method. if i evaluate using intelliJ IDEA then i can view values of the dbValidationRequest/apiValidationRequest inside executeService method (as arg$2, see attached picture). I need to print those objects for logging purpose, i also don't want to use aspect at all. How can i do this. If intelliJ IDEA can see the values, why can't i programatically?

Cristian Bianco · Accepted Answer · 2020-02-04T08:33:03.137

arg$1 and arg$2 can be treated as fields of a class, so they can be obtained by reflection.

    String var1 = "Content Var 1";
    String var2 = "Content Var 2";

    Supplier<String> stringSupplier = () -> var1 + var2;

    Field[] declaredFields = stringSupplier.getClass().getDeclaredFields();

    for (Field f : declaredFields) {
        f.setAccessible(true);
        System.out.println(
            "Field Name: " + f.getName() +
            ", value: " + f.get(stringSupplier)
        );
    }

    // Field Name: arg$1, value: Content Var 1
    // Field Name: arg$2, value: Content Var 2

How to get arguments from an instance of functional interface object passed as lambda?

1 Answers1