Java – Uses predicates to validate search parameters

I have a validate() method to check the parameters passed in the rest url.
The parameters are linked to the following model classes

class SearchCriteria {

String regno;
String hostid;
String domid;
String location;
String provider;

/*Getters and Setters*/
}

I have a utility class to check if the parameters are set.

public class SearchCriteriaUtil {

public static boolean isRegnoSet(SearchCriteria criteria) {
        return null != criteria.getRegno();
    }

public static boolean isHostIdSet(SearchCriteria criteria) {
        return null != criteria.getHostId();
    }

/* Similarly for domid, location, provider */
}

I have a predicate that tests against the conditions provided in util and generates a truth string

public class ParameterPredicate<T> implements Predicate<T>{

final Predicate<T> predicate;
    final String sequence;

public ParameterPredicate(Predicate<T> predicate, String sequence) {
        this.predicate = predicate;
        this.sequence = sequence;
    }

@Override
    public String toString() {
        return sequence;
    }

@Override
    public boolean test(T t) {
        return predicate.test(t);
    }
}

Now, based on the parameter set/notset,
regno -set, hostid -set, domid – notset, location – notset, provider – set

My predicate should be evaluated against the condition in SearchCriteriaUtil with the sequence set to the appropriate truth value… In this case,

“T T F F T”

In my verification method,

public void validateCriteria(SearchCriteria criteria) {
            List<Predicate<SearchCriteria>> SearchCriteriaPredicate = Arrays.asList(SearchCriteriaUtil::isRegnoSet, SearchCriteriaUtil::isHostIdSet,
                    SearchCriteriaUtil::isDomidSet,
                    SearchCriteriaUtil::isLocationSet,
                    SearchCriteriaUtil::isProviderSet,

Collection<String> desired = Arrays.asList("T F F F F", "T F T T F", "T F T T F", "T F F F T", "T F F F T", "F T F F F");

I

can’t go beyond that, I have to set the sequence and check if it exists in the desired truth list.

I was referring to previous posts: Filtering with truth tables

Since I’m new to Java 8, any help is greatly appreciated.

Instead of using the util class and processing strings to check if a combination of conditions is valid, add the following to the SearchCriteria class

public boolean hasDesiredCombination() {
    return Criterion.DESIRED_COMBINATONS.contains(
            Arrays.stream(Criterion.values())
            .filter(s -> s.predicate.test(this))
            .collect(Collectors.toCollection(
                    () -> EnumSet.noneOf(Criterion.class)))
            );
}

private static enum Criterion {
    REGNO(s -> s.regno != null),
    HOSTID(s -> s.hostid != null),
    DOMID(s -> s.domid != null),
    LOCATION(s -> s.location != null),
    PROVIDER(s -> s.provider != null);

private static Set<Set<Criterion>> DESIRED_COMBINATONS =
            new HashSet<>(Arrays.asList(
                    EnumSet.of(REGNO),
                    EnumSet.of(REGNO, DOMID, LOCATION),
                    EnumSet.of(REGNO, PROVIDER),
                    EnumSet.of(HOSTID)
                    ));

private Predicate<SearchCriteria> predicate;

private Criterion(Predicate<SearchCriteria> predicate) {
        this.predicate = predicate;
    }
}

Pros:

• You don’t have to expose getters and setters
• It is immediately clear from the source code which combinations are needed
• The logic is where it belongs: (indirectly) in the SearchCriteria class