比较器未正确排序

Question

I am trying to write a test to put under stress the behaviour of the following class. It is a comparator for a website, but for some reason the section of 'propertiesCreatedBy' is not working. This is a very strange issue as long as the rest of fields are working and can be sorted properly, but when trying to sort by this column the order seems to be random:

import java.io.Serializable;
import java.util.Comparator;
import java.util.HashMap;
import java.util.Map;


public class CaseNoteDTOComparator implements Comparator, Serializable {

    /**
     *
     */
    private static final long serialVersionUID = 1L;

    protected class CaseNoteDTOComparatorInternal implements Serializable  {
        private String[] properties = null;
        boolean[] shouldReverse = null;

        public CaseNoteDTOComparatorInternal(String[] properties, boolean[] shouldReverse) {
            this.properties = properties;
            this.shouldReverse = shouldReverse;
        }

        public int compare(Object obj1, Object obj2) {
            int result = 0;
            for (int i = 0; i < properties.length; i++) {
                JavaBeanNamedPropertyComparator comparator =
                    new JavaBeanNamedPropertyComparator(properties[i], shouldReverse[i]);
                result = comparator.compare(obj1, obj2);
                if(result != ComparatorConstants.EQUAL) {
                    return result;
                }
            }
            //actually object are equals....
            return ComparatorConstants.LESS_THAN;
        }

        public void setDescending(boolean descending) {
            for (int i = 0; i < shouldReverse.length; i++) {
                shouldReverse[i] = descending;
            }
        }
    }

    private static Map comparators = new HashMap();

    //statically initialise comparators
    {
        final String[] propertiesEffectiveDate = { EFFECTIVE_DATE_NAME, CREATED_ON };
        boolean[] shouldReverseEffectiveDate= {false, false};
        comparators.put(EFFECTIVE_DATE_NAME, new CaseNoteDTOComparatorInternal(propertiesEffectiveDate, shouldReverseEffectiveDate));

        final String[] propertiesId = { ID_NAME };
        boolean[] shouldReverseId = {false};
        comparators.put(ID_NAME, new CaseNoteDTOComparatorInternal( propertiesId, shouldReverseId));

        final String[] propertiesType = { TYPE_NAME, ID_NAME };
        boolean[] shouldReverseType = {false, false};
        comparators.put(TYPE_NAME, new CaseNoteDTOComparatorInternal( propertiesType, shouldReverseType));

        final String[] propertiesTitle = { TITLE_NAME, ID_NAME };
        boolean[] shouldReverseTitle = {false, false};
        comparators.put(TITLE_NAME, new CaseNoteDTOComparatorInternal( propertiesTitle, shouldReverseTitle));

        final String[] propertiesRecordedVS = { PERSON_LASTNAME_NAME, PERSON_FIRSTNAME_NAME, ID_NAME };
        boolean[] shouldReverseRecordedVS= {false, false, false};
        comparators.put(RECORDED_VS, new CaseNoteDTOComparatorInternal( propertiesRecordedVS, shouldReverseRecordedVS));

        final String[] propertiesCreatedBy = { CREATED_BY_LASTNAME_NAME, CREATED_BY_FIRSTNAME_NAME, ID_NAME };
        boolean[] shouldReverseCreatedBy= {false, false, false};
        comparators.put(CREATED_BY_NAME, new CaseNoteDTOComparatorInternal( propertiesCreatedBy, shouldReverseCreatedBy));

        final String[] propertiesOrganisation = { ORGANISATION_NAME, ID_NAME };
        boolean[] shouldReverseOrganisation= {false, false};
        comparators.put(ORGANISATION_NAME, new CaseNoteDTOComparatorInternal( propertiesOrganisation, shouldReverseOrganisation));

        final String[] propertiesScore = { LUCENE_INDEX_SCORE};
        boolean[] shouldReverseScore = {false};
        comparators.put(LUCENE_INDEX_SCORE, new CaseNoteDTOComparatorInternal( propertiesScore, shouldReverseScore));

    }

    private CaseNoteDTOComparatorInternal comparator = null;

    public static final String ID_NAME = "id";
    public static final String EFFECTIVE_DATE_NAME = "effectiveDate";
    public static final String TYPE_NAME = "displayCaseNoteType";
    public static final String TITLE_NAME = "title";
    public static final String PERSON_LASTNAME_NAME = "personLastName";
    public static final String PERSON_FIRSTNAME_NAME = "personFirstName";
    public static final String RECORDED_VS = "recordedVS";
    public static final String CREATED_BY_NAME = "createdBy";
    public static final String CREATED_BY_FIRSTNAME_NAME = "createdByFirstName";
    public static final String CREATED_BY_LASTNAME_NAME =  "createdByLastName";
    public static final String CREATED_ON = "createdOn";
    public static final String ORGANISATION_NAME = "organisationName";
    public static final String DEFAULT_FIELD_NAME = EFFECTIVE_DATE_NAME;
    public static final String LUCENE_INDEX_SCORE = "score";

    public CaseNoteDTOComparator(String fieldKeyName, boolean descending) {
        this.comparator = (CaseNoteDTOComparatorInternal)comparators.get(fieldKeyName);
        if(comparator==null) {
            this.comparator = (CaseNoteDTOComparatorInternal)comparators.get(DEFAULT_FIELD_NAME);
        }
        comparator.setDescending(descending);
    }

    public int compare(Object obj1, Object obj2) {

        return comparator.compare(obj1, obj2);
    }
}

I spent several hours looking at the code and making experiments but can't find what's wrong. More than implementing the test for the class, I'd like to fix it, but can't find the problem. I will really appreciate any hint.

Thanks!

Answer 1

My guess: this is a data problem. You return ComparatorConstants.LESS_THAN on equal values (why?) which means that equivalent data will be ordered arbitrarily.

Returning less-than on equal values also risks introducing infinite loops if the sorting algorithm isn't tolerant of that case.

Are you sure these fields are correctly populated, and you're referring to them by the correct name?