RankableObjectWithFields.java

package storm.starter.tools;

import java.util.List;

import backtype.storm.tuple.Tuple;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.Lists;

/**
 * This class wraps an objects and its associated count, including any additional data fields.
 * 
 * This class can be used, for instance, to track the number of occurrences of an object in a Storm topology.
 * 
 */
public class RankableObjectWithFields implements Rankable {

    private static final String toStringSeparator = "|";

    private final Object obj;
    private final long count;
    private final ImmutableList<Object> fields;

    public RankableObjectWithFields(Object obj, long count, Object... otherFields) {
        if (obj == null) {
            throw new IllegalArgumentException("The object must not be null");
        }
        if (count < 0) {
            throw new IllegalArgumentException("The count must be >= 0");
        }
        this.obj = obj;
        this.count = count;
        fields = ImmutableList.copyOf(otherFields);

    }

    /**
     * Construct a new instance based on the provided {@link Tuple}.
     * 
     * This method expects the object to be ranked in the first field (index 0) of the provided tuple, and the number of
     * occurrences of the object (its count) in the second field (index 1). Any further fields in the tuple will be
     * extracted and tracked, too. These fields can be accessed via {@link RankableObjectWithFields#getFields()}.
     * 
     * @param tuple
     * @return
     */
    public static RankableObjectWithFields from(Tuple tuple) {
        List<Object> otherFields = Lists.newArrayList(tuple.getValues());
        Object obj = otherFields.remove(0);
        Long count = (Long) otherFields.remove(0);
        return new RankableObjectWithFields(obj, count, otherFields.toArray());
    }

    public Object getObject() {
        return obj;
    }

    public long getCount() {
        return count;
    }

    /**
     * @return an immutable list of any additional data fields of the object (may be empty but will never be null)
     */
    public List<Object> getFields() {
        return fields;
    }

    @Override
    public int compareTo(Rankable other) {
        long delta = this.getCount() - other.getCount();
        if (delta > 0) {
            return 1;
        }
        else if (delta < 0) {
            return -1;
        }
        else {
            return 0;
        }
    }

    @Override
    public boolean equals(Object o) {
        if (this == obj) {
            return true;
        }
        if (!(o instanceof RankableObjectWithFields)) {
            return false;
        }
        RankableObjectWithFields other = (RankableObjectWithFields) o;
        return obj.equals(other.obj) && count == other.count;
    }

    @Override
    public int hashCode() {
        int result = 17;
        int countHash = (int) (count ^ (count >>> 32));
        result = 31 * result + countHash;
        result = 31 * result + obj.hashCode();
        return result;
    }

    public String toString() {
        StringBuffer buf = new StringBuffer();
        buf.append("[");
        buf.append(obj);
        buf.append(toStringSeparator);
        buf.append(count);
        for (Object field : fields) {
            buf.append(toStringSeparator);
            buf.append(field);
        }
        buf.append("]");
        return buf.toString();
    }
}