Hits.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.nutch.searcher;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;

import org.apache.hadoop.io.Writable;
import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.io.Text;

/** A set of hits matching a query. */
public final class Hits implements Writable {

  private long total;
  private boolean totalIsExact = true;
  private Hit[] top;

  public Hits() {}

  public Hits(long total, Hit[] top) {
    this.total = total;
    this.top = top;
  }

  /** Returns the total number of hits for this query.  This may be an estimate
   * when (@link #totalIsExact()} is false. */
  public long getTotal() { return total; }

  /** True if {@link #getTotal()} gives the exact number of hits, or false if
   * it is only an estimate of the total number of hits. */
  public boolean totalIsExact() { return totalIsExact; }

  /** Set {@link #totalIsExact()}. */
  public void setTotalIsExact(boolean isExact) { totalIsExact = isExact; }

  /** Returns the number of hits included in this current listing. */
  public int getLength() { return top.length; }

  /** Returns the <code>i</code><sup>th</sup> hit in this list. */
  public Hit getHit(int i) { return top[i]; }

  /** Returns a subset of the hit objects. */
  public Hit[] getHits(int start, int length) {
    Hit[] results = new Hit[length];
    for (int i = 0; i < length; i++) {
      results[i] = top[start+i];
    }
    return results;
  }

  public void write(DataOutput out) throws IOException {
    out.writeLong(total);                         // write total hits
    out.writeInt(top.length);                     // write hits returned
    if (top.length > 0)                           // write sort value class
      Text.writeString(out, top[0].getSortValue().getClass().getName());
                      
    for (int i = 0; i < top.length; i++) {
      Hit h = top[i];
      Text.writeString(out, h.getUniqueKey());    // write uniqueKey
      h.getSortValue().write(out);                // write sortValue
      Text.writeString(out, h.getDedupValue());   // write dedupValue
    }
  }

  @SuppressWarnings("unchecked")
  public void readFields(DataInput in) throws IOException {
    total = in.readLong();                        // read total hits
    top = new Hit[in.readInt()];                  // read hits returned
    Class sortClass = null;
    if (top.length > 0) {                         // read sort value class
      try {
        sortClass = Class.forName(Text.readString(in));
      } catch (ClassNotFoundException e) {
        throw new IOException(e.toString());
      }
    }

    for (int i = 0; i < top.length; i++) {
      String uniqueKey = Text.readString(in);            // read uniqueKey

      WritableComparable sortValue = null;
      try {
        sortValue = (WritableComparable)sortClass.newInstance();
      } catch (Exception e) {
        throw new IOException(e.toString());
      }
      sortValue.readFields(in);                   // read sortValue

      String dedupValue = Text.readString(in);    // read dedupValue

      top[i] = new Hit(uniqueKey, sortValue, dedupValue);
    }
  }

}