hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/TestWritable.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.hadoop.io;

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

import org.apache.hadoop.conf.Configurable;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.util.ReflectionUtils;

import org.junit.Test;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotNull;
import static org.junit.Assert.assertNull;
import static org.junit.Assert.assertTrue;

/** Unit tests for Writable. */
public class TestWritable {
private static final String TEST_CONFIG_PARAM = "frob.test";
private static final String TEST_CONFIG_VALUE = "test";
private static final String TEST_WRITABLE_CONFIG_PARAM = "test.writable";
private static final String TEST_WRITABLE_CONFIG_VALUE = TEST_CONFIG_VALUE;

  /** Example class used in test cases below. */
  public static class SimpleWritable implements Writable {
    private static final Random RANDOM = new Random();

    int state = RANDOM.nextInt();

    @Override
    public void write(DataOutput out) throws IOException {
      out.writeInt(state);
    }

    @Override
    public void readFields(DataInput in) throws IOException {
      this.state = in.readInt();
    }

    public static SimpleWritable read(DataInput in) throws IOException {
      SimpleWritable result = new SimpleWritable();
      result.readFields(in);
      return result;
    }

    /** Required by test code, below. */
    @Override
    public boolean equals(Object o) {
      if (!(o instanceof SimpleWritable))
        return false;
      SimpleWritable other = (SimpleWritable)o;
      return this.state == other.state;
    }
  }

  public static class SimpleWritableComparable extends SimpleWritable
      implements WritableComparable<SimpleWritableComparable>, Configurable {
    private Configuration conf;

    public SimpleWritableComparable() {}

    public void setConf(Configuration conf) {
      this.conf = conf;
    }

    public Configuration getConf() {
      return this.conf;
    }

    public int compareTo(SimpleWritableComparable o) {
      return this.state - o.state;
    }
  }

  /** Test 1: Check that SimpleWritable. */
  @Test
  public void testSimpleWritable() throws Exception {
    testWritable(new SimpleWritable());
  }
  @Test
  public void testByteWritable() throws Exception {
    testWritable(new ByteWritable((byte)128));
  }
  @Test
  public void testShortWritable() throws Exception {
    testWritable(new ShortWritable((byte)256));
  }
  @Test
  public void testDoubleWritable() throws Exception {
    testWritable(new DoubleWritable(1.0));
  }

  /** Utility method for testing writables. */
  public static Writable testWritable(Writable before) 
  	throws Exception {
  	return testWritable(before, null);
  }
  
  /** Utility method for testing writables. */
  public static Writable testWritable(Writable before
  		, Configuration conf) throws Exception {
    DataOutputBuffer dob = new DataOutputBuffer();
    before.write(dob);

    DataInputBuffer dib = new DataInputBuffer();
    dib.reset(dob.getData(), dob.getLength());
    
    Writable after = (Writable)ReflectionUtils.newInstance(
    		before.getClass(), conf);
    after.readFields(dib);

    assertEquals(before, after);
    return after;
  }
	
  private static class FrobComparator extends WritableComparator {
    public FrobComparator() { super(Frob.class); }
    @Override public int compare(byte[] b1, int s1, int l1,
                                 byte[] b2, int s2, int l2) {
      return 0;
    }
  }

  private static class Frob implements WritableComparable<Frob> {
    static {                                     // register default comparator
      WritableComparator.define(Frob.class, new FrobComparator());
    }
    @Override public void write(DataOutput out) throws IOException {}
    @Override public void readFields(DataInput in) throws IOException {}
    @Override public int compareTo(Frob o) { return 0; }
  }

  /** Test that comparator is defined and configured. */
  public static void testGetComparator() throws Exception {
    Configuration conf = new Configuration();

    // Without conf.
    WritableComparator frobComparator = WritableComparator.get(Frob.class);
    assert(frobComparator instanceof FrobComparator);
    assertNotNull(frobComparator.getConf());
    assertNull(frobComparator.getConf().get(TEST_CONFIG_PARAM));

    // With conf.
    conf.set(TEST_CONFIG_PARAM, TEST_CONFIG_VALUE);
    frobComparator = WritableComparator.get(Frob.class, conf);
    assert(frobComparator instanceof FrobComparator);
    assertNotNull(frobComparator.getConf());
    assertEquals(conf.get(TEST_CONFIG_PARAM), TEST_CONFIG_VALUE);

    // Without conf. should reuse configuration.
    frobComparator = WritableComparator.get(Frob.class);
    assert(frobComparator instanceof FrobComparator);
    assertNotNull(frobComparator.getConf());
    assertEquals(conf.get(TEST_CONFIG_PARAM), TEST_CONFIG_VALUE);

    // New conf. should use new configuration.
    frobComparator = WritableComparator.get(Frob.class, new Configuration());
    assert(frobComparator instanceof FrobComparator);
    assertNotNull(frobComparator.getConf());
    assertNull(frobComparator.getConf().get(TEST_CONFIG_PARAM));
  }

  /**
   * Test a user comparator that relies on deserializing both arguments for each
   * compare.
   */
  @Test
  public void testShortWritableComparator() throws Exception {
    ShortWritable writable1 = new ShortWritable((short)256);
    ShortWritable writable2 = new ShortWritable((short) 128);
    ShortWritable writable3 = new ShortWritable((short) 256);
    
    final String SHOULD_NOT_MATCH_WITH_RESULT_ONE = "Result should be 1, should not match the writables";
    assertTrue(SHOULD_NOT_MATCH_WITH_RESULT_ONE,
        writable1.compareTo(writable2) == 1);
    assertTrue(SHOULD_NOT_MATCH_WITH_RESULT_ONE, WritableComparator.get(
        ShortWritable.class).compare(writable1, writable2) == 1);

    final String SHOULD_NOT_MATCH_WITH_RESULT_MINUS_ONE = "Result should be -1, should not match the writables";
    assertTrue(SHOULD_NOT_MATCH_WITH_RESULT_MINUS_ONE, writable2
        .compareTo(writable1) == -1);
    assertTrue(SHOULD_NOT_MATCH_WITH_RESULT_MINUS_ONE, WritableComparator.get(
        ShortWritable.class).compare(writable2, writable1) == -1);

    final String SHOULD_MATCH = "Result should be 0, should match the writables";
    assertTrue(SHOULD_MATCH, writable1.compareTo(writable1) == 0);
    assertTrue(SHOULD_MATCH, WritableComparator.get(ShortWritable.class)
        .compare(writable1, writable3) == 0);
  }

  /**
   * Test that Writable's are configured by Comparator.
   */
  @Test
  public void testConfigurableWritableComparator() throws Exception {
    Configuration conf = new Configuration();
    conf.set(TEST_WRITABLE_CONFIG_PARAM, TEST_WRITABLE_CONFIG_VALUE);

    WritableComparator wc = WritableComparator.get(SimpleWritableComparable.class, conf);
    SimpleWritableComparable key = ((SimpleWritableComparable)wc.newKey());
    assertNotNull(wc.getConf());
    assertNotNull(key.getConf());
    assertEquals(key.getConf().get(TEST_WRITABLE_CONFIG_PARAM), TEST_WRITABLE_CONFIG_VALUE);
  }
}