testversionedwritable.java

Hadoop是一个用于运行应用程序在大型集群的廉价硬件设备上的框架。Hadoop为应用程序透明的提供了一组稳定/可靠的接口和数据运动。在 Hadoop中实现了Google的MapReduce算法

/**
 * Copyright 2005 The Apache Software Foundation
 *
 * Licensed 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.*;
import java.util.Random;
import junit.framework.TestCase;

/** Unit tests for VersionedWritable. */

public class TestVersionedWritable extends TestCase {

	public TestVersionedWritable(String name) { super(name); }
	
	
	/** Example class used in test cases below. */
	public static class SimpleVersionedWritable extends VersionedWritable {
		
		private static final Random RANDOM = new Random();
		int state = RANDOM.nextInt();

		
		private static byte VERSION = 1;
		public byte getVersion() { 
			return VERSION; 
		}		
		

		public void write(DataOutput out) throws IOException {
			super.write(out); // version.
			out.writeInt(state);
		}
		
		public void readFields(DataInput in) throws IOException {
			super.readFields(in); // version
			this.state = in.readInt();
		}
		

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

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

	}


	
	public static class AdvancedVersionedWritable extends SimpleVersionedWritable {

		String shortTestString = "Now is the time for all good men to come to the aid of the Party";
		String longTestString = "Four score and twenty years ago. Blah. Blah. Blah. Blah. Blah. Blah. Blah. Blah.";
		
		String compressableTestString = 
			"Blah. Blah. Blah. Blah. Blah. Blah. Blah. Blah. Blah. Blah. Blah. Blah. " +
			"Blah. Blah. Blah. Blah. Blah. Blah. Blah. Blah. Blah. Blah. Blah. Blah. " +
			"Blah. Blah. Blah. Blah. Blah. Blah. Blah. Blah. Blah. Blah. Blah. Blah. " ;

		SimpleVersionedWritable containedObject = new SimpleVersionedWritable();
		String[] testStringArray = {"The", "Quick", "Brown", "Fox", "Jumped", "Over", "The", "Lazy", "Dog"};

		public void write(DataOutput out) throws IOException {
			super.write(out);
			out.writeUTF(shortTestString); 
			WritableUtils.writeString(out,longTestString); 
			int comp = WritableUtils.writeCompressedString(out,compressableTestString); 
			System.out.println("Compression is " + comp + "%");
			containedObject.write(out); // Warning if this is a recursive call, you need a null value.
			WritableUtils.writeStringArray(out,testStringArray); 

		}
		
		
		public void readFields(DataInput in) throws IOException {
			super.readFields(in);
			shortTestString = in.readUTF();
			longTestString = WritableUtils.readString(in); 
			compressableTestString = WritableUtils.readCompressedString(in);
			containedObject.readFields(in); // Warning if this is a recursive call, you need a null value.
			testStringArray = WritableUtils.readStringArray(in); 
		}
			


		public boolean equals(Object o) {
			super.equals(o);

			if (!shortTestString.equals(((AdvancedVersionedWritable)o).shortTestString)) { return false;}
			if (!longTestString.equals(((AdvancedVersionedWritable)o).longTestString)) { return false;}
			if (!compressableTestString.equals(((AdvancedVersionedWritable)o).compressableTestString)) { return false;}
			
			if (testStringArray.length != ((AdvancedVersionedWritable)o).testStringArray.length) { return false;}
			for(int i=0;i< testStringArray.length;i++){
				if (!testStringArray[i].equals(((AdvancedVersionedWritable)o).testStringArray[i])) {
					return false;
				}
			}
			
			if (!containedObject.equals(((AdvancedVersionedWritable)o).containedObject)) { return false;}
			
			return true;
		}
		


	}

	/* This one checks that version mismatch is thrown... */
	public static class SimpleVersionedWritableV2 extends SimpleVersionedWritable {
		static byte VERSION = 2;
		public byte getVersion() { 
			return VERSION; 
		}		
	}


	/** Test 1: Check that SimpleVersionedWritable. */
	public void testSimpleVersionedWritable() throws Exception {
		TestWritable.testWritable(new SimpleVersionedWritable());
	}

	/** Test 2: Check that AdvancedVersionedWritable Works (well, why wouldn't it!). */
	public void testAdvancedVersionedWritable() throws Exception {
		TestWritable.testWritable(new AdvancedVersionedWritable());
	}

	/** Test 3: Check that SimpleVersionedWritable throws an Exception. */
	public void testSimpleVersionedWritableMismatch() throws Exception {
		TestVersionedWritable.testVersionedWritable(new SimpleVersionedWritable(), new SimpleVersionedWritableV2());
	}



	
  /** Utility method for testing VersionedWritables. */
  public static void testVersionedWritable(Writable before, Writable after) throws Exception {
      DataOutputBuffer dob = new DataOutputBuffer();
      before.write(dob);
	
      DataInputBuffer dib = new DataInputBuffer();
      dib.reset(dob.getData(), dob.getLength());

      try {
          after.readFields(dib);
      } catch (VersionMismatchException vmme) {
          System.out.println("Good, we expected this:" + vmme);
          return;
      }
	
      throw new Exception("A Version Mismatch Didn't Happen!");
  }
}