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Apache Hadoop MapReduce Streaming
/**
* 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.streaming.io;
import org.apache.hadoop.io.BytesWritable;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.typedbytes.TypedBytesWritable;
/**
* This class is used to resolve a string identifier into the required IO
* classes. By extending this class and pointing the property
* stream.io.identifier.resolver.class to this extension, additional
* IO classes can be added by external code.
*/
public class IdentifierResolver {
// note that the identifiers are case insensitive
public static final String TEXT_ID = "text";
public static final String RAW_BYTES_ID = "rawbytes";
public static final String TYPED_BYTES_ID = "typedbytes";
public static final String KEY_ONLY_TEXT_ID = "keyonlytext";
private Class inputWriterClass = null;
private Class outputReaderClass = null;
private Class outputKeyClass = null;
private Class outputValueClass = null;
/**
* Resolves a given identifier. This method has to be called before calling
* any of the getters.
*/
public void resolve(String identifier) {
if (identifier.equalsIgnoreCase(RAW_BYTES_ID)) {
setInputWriterClass(RawBytesInputWriter.class);
setOutputReaderClass(RawBytesOutputReader.class);
setOutputKeyClass(BytesWritable.class);
setOutputValueClass(BytesWritable.class);
} else if (identifier.equalsIgnoreCase(TYPED_BYTES_ID)) {
setInputWriterClass(TypedBytesInputWriter.class);
setOutputReaderClass(TypedBytesOutputReader.class);
setOutputKeyClass(TypedBytesWritable.class);
setOutputValueClass(TypedBytesWritable.class);
} else if (identifier.equalsIgnoreCase(KEY_ONLY_TEXT_ID)) {
setInputWriterClass(KeyOnlyTextInputWriter.class);
setOutputReaderClass(KeyOnlyTextOutputReader.class);
setOutputKeyClass(Text.class);
setOutputValueClass(NullWritable.class);
} else { // assume TEXT_ID
setInputWriterClass(TextInputWriter.class);
setOutputReaderClass(TextOutputReader.class);
setOutputKeyClass(Text.class);
setOutputValueClass(Text.class);
}
}
/**
* Returns the resolved {@link InputWriter} class.
*/
public Class getInputWriterClass() {
return inputWriterClass;
}
/**
* Returns the resolved {@link OutputReader} class.
*/
public Class getOutputReaderClass() {
return outputReaderClass;
}
/**
* Returns the resolved output key class.
*/
public Class getOutputKeyClass() {
return outputKeyClass;
}
/**
* Returns the resolved output value class.
*/
public Class getOutputValueClass() {
return outputValueClass;
}
/**
* Sets the {@link InputWriter} class.
*/
protected void setInputWriterClass(Class
inputWriterClass) {
this.inputWriterClass = inputWriterClass;
}
/**
* Sets the {@link OutputReader} class.
*/
protected void setOutputReaderClass(Class
outputReaderClass) {
this.outputReaderClass = outputReaderClass;
}
/**
* Sets the output key class class.
*/
protected void setOutputKeyClass(Class outputKeyClass) {
this.outputKeyClass = outputKeyClass;
}
/**
* Sets the output value class.
*/
protected void setOutputValueClass(Class outputValueClass) {
this.outputValueClass = outputValueClass;
}
}