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MarkLogic Connector for Hadoop MapReduce
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/*
 * Copyright 2003-2019 MarkLogic Corporation
 *
 * 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 com.marklogic.mapreduce.examples;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.util.GenericOptionsParser;
import org.w3c.dom.Element;
import org.xml.sax.SAXException;

import com.marklogic.mapreduce.DocumentURI;
import com.marklogic.mapreduce.MarkLogicConstants;
import com.marklogic.mapreduce.MarkLogicNode;
import com.marklogic.mapreduce.PropertyOutputFormat;
import com.marklogic.mapreduce.ValueInputFormat;

/**
 * Read title attributes in links as text and write summary as property to
 * referenced documents.  Used with config file conf/marklogic-textin-propout.xml.
 */
public class LinkCountInProperty {
    public static class RefMapper 
    extends Mapper {
        
        private final static IntWritable one = new IntWritable(1);
        private Text refURI = new Text();
        
        public void map(LongWritable key, Text value, Context context) 
        throws IOException, InterruptedException {
            refURI.set(value.toString().trim());
            context.write(refURI, one);
        }
    }
    
    public static class IntSumReducer
    extends Reducer {
        private final static String TEMPLATE = "0";
        private final static String BASE_URI_PARAM_NAME = "mapreduce.linkcount.baseuri";
        
        private DocumentURI docUri = new DocumentURI();
        private Element element;
        private MarkLogicNode result;
        private String baseUri;
        
        protected void setup(Context context) 
        throws IOException, InterruptedException {
            try {
                DocumentBuilder docBuilder = 
                    DocumentBuilderFactory.newInstance().newDocumentBuilder();
                InputStream sbis = new ByteArrayInputStream(TEMPLATE.getBytes());
                element = docBuilder.parse(sbis).getDocumentElement();
                
                result = new MarkLogicNode(element);
                baseUri = context.getConfiguration().get(BASE_URI_PARAM_NAME);
            } catch (ParserConfigurationException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (SAXException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        
        public void reduce(Text key, Iterable values, 
                Context context
                ) throws IOException, InterruptedException {        
            int sum = 0;
            if (isInvalidName(key)) {
                return;
            }
            for (IntWritable val : values) {
                sum += val.get();
            }
            StringBuilder buf = new StringBuilder();
            buf.append(baseUri).append(key);
            docUri.setUri(buf.toString());
            element.setTextContent(Integer.toString(sum));
            context.write(docUri, result);
        }
        
        // exclude key that is invalid for a document URI
        private boolean isInvalidName(Text key) {
            String keyString = key.toString();
            return keyString == null || keyString.isEmpty() || 
                    keyString.matches("( )*");
        }
    }
    
    public static void main(String[] args) throws Exception {
        Configuration conf = new Configuration();
        if (args.length < 1) {
            System.err.println("Usage: LinkCountInProperty configFile");
            System.exit(2);
        }
        String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();
        
        Job job = Job.getInstance(conf, "link count in property");
        job.setJarByClass(LinkCountInProperty.class);
        job.setInputFormatClass(ValueInputFormat.class);
        job.setMapperClass(RefMapper.class);
        job.setMapOutputKeyClass(Text.class);
        job.setMapOutputValueClass(IntWritable.class);
        job.setReducerClass(IntSumReducer.class);
        job.setOutputFormatClass(PropertyOutputFormat.class);
        job.setOutputKeyClass(DocumentURI.class);
        job.setOutputValueClass(MarkLogicNode.class);
        
        conf = job.getConfiguration();
        conf.addResource(otherArgs[0]);
        conf.setClass(MarkLogicConstants.INPUT_VALUE_CLASS, Text.class, 
                Writable.class);
    
        System.exit(job.waitForCompletion(true) ? 0 : 1);
    }
}