Shulou(Shulou.com)05/31 Report--

This article mainly introduces how to achieve DBInputFormat in hadoop, has a certain reference value, interested friends can refer to, I hope you can learn a lot after reading this article, the following let the editor take you to understand it.

Take notes before the code is tested

Package com.test;import java.io.DataInput;import java.io.DataOutput;import java.io.IOException;import java.net.URI;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;import org.apache.hadoop.conf.Configuration;import org.apache.hadoop.conf.Configured;import org.apache.hadoop.fs.FileSystem;import org.apache.hadoop.fs.Path;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.lib.db.DBConfiguration;import org.apache.hadoop.mapreduce.lib.db.DBInputFormat;import org.apache.hadoop.mapreduce.lib.db.DBWritable;import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;import org.apache.hadoop.util.Tool;import org.apache.hadoop.util.ToolRunner / * to run this example * 1, put the jdbc driver of mysql into the lib directory of taskTracker, restart the cluster * * / public class WordCountDB extends Configured implements Tool {private String OUT_PATH = "hdfs://grid131:9000/output"; public static class Map extends Mapper {public void map (LongWritable key, MyUser value, Context context) throws IOException, InterruptedException {context.write (key, new Text (value.toString () }} public int run (String [] args) throws Exception {Configuration conf = this.getConf (); DBConfiguration.configureDB (conf, "com.mysql.jdbc.Driver", "jdbc:mysql://grid131:3306/test", "root", "admin"); / / if the output path exists, delete FileSystem fs = FileSystem.get (new URI (OUT_PATH), conf); fs.delete (new Path (OUT_PATH), true) Job job = new Job (conf, WordCountDB.class.getSimpleName ()); job.setJarByClass (WordCountDB.class); FileOutputFormat.setOutputPath (job, new Path (args [1])); / / write map output directly to hdfs job.setNumReduceTasks (0); job.setInputFormatClass (DBInputFormat.class) without the need for reduce / / specify tables, fields / / DBInputFormat.setInput (job, inputClass, tableName, conditions, orderBy, fieldNames) DBInputFormat.setInput (job, MyUser.class, "myuser", null, null, "id", "name"); job.setMapperClass (Map.class); / / when the reduce output type is consistent with the map output type, map's output type may not be set job.setMapOutputKeyClass (LongWritable.class); job.setMapOutputValueClass (Text.class); job.waitForCompletion (true) Return job.isSuccessful ()? 0args 1;} public static void main (String [] args) throws Exception {int exit = ToolRunner.run (new WordCount (), args); System.exit (exit);}} class MyUser implements Writable, DBWritable {private Long id; private String name; public Long getId () {return id;} public void setId (Long id) {this.id = id;} public String getName () {return name;} public void setName (String name) {this.name = name @ Override public void write (DataOutput out) throws IOException {out.writeLong (this.id); Text.writeString (out, this.name);} @ Override public void readFields (DataInput in) throws IOException {this.id = in.readLong (); this.name = Text.readString (in);} @ Override public void write (PreparedStatement statement) throws SQLException {statement.setLong (1, this.id); statement.setString (2, this.name) } @ Override public void readFields (ResultSet resultSet) throws SQLException {this.id = resultSet.getLong (1); this.name = resultSet.getString (2);} @ Override public String toString () {return this.id + "\ t" + this.name }} Thank you for reading this article carefully. I hope the article "how to achieve DBInputFormat in hadoop" shared by the editor will be helpful to everyone. At the same time, I also hope that you will support us and pay attention to the industry information channel. More related knowledge is waiting for you to learn!

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.