hadoop与mysql数据库相连读出数据

用0.20.2版本 有些类已经过时 但必须要用 因为新版本对数据库连接支持不够

 

运行mysql创建数据库School，建立teacher表，并自行填写值

DROP TABLE IF EXISTS `school`.`teacher`;CREATE TABLE `school`.`teacher` ( `id` int(11) default NULL, `name` char(20) default NULL, `age` int(11) default NULL, `departmentID` int(11) default NULL) ENGINE=InnoDB DEFAULT CHARSET=latin1;

 

在eclipse中运行编译通过 但要加入必须的库 以及 hadoop0.20.2的eclipse的插件

import java.io.IOException;import org.apache.hadoop.fs.Path;import org.apache.hadoop.io.LongWritable;import org.apache.hadoop.io.Text;import org.apache.hadoop.mapred.FileOutputFormat;import org.apache.hadoop.mapred.JobClient;import org.apache.hadoop.mapred.JobConf;import org.apache.hadoop.mapred.lib.IdentityReducer;import org.apache.hadoop.mapred.lib.db.DBConfiguration;import org.apache.hadoop.mapred.lib.db.DBInputFormat;public class DBAccess2 { public static void main(String[] args) throws IOException { JobConf conf = new JobConf(DBAccess2.class); conf.setOutputKeyClass(LongWritable.class); conf.setOutputValueClass(Text.class); conf.setInputFormat(DBInputFormat.class); FileOutputFormat.setOutputPath(conf, new Path("hdfs://localhost:9000/dbout")); DBConfiguration.configureDB(conf,"com.mysql.jdbc.Driver", "jdbc:mysql://localhost:3306/school","root","zxcvbnm"); String [] fields = {"id", "name", "age", "departmentID"}; DBInputFormat.setInput(conf, TeacherRecord.class, "teacher", null, "id", fields); conf.setMapperClass(DBAccessMapper.class); conf.setReducerClass(IdentityReducer.class); JobClient.runJob(conf); } }

 

注：请自行修改数据库连接语句 用户名 密码 等等。

 

import java.io.IOException;import org.apache.hadoop.io.LongWritable;import org.apache.hadoop.io.Text;import org.apache.hadoop.mapred.MapReduceBase;import org.apache.hadoop.mapred.Mapper;import org.apache.hadoop.mapred.OutputCollector;import org.apache.hadoop.mapred.Reporter;public class DBAccessMapper extends MapReduceBase implementsMapper<LongWritable, TeacherRecord, LongWritable, Text> { @Override public void map(LongWritable key, TeacherRecord value, OutputCollector<LongWritable, Text> collector, Reporter reporter) throws IOException { // TODO Auto-generated method stubcollector.collect(new LongWritable(value.id), new Text(value.toString())); } }

 

 import java.io.DataInput;import java.io.DataOutput;import java.io.IOException;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;import org.apache.hadoop.io.Text;import org.apache.hadoop.io.Writable;import org.apache.hadoop.mapred.lib.db.DBWritable;public class TeacherRecord implements Writable, DBWritable{ int id; String name; int age; int departmentID; @Override public void readFields(DataInput in) throws IOException { // TODO Auto-generated method stub this.id = in.readInt(); this.name = Text.readString(in); this.age = in.readInt(); this.departmentID = in.readInt(); } @Override public void write(DataOutput out) throws IOException { // TODO Auto-generated method stub out.writeInt(this.id); Text.writeString(out, this.name); out.writeInt(this.age); out.writeInt(this.departmentID); } @Override public void readFields(ResultSet result) throws SQLException { // TODO Auto-generated method stub this.id = result.getInt(1); this.name = result.getString(2); this.age = result.getInt(3); this.departmentID = result.getInt(4); } @Override public void write(PreparedStatement stmt) throws SQLException { // TODO Auto-generated method stub stmt.setInt(1, this.id); stmt.setString(2, this.name); stmt.setInt(3, this.age); stmt.setInt(4, this.departmentID); } @Override public String toString() { // TODO Auto-generated method stub return new String(this.name + " " + this.age + " " + this.departmentID); } }