使用MapReduce将mysql数据导入HDFS

package com.zhen.mysqlToHDFS;

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.conf.Configuration;
import org.apache.hadoop.conf.Configured;
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.mapred.lib.db.DBWritable;
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.output.FileOutputFormat;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;

/**
 * @author FengZhen
 * 将mysql数据导入hdfs
 */
public class DBInputFormatApp extends Configured implements Tool {

    /**
     * JavaBean
     * 需要实现Hadoop序列化接口Writable以及与数据库交互时的序列化接口DBWritable
     * 官方API中解释如下：
     * public class DBInputFormat<T extends DBWritable>
     *   extends InputFormat<LongWritable, T> implements Configurable
     * 即Mapper的Key是LongWritable类型，不可改变；Value是继承自DBWritable接口的自定义JavaBean
     */
    public static class BeanWritable implements Writable, DBWritable {

        private int id;
        private String name;
        private double height;

        public void readFields(ResultSet resultSet) throws SQLException {
            this.id = resultSet.getInt();
            this.name = resultSet.getString();
            this.height = resultSet.getDouble();
        }

        public void write(PreparedStatement preparedStatement) throws SQLException {
            preparedStatement.setInt(, id);
            preparedStatement.setString(, name);
            preparedStatement.setDouble(, height);
        }

        public void readFields(DataInput dataInput) throws IOException {
            this.id = dataInput.readInt();
            this.name = dataInput.readUTF();
            this.height = dataInput.readDouble();
        }

        public void write(DataOutput dataOutput) throws IOException {
            dataOutput.writeInt(id);
            dataOutput.writeUTF(name);
            dataOutput.writeDouble(height);
        }

        @Override
        public String toString() {
            return id + "\t" + name + "\t" + height;
        }

    }

    /**
     * Map
     * 当Map的输出key为LongWritable，value为Text时，reduce可以省略不写，默认reduce也是输出LongWritable:Text
     * */
    public static class DBInputMapper extends Mapper<LongWritable, BeanWritable, LongWritable, Text> {

        private LongWritable outputKey;
        private Text outputValue;

        @Override
        protected void setup(Mapper<LongWritable, BeanWritable, LongWritable, Text>.Context context)
                throws IOException, InterruptedException {
            this.outputKey = new LongWritable();
            this.outputValue = new Text();
        }

        @Override
        protected void map(LongWritable key, BeanWritable value,
                Mapper<LongWritable, BeanWritable, LongWritable, Text>.Context context)
                throws IOException, InterruptedException {
            outputKey.set(key.get());;
            outputValue.set(value.toString());
            context.write(outputKey, outputValue);
        }

    }

    public int run(String[] arg0) throws Exception {
        Configuration configuration = getConf();
        //配置当前作业需要使用的JDBC配置
        DBConfiguration.configureDB(configuration, "com.mysql.jdbc.Driver", "jdbc:mysql://localhost:3306/hadoop",
                "root", "123qwe");
        Job job = Job.getInstance(configuration, DBInputFormatApp.class.getSimpleName());

        job.setJarByClass(DBInputFormatApp.class);
        job.setMapperClass(DBInputMapper.class);
        job.setMapOutputKeyClass(LongWritable.class);
        job.setMapOutputValueClass(Text.class);

        job.setOutputKeyClass(LongWritable.class);
        job.setOutputValueClass(Text.class);

        //配置作业的输入数据格式
        job.setInputFormatClass(DBInputFormat.class);
        //配置当前作业需要查询的sql语句及接收sql语句的bean
        DBInputFormat.setInput(
                job,
                BeanWritable.class,
                "select * from people",
                "select count(1) from people");

        FileOutputFormat.setOutputPath(job, new Path(arg0[]));

        return job.waitForCompletion(true) ?  : ;
    }

    public static int createJob(String[] args) {
        Configuration conf = new Configuration();
        conf.set("dfs.datanode.socket.write.timeout", "");
        conf.set("mapreduce.input.fileinputformat.split.minsize", "");
        conf.set("mapreduce.input.fileinputformat.split.maxsize", "");
        int status = ;
        try {

            status = ToolRunner.run(conf,new DBInputFormatApp(), args);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return status;
    }

    public static void main(String[] args) {
        args = new String[] { "/user/hadoop/mapreduce/mysqlToHdfs/people" };
        int status = createJob(args);
        System.exit(status);
    }
}

在mysql新建一张表 people

CREATE TABLE `people` (
  `id` int() NOT NULL,
  `name` varchar() DEFAULT NULL,
  `height` double DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8

写入几条测试数据。

将mapreduce作业打成jar包，上传到Hadoop集群服务器，执行。

hadoop jar /Users/FengZhen/Desktop/Hadoop/other/mapreduce_jar/MysqlToHDFS.jar com.zhen.mysqlToHDFS.DBInputFormatApp

因为代码中已经指定了写入HDFS的路径，所以此处不需要传参，只需指定job所在类即可。

在运行中如果提示mysql驱动找不到，如下

Caused by: java.lang.ClassNotFoundException: com.jdbc.mysql.Driver
    at java.net.URLClassLoader$.run(URLClassLoader.java:)
    at java.net.URLClassLoader$.run(URLClassLoader.java:)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:)
    at org.apache.hadoop.mapreduce.lib.db.DBConfiguration.getConnection(DBConfiguration.java:)
    at org.apache.hadoop.mapreduce.lib.db.DBInputFormat.createConnection(DBInputFormat.java:)
    ...  more

解决办法：

将mysql jdbc驱动放入 .../hadoop/share/hadoop/mapreduce/lib下,然后重启集群再次执行即可。

使用MapReduce将HDFS数据导入MySql