使用MapReduce将HDFS数据导入Mysql

使用MapReduce将Mysql数据导入HDFS代码链接

将HDFS数据导入Mysql,代码示例

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.io.LongWritable;
import org.apache.hadoop.io.NullWritable;
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.Counter;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.db.DBConfiguration;
import org.apache.hadoop.mapreduce.lib.db.DBOutputFormat;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.input.TextInputFormat;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;

/**
 * @author FengZhen
 * 将hdfs数据导入mysql
 * 使用DBOutputFormat将HDFS路径下的结构化数据写入mysql中，结构化数据如下,第一列为key,后边三列为数据
 * 0    1    Enzo    180.66
 * 1    2    Din    170.666
 *
 */
public class DBOutputFormatApp 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);
        }

        public void set(int id,String name,double height){
            this.id = id;
            this.name = name;
            this.height = height;
        }

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

    }

    public static class DBOutputMapper extends Mapper<LongWritable, Text, NullWritable, BeanWritable>{
        private NullWritable outputKey;
        private BeanWritable outputValue;

        @Override
        protected void setup(Mapper<LongWritable, Text, NullWritable, BeanWritable>.Context context)
                throws IOException, InterruptedException {
            this.outputKey = NullWritable.get();
            this.outputValue = new BeanWritable();
        }
        @Override
        protected void map(LongWritable key, Text value,
                Mapper<LongWritable, Text, NullWritable, BeanWritable>.Context context)
                throws IOException, InterruptedException {
            //插入数据库成功的计数器
            final Counter successCounter = context.getCounter("exec", "successfully");
            //插入数据库失败的计数器
            final Counter faildCounter = context.getCounter("exec", "faild");
            //解析结构化数据
            String[] fields = value.toString().split("\t");
            //DBOutputFormatApp这个MapReduce应用导出的数据包含long类型的key，所以忽略key从1开始
            if (fields.length > ) {
                int id = Integer.parseInt(fields[]);
                String name = fields[];
                double height = Double.parseDouble(fields[]);
                this.outputValue.set(id, name, height);
                context.write(outputKey, outputValue);
                //如果插入数据库成功则递增1，表示成功计数
                successCounter.increment(1L);
            }else{
                //如果插入数据库失败则递增1，表示失败计数
                faildCounter.increment(1L);
            }

        }
    }

    /**
     * 输出的key必须是继承自DBWritable的类型，DBOutputFormat要求输出的key必须是DBWritable类型
     * */
    public static class DBOutputReducer extends Reducer<NullWritable, BeanWritable, BeanWritable, NullWritable>{
        @Override
        protected void reduce(NullWritable key, Iterable<BeanWritable> values,
                Reducer<NullWritable, BeanWritable, BeanWritable, NullWritable>.Context context)
                throws IOException, InterruptedException {
            for (BeanWritable beanWritable : values) {
                context.write(beanWritable, key);
            }
        }
    }

    public int run(String[] arg0) throws Exception {
        Configuration configuration = getConf();
        //在创建Configuration的时候紧接着配置数据库连接信息
        DBConfiguration.configureDB(configuration, "com.mysql.jdbc.Driver", "jdbc:mysql://localhost:3306/hadoop", "root", "123qwe");
        Job job = Job.getInstance(configuration, DBOutputFormatApp.class.getSimpleName());
        job.setJarByClass(DBOutputFormatApp.class);
        job.setMapperClass(DBOutputMapper.class);
        job.setMapOutputKeyClass(NullWritable.class);
        job.setMapOutputValueClass(BeanWritable.class);

        job.setReducerClass(DBOutputReducer.class);
        job.setOutputFormatClass(DBOutputFormat.class);
        job.setOutputKeyClass(BeanWritable.class);
        job.setOutputValueClass(NullWritable.class);

        job.setInputFormatClass(TextInputFormat.class);
        FileInputFormat.setInputPaths(job, arg0[]);
        //配置当前作业输出到数据库表、字段信息
        DBOutputFormat.setOutput(job, "people", new String[]{"id","name","height"});

        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 DBOutputFormatApp(), 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);
    }

}

打成jar包，放在服务器上，执行hadoop jar命令

hadoop jar /Users/FengZhen/Desktop/Hadoop/other/mapreduce_jar/HDFSToMysql.jar com.zhen.mysqlToHDFS.DBOutputFormatApp

任务结束后mysql表中即可发现数据已经有了。