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MapReduce 读写数据库
经常听到小伙伴吐槽 MapReduce 计算的结果无法直接写入数据库，
实际上 MapReduce 是有操作数据库实现的
本案例代码将实现 MapReduce 数据库读写操作和将数据表中数据复制到另外一张数据表中
准备数据表
create database htu;
use htu;
create table word(name varchar(255) comment '单词',count int comment '数量'
);
create table new_word(name varchar(255) comment '单词',count int comment '数量'
);
数据库持久化类
package com.lihaozhe.db;import lombok.AllArgsConstructor;
import lombok.Getter;
import lombok.NoArgsConstructor;
import lombok.Setter;
import org.apache.hadoop.mapreduce.lib.db.DBWritable;import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;/*** @author 李昊哲* @version 1.0.0* @create 2023/11/7*/
@Getter
@Setter
@NoArgsConstructor
@AllArgsConstructor
public class Word implements DBWritable {/*** 单词*/private String name;/*** 单词数量*/private int count;@Overridepublic String toString() {return this.name + "\t" + this.count;}@Overridepublic void write(PreparedStatement pst) throws SQLException {pst.setString(1, this.name);pst.setInt(2, this.count);}@Overridepublic void readFields(ResultSet rs) throws SQLException {this.name = rs.getString(1);this.count = rs.getInt(2);}
}MapReduce 将数据写入数据库
package com.lihaozhe.db;import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
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.DBOutputFormat;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;import java.io.IOException;/*** @author 李昊哲* @version 1.0* @create 2023-11-7*/
public class Write {public static class WordMapper extends Mapper<LongWritable, Text, Word, NullWritable> {@Overrideprotected void map(LongWritable key, Text value, Mapper<LongWritable, Text, Word, NullWritable>.Context context) throws IOException, InterruptedException {String[] split = value.toString().split("\t");Word word = new Word();word.setName(split[0]);word.setCount(Integer.parseInt(split[1]));context.write(word, NullWritable.get());}}public static void main(String[] args) throws IOException, InterruptedException, ClassNotFoundException {// 设置环境变量 hadoop 用户名 为 rootSystem.setProperty("HADOOP_USER_NAME", "root");// 参数配置对象Configuration conf = new Configuration();// 配置JDBC 参数DBConfiguration.configureDB(conf,"com.mysql.cj.jdbc.Driver","jdbc:mysql://spark03:3306/htu?useUnicode=true&createDatabaseIfNotExist=true&characterEncoding=UTF8&useSSL=false&serverTimeZone=Asia/Shanghai","root", "Lihaozhe!!@@1122");// 跨平台提交conf.set("mapreduce.app-submission.cross-platform", "true");// 本地运行// conf.set("mapreduce.framework.name", "local");// 设置默认文件系统为 本地文件系统// conf.set("fs.defaultFS", "file:///");// 声明Job对象 就是一个应用Job job = Job.getInstance(conf, "write db");// 指定当前Job的驱动类// 本地提交 注释该行job.setJarByClass(Write.class);// 本地提交启用该行// job.setJar("D:\\work\\河南师范大学\\2023\\bigdata2023\\Hadoop\\code\\hadoop\\target\\hadoop.jar");// 指定当前Job的 Mapperjob.setMapperClass(WordMapper.class);// 指定当前Job的 Combiner 注意：一定不能影响最终计算结果 否则 不使用// job.setCombinerClass(WordCountReduce.class);// 指定当前Job的 Reducer// job.setReducerClass(WordCountReduce.class);// 设置 reduce 数量为 零job.setNumReduceTasks(0);// 设置 map 输出 key 的数据类型job.setMapOutputValueClass(WordMapper.class);// 设置 map 输出 value 的数据类型job.setMapOutputValueClass(NullWritable.class);// 设置最终输出 key 的数据类型// job.setOutputKeyClass(Text.class);// 设置最终输出 value 的数据类型// job.setOutputValueClass(NullWritable.class);// 定义 map 输入的路径 注意：该路径默认为hdfs路径FileInputFormat.addInputPath(job, new Path("/wordcount/result/part-r-00000"));// 定义 reduce 输出数据持久化的路径 注意：该路径默认为hdfs路径
// Path dst = new Path("/video/ods");
// // 保护性代码 如果 reduce 输出目录已经存在则删除 输出目录
// DistributedFileSystem dfs = new DistributedFileSystem();
// String nameService = conf.get("dfs.nameservices");
// String hdfsRPCUrl = "hdfs://" + nameService + ":" + 8020;
// dfs.initialize(URI.create(hdfsRPCUrl), conf);
// if (dfs.exists(dst)) {
// dfs.delete(dst, true);
// }// FileSystem fs = FileSystem.get(conf);
// if (fs.exists(dst)) {
// fs.delete(dst, true);
// }
// FileOutputFormat.setOutputPath(job, dst);// 设置输出类job.setOutputFormatClass(DBOutputFormat.class);// 配置将数据写入表DBOutputFormat.setOutput(job, "word", "name", "count");// 提交 job// job.submit();System.exit(job.waitForCompletion(true) ? 0 : 1);}
}MapReduce 从数据库读取数据
注意：
由于集群环境 导致 MapTask数量不可控可导致最终输出文件可能不止一个，
可以在代码使用 conf.set(“mapreduce.job.maps”, “1”) 设置 MapTask 数量
package com.lihaozhe.db;import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.hdfs.DistributedFileSystem;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.NullWritable;
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 java.io.IOException;
import java.net.URI;/*** @author 李昊哲* @version 1.0* @create 2023-11-7*/
public class Read {public static class WordMapper extends Mapper<LongWritable, Word, Word, NullWritable> {@Overrideprotected void map(LongWritable key, Word value, Mapper<LongWritable, Word, Word, NullWritable>.Context context) throws IOException, InterruptedException {context.write(value, NullWritable.get());}}public static void main(String[] args) throws IOException, InterruptedException, ClassNotFoundException {// 设置环境变量 hadoop 用户名 为 rootSystem.setProperty("HADOOP_USER_NAME", "root");// 参数配置对象Configuration conf = new Configuration();// 配置JDBC 参数DBConfiguration.configureDB(conf,"com.mysql.cj.jdbc.Driver","jdbc:mysql://spark03:3306/htu?useUnicode=true&createDatabaseIfNotExist=true&characterEncoding=UTF8&useSSL=false&serverTimeZone=Asia/Shanghai","root", "Lihaozhe!!@@1122");// 跨平台提交conf.set("mapreduce.app-submission.cross-platform", "true");// 设置 MapTask 数量conf.set("mapreduce.job.maps", "1");// 本地运行// conf.set("mapreduce.framework.name", "local");// 设置默认文件系统为 本地文件系统// conf.set("fs.defaultFS", "file:///");// 声明Job对象 就是一个应用Job job = Job.getInstance(conf, "read db");// 指定当前Job的驱动类// 本地提交 注释该行job.setJarByClass(Read.class);// 本地提交启用该行// job.setJar("D:\\work\\河南师范大学\\2023\\bigdata2023\\Hadoop\\code\\hadoop\\target\\hadoop.jar");// 指定当前Job的 Mapperjob.setMapperClass(WordMapper.class);// 指定当前Job的 Combiner 注意：一定不能影响最终计算结果 否则 不使用// job.setCombinerClass(WordCountReduce.class);// 指定当前Job的 Reducer// job.setReducerClass(WordCountReduce.class);// 设置 reduce 数量为 零job.setNumReduceTasks(0);// 设置 map 输出 key 的数据类型job.setMapOutputValueClass(Word.class);// 设置 map 输出 value 的数据类型job.setMapOutputValueClass(NullWritable.class);// 设置最终输出 key 的数据类型// job.setOutputKeyClass(Text.class);// 设置最终输出 value 的数据类型// job.setOutputValueClass(NullWritable.class);// 设置输入类job.setInputFormatClass(DBInputFormat.class);// 配置将数据写入表DBInputFormat.setInput(job, Word.class,"select name,count from word","select count(*) from word");// 定义 map 输入的路径 注意：该路径默认为hdfs路径// FileInputFormat.addInputPath(job, new Path("/wordcount/result/part-r-00000"));// 定义 reduce 输出数据持久化的路径 注意：该路径默认为hdfs路径Path dst = new Path("/wordcount/db");// 保护性代码 如果 reduce 输出目录已经存在则删除 输出目录DistributedFileSystem dfs = new DistributedFileSystem();String nameService = conf.get("dfs.nameservices");String hdfsRPCUrl = "hdfs://" + nameService + ":" + 8020;dfs.initialize(URI.create(hdfsRPCUrl), conf);if (dfs.exists(dst)) {dfs.delete(dst, true);}// FileSystem fs = FileSystem.get(conf);
// if (fs.exists(dst)) {
// fs.delete(dst, true);
// }FileOutputFormat.setOutputPath(job, dst);// 提交 job// job.submit();System.exit(job.waitForCompletion(true) ? 0 : 1);}
}MapReduce 实现数据库表复制
MapReduce 实现将数据库一张数据表的数据复制到另外一张数据表中
package com.lihaozhe.db;import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.NullWritable;
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.DBOutputFormat;import java.io.IOException;/*** @author 李昊哲* @version 1.0* @create 2023-11-7*/
public class Copy {public static class RWMapper extends Mapper<LongWritable, Word, Word, NullWritable> {@Overrideprotected void map(LongWritable key, Word value, Mapper<LongWritable, Word, Word, NullWritable>.Context context) throws IOException, InterruptedException {context.write(value, NullWritable.get());}}public static void main(String[] args) throws IOException, InterruptedException, ClassNotFoundException {System.setProperty("HADOOP_USER_NAME", "root");// 参数配置对象Configuration conf = new Configuration();// 配置JDBC 参数DBConfiguration.configureDB(conf,"com.mysql.cj.jdbc.Driver","jdbc:mysql://spark03:3306/htu?useUnicode=true&createDatabaseIfNotExist=true&characterEncoding=UTF8&useSSL=false&serverTimeZone=Asia/Shanghai","root", "Lihaozhe!!@@1122");// 跨平台提交conf.set("mapreduce.app-submission.cross-platform", "true");// 设置 MapTask 数量// conf.set("mapreduce.job.maps", "1");// 声明Job对象 就是一个应用Job job = Job.getInstance(conf, "read db");job.setJarByClass(Read.class);job.setMapperClass(Read.WordMapper.class);job.setNumReduceTasks(0);job.setMapOutputValueClass(Word.class);job.setMapOutputValueClass(NullWritable.class);// 设置输入类job.setInputFormatClass(DBInputFormat.class);// 配置将数据写入表DBInputFormat.setInput(job, Word.class,"select name,count from word","select count(*) from word");// 设置输出类job.setOutputFormatClass(DBOutputFormat.class);// 配置将数据写入表DBOutputFormat.setOutput(job, "new_word", "name", "count");System.exit(job.waitForCompletion(true) ? 0 : 1);}
}