hadoop mapreduce 例子项目，运行了单机wordcount

package mysqlAndHdfs; 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.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.Reducer; 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 org.apache.hadoop.mapreduce.lib.db.DBWritable; import org.apache.hadoop.mapreduce.lib.input.FileInputFormat; import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat; /** * Function: 测试 mr 与 mysql 的数据交互，此测试用例将一个表中的数据复制到另一张表中 实际当中，可能只需要从 mysql 读，或者写到 * mysql 中。 * * @author administrator * */ public class AppMySQL2MR { public static class StudentinfoRecord implements Writable, DBWritable { int id; String name; public StudentinfoRecord() { } public String toString() { return new String(this.id + " " + this.name); } @Override public void readFields(ResultSet result) throws SQLException { this.id = result.getInt(1); this.name = result.getString(2); } @Override public void write(PreparedStatement stmt) throws SQLException { stmt.setInt(1, this.id); stmt.setString(2, this.name); } @Override public void readFields(DataInput in) throws IOException { this.id = in.readInt(); this.name = Text.readString(in); } @Override public void write(DataOutput out) throws IOException { out.writeInt(this.id); Text.writeString(out, this.name); } } // 记住此处是静态内部类，要不然你自己实现无参构造器，或者等着抛异常： // Caused by: java.lang.NoSuchMethodException: DBInputMapper.<init>() // http://stackoverflow.com/questions/7154125/custom-mapreduce-input-format-cant-find-constructor // 网上脑残式的转帖，没见到一个写对的。。。 public static class DBInputMapper extends Mapper<LongWritable, StudentinfoRecord, LongWritable, Text> { @Override public void map(LongWritable key, StudentinfoRecord value, Context context) throws IOException, InterruptedException { context.write(new LongWritable(value.id), new Text(value.toString())); } } public static class MyReducer extends Reducer<LongWritable, Text, StudentinfoRecord, Text> { @Override public void reduce(LongWritable key, Iterable<Text> values, Context context) throws IOException, InterruptedException { String[] splits = values.iterator().next().toString().split(" "); StudentinfoRecord r = new StudentinfoRecord(); r.id = Integer.parseInt(splits[0]); r.name = splits[1]; context.write(r, new Text(r.name)); } } public static void main(String[] args) throws IOException, InterruptedException, ClassNotFoundException { Configuration conf = new Configuration(); // 这句话很关键 conf.set("mapred.job.tracker", "127.0.0.1:9001"); DBConfiguration.configureDB(conf, "com.mysql.jdbc.Driver", "jdbc:mysql://127.0.0.1:3306/houzw?serverTimezone=UTC", "root", "root"); // Job job = copyMysqltoMysql(conf); // System.exit(job.waitForCompletion(true) ? 0 : 1); // Job job1 = hdfs2MysqlAndHdfs(conf); // System.exit(job1.waitForCompletion(true) ? 0 : 1); } @SuppressWarnings("unused") private static Job hdfs2MysqlAndHdfs(Configuration conf) throws IOException { @SuppressWarnings("deprecation") Job job1 = new Job(conf, "Mysql2Mr"); // job.setJarByClass(Mysql2Mr.class); job1.setMapOutputKeyClass(LongWritable.class); job1.setMapOutputValueClass(Text.class); job1.setMapperClass(DBInputMapper.class); job1.setReducerClass(MyReducer.class); job1.setOutputKeyClass(LongWritable.class); job1.setOutputValueClass(Text.class); job1.setOutputFormatClass(DBOutputFormat.class); // job1.setInputFormatClass(DBInputFormat.class); Path outputDir1 = new Path("hdfs://localhost:9000/user/output/mysql/data1/" + 111111 + "/"); Path outputDir = new Path("hdfs://localhost:9000/user/output/mysql/data1/" + 22222 + "/"); FileOutputFormat.setOutputPath(job1, outputDir); FileInputFormat.setInputPaths(job1, outputDir1); String[] fields1 = { "id", "name" }; // 从 t 表读数据 DBInputFormat.setInput(job1, StudentinfoRecord.class, "t", null, "id", fields1); // mapreduce 将数据输出到 t2 表 DBOutputFormat.setOutput(job1, "t3", "id", "name"); return job1; } @SuppressWarnings("unused") private static Job copyMysqltoMysql(Configuration conf) throws IOException { @SuppressWarnings("deprecation") Job job = new Job(conf, "Mysql2Mr"); // job.setJarByClass(Mysql2Mr.class); job.setMapOutputKeyClass(LongWritable.class); job.setMapOutputValueClass(Text.class); job.setMapperClass(DBInputMapper.class); job.setReducerClass(MyReducer.class); job.setOutputKeyClass(LongWritable.class); job.setOutputValueClass(Text.class); job.setOutputFormatClass(DBOutputFormat.class); // job.setOutputFormatClass(CustomeDBOutputFormat.class); job.setInputFormatClass(DBInputFormat.class); Path outputDir = new Path("hdfs://localhost:9000/user/output/mysql/data/" + 111111 + "/"); FileOutputFormat.setOutputPath(job, outputDir); String[] fields = { "id", "name" }; // 从 t 表读数据 DBInputFormat.setInput(job, StudentinfoRecord.class, "t", null, "id", fields); // mapreduce 将数据输出到 t2 表 DBOutputFormat.setOutput(job, "t2", "id", "name"); // CustomeDBOutputFormat.setOutput(job, "t3", "id", "name"); // MultipleTextOutputFormat return job; } }