一:自定义OutputFormat类
MapReduce默认的OutPutFormat会将结果输出文件放置到一个我们指定的目录下,但如果想把输出文件根据某个条件,把满足不同条件的内容分别输出到不同的目录下,
就需要自定义实现OutputFormat类,且重写RecordWriter方法。在驱动类中设置job.setOutputFormatClass方法为自定义实现的OutputFormat类
下面案例是一组购物文本数据,将其中的好评和差评分别输出到对应的好评文件夹下、差评文件夹下。
二:自定义实现OutputFormat类代码实现
import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.fs.FSDataOutputStream; import org.apache.hadoop.fs.FileSystem; import org.apache.hadoop.fs.Path; import org.apache.hadoop.io.NullWritable; import org.apache.hadoop.io.Text; import org.apache.hadoop.mapreduce.RecordWriter; import org.apache.hadoop.mapreduce.TaskAttemptContext; import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat; import java.io.IOException; /** * 自定义实现OutputFormat类 */ public class MyOutputFormat extends FileOutputFormat<Text,NullWritable> { @Override public RecordWriter<Text, NullWritable> getRecordWriter(TaskAttemptContext context) throws IOException, InterruptedException { //从这个方法里面可以获取一个configuration Configuration configuration = context.getConfiguration(); //获取文件系统的对象 FileSystem fileSystem = FileSystem.get(configuration); //好评文件的输出路径 Path goodComment = new Path("file:///F:\\goodComment\\1.txt"); //差评文件的输出路径 Path badComment = new Path("file:///F:\\badComment\\1.txt"); //获取到了两个输出流 FSDataOutputStream fsDataOutputStream = fileSystem.create(goodComment); FSDataOutputStream fsDataOutputStream1 = fileSystem.create(badComment); MyRecordWriter myRecordWriter = new MyRecordWriter(fsDataOutputStream, fsDataOutputStream1); return myRecordWriter; } }
三:自定义实现RecordWriter类
import org.apache.hadoop.fs.FSDataOutputStream; import org.apache.hadoop.io.IOUtils; import org.apache.hadoop.io.NullWritable; import org.apache.hadoop.io.Text; import org.apache.hadoop.mapreduce.RecordWriter; import org.apache.hadoop.mapreduce.TaskAttemptContext; import java.io.IOException; public class MyRecordWriter extends RecordWriter<Text,NullWritable> { private FSDataOutputStream goodStream; private FSDataOutputStream badSteam; public MyRecordWriter(){ } public MyRecordWriter(FSDataOutputStream goodStream,FSDataOutputStream badSteam){ this.goodStream = goodStream; this.badSteam= badSteam; } /** * 重写write方法 * 这个write方法就是往外写出去数据,我们可以根据这个key,来判断文件究竟往哪个目录下面写 * goodStream:指定输出文件 * badSteam:自定输出文件 * @param key:k3 * @param value * @throws IOException * @throws InterruptedException */ @Override public void write(Text key, NullWritable value) throws IOException, InterruptedException { String[] split = key.toString().split("\t"); //获取评论状态 0 好评 1 中评 2 差评 // split[9] //判断评评论状态,如果是小于等于1,都写到好评文件里面去 if(Integer.parseInt(split[9])<=1){ //好评 goodStream.write(key.getBytes()); goodStream.write("\r\n".getBytes()); }else{ //差评 badSteam.write(key.getBytes()); badSteam.write("\r\n".getBytes()); } } /** * 关闭资源 * @param context:上下文对象 * @throws IOException * @throws InterruptedException */ @Override public void close(TaskAttemptContext context) throws IOException, InterruptedException { IOUtils.closeStream(badSteam); IOUtils.closeStream(goodStream); } }
四:自定义Map类
import org.apache.hadoop.io.LongWritable; import org.apache.hadoop.io.NullWritable; import org.apache.hadoop.io.Text; import org.apache.hadoop.mapreduce.Mapper; import java.io.IOException; public class MyOutputMapper extends Mapper<LongWritable,Text,Text,NullWritable> { @Override protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException { context.write(value,NullWritable.get()); } }
五:驱动程序
import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.conf.Configured; import org.apache.hadoop.fs.Path; import org.apache.hadoop.io.NullWritable; import org.apache.hadoop.io.Text; import org.apache.hadoop.mapreduce.Job; import org.apache.hadoop.mapreduce.lib.input.TextInputFormat; import org.apache.hadoop.util.Tool; import org.apache.hadoop.util.ToolRunner; public class MyOutputMain extends Configured implements Tool { @Override public int run(String[] args) throws Exception { Job job = Job.getInstance(super.getConf(), "ownOutputFormat"); job.setInputFormatClass(TextInputFormat.class); TextInputFormat.addInputPath(job,new Path("file:///F:\\input")); job.setMapperClass(MyOutputMapper.class); job.setMapOutputKeyClass(Text.class); job.setMapOutputValueClass(NullWritable.class); job.setOutputFormatClass(MyOutputFormat.class); //由于重写了FileOutputFormat,所以下面这个指定的目录内不会有输出文件 //输出文件在MyOutputFormat中重新指定 MyOutputFormat.setOutputPath(job ,new Path("file:///F:\\output")); boolean b = job.waitForCompletion(true); return b?0:1; } public static void main(String[] args) throws Exception { int run = ToolRunner.run(new Configuration(), new MyOutputMain(), args); System.exit(run); } }