自定义实现InputFormat、OutputFormat、输出到多个文件目录中去、hadoop1.x api写单词计数的例子、运行时接收命令行参数，代码例子
一:自定义实现InputFormat
*数据源来自于内存
*1.InputFormat是用于处理各种数据源的,下面是实现InputFormat,数据源是来自于内存.
*1.1 在程序的job.setInputFormatClass(MyselfmemoryInputFormat.class);
*1.2 实现InputFormat,extends InputFormat< , >,实现其中的两个方法,分别是getSplits(..),createRecordReader(..).
*1.3 getSplits(..)返回的是一个java.util.List<T>,List中的每个元素是InputSplit.每个InputSplit对应一个mappper任务.
*1.4 InputSplit是对原始海量数据源的划分,因为我们处理的是海量数据,不划分不行.InputSplit数据的大小完全是我们自己来定的.本例中是在内存中产生数据,然后封装到InputSplit.
*1.5 InputSplit封装的是hadoop数据类型,实现Writable接口.
*1.6 RecordReader读取每个InputSplit中的数据.解析成一个个<k,v>,供map处理.
*1.7 RecordReader有4个核心方法,分别是initalize(..).nextKeyValue(),getCurrentKey(),getCurrentValue().
*1.8 initalize重要性在于是拿到InputSplit和定义临时变量.
*1.9 nexKeyValue(..)该方法的每次调用,可以获得key和value值.
*1.10 当nextKeyValue(..)调用后,紧接着调用getCurrentKey(),getCurrentValue().
* mapper方法中的run方法调用.
public class MyselInputFormatApp { private static final String OUT_PATH = "hdfs://hadoop1:9000/out";// 输出路径,reduce作业输出的结果是一个目录 public static void main(String[] args) { Configuration conf = new Configuration();// 配置对象 try { FileSystem fileSystem = FileSystem.get(new URI(OUT_PATH), conf); fileSystem.delete(new Path(OUT_PATH), true); Job job = new Job(conf, WordCountApp.class.getSimpleName());// jobName:作业名称 job.setJarByClass(WordCountApp.class); job.setInputFormatClass(MyselfMemoryInputFormat.class); job.setMapperClass(MyMapper.class);// 指定自定义map类 job.setMapOutputKeyClass(Text.class);// 指定map输出key的类型 job.setMapOutputValueClass(LongWritable.class);// 指定map输出value的类型 job.setReducerClass(MyReducer.class);// 指定自定义Reduce类 job.setOutputKeyClass(Text.class);// 设置Reduce输出key的类型 job.setOutputValueClass(LongWritable.class);// 设置Reduce输出的value类型 FileOutputFormat.setOutputPath(job, new Path(OUT_PATH));// Reduce输出完之后,就会产生一个最终的输出,指定最终输出的位置 job.waitForCompletion(true);// 提交给jobTracker并等待结束 } catch (Exception e) { e.printStackTrace(); } } public static class MyMapper extends Mapper<NullWritable, Text, Text, LongWritable> { @Override protected void map(NullWritable key, Text value, Context context) throws IOException, InterruptedException { String line = value.toString(); String[] splited = line.split("\t"); for (String word : splited) { context.write(new Text(word), new LongWritable(1));// 把每个单词出现的次数1写出去. } } } public static class MyReducer extends Reducer<Text, LongWritable, Text, LongWritable> { @Override protected void reduce(Text key, Iterable<LongWritable> values, Context context) throws IOException, InterruptedException { long count = 0L; for (LongWritable times : values) { count += times.get(); } context.write(key, new LongWritable(count)); } } /** * 从内存中产生数据,然后解析成一个个的键值对 * */ public static class MyselfMemoryInputFormat extends InputFormat<NullWritable,Text>{ @Override public List<InputSplit> getSplits(JobContext context) throws IOException, InterruptedException { ArrayList<InputSplit> result = new ArrayList<InputSplit>(); result.add(new MemoryInputSplit()); result.add(new MemoryInputSplit()); result.add(new MemoryInputSplit()); return result; } @Override public RecordReader<NullWritable, Text> createRecordReader( InputSplit split, TaskAttemptContext context) throws IOException, InterruptedException { return new MemoryRecordReader(); } } public static class MemoryInputSplit extends InputSplit implements Writable{ int SIZE = 10; //java中的数组在hadoop中不被支持,所以这里使用hadoop的数组 //在hadoop中使用的是这种数据结构,不能使用java中的数组表示. ArrayWritable arrayWritable = new ArrayWritable(Text.class); /** * 先创建一个java数组类型,然后转化为hadoop的数据类型. * @throws FileNotFoundException */ public MemoryInputSplit() throws FileNotFoundException { //一个inputSplit供一个map使用,map函数如果要被调用多次的话,意味着InputSplit必须解析出多个键值对 Text[] array = new Text[SIZE]; Random random = new Random(); for(int i=0;i<SIZE;i++){ int nextInt = random.nextInt(999999); Text text = new Text("Text"+nextInt); array[i] = text ; } // FileInputStream fs = new FileInputStream(new File("\\etc\\profile"));//从文件中读取 // 将流中的数据解析出来放到数据结构中. arrayWritable.set(array); } @Override public long getLength() throws IOException, InterruptedException { return SIZE; } @Override public String[] getLocations() throws IOException, InterruptedException { return new String[]{}; } public ArrayWritable getValues() { return arrayWritable; } @Override public void write(DataOutput out) throws IOException { arrayWritable.write(out); } @Override public void readFields(DataInput in) throws IOException { arrayWritable.readFields(in); } } public static class MemoryRecordReader extends RecordReader<NullWritable, Text>{ private Writable[] values = null ; private Text value = null ; private int i = 0; @Override public void initialize(InputSplit split, TaskAttemptContext context) throws IOException, InterruptedException { MemoryInputSplit inputSplit = (MemoryInputSplit)split; ArrayWritable writables = inputSplit.getValues(); this.values = writables.get(); this.i = 0 ; } @Override public boolean nextKeyValue() throws IOException, InterruptedException { if(i >= values.length){ return false ; } if(null == this.value){ value = new Text(); } value.set((Text)values[i]); i++ ; return true; } @Override public NullWritable getCurrentKey() throws IOException, InterruptedException { return NullWritable.get(); } @Override public Text getCurrentValue() throws IOException, InterruptedException { return value; } @Override public float getProgress() throws IOException, InterruptedException { // TODO Auto-generated method stub return 0; } /** * 程序结束的时候,关闭 */ @Override public void close() throws IOException { } } }
二:自定义实现OutputFormat
常见的输出类型:TextInputFormat:默认输出格式,key和value中间用tab隔开.
DBOutputFormat:写出到数据库的.
SequenceFileFormat:将key,value以Sequence格式输出的.
SequenceFileAsOutputFormat:SequenceFile以原始二进制的格式输出.
MapFileOutputFormat:将key和value写入MapFile中.由于MapFile中key是有序的,所以写入的时候必须保证记录是按key值顺序入的.
MultipleOutputFormat:多文件的一个输出.默认情况下一个reducer产生一个输出,但是有些时候我们想一个reducer产生多个输出,MultipleOutputFormat和MultipleOutputs就可以实现这个功能.
MultipleOutputFormat:可以自定义输出文件的名称.
继承MultipleOutputFormat 需要实现
getBaseRecordWriter():
generateFileNameForKeyvalue():根据键值确定文件名.
/** *自定义输出OutputFormat:用于处理各种输出目的地的. *1.OutputFormat需要写出的键值对是来自于Reducer类.是通过RecordWriter获得的. *2.RecordWriter(..)中write只有key和value,写到那里去哪?这要通过单独传入输出流来处理.write方法就是把k,v写入到outputStream中的. *3.RecordWriter类是位于OutputFormat中的.因此,我们自定义OutputFormat必须继承OutputFormat类.那么流对象就必须在getRecordWriter(..)中获得. */ public class MySelfOutputFormatApp { private static final String INPUT_PATH = "hdfs://hadoop1:9000/abd/hello";// 输入路径 private static final String OUT_PATH = "hdfs://hadoop1:9000/out";// 输出路径,reduce作业输出的结果是一个目录 private static final String OUT_FIE_NAME = "/abc"; public static void main(String[] args) { Configuration conf = new Configuration(); try { FileSystem fileSystem = FileSystem.get(new URI(OUT_PATH), conf); fileSystem.delete(new Path(OUT_PATH), true); Job job = new Job(conf, WordCountApp.class.getSimpleName()); job.setJarByClass(WordCountApp.class); FileInputFormat.setInputPaths(job, INPUT_PATH); job.setMapperClass(MyMapper.class); job.setMapOutputKeyClass(Text.class); job.setMapOutputValueClass(LongWritable.class); job.setReducerClass(MyReducer.class); job.setOutputKeyClass(Text.class); job.setOutputValueClass(LongWritable.class); job.setOutputFormatClass(MySelfTextOutputFormat.class); job.waitForCompletion(true); } catch (Exception e) { e.printStackTrace(); } } public static class MyMapper extends Mapper<LongWritable, Text, Text, LongWritable> { @Override protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException { String line = value.toString(); String[] splited = line.split("\t"); for (String word : splited) { context.write(new Text(word), new LongWritable(1));// 把每个单词出现的次数1写出去. } } } public static class MyReducer extends Reducer<Text, LongWritable, Text, LongWritable> { @Override protected void reduce(Text key, Iterable<LongWritable> values, Context context) throws IOException, InterruptedException { long count = 0L; for (LongWritable times : values) { count += times.get(); } context.write(key, new LongWritable(count)); } } /** *自定义输出类型 */ public static class MySelfTextOutputFormat extends OutputFormat<Text,LongWritable>{ FSDataOutputStream outputStream = null ; @Override public RecordWriter<Text, LongWritable> getRecordWriter( TaskAttemptContext context) throws IOException, InterruptedException { try { FileSystem fileSystem = FileSystem.get(new URI(MySelfOutputFormatApp.OUT_PATH), context.getConfiguration()); //指定的是输出文件的路径 String opath = MySelfOutputFormatApp.OUT_PATH+OUT_FIE_NAME; outputStream = fileSystem.create(new Path(opath)); } catch (URISyntaxException e) { e.printStackTrace(); } return new MySelfRecordWriter(outputStream); } @Override public void checkOutputSpecs(JobContext context) throws IOException, InterruptedException { } /** * OutputCommitter:在作业初始化的时候创建一些临时的输出目录,作业的输出目录,管理作业和任务的临时文件的. * 作业运行过程中,会产生很多的Task,Task在处理的时候也会产生很多的输出.也会创建这个输出目录. * 当我们的Task或者是作业都运行完成之后,输出目录由OutputCommitter给删了.所以程序在运行结束之后,我们根本看不见任何额外的输出. * 在程序运行中会产生很多的临时文件,临时文件全交给OutputCommitter处理,真正的输出是RecordWriter(..),我们只需要关注最后的输出就可以了.中间的临时文件就是程序运行时产生的. */ @Override public OutputCommitter getOutputCommitter(TaskAttemptContext context) throws IOException, InterruptedException { //提交任务的输出,包括初始化路径,包括在作业完成的时候清理作业,删除临时目录,包括作业和任务的临时目录. //作业的输出路径应该是一个路径 return new FileOutputCommitter(new Path(MySelfOutputFormatApp.OUT_PATH), context); } } public static class MySelfRecordWriter extends RecordWriter<Text, LongWritable>{ FSDataOutputStream outputStream = null ; public MySelfRecordWriter(FSDataOutputStream outputStream) { this.outputStream = outputStream ; } @Override public void write(Text key, LongWritable value) throws IOException, InterruptedException { this.outputStream.writeBytes(key.toString()); this.outputStream.writeBytes("\t"); this.outputStream.writeLong(value.get()); } @Override public void close(TaskAttemptContext context) throws IOException, InterruptedException { this.outputStream.close(); } } }
三：输出到多个文件目录中去
/** *输出到多个文件目录中去 *使用旧api */ public class MyMultipleOutputFormatApp { private static final String INPUT_PATH = "hdfs://hadoop1:9000/abd";// 输入路径 private static final String OUT_PATH = "hdfs://hadoop1:9000/out";// 输出路径,reduce作业输出的结果是一个目录 public static void main(String[] args) { Configuration conf = new Configuration(); try { FileSystem fileSystem = FileSystem.get(new URI(OUT_PATH), conf); fileSystem.delete(new Path(OUT_PATH), true); JobConf job = new JobConf(conf, WordCountApp.class); job.setJarByClass(WordCountApp.class); FileInputFormat.setInputPaths(job, INPUT_PATH); job.setMapperClass(MyMapper.class); job.setMapOutputKeyClass(Text.class); job.setMapOutputValueClass(LongWritable.class); job.setReducerClass(MyReducer.class); job.setOutputKeyClass(Text.class); job.setOutputValueClass(LongWritable.class); job.setOutputFormat(MyMutipleFilesTextOutputFormat.class); FileOutputFormat.setOutputPath(job, new Path(OUT_PATH)); JobClient.runJob(job); } catch (Exception e) { e.printStackTrace(); } } public static class MyMapper extends MapReduceBase implements Mapper<LongWritable, Text, Text, LongWritable> { @Override public void map(LongWritable key, Text value, OutputCollector<Text, LongWritable> output, Reporter reporter) throws IOException { String line = value.toString(); String[] splited = line.split("\t"); for (String word : splited) { output.collect(new Text(word), new LongWritable(1)); } } } public static class MyReducer extends MapReduceBase implements Reducer<Text, LongWritable, Text, LongWritable> { @Override public void reduce(Text key, Iterator<LongWritable> values, OutputCollector<Text, LongWritable> output, Reporter reporter) throws IOException { long count = 0L ; while(values.hasNext()){ LongWritable times = values.next(); count += times.get(); } output.collect(key, new LongWritable(count)); } } public static class MyMutipleFilesTextOutputFormat extends MultipleOutputFormat<Text,LongWritable>{ @Override protected org.apache.hadoop.mapred.RecordWriter<Text, LongWritable> getBaseRecordWriter( FileSystem fs, JobConf job, String name, Progressable progress) throws IOException { TextOutputFormat<Text, LongWritable> textOutputFormat = new TextOutputFormat<Text,LongWritable>(); return textOutputFormat.getRecordWriter(fs, job, name, progress); } @Override protected String generateFileNameForKeyValue(Text key, LongWritable value, String name) { String keyString = key.toString(); if(keyString.startsWith("hello")){ return "hello"; }else{ //输出的文件名就是k3的值 return keyString ; } } } }
四：hadoop1.x api写单词计数的例子
/** *hadoop1.x *使用旧api写单词计数的例子 */ public class WordCountApp { private static final String INPUT_PATH = "hdfs://hadoop1:9000/abd/hello"; private static final String OUT_PATH = "hdfs://hadoop1:9000/out"; public static void main(String[] args) { try { Configuration conf = new Configuration(); FileSystem fs = FileSystem.get(conf); fs.delete(new Path(OUT_PATH),true); JobConf job = new JobConf(conf, WordCountApp.class); job.setJarByClass(WordCountApp.class); FileInputFormat.setInputPaths(job, INPUT_PATH); job.setMapperClass(MyMapper.class); job.setMapOutputKeyClass(Text.class); job.setMapOutputValueClass(LongWritable.class); job.setReducerClass(MyReducer.class); job.setOutputKeyClass(Text.class); job.setOutputValueClass(LongWritable.class); FileOutputFormat.setOutputPath(job, new Path(OUT_PATH)); JobClient.runJob(job); } catch (IOException e) { e.printStackTrace(); } } public static class MyMapper extends MapReduceBase implements Mapper<LongWritable, Text, Text, LongWritable>{ @Override public void map(LongWritable key, Text value, OutputCollector<Text, LongWritable> output, Reporter reporter) throws IOException { String line = value.toString(); String[] splited = line.split("\t"); for (String word : splited) { output.collect(new Text(word), new LongWritable(1L)); } } } public static class MyReducer extends MapReduceBase implements Reducer<Text, LongWritable, Text, LongWritable>{ @Override public void reduce(Text key, Iterator<LongWritable> values, OutputCollector<Text, LongWritable> output, Reporter reporter) throws IOException { long times = 0L ; while (values.hasNext()) { LongWritable longWritable = (LongWritable) values.next(); times += longWritable.get(); } output.collect(key, new LongWritable(times)); } } }
五：运行时接收命令行参数
/** *运行时会接收一些命令行的参数 *Tool接口:支持命令行的参数 *命令行执行: * hadoop jar jar.jar cmd.WordCountApp hdfs://hadoop1:9000/abd/hello hdfs://hadoop1:9000/out */ public class WordCountApp extends Configured implements Tool { private static String INPUT_PATH = null;// 输入路径 private static String OUT_PATH = null;// 输出路径,reduce作业输出的结果是一个目录 @Override public int run(String[] args) throws Exception { INPUT_PATH = args[0]; OUT_PATH = args[1]; Configuration conf = getConf();// 配置对象 try { FileSystem fileSystem = FileSystem.get(new URI(OUT_PATH), conf); fileSystem.delete(new Path(OUT_PATH), true); Job job = new Job(conf, WordCountApp.class.getSimpleName());// jobName:作业名称 job.setJarByClass(WordCountApp.class); FileInputFormat.setInputPaths(job, INPUT_PATH);// 指定数据的输入 job.setMapperClass(MyMapper.class);// 指定自定义map类 job.setMapOutputKeyClass(Text.class);// 指定map输出key的类型 job.setMapOutputValueClass(LongWritable.class);// 指定map输出value的类型 job.setReducerClass(MyReducer.class);// 指定自定义Reduce类 job.setOutputKeyClass(Text.class);// 设置Reduce输出key的类型 job.setOutputValueClass(LongWritable.class);// 设置Reduce输出的value类型 FileOutputFormat.setOutputPath(job, new Path(OUT_PATH));// Reduce输出完之后,就会产生一个最终的输出,指定最终输出的位置 job.waitForCompletion(true);// 提交给jobTracker并等待结束 } catch (Exception e) { e.printStackTrace(); } return 0; } public static void main(String[] args) { try { ToolRunner.run(new Configuration(), new WordCountApp(),args); } catch (Exception e) { e.printStackTrace(); } } public static class MyMapper extends Mapper<LongWritable, Text, Text, LongWritable> { @Override protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException { String line = value.toString(); String[] splited = line.split("\t"); for (String word : splited) { context.write(new Text(word), new LongWritable(1));// 把每个单词出现的次数1写出去. } } } public static class MyReducer extends Reducer<Text, LongWritable, Text, LongWritable> { @Override protected void reduce(Text key, Iterable<LongWritable> values, Context context) throws IOException, InterruptedException { long count = 0L; for (LongWritable times : values) { count += times.get(); } context.write(key, new LongWritable(count)); } } }