ArrayWritable实例

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概述

作用
Array类构造示例
Array类使用示例

作用

类似于java的动态数据ArrayList，可以在不知有多少数据量的情况下，动态向里面加数据

Array类构造示例

数组里添加很多歌Text，类似于ArrayList<string>

public class CookieArray extends ArrayWritable{public CookieArray(){super(Text.class);}public String toString() {String[] abc = toStrings();StringBuffer sBuffer = new StringBuffer();for (String string : abc) {sBuffer.append(string + ",");}if (sBuffer.length()==0) {return "";}sBuffer.deleteCharAt(sBuffer.lastIndexOf(","));return sBuffer.toString();}}

Array类构造示例

Map端用其读取数据对象

public class logMapper extends Mapper<Text, CookieArray, xxx, yyy> {public void map(Text key, CookieArray value, Context context)throws IOException, InterruptedException {Writable[] loglist=value.get();for (Writable writable : loglist) {    Text temp=(Text)writable;    // do something using this temp}context.write(xxx, yyy);}}

reduce端用其聚合

public class logReducer extends Reducer<Text, Text, Text, CookieArray> {public void reduce(Text key,Iterable<Text> values, Context context)throws IOException, InterruptedException {CookieArray cookieArray = new CookieArray();List<Text> littleCollection = new ArrayList<Text>();for (Text text : values) {littleCollection.add(text);}cookieArray.set(littleCollection.toArray(new Text[0]));context.write(key, cookieArray);}}