Redisson-分布式映射（Map）类型的使用范例

Redisson提供的RMap、 RMapCache和RLocalCachedMap这三种映射（Map）类型的对象均可以使用这种分布式映射归纳（MapReduce）服务。

以下是在映射（Map）类型的基础上采用映射归纳（MapReduce）来实现字数统计的范例：

1、Mapper对象将每个映射的值用空格且分开。

public class WordMapper implements RMapper<String, String, String, Integer> {
     @Override
     public void map(String key, String value, RCollector<String, Integer> collector) {
         String[] words = value.split("[^a-zA-Z]");
         for (String word : words) {
             collector.emit(word, 1);
         }
     }
 }           

2、Reducer对象计算统计所有单词的使用情况。

public class WordReducer implements RReducer<String, Integer> {
     @Override
     public Integer reduce(String reducedKey, Iterator<Integer> iter) {
         int sum = 0;
         while (iter.hasNext()) {
            Integer i = (Integer) iter.next();
            sum += i;
         }
         return sum;
     }
 }           

3、 Collator对象统计所有单词的使用情况。

public class WordCollator implements RCollator<String, Integer, Integer> {
     @Override
     public Integer collate(Map<String, Integer> resultMap) {
         int result = 0;
         for (Integer count : resultMap.values()) {
             result += count;
         }
         return result;
     }
 }           

把上面的各个对象串起来使用：

RMap<String, String> map = redisson.getMap("wordsMap");
 map.put("line1", "Alice was beginning to get very tired");
 map.put("line2", "of sitting by her sister on the bank and");
 map.put("line3", "of having nothing to do once or twice she");
 map.put("line4", "had peeped into the book her sister was reading");
 map.put("line5", "but it had no pictures or conversations in it");
 map.put("line6", "and what is the use of a book");
 map.put("line7", "thought Alice without pictures or conversation");
 RMapReduce<String, String, String, Integer> mapReduce
          = map.<String, Integer>mapReduce()
               .mapper(new WordMapper())
               .reducer(new WordReducer());
 // 统计词频
 Map<String, Integer> mapToNumber = mapReduce.execute();
 // 统计字数
 Integer totalWordsAmount = mapReduce.execute(new WordCollator());