【Storm 入门】 Blot分流

场景介绍

这是一个很普通的使用场景，spout 发送数据至blot1，blot1根据数据分类发送至blotA 和 blotB

Spout->Blot1
Blot1->BlotA
Blot1->BlotB

代码介绍

1. 在总blot中声明几个流streamId，在execute中emit中指定发送的流
2. 在Topology中，指定blot读取哪个streamId的stream

# in Blot1.java
public void declareOutputFields(OutputFieldsDeclarer declarer) {
          declarer.declareStream("blota", new Fields("afield"));
          declarer.declareStream("blotb", new Fields("bfield"));
          }
public void execute(Tuple tuple) {
int t = (int)tuple.getValue(0);
if(t%2==0)
           _collector.emit("blota", new Values(t));
else
           _collector.emit("blotb", new Values(t));
}
# in Topology
public static void main(String[] args) throws Exception {
TopologyBuilder builder = new TopologyBuilder();
builder.setSpout("num", new NumSpout(), 10);
    builder.setBolt("blot1", new RouterBolt(), 3).shuffleGrouping("num");
    builder.setBolt("b1", new Bolt1(), 3).shuffleGrouping("blot1","blota");
    builder.setBolt("b2", new Bolt2(), 2).shuffleGrouping("blot1","blotb");
}