Curator 异步获取结果

原声的ZooKeeper 的CRUD API有同步和异步之分，对于异步API，需要传递AsyncCallback回调。对于getData,getChildren，exists这三个API，还可以设置Watcher。这些功能在Curator中是如何实现的？

在Curator中，可以通过如下三种方式来异步获取结果：

1.inBackground()+CuratorListener

2.inBackground(new BackgroundCallback(){ public void processResult(CuratorFramework client,CuratorEvent event){}})

3.inBackground(newBackgroundCallback(){},Executor)

以inBackground()+CuratorListener这种方式来使用异步API，如下：

             client.getCuratorListenable().addListener(new CuratorListener(){

                @Override
                public void eventReceived(CuratorFramework client, CuratorEvent event) throws Exception {
                     // TODO Auto-generated method stub
                    if(event.getType()==CuratorEventType.CREATE){
                        System.out.println("create path="+event.getPath()+",code="+event.getResultCode());
                    }else if(event.getType()==CuratorEventType.GET_DATA){
                        System.out.println("get path="+event.getPath()+",data="+new String(event.getData()));
                    }else if(event.getType()==CuratorEventType.SET_DATA){

                        System.out.println("set path="+event.getPath()+",data="+new String(client.getData().forPath(event.getPath()))/*+",data="+new String(event.getData())*/);
                    }else if(event.getType()==CuratorEventType.DELETE){
                        System.out.println("delete path="+event.getPath());
                    }

                }});

接下来client的所有以inBackground()方式使用的API，其异步处理结果都是通过这个CuratorListener来处理。

在第二中方式inBackground(BackgroundCallback)中，如下：

client.create()
            .creatingParentsIfNeeded()
            .withProtection()
            .withMode(CreateMode.EPHEMERAL)
            .inBackground(new BackgroundCallback(){

                @Override
                public void processResult(CuratorFramework client, CuratorEvent event) throws Exception {
                    // TODO Auto-generated method stub
                  if(event.getType()==CuratorEventType.CREATE){
                      System.out.println("code:"+event.getResultCode()+"path:"+event.getPath()); 

                      //client.getData().inBackground().forPath(event.getPath());
                  }
                }
              } )
            .forPath("/francis/tmp/a","wbs".getBytes());