CheckpointedFunction#snapshotState????????????????

[cs]

class A extends KeyedProcessFunction<String, Object, String&gt; implements 
CheckpointedFunction {


        private MapState<String, LiveBean&gt; liveBeanState;
        
&nbsp;  @Override
&nbsp; &nbsp; public void initializeState(FunctionInitializationContext 
context) throws Exception {
&nbsp; &nbsp; &nbsp; &nbsp; MapStateDescriptor<String, LiveBean&gt; descriptor 
= new MapStateDescriptor<&gt;("liveState", BasicTypeInfo.STRING_TYPE_INFO, 
TypeInformation.of(LiveBean.class));
&nbsp; &nbsp; &nbsp; &nbsp; this.liveBeanState = 
context.getKeyedStateStore().getMapState(descriptor);
&nbsp; &nbsp; }


&nbsp; &nbsp; &nbsp;@Override
&nbsp; &nbsp; public void snapshotState(FunctionSnapshotContext context) throws 
Exception {
&nbsp; &nbsp; &nbsp; &nbsp; Iterator<Map.Entry<String, LiveBean&gt;&gt; iter = 
liveBeanState.iterator(); // -&gt; Exception here
&nbsp; &nbsp; &nbsp; &nbsp; while (iter.hasNext()) {
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Map.Entry<String, LiveBean&gt; e = 
iter.next();
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; hbaseDao.singlePut("table", 
StringUtils.reverse(e.getKey()), "cf", "info", JSON.toJSONString(e.getValue()));
&nbsp; &nbsp; &nbsp; &nbsp; }
&nbsp; &nbsp; }


}



????????????
java.lang.NullPointerException: No key set. This method should not be called 
outside of a keyed context.
??????checkpoint????????????????????hbase??????????????