Flink -状态管理

open 是生命周期函数。只有在open之后才能够使用getRuntimeContext
键控状态的每一个分区都会维护一组状态，每个分区的状态互不干涉。

@Override
        public Integer map(Sensor value) throws Exception {
            System.out.println("map method is called.... the current value is = " + value.getId());
            for (String str : myListState.get()) {
                System.out.println("value is = " + str);
            }
            myListState.add("hello");
            Integer count = valueState.value();
            System.out.println("value state count is " + count);
            count = count == null ? 0 : count;
            ++count;
            valueState.update(count);
            return count;
        }```
通过上面的输出发现，每一条记录都会触发一次map函数执行

```java
@Override
        public Integer map(Sensor value) throws Exception {
            System.out.println("map method is called.... the current value is = " + value.getId());
            for (String str : myListState.get()) {
                System.out.println("value is = " + str);
            }
            myListState.add("hello");
//            myMapState.get("1");
//            myMapState.put("2", 12.3);
//            myMapState.remove("2");
//            myMapState.clear();
            Integer count = valueState.value();
            System.out.println("value state count is " + count);
            count = count == null ? 0 : count;
            ++count;
            valueState.update(count);
            return count;
        }