Flink教程(15) Keyed State状态管理之ListState使用 ValueState实现

系列文章

Flink教程(13) Keyed State状态管理之ValueState的使用 温差报警
Flink教程(14) Keyed State状态管理之MapState使用案例
Flink教程(15) Keyed State状态管理之ListState使用 ValueState实现
Flink教程(16) Keyed State状态管理之ReducingState使用案例 求最大值
Flink教程(17) Keyed State状态管理之AggregatingState使用案例 求平均值

一、ListState的方法

• get()方法获取值
• add(IN value)，addAll(List values)方法更新值
• update(List values) 用新List 替换 原来的List
• clear() 清空List，List还存在，但是没有元素
  

二、代码案例

1. 需求

记录每个人的历史操作信息，例如输入

1,login
1,buy something
1,logout
2,login
2,click book
1,login

要输出

(1,[login])
(1,[login, buy something])
(1,[login, buy something, logout])
(2,[login])
(2,[login, click book])
(1,[login, buy something, logout, login])

2. 主体

public class Test03_ListState {
    
    

    public static void main(String[] args) throws Exception {
    
    

        StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();

        env.setParallelism(1);

        DataStreamSource<String> source = env.socketTextStream(BaseConstant.URL, BaseConstant.PORT);

        SingleOutputStreamOperator<Tuple2<String, String>> dataStream = source
                .map(new MapFunction<String, Tuple2<String, String>>() {
    
    

                    @Override
                    public Tuple2<String, String> map(String value) throws Exception {
    
    
                        String[] split = value.split(",");
                        if (split != null && split.length == 2) {
    
    
                            return Tuple2.of(split[0], split[1]);
                        }
                        return null;
                    }
                });


        dataStream
                .keyBy(t -> t.f0)
                .process(new MyKeyedProcessFunction())
                .print();

        env.execute();
    }
}

3. 处理方法

public static class MyKeyedProcessFunction extends KeyedProcessFunction<String, Tuple2<String, String>, Tuple2<String, List<String>>> {
    
    

    //之前的操作记录
    private transient ListState<String> listState;

    @Override
    public void open(Configuration parameters) throws Exception {
    
    
        super.open(parameters);

        ListStateDescriptor<String> recentOperatorsDescriptor = new ListStateDescriptor<String>(
                "recent-operator",
                String.class);

        listState = getRuntimeContext().getListState(recentOperatorsDescriptor);
    }

    @Override
    public void processElement(Tuple2<String, String> value, Context ctx, Collector<Tuple2<String, List<String>>> out) throws Exception {
    
    

        String action = value.f1;

        listState.add(action);

        Iterable<String> iterable = listState.get();
        ArrayList<String> events = new ArrayList<>();

        for (String actionName : iterable) {
    
    
            events.add(actionName);
        }

        out.collect(Tuple2.of(value.f0, events));

        listState.update(events);

    }
}

4. 运行结果

5. 用ValueState实现ListState

用ValueState实现ListState可以实现ListState，只要ValueState里装的是List

public static class MyKeyedProcessFunction extends KeyedProcessFunction<String, Tuple2<String, String>, Tuple2<String, List<String>>> {
    
    

    //之前的操作记录
    private transient ValueState<List<String>> listState;

    @Override
    public void open(Configuration parameters) throws Exception {
    
    
        super.open(parameters);

        ValueStateDescriptor<List<String>> recentOperatorsDescriptor = new ValueStateDescriptor<List<String>>(
                "recent-operator",
                TypeInformation.of(new TypeHint<List<String>>(){
    
    }));

        listState = getRuntimeContext().getState(recentOperatorsDescriptor);
    }

    @Override
    public void processElement(Tuple2<String, String> value, Context ctx, Collector<Tuple2<String, List<String>>> out) throws Exception {
    
    

        String action = value.f1;

        List<String> lst = listState.value();

        if (lst == null){
    
    
            lst = new ArrayList<>();
        }
        lst.add(action);

        listState.update(lst);

        out.collect(Tuple2.of(value.f0, listState.value()));
    }
}