大数据之Flink(9) | 状态管理_代码调用

灰太狼 2022-12-17 05:58 246阅读 0赞

**对于定义state有两种方法**

## ValueState ##

第一种方法

class MyProcessor extends KeyedProcessFunction[String,SensorReading,Int]{ 
      lazy val myState:ValueState[Int] = getRuntimeContext.getState(new ValueStateDescriptor[Int]("my-state",classOf[Int]))
    
      override def processElement(value: SensorReading, ctx: KeyedProcessFunction[String, SensorReading, Int]
        #Context, out: Collector[Int]): Unit = { 
        //取出状态 更新状态
        myState.value()
        myState.update(1)
    
      }
    }

第二种方法

class MyProcessor extends KeyedProcessFunction[String,SensorReading,Int]{ 
    
      var myState:ValueState[Int] = _
      
      override def open(parameters: Configuration): Unit = { 
        myState = getRuntimeContext.getState(new ValueStateDescriptor[Int]("my-state",classOf[Int]))
      }
    
      override def processElement(value: SensorReading, ctx: KeyedProcessFunction[String, SensorReading, Int]
          #Context, out: Collector[Int]): Unit = { 
          //取出状态 更新状态
          myState.value()
          myState.update(1)
        }
    }

## ListState ##

class MyProcessor extends KeyedProcessFunction[String,SensorReading,Int]{ 
      lazy val myListState:ListState[String] = getRuntimeContext.getListState(new ListStateDescriptor[String]
      ("my-list",classOf[String]))
      
      override def processElement(value: SensorReading, ctx: KeyedProcessFunction[String, SensorReading, Int]
        #Context, out: Collector[Int]): Unit ={ 
        myListState.add("hello")
        myListState.update(new java.util.ArrayList[String]())
        
      }
    }

## MapState ##

class MyProcessor extends KeyedProcessFunction[String,SensorReading,Int]{ 
    
      lazy val myMapState:MapState[String,Double] = getRuntimeContext.getMapState(new MapStateDescriptor[String,Double]
      ("my-map",classOf[String],classOf[Double]))
    
      override def processElement(value: SensorReading, ctx: KeyedProcessFunction[String, SensorReading, Int]
        #Context, out: Collector[Int]): Unit ={ 
        myMapState.put("sensor_1",10.0)
        myMapState.get("sensor_1")
    
      }
    }

## ReducingState ##

class MyProcessor extends KeyedProcessFunction[String,SensorReading,Int]{ 
    
      lazy val myReducingState:ReducingState[SensorReading] = getRuntimeContext.getReducingState(new
          ReducingStateDescriptor[SensorReading]("my-reduce",
            new ReduceFunction[SensorReading] { 
              override def reduce(value1: SensorReading, value2: SensorReading): SensorReading =
                SensorReading(value1.id,value1.timestamp.max(value2.timestamp),value1.temperature.min(value2.temperature))
            },
            classOf[SensorReading]))
    
      override def processElement(value: SensorReading, ctx: KeyedProcessFunction[String, SensorReading, Int]
        #Context, out: Collector[Int]): Unit ={ 
        myReducingState.add(value)
        myReducingState.clear()
    
      }
    }