我运行简单的流式处理作业，计算活动的每小时印象：

.keyBy(imp => imp.campaign_id) 
.window(TumblingEventTimeWindows.of(...)) 
.aggregate(new BudgetSpendingByImpsAggregateFunction(), new BudgetSpendingByImpsWindowFunction())

聚合函数和：

class BudgetSpendingByImpsAggregateFunction extends 
AggregateFunction[ImpressionEvent, BudgetSpending, BudgetSpending]{ 
    override def add(value: ImpressionEvent, accumulator: BudgetSpending): = { 
        accumulator + value 
    } 
... 
}

budgetspending只是一个简单的scala案例类累加器：

case class BudgetSpending(var impressions: Int = 0){ 
    def +(imp: ImpressionEvent): BudgetSpending =_ 
}

我需要向budgetspending累加器类添加一个新计数器，该类用于计算支出。

@SerialVersionUID(-7854299638715463891L) 
case class BudgetSpending(var impressions: Int = 0, var spent: Double = 0)

但是，当我使用上一版本的savepoint运行flink作业时，出现了一个错误：

java.lang.Exception: Exception while creating StreamOperatorStateContext. 
        at 
org.apache.flink.streaming.api.operators.StreamTaskStateInitializerImpl.streamOperatorStateContext(StreamTaskStateInitializerImpl.java:191) 
        at 
org.apache.flink.streaming.api.operators.AbstractStreamOperator.initializeState(AbstractStreamOperator.java:227) 
        at 
org.apache.flink.streaming.runtime.tasks.StreamTask.initializeState(StreamTask.java:730) 
        at 
org.apache.flink.streaming.runtime.tasks.StreamTask.invoke(StreamTask.java:295) 
        at org.apache.flink.runtime.taskmanager.Task.run(Task.java:703) 
        at java.lang.Thread.run(Thread.java:745) 
Caused by: org.apache.flink.util.FlinkException: Could not restore keyed 
state backend for WindowOperator_74af6afa20f38ce575bfc2d1386aa434_(1/2) from 
any of the 1 provided restore options. 
        at 
org.apache.flink.streaming.api.operators.BackendRestorerProcedure.createAndRestore(BackendRestorerProcedure.java:137) 
        at 
org.apache.flink.streaming.api.operators.StreamTaskStateInitializerImpl.keyedStatedBackend(StreamTaskStateInitializerImpl.java:276) 
        at 
org.apache.flink.streaming.api.operators.StreamTaskStateInitializerImpl.streamOperatorStateContext(StreamTaskStateInitializerImpl.java:132) 
        ... 5 more 
Caused by: java.lang.ArrayIndexOutOfBoundsException: 2 
        at 
ga.p2502.streams.flink.budget.spending.HourlyBudgetSpendingJob$$anon$18$$anon$8.createInstance(HourlyBudgetSpendingJob.scala:60) 
        at 
ga.p2502.streams.flink.budget.spending.HourlyBudgetSpendingJob$$anon$18$$anon$8.createInstance(HourlyBudgetSpendingJob.scala:60) 
        at 
org.apache.flink.api.scala.typeutils.CaseClassSerializer.deserialize(CaseClassSerializer.scala:133) 
        at 
org.apache.flink.api.scala.typeutils.CaseClassSerializer.deserialize(CaseClassSerializer.scala:32) 
        at 
org.apache.flink.runtime.state.heap.StateTableByKeyGroupReaders$StateTableByKeyGroupReaderV2V3.readMappingsInKeyGroup(StateTableByKeyGroupReaders.java:133) 
        at 
org.apache.flink.runtime.state.heap.HeapKeyedStateBackend.restorePartitionedState(HeapKeyedStateBackend.java:430) 
        at 
org.apache.flink.runtime.state.heap.HeapKeyedStateBackend.restore(HeapKeyedStateBackend.java:315) 
        at 
org.apache.flink.runtime.state.heap.HeapKeyedStateBackend.restore(HeapKeyedStateBackend.java:95) 
        at 
org.apache.flink.streaming.api.operators.BackendRestorerProcedure.attemptCreateAndRestore(BackendRestorerProcedure.java:151) 
        at 
org.apache.flink.streaming.api.operators.BackendRestorerProcedure.createAndRestore(BackendRestorerProcedure.java:123) 
        ... 7 more

非常常见的用例，但flink似乎有问题。你知道如何处理flink中的案例类进化吗？
谢谢