flink java.lang.RuntimeException:null异常

flink程序在华为云上运行一段时间后，程序突然有问题，抛出异常了。

一、异常：

java.lang.RuntimeException: null
	at org.apache.flink.streaming.runtime.io.RecordWriterOutput.pushToRecordWriter(RecordWriterOutput.java:110)
	at org.apache.flink.streaming.runtime.io.RecordWriterOutput.collect(RecordWriterOutput.java:89)
	at org.apache.flink.streaming.runtime.io.RecordWriterOutput.collect(RecordWriterOutput.java:45)
	at org.apache.flink.streaming.api.operators.AbstractStreamOperator$CountingOutput.collect(AbstractStreamOperator.java:683)
	at org.apache.flink.streaming.api.operators.AbstractStreamOperator$CountingOutput.collect(AbstractStreamOperator.java:661)
	at org.apache.flink.streaming.api.operators.StreamSourceContexts$NonTimestampContext.collect(StreamSourceContexts.java:104)
	at org.apache.flink.streaming.api.operators.StreamSourceContexts$NonTimestampContext.collectWithTimestamp(StreamSourceContexts.java:111)
	at org.apache.flink.streaming.connectors.kafka.internals.AbstractFetcher.emitRecordWithTimestamp(AbstractFetcher.java:398)
	at org.apache.flink.streaming.connectors.kafka.internal.Kafka010Fetcher.emitRecord(Kafka010Fetcher.java:89)
	at org.apache.flink.streaming.connectors.kafka.internal.Kafka09Fetcher.runFetchLoop(Kafka09Fetcher.java:154)
	at org.apache.flink.streaming.connectors.kafka.FlinkKafkaConsumerBase.run(FlinkKafkaConsumerBase.java:738)
	at org.apache.flink.streaming.api.operators.StreamSource.run(StreamSource.java:87)
	at org.apache.flink.streaming.api.operators.StreamSource.run(StreamSource.java:56)
	at org.apache.flink.streaming.runtime.tasks.SourceStreamTask.run(SourceStreamTask.java:99)
	at org.apache.flink.streaming.runtime.tasks.StreamTask.invoke(StreamTask.java:306)
	at org.apache.flink.runtime.taskmanager.Task.run(Task.java:712)
	at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.NullPointerException: null
	at org.apache.flink.runtime.state.KeyGroupRangeAssignment.assignToKeyGroup(KeyGroupRangeAssignment.java:59)
	at org.apache.flink.runtime.state.KeyGroupRangeAssignment.assignKeyToParallelOperator(KeyGroupRangeAssignment.java:48)
	at org.apache.flink.streaming.runtime.partitioner.KeyGroupStreamPartitioner.selectChannels(KeyGroupStreamPartitioner.java:63)
	at org.apache.flink.streaming.runtime.partitioner.KeyGroupStreamPartitioner.selectChannels(KeyGroupStreamPartitioner.java:32)
	at org.apache.flink.runtime.io.network.api.writer.RecordWriter.emit(RecordWriter.java:106)
	at org.apache.flink.streaming.runtime.io.StreamRecordWriter.emit(StreamRecordWriter.java:81)
	at org.apache.flink.streaming.runtime.io.RecordWriterOutput.pushToRecordWriter(RecordWriterOutput.java:107)
	... 16 common frames omitted

二、解决思路

查看异常报告，发现

java.lang.NullPointerException: null
    at org.apache.flink.runtime.state.KeyGroupRangeAssignment.assignToKeyGroup(KeyGroupRangeAssignment.java:59)

发现异常出现在这一行，查看源码，发现：

发现24行能报null的只有key.hashCode()；判断应该是key是null，到这里发现是我们的flink程序key可能为null。

查看程序：我们将plateNo设为flink的key

应该是flink消费kafka数据中的plateNo 属性有为null的数据。

解决：

if(plateNo ==null ||plateNo.equals("")){
     value.setPlateNo("null");
 }

修改后发现程序没有问题了。问题定位准确。