Input/Output data to kafka exception

[????]

Hi,    I used beam API to write code to read Kafka data and run with Flink, but 
run to throw the following exception:
Caused by: org.apache.flink.streaming.runtime.tasks.StreamTaskException: Cannot 
load user class: 
org.apache.beam.runners.flink.translation.wrappers.streaming.io.UnboundedSourceWrapper
ClassLoader info: URL ClassLoader:
    file: 
'/var/folders/vq/887txtm92w508tj7gknjpflc0000gp/T/blobStore-78ed2c9c-03e5-438b-b2ec-514ac394eb11/cache/blob_7123d3372a6822ba044c5ea153ee6801cd5377ff'
 (valid JAR)
Class not resolvable through given classloader.
        at 
org.apache.flink.streaming.api.graph.StreamConfig.getStreamOperator(StreamConfig.java:210)
        at 
org.apache.flink.streaming.runtime.tasks.OperatorChain.<init>(OperatorChain.java:81)
        at 
org.apache.flink.streaming.runtime.tasks.StreamTask.invoke(StreamTask.java:231)
        at org.apache.flink.runtime.taskmanager.Task.run(Task.java:665)
        at java.lang.Thread.run(Thread.java:745)



code:
 
KafkaOptions options = 
PipelineOptionsFactory.fromArgs(args).withValidation().as(KafkaOptions.class);
 
                options.setJobName("KafkaExample - WindowSize: " + 
options.getWindowSize() + " seconds");
 
                options.setStreaming(true);
 
                options.setCheckpointingInterval(1000L);
 
                options.setNumberOfExecutionRetries(5);
 
                options.setExecutionRetryDelay(3000L);
 
                options.setRunner(FlinkRunner.class);
 


 
                Pipeline pipeline = Pipeline.create(options);
 


 
                pipeline.apply(KafkaIO.<String, String>read()
 
                               .withBootstrapServers("localhost:9092")
 
                               .withTopic(KAFKA_TOPIC)  // use 
withTopics(List<String>) to read from multiple topics.
 
                               .withKeyDeserializer(StringDeserializer.class)
 
                               .withValueDeserializer(StringDeserializer.class)
 
                               .withoutMetadata() // PCollection<KV<String, 
String>>
 
                ).apply(Values.<String> create());
 
//                              .apply(KafkaIO.<Void, String>write()
 
//                                      .withBootstrapServers("localhost:9092")
 
//                                      .withTopic(KAFKA_OUTPUT_TOPIC)
 
//                                      
.withValueSerializer(StringSerializer.class)
 
//                                      .values());
 
                               
 
                pipeline.run();//.waitUntilFinish();




How to fix it ?




Thank you??