根据flink文档以避免动态类加载，可以执行以下操作。 当运行Flink JobManager和TaskManagers独占于一个特定作业的设置时，可以将JAR文件直接放入/ lib文件夹，以确保它们是类路径的一部分，而不是加载动态类加载。
但是当jar被添加到/ lib文件夹接收以下异常时。 对于此错误，是否有任何解决方法。
org.apache.flink.streaming.runtime.tasks.StreamTaskException: Cannot instantiate user function.
at org.apache.flink.streaming.api.graph.StreamConfig.getStreamOperator(StreamConfig.java:235) ~[iot-mirror-device.jar:na]
at org.apache.flink.streaming.runtime.tasks.OperatorChain.<init>(OperatorChain.java:95) ~[iot-mirror-device.jar:na]
at org.apache.flink.streaming.runtime.tasks.StreamTask.invoke(StreamTask.java:231) ~[iot-mirror-device.jar:na]
at org.apache.flink.runtime.taskmanager.Task.run(Task.java:718) ~[iot-mirror-device.jar:na]
at java.lang.Thread.run(Thread.java:745) ~[na:1.8.0_91]
Caused by: java.lang.ClassCastException: cannot assign instance of org.apache.commons.collections.map.LinkedMap to field org.apache.flink.streaming.connectors.kafka.FlinkKafkaConsumerBase.pendingOffsetsToCommit of type org.apache.commons.collections.map.LinkedMap in instance of org.apache.flink.streaming.connectors.kafka.FlinkKafkaConsumer010
at java.io.ObjectStreamClass$FieldReflector.setObjFieldValues(ObjectStreamClass.java:2133) ~[na:1.8.0_91]
at java.io.ObjectStreamClass.setObjFieldValues(ObjectStreamClass.java:1305) ~[na:1.8.0_91]
at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:2024) ~[na:1.8.0_91]
at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1942) ~[na:1.8.0_91]
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1808) ~[na:1.8.0_91]
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1353) ~[na:1.8.0_91]
at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:2018) ~[na:1.8.0_91]
at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1942) ~[na:1.8.0_91]
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1808) ~[na:1.8.0_91]
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1353) ~[na:1.8.0_91]
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:373) ~[na:1.8.0_91]
at org.apache.flink.util.InstantiationUtil.deserializeObject(InstantiationUtil.java:290) ~[iot-mirror-device.jar:na]
at org.apache.flink.util.InstantiationUtil.readObjectFromConfig(InstantiationUtil.java:248) ~[iot-mirror-device.jar:na]
at org.apache.flink.streaming.api.graph.StreamConfig.getStreamOperator(StreamConfig.java:220) ~[iot-mirror-device.jar:na]
... 4 common frames omitted
Timestamp=2018-03-26 13:46:42,433 LogLevel=INFO ThreadId=[flink-akka.actor.default-dispatcher-6] Class=o.a.f.r.e.ExecutionGraph Msg=Source: Custom Source -> Sink: Unnamed (1/1) (3f12f6953a235eb43f07cdf7966b5fcf) switched from RUNNING to FAILED.
org.apache.flink.streaming.runtime.tasks.StreamTaskException: Cannot instantiate user function.
at org.apache.flink.streaming.api.graph.StreamConfig.getStreamOperator(StreamConfig.java:235) ~[iot-mirror-device.jar:na]
at org.apache.flink.streaming.runtime.tasks.OperatorChain.<init>(OperatorChain.java:95) ~[iot-mirror-device.jar:na]
at org.apache.flink.streaming.runtime.tasks.StreamTask.invoke(StreamTask.java:231) ~[iot-mirror-device.jar:na]
at org.apache.flink.runtime.taskmanager.Task.run(Task.java:718) ~[iot-mirror-device.jar:na]
at java.lang.Thread.run(Thread.java:745) ~[na:1.8.0_91]
Caused by: java.lang.ClassCastException: cannot assign instance of org.apache.commons.collections.map.LinkedMap to field org.apache.flink.streaming.connectors.kafka.FlinkKafkaConsumerBase.pendingOffsetsToCommit of type org.apache.commons.collections.map.LinkedMap in instance of org.apache.flink.streaming.connectors.kafka.FlinkKafkaConsumer010
at java.io.ObjectStreamClass$FieldReflector.setObjFieldValues(ObjectStreamClass.java:2133) ~[na:1.8.0_91]
at java.io.ObjectStreamClass.setObjFieldValues(ObjectStreamClass.java:1305) ~[na:1.8.0_91]
at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:2024) ~[na:1.8.0_91]
at java.io.ObjectStreamClass$FieldReflector.setObjFieldValues(ObjectStreamClass.java:2133) ~[na:1.8.0_91]
at java.io.ObjectStreamClass.setObjFieldValues(ObjectStreamClass.java:1305) ~[na:1.8.0_91]
at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:2024) ~[na:1.8.0_91]
at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1942) ~[na:1.8.0_91]
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1808) ~[na:1.8.0_91]
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1353) ~[na:1.8.0_91]
at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:2018) ~[na:1.8.0_91]
at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1942) ~[na:1.8.0_91]
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1808) ~[na:1.8.0_91]
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1353) ~[na:1.8.0_91]
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:373) ~[na:1.8.0_91]
at org.apache.flink.util.InstantiationUtil.deserializeObject(InstantiationUtil.java:290) ~[iot-mirror-device.jar:na]
at org.apache.flink.util.InstantiationUtil.readObjectFromConfig(InstantiationUtil.java:248) ~[iot-mirror-device.jar:na]
at org.apache.flink.streaming.api.graph.StreamConfig.getStreamOperator(StreamConfig.java:220) ~[iot-mirror-device.jar:na]
... 4 common frames omitted
答案 0 :(得分：1)
LinkedMap类是从两个不同的包中加载的，并且它们彼此分配在一起。这是类型"X cannot be cast to X exceptions"的错误。
常见的原因是库与Flink的反向类加载方法不兼容。您可以通过在conf / flink-conf.yaml中添加以下配置并重新启动flink来解决此问题。
classloader.resolve-order: parent-first
这应该可以解决问题。
答案 1 :(得分：0)
乍一看，您似乎将appache-commons-collections版本4.x添加到了libs目录中。 LinkedMap在版本4中成为通用版。这可能会导致您的问题，因为flink依赖于较旧的commons-collections版本。这条线很可能会造成麻烦：
/** Data for pending but uncommitted offsets. */
private final LinkedMap pendingOffsetsToCommit = new LinkedMap();
一种简单的方法是从libs目录中删除commons-collections 4.x.如果您很幸运，您的依赖项也可以处理提供的版本。否则你有麻烦;-)。比你做了阴影共享集合。
希望这有帮助。