kafka消费者报错：Class org.apache.kafka.common.serialization.StringDeserializer could not be found.

org.apache.kafka.common.config.ConfigException: Invalid value org.apache.kafka.common.serialization.StringDeserializer for configuration key.deserializer: Class org.apache.kafka.common.serialization.StringDeserializer could not be found.

 

是因为classloader不是同一个所以加载不到

在之前加上

Thread.currentThread().setContextClassLoader(null);

就可以了，看下面

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

kafka client use Class.forName(trimmed, true, Utils.getContextOrKafkaClassLoader()) to get the Class object, and the create the instance, the key point is the classLoader, which is specified by the last param, the implementation of method Utils.getContextOrKafkaClassLoader() is

public static ClassLoader getContextOrKafkaClassLoader() {
    ClassLoader cl = Thread.currentThread().getContextClassLoader();
    if (cl == null)
        return getKafkaClassLoader();
    else
        return cl;
}

so, by default, the Class object of org.apache.kafka.common.serialization.StringSerializer is load by the applicationClassLoader, if your target class is not loaded by the applicationClassLoader, this problem will happend !

to solve the problem, simply set the ContextClassLoader of current thread to null before new KafkaProducer instance like this

Thread.currentThread().setContextClassLoader(null);
Producer producer = new KafkaProducer(props);