Hi Harsha,
Thanks for suggestion!
I have checked this link before, and I tried to create the partition key like
the following:
val hardKey = "2"
val parkey = hardKey.getBytes("UTF8")
But I still get the same exception. I also tried set "UTF8" as "UTF-8", but no
luck...
Regards,
Haoming
> From: ka...@harsha.io
> To: users@kafka.apache.org
> Subject: Re: Partition Key Cannot be Send Out by Producer
> Date: Thu, 20 Nov 2014 16:43:11 -0800
>
> Hi Haoming,
> Take a look at the code here
>
> https://github.com/stealthly/scala-kafka/blob/master/src/main/scala/KafkaProducer.scala
> for your partKey it should be string and when you converting it into
> byte array you can use partKey.getBytes("UTF8")
> -Harsha
>
> On Thu, Nov 20, 2014, at 03:57 PM, Haoming Zhang wrote:
> > Hi all,
> >
> > I'm a beginner of Kafka, currently I'm stuck by how to send out a
> > KeyedMessage by producer. I would like to design a partition
> > function to route the message based on the key, but the producer cannot
> > send the KeyedMessage and I got this exception:
> > java.lang.ClassCastException: [B cannot be cast to java.lang.String
> >
> > What I tried is hardcode a partition key ( I tried String and Integer,
> > currently it is Integer ), then convert the partition key to Byte Array:
> > val converter = new DataTypeConvertion
> > val hardKey = 2
> > val partkey = converter.intToByteArray(hardKey)
> >
> > Then create a KeyedMessage by the following function:
> >
> > private def toMessage(value: Val, key: Option[Key] = None, topic:
> > Option[String] = None): KeyedMessage[Key, Val] = {
> > val t = topic.get
> > require(!t.isEmpty, "Topic must not be empty")
> > key match {
> > case Some(key) => new KeyedMessage(t, key, value)
> > case _ => new KeyedMessage(t, value)
> > }
> > }
> >
> > Then try to send the KeyedMessage by a Kafka producer:
> >
> > def send(key: Key, value: Val, topic: Option[String] = None) {
> > val msg = toMessage(value, Option(key), topic)
> > print(msg + "\n")
> > print("msg.key" + msg.key + "\n")
> > print("msg.message" + msg.message + "\n")
> > print("msg.partKey" + msg.partKey + "\n")
> > print("msg.topic" + msg.topic + "\n")
> > try {
> > p.send(msg) //P is an instance of producer, exception happens in
> > this line
> > } catch {
> > case e: Exception =>
> > e.printStackTrace()
> > System.exit(1)
> > }
> > }
> >
> > As you can see, I added many print statement in the above function, and
> > the following is the output of above function:
> > KeyedMessage(testingInput,[B@7ad40950,[B@7ad40950,[B@7ce18764)
> > msg.key: [B@7ad40950
> > msg.message: [B@7ce18764
> > msg.partKey: [B@7ad40950
> > msg.topic: testingInput
> >
> > The key of KeyedMessage is displayed as [B@7ad40950 , I think it is a
> > memory address and the exception (java.lang.ClassCastException: [B cannot
> > be cast to java.lang.String) happens when "send" function try to convert
> > the Byte Array to String.
> >
> > Am I wrong on creating a key in Byte Array type?
> > Some examples of how to use KeyedMessage will be great!
> >
> > Regards,
> > Haoming
> >
> >
