protobuf not accepting dynamic input

[Imran Raza Khan]

I have route like below

from("direct:marshal").unmarshal()
.protobuf("my.dataformat.protobuf.generated.AddressBookProtos$Person")
.to("mock:reverse");

Now i want to give classpath dynamically but its not accepting

from("direct:marshal").unmarshal()
.protobuf( simple("
my.dataformat.protobuf.generated.AddressBookProtos$${body.className}"))
.to("mock:reverse");

But its throwing error

Caused by: java.lang.ClassNotFoundException:
my.dataformat.protobuf.generated.AddressBookProtos$${body.className}
        at
org.apache.camel.impl.DefaultClassResolver.resolveMandatoryClass(DefaultClassResolver.java:81)
~[camel-core-2.24.2.jar:2.24.2]
        at
org.apache.camel.dataformat.protobuf.ProtobufDataFormat.loadDefaultInstance(ProtobufDataFormat.java:164)
~[camel-protobuf-2.24.2.jar:2.24.2]
        at
org.apache.camel.dataformat.protobuf.ProtobufDataFormat.doStart(ProtobufDataFormat.java:181)
~[camel-protobuf-2.24.2.jar:2.24.2]
        at
org.apache.camel.support.ServiceSupport.start(ServiceSupport.java:72)
~[camel-core-2.24.2.jar:2.24.2]