Problema ao fazer o split dos itens em RotaPedidos.java

Olá, estava seguindo a aula porém ao colocar o split, comecei a receber o seguinte erro:

org.apache.camel.TypeConversionException: Error during type conversion from type: java.lang.String to the required type: java.io.InputStream with value [item: null] due java.lang.NoClassDefFoundError: org/apache/xml/serializer/TreeWalker

Meu código:

package br.com.caelum.camel;

import org.apache.camel.CamelContext;
import org.apache.camel.builder.RouteBuilder;
import org.apache.camel.impl.DefaultCamelContext;

public class RotaPedidos {

    public static void main(String[] args) throws Exception {

        CamelContext context = new DefaultCamelContext();
        context.addRoutes(new RouteBuilder() {

            @Override
            public void configure() throws Exception {
                from("file:pedidos?delay=5s&noop=true").
                    split().
                        xpath("/pedido/itens/item").
                        log("${body}").
                    filter().
                        xpath("/item/formato[text()='EBOOK']").
                    marshal().xmljson().
                    log("${body}").
                    setHeader("CamelFileName", simple("${file:name.noext}.json")).
                to("file:saida");

            }
        });

        context.start();
        Thread.sleep(5000);
        context.stop();

    }    
}