anchor.diff:  
       @StreamListener(Processor.INPUT)
       @Output(Processor.OUTPUT)
  -    public Map<String, Object> transform(Map<String, Object> doc) {
  +    public Map<String, Object> transform(@Payload Map<String, Object> doc) {
           Map<String, Object> map = new HashMap<>();
           map.put("sensor_id", doc.getOrDefault("id", "-1"));
           map.put("temp_val", doc.getOrDefault("temperature", "-999"));
  
positive.code: 
  java -Dlog.level=WARN \
       -Dspring.cloud.stream.bindings.input.destination=normalizedSensorData \
       -jar log-sink-rabbit-1.1.1.RELEASE.jar
  ----
  
  Now you can post some content to the http source application, as follows:
  
negative.code: To do so:
  
  . Visit the link:https://start.spring.io/[Spring Initialzr] site.
  .. Create a new Maven project with a *Group* name of `io.spring.stream.sample` and an *Artifact* name of `transformer`.
  .. In the Dependencies text box, type `stream` to select the Spring Cloud Stream dependency.
  .. In the Dependencies text box, type either `kafka` or `rabbit` and select which middleware you want to use.
  .. Click the *Generate Project* button
  . Unzip the project and bring the project into your favorite IDE.
  . Create a class called Transformer in the `io.spring.stream.sample` package with the following contents:
  +
  [source,java]
  ----
  package io.spring.stream.sample.transformer;
  
  import org.springframework.cloud.stream.annotation.EnableBinding;
  import org.springframework.cloud.stream.annotation.Output;
  import org.springframework.cloud.stream.annotation.StreamListener;
  import org.springframework.cloud.stream.messaging.Processor;
  import org.springframework.messaging.handler.annotation.Payload;
  
  import java.util.HashMap;
  import java.util.Map;
  