anchor.diff:  
   [source,bash]
   ----
  -java -Dlog.level=WARN -Dspring.cloud.stream.bindings.input.destination=sensorData -jar log-sink-rabbit-1.1.1.RELEASE.jar
  +java -Dlog.level=WARN -Dspring.cloud.stream.bindings.input.destination=sensorData -jar log-sink-rabbit-1.3.1.RELEASE.jar
   ----
   
   The `log.level` property comes from the log sink application,  link:https://github.com/spring-cloud-stream-app-starters/log/blob/master/spring-cloud-starter-stream-sink-log/src/main/java/org/springframework/cloud/stream/app/log/sink/LogSinkProperties.java[LogSinkProperties].
  
positive.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 rabbit` to select the Spring Cloud Stream dependency that uses the RabbitMQ binder.
  . 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;
  
  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 java.util.HashMap;
  import java.util.Map;
  
negative.code: 
      @StreamListener(Processor.INPUT)
      @Output(Processor.OUTPUT)
      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"));
  