public void setStartMessage(Object startMessage) {
		this.startMessage = startMessage;
	}
Create a {@literal ThroughputSamplerMessageHandler} using the {@code String} {@literal START} as the start
message and the {@code String} {@literal END} as the end message and measure throughput in seconds.
extensions/spring-xd-extension-throughput/src/main/java/org/springframework/xd/integration/throughput/ThroughputSamplerMessageHandler.java