我正在研究這個(gè)Spring 郵件樣本。這段代碼的作用是每次有新郵件到達(dá) Gmail 收件箱時(shí)都會(huì)打印消息。package org.springframework.integration.samples.mail.imapidle;import org.apache.commons.logging.Log;import org.apache.commons.logging.LogFactory;import org.springframework.context.support.ClassPathXmlApplicationContext;import org.springframework.integration.channel.DirectChannel;import org.springframework.messaging.Message;import org.springframework.messaging.MessageHandler;import org.springframework.messaging.MessagingException;/** * @author Oleg Zhurakousky * @author Gary Russell * */public class GmailInboundImapIdleAdapterTestApp {    private static Log logger = LogFactory.getLog(GmailInboundImapIdleAdapterTestApp.class);    public static void main (String[] args) throws Exception {        @SuppressWarnings("resource")        ClassPathXmlApplicationContext ac = new ClassPathXmlApplicationContext(                "/META-INF/spring/integration/gmail-imap-idle-config.xml");        DirectChannel inputChannel = ac.getBean("receiveChannel", DirectChannel.class);        inputChannel.subscribe(new MessageHandler() {            public void handleMessage(Message<?> message) throws MessagingException {                logger.info("Message: " + message);            }        });    }}我發(fā)送了 2 封電子郵件，最終這些行出現(xiàn)在 Eclipse 控制臺(tái)上：16:04:52.851 信息 [pool-2-thread-1][org.springframework.integration.samples.mail.imapidle.GmailInboundImapIdleAdapterTestApp] 消息：GenericMessage [payload=org.springframework.integration.mail.AbstractMailReceiver$IntegrationMimeMessage@4ac650aa， headers={id=869e46a9-8fd0-4351-4f1e-bb181286b05f，timestamp=1570611892844}] 16:09:31.063 信息 [pool-2-thread-1][org.springframework.integration.samples.mail.imapidle.GmailInboundImapIdleAdapterTestApp]消息：GenericMessage [payload=org.springframework.integration.mail.AbstractMailReceiver$IntegrationMimeMessage@76114690，標(biāo)頭={id=6c791751-668e-69c5-3e05-1ae1ec72f853，時(shí)間戳=1570612171063}]現(xiàn)在如何檢索正文內(nèi)容？例如郵件正文上是“hello world 123”？