我正在尝试使用Spring Framework从Gmail实施JavaMail Api接收消息。
当我调试它时，一切都很顺利，但最后它失败了：
o.s.w.s.m.s.DefaultHandlerExceptionResolver - Failed to write HTTP message: org.springframework.http.converter.HttpMessageNotWritableException: Could not write content: Not connected (through reference chain: java.util.ArrayList[0]-com.sun.mail.pop3.POP3Message["folder"]->com.sun.mail.pop3.POP3Folder["store"]-com.sun.mail.pop3.POP3SSLStore["defaultFolder"]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: Not connected (through reference chain: java.util.ArrayList[0]->com.sun.mail.pop3.POP3Message["folder"]-com.sun.mail.pop3.POP3Folder["store"]-com.sun.mail.pop3.POP3SSLStore["defaultFolder"])