Java HttpResponseBodyPart XML解析错误

Question

从服务器获得响应时，我面临以下错误。

org.jdom.input.JDOMParseException: Error on line 1: Content is not allowed in prolog.
at org.jdom.input.SAXBuilder.build(SAXBuilder.java:468)
at org.jdom.input.SAXBuilder.build(SAXBuilder.java:851)

在获得回复的同时，我得到的内容也低于

content = ?<?xml version="1.0" encoding="UTF-8"?>

尽管文件的实际内容是

content = <?xml version="1.0" encoding="UTF-8"?>

我使用的方法如下

@Override
public State onBodyPartReceived(HttpResponseBodyPart bodyPart) throws Exception {
      System.out.println("onBodyPartReceived");
      content += new String(bodyPart.getBodyByteBuffer().array(), "UTF-8");
      return State.CONTINUE;
}