xstream。fromXML返回一个类

使用XStream 1.2.2

XML文档:

<?xml version="1.0" encoding="ISO-8859-1"?>
<Document xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" protocol="OCI" xmlns="C">  
<sessionId xmlns="">192.168.1.19,299365097130,1517884537</sessionId>  
  <command xsi:type="AuthenticationRequest" xmlns="">    
    <userId>me@somewhere.com</userId>  
  </command>
</Document>

我正试图解析为 Document ;

public class Document {
    private String sessionId;
    public Command command;
    public Command getCommand() {
        return this.command;
    }
    public void setCommand(Command command) {
        this.command = command;
    }
    public String getSessionId() {
        return sessionId;
    }
    public void setSessionId(String sessionId) {
        this.sessionId = sessionId;
    }
}

分析代码为:

    XStream xstream = new XStream();
    xstream.alias("Document", Document.class);
    xstream.alias("sessionId", String.class);
    xstream.alias("command", Command.class);
    xstream.alias("userId", String.class);

    Document doc = (Document) xstream.fromXML(theInput, Document.class);

但这会引发:

Java语言lang.ClassCastException:java。lang.类不能转换为com。我的公司。ocip。服务器模型文件

因为返回的对象来自 fromXml 类型为: Class<com.mycompany.ocip.server.model.Document>

我不应该期望它返回一个 com.mycompany.ocip.server.model.Document 例子