如何使用xStream控制解析xml？

Question

现在我使用xStream将对象解析为xml格式的String。我希望当我解析xml时，我可以根据不同的文件做我想做的事情，比如如果我遇到提交的A，我会在它之前添加CDATA Block，当我遇到提交的B时，我会把它变成大写，像这样的东西，这就是我现在正在做的事情。

public static String textMessageToXml(ResponseTextMessage textMsg){
    xstream.alias("xml", textMsg.getClass());
    return xstream.toXML(textMsg);
}  

private static XStream xstream = new XStream(new XppDriver() {
        @Override
        public HierarchicalStreamWriter createWriter(Writer out) {  
            return new PrettyPrintWriter(out) {  
                // Add CDATA block  
                boolean cdata = ...;//I need to add cdata for some fields only  
                boolean isNeedUpper=...;//only some will need this

                protected void writeText(QuickWriter writer, String text) {  
                    if (cdata) {  
                        writer.write("<![CDATA[");  
                        writer.write(text);  
                        writer.write("]]>");  
                    } else if (isNeedUpper){  
                        writer.write(text.toUpperCase());  
                    }  
                    else writer.write(text);
                }  
            };  
        }  
    });