XML无法解析大字段数据、富文本数据

//封装数据的时候需要用以下数据转化一下
public static String htmlEncodeSize(String str) {
		if(str ==null || str.trim().equals("")) {
	    	return str;
	    }
		StringBuilder encodeStrBuilder = new StringBuilder();
	    str = str.trim();
	    str= changePlainText(str);
	    for (int i = 0, len = str.length(); i < len; i++) {

	       encodeStrBuilder.append(htmlEncode(str.charAt(i)));

	    }

	    String content = encodeStrBuilder.toString().replaceAll(" ", " ");
		try {
			if(TzStringUtils.getChineseSize(content) == 0)
				return new String(content.getBytes("ISO-8859-1"),"UTF-8");
		} catch (UnsupportedEncodingException e) {
			e.printStackTrace();
		}
		return content;
	}