如何将符合xml规范的String转化为XML文档中的element对象

如何将符合xml规范的String转化为XML文档中的element对象：

/**
	 * 字符串转化为XML对象并加入到XML中的某一个节点下
	 * @throws DocumentException
	 */
	public void stringToXml() throws DocumentException{
		
		SAXReader saxReader = new SAXReader();
		Document doc;
		try {
			doc = saxReader.read(new ByteArrayInputStream(xmlStr.getBytes("UTF-8")));
			if (doc!=null){            
				Element element=doc.getRootElement(); 
				SAXReader saxReader1 = new SAXReader();
				Document document1 = saxReader1.read(fileName);
				Element element1 = (Element)document1.selectSingleNode("//template");
				element1.add(element);
				writeXML(document1);
		    }
		} catch (UnsupportedEncodingException e) {
			e.printStackTrace();
		}
	}
	
	/**
	 * 写XML
	 * @param doc
	 */
	private void writeXML(Document doc){
        OutputFormat of = OutputFormat.createPrettyPrint();
        of.setEncoding("utf-8");
        FileOutputStream fos = null;
        XMLWriter xmlout = null;
        String lockfilename = fileName + ".lock";
        MessageLock lock = new MessageLock(lockfilename);
        try{
        	if(lock.lock()) {
        		fos = new FileOutputStream(this.fileName);
                xmlout = new XMLWriter(new OutputStreamWriter(fos, "utf-8"), of);
                xmlout.write(doc);
                xmlout.flush();
        	}
        }catch (Exception ex){
        	log.error("-->writeXml",ex);
        }finally{
        	lock.unlock();
            if (fos != null){
                try{
                	fos.close();
                }catch (IOException ex1){
                	log.error("-->writeXml",ex1);
                }
            }
            if (xmlout != null){
                try{
                    xmlout.close();
                }catch (IOException ex2){
                	log.error("-->writeXml",ex2);
                }
            }
        }
    }