js

var xmlHttp; // ajax
	if (window.XMLHttpRequest) {// code for IE7+,Firefox,Chrome,Opera,Safari
		xmlHttp = new XMLHttpRequest();
	} else {// code for IE6,IE5
		xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
	}

	xmlHttp.onreadystatechange = function() {
		if (xmlHttp.readyState == 4) {// 4 = loaded
			if (xmlHttp.status == 200) {// 200 = "OK"
				var retstr = xmlHttp.responseText;
				var xmlDoc = new ActiveXObject("Microsoft.XmlDom");
				xmlDoc.loadXML(retstr);
				var result = xmlDoc.getElementsByTagName("result")[0].firstChild.nodeValue;
				alert(result);
			} else {
				alert(xmlHttp.status);
				alert("出现错误，操作失败！");
			}
		}
	}
	var url = "header.do";
	xmlHttp.open("POST",url,true);
	xmlHttp.setRequestHeader("Content-type","application/x-www-form-urlencoded");
	xmlHttp.send("method=citeOneHeader&headerId=" + headerId + "&str=" + str);

action

response.setCharacterEncoding("utf-8");
		response.setContentType("txet/xml;charset=utf-8");
		response.setHeader("Cache-Control","no-cache");
		response.getWriter().write("<?xml version=\"1.0\"  encoding=\"UTF-8\"?>");
		StringBuffer sb=new StringBuffer();
		sb.append("<res>");
		sb.append("<result>"+result+"</result>");
		sb.append("</res>");
        sendResponse(response,sb.toString());

private void sendResponse(HttpServletResponse response,String responseText)
			throws IOException {
		response.getWriter().write(responseText);
	}