纯js的ajax

/**
 * 得到ajax对象
 */
function getajaxHttp() {
	var xmlHttp;
	try {
		// Firefox, Opera 8.0+, Safari
		xmlHttp = new XMLHttpRequest();
		} catch (e) {
			// Internet Explorer
			try {
				xmlHttp = new ActiveXObject("Msxml2.XMLHTTP");
			} catch (e) {
			try {
				xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
			} catch (e) {
				alert("您的浏览器不支持AJAX！");
				return false;
			}
		}
	}
	return xmlHttp;
}

/**
 * 发送ajax请求
 * url--url
 * methodtype(post/get)
 * con (true(异步)|false(同步))
 * functionName(回调方法名，不需要引号,这里只有成功的时候才调用)
 * (注意：这方法有二个参数，一个就是xmlhttp,一个就是要处理的对象)
 * obj需要到回调方法中处理的对象
 */
function ajaxrequest(url,methodtype,con,functionName,obj){
	var xmlhttp=getajaxHttp();
	xmlhttp.onreadystatechange=function(){
		if (xmlhttp.readyState==4){ 
		   if (xmlhttp.status==200){ 
			   functionName(xmlhttp.responseText);
		    }
		  }
		
	}; 
	xmlhttp.open(methodtype,url,con);
	xmlhttp.send();
}
function onSuccess(response){
	if(response=="fail"){
		alert("时间段已存在,请更改其他时间段");
		return false;
	}else{
		$("msgStraForm").submit();
	}
}
function checkSub(){
	var send_content=document.getElementById("send_content").value;
	var start_time=document.getElementById("start_time").value;
	var end_time=document.getElementById("end_time").value;
	var msgStraBtnSub=document.getElementById("msgStraBtnSub").value;
	var url;
	var editMsgsid;
	editMsgsid=document.getElementById("EditMsgsid").value;
	if(send_content==""){
		alert("请输入内容");
		return false;
	}if(send_content.length>195){
		alert("发送内容不能超过195个汉字");
		return false;
	}
	if(parseInt(start_time)>parseInt(end_time)||parseInt(end_time)==parseInt(start_time)){
		alert("时间段选择错误,请重新选择");
		return false;
	}
	var url="./strategy!checkData?editId="+editMsgsid+"&start_time="+start_time+"&end_time="+end_time;
	ajaxrequest(url,"post",true,onSuccess,document);
}

java action 代码

public String checkData() {
		try {
			HttpServletRequest request = ServletActionContext.getRequest();
			HttpServletResponse response=ServletActionContext.getResponse();
			PrintWriter writer = response.getWriter();
			String editId=request.getParameter("editId");
			String startTime=request.getParameter("start_time");
			String endTime=request.getParameter("end_time");
			boolean flag=false;
			flag=sendPlanMgr.checkByCallType(editId,startTime, endTime);
			if (flag)
				writer.write("fail");
		    else {
		    	writer.write("success");
		    }
		    writer.flush();
		    writer.close();
		} catch (Exception e) {
			log.error(e.getMessage());
			e.printStackTrace();
		}
		return null;
	}