ajax simple use

JS脚本：

 //页面调用方法
 function getInfo(obj){
     var ajax=getAjaxObject();
     url="ajaxAction.do?method=ajaxCheck";
     ajax.onreadystatechange =function(){
         var buffer="";
         if (ajax.readyState == 4&&ajax.status == 200){
            buffer=ajax.responseText;
             //*回调调用方法
            ajaxCallback(buffer);
        }
    }
     ajax.open("POST",url);
     ajax.setRequestHeader("Content-Type","application/x-www-form-urlencoded;charset=UTF-8");
     ajax.send("para="+obj);
}
 //*get Ajax Object
 function getAjaxObject(){
     if (window.ActiveXObject) {
         try{
             ajax = new ActiveXObject("Microsoft.XMLHTTP");
         }catch(e){
             alert("创建Microsoft.XMLHTTP对象失败,AJAX不能正常运行.请检查您的浏览器设置.");
        }
     } else {
         if (window.XMLHttpRequest) {
             try{
                 ajax = new XMLHttpRequest();
             }catch(e){
                 alert("创建XMLHttpRequest对象失败,AJAX不能正常运行.请检查您的浏览器设置.");
            }
        }
    }
     return ajax;
}

 //页面调用方法
function getInfo(obj){
	var ajax=getAjaxObject();
	url="ajaxAction.do?method=ajaxCheck";
	ajax.onreadystatechange =function(){
		var buffer="";
		if (ajax.readyState == 4&&ajax.status == 200){
			buffer=ajax.responseText;
			//*回调调用方法
			ajaxCallback(buffer);
		}	
	}
	ajax.open("POST",url);
	ajax.setRequestHeader("Content-Type","application/x-www-form-urlencoded;charset=UTF-8");
	ajax.send("para="+obj);
}
//*get Ajax Object
function getAjaxObject(){
	if (window.ActiveXObject) {	
		try{		
			ajax = new ActiveXObject("Microsoft.XMLHTTP");			
		}catch(e){		
			alert("创建Microsoft.XMLHTTP对象失败,AJAX不能正常运行.请检查您的浏览器设置.");
		}		
	} else {	
		if (window.XMLHttpRequest) {			
			try{
				ajax = new XMLHttpRequest();				
			}catch(e){			
				alert("创建XMLHttpRequest对象失败,AJAX不能正常运行.请检查您的浏览器设置.");
			}			
		}
	}		
	return ajax;
}

 struts1.x action:

public ActionForward ajaxCheck(ActionMapping mapping, ActionForm form,
        HttpServletRequest request, HttpServletResponse response){
    PrintWriter writer;
     response.setContentType("text/plain;charset=GBK");
     response.setHeader("Pragma","No-Cache");
     response.setHeader("Cache-Control","No-Cache");
     response.setDateHeader("Expires", 0);
     boolean enable=false;
     try{
        writer=response.getWriter();
         AjaxService ajax=new AjaxService ();
         String para=request.getParameter("para");
        enable = ajax.checkSomething(para);
     } catch (Exception e) {
                                               log.error(e.getMessage());
         return mapping.findForward("exception");
    }
    writer.print(enable);
    writer.close();
     return null;
}

	public ActionForward ajaxCheck(ActionMapping mapping, ActionForm form,
			HttpServletRequest request, HttpServletResponse response){ 
		PrintWriter writer;
		response.setContentType("text/plain;charset=GBK");
		response.setHeader("Pragma","No-Cache");
		response.setHeader("Cache-Control","No-Cache");
		response.setDateHeader("Expires", 0);
		boolean enable=false;
		try{
			writer=response.getWriter();
			AjaxService ajax=new AjaxService ();
			String para=request.getParameter("para");
			enable = ajax.checkSomething(para);
		} catch (Exception e) {
                                                log.error(e.getMessage());
			return mapping.findForward("exception");
		}
		writer.print(enable);
		writer.close();
		return null;
	}

 备注：

       如果需要向页面返回一个JS对象，可以在java中拼装一个对象字符串（{name:'jack',sex:'m'}），在前台得到这个字符串后将其转换成一个JS对象（var obj=null;  eval("obj="+outputString);  return obj;）。