/**
	 * 
	 * @param msg   alert提示信息
	 * @param redirectUrl  重定向url，如果为空，则返回到操作当前页
	 */
	public void alertMsg(String msg,String redirectUrl){
        if(msg==null||"".equals(msg.trim())){
        	return ;
        }
        PrintWriter out=null; 
		 try { 
		 //设置回发内容编码       
		 ServletActionContext.getResponse().setContentType("text/html;charset=gbk");  
		 out = ServletActionContext.getResponse().getWriter(); 
		 } catch (IOException e) { 
		      e.printStackTrace(); 
		 } 
		 StringBuilder sb=new StringBuilder();
		 sb.append("<script>alert('" +msg+"！');");
		 if(redirectUrl==null||"".equals(redirectUrl.trim())){
			 sb.append("history.go(-1);");
		 }else{
			 sb.append("location='"+redirectUrl+"';");
		 }
		 sb.append("</script>");
		 out.print(sb.toString());
		 out.flush();
		 out.close();
	}
	/**
	 * alert 提示后跳到当前页面
	 * @param msg alert提示信息
	 */
	public void alertMsg(String msg){
		alertMsg( msg,null);
	}

public String delete(){
			defaultUrl();
			..  your code 
                    this.alertMsg("操作成功", this.getBasePath()+"course/course_list.do");
			return null;
		}