Cannot forward after response has been committed异常处理

当进行验证码判断时候，用转发重新回到登录界面并在request域对象中放入错误信息提示，在页面中显示错误信息，这个时候在转发之后一定要加return，否则就会报Cannot forward after response has been committed异常，500错误

//判断
		if(null!=checkImg && null!=checkcode_session) {
			if(!checkImg.equals(checkcode_session)) {
				request.setAttribute("info", "验证码不正确！");
				request.getRequestDispatcher("/login.jsp").forward(request, response);
				return;
			}
		}