如何在JSP中将页面上下文附加到不在DOM标记中的URL字符串

我使用页面上下文来引用Tomcat web服务器上的某些资源。例如，我使用它来获取图像，如下所示:

<img src="${pageContext.request.contextPath}/images/ajax-loader.gif" id="loading">

当我尝试为一个只是字符串的src做同样的事情时，而不是像上面那样在文档标记内，我得到一个错误。如何将上下文添加到普通字符串?还是不允许。

//This does not work and gives me syntax errors
if(response.validation === "success")
        window.location.href=${pageContext.request.contextPath}+"dashboard.jsp";
    else{
        $("#notification").append("<td><center>You have entered an incorrect username or password</center></td>");
    }
    });
//This works but I don't want to do it this way
  if(response.validation === "success")
        window.location.href="http://69.164.xx.xx:8080/MySite/dashboard.jsp";
    else{
        $("#notification").append("<td><center>You have entered an incorrect username or password</center></td>");
    }
  });
//Edit: Rendered Page after using first option
if(response.validation === "success")
        window.location.href=/RiverBoat+"dashboard.jsp";
    else{
        $("#notification").append("<td><center>You have entered an incorrect username or password</center></td>");
    }
  });