How to use a server attribute (ServerAttribute_env_url) in json data adapter's url element

1. I created a server attribute with name 'env_url' and value ="http://......."

2. I want to use this in the JSON data adapter.

Is it possible to pass a server attribute like below to a JSON data adapter ?

<?xml version="1.0" encoding="UTF-8" ?>
<jsonDataAdapter class="net.sf.jasperreports.data.json.JsonDataAdapterImpl"><name>smc-per-calendar-json-adapter_2</name>
<dataFile xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="httpDataLocation">

<url>$P{ServerAttribute_env_url}+"/users"</url>
<method>GET</method>
<header>
    <name>contentType</name><value>application/json;charset=utf-8</value>    
</header>
<header>
    <name>accept</name><value>application/json;charset=utf-8</value>
</header>
<urlParameter>

......

I get :

net.sf.jasperreports.engine.JRRuntimeException: net.sf.jasperreports.engine.JRException: Error opening input stream from URL: repo:/reports/dataadapter/myJsonDataAdapter.xml.
    at net.sf.jasperreports.repo.DefaultRepositoryService.getInputStream(DefaultRepositoryService.java:116)
    at net.sf.jasperreports.repo.InputStreamPersistenceService.load(InputStreamPersistenceService.java:45)
    at net.sf.jasperreports.repo.DefaultRepositoryService.getResource(DefaultRepositoryService.java:149)

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The data source url changes per environment (dev, qa, prod), so I would like it dynamically set. I am trying achieve it with server attributes (I may have a jasper server instance running per environment). Any other suggestions are appreciated.