<!-- https://mvnrepository.com/artifact/com.alibaba/fastjson -->  
<dependency>  
    <groupId>com.alibaba</groupId>  
    <artifactId>fastjson</artifactId>  
    <version>1.2.41</version>  
</dependency> 

com.alibaba.fastjson.JSON

不是

com.alibaba.dubbo.common.json.JSONObject; 

字符串转JSON ：

JSONObject jsonResult = JSONObject.parseObject(contract.getParam());