web JMessage 上传图片 有返回值 接下来该如何从极光服务器获取图片

返回值 如下

onMsgReceive -- {
        "uid":19335754,
        "messages":[{
            "ctime_ms":1484444668293,
            "from_gid":18763995,
            "msg_type":4,
            "ctime":1484444668,
            "msg_id":222182170,
            "msg_level":0,
            "from_uid":19344194,
            "content":{
                  "from_type":"user",
                  "from_id":"13783682555",
                  "set_from_name":0,
                  "target_name":"zhuziGroup",
                  "create_time":1484444668125,
                  "target_type":"group",
                  "msg_body":{
                        "fsize":5368,
                        "width":147,
                        "format":"jpg",
                        "media_id":"qiniu/image/j/F329FC411B0758156E4C636145CDDFB5",
                        "media_crc32":2895759877,
                        "height":220},
                  "from_platform":"web",
                  "msg_type":"image",
                  "target_id":"18763995",
                  "from_name":"13783682555",
                  "version":1}}],
        "rid":222182170,
        "event":"msg_sync"}