### Question:
WxMaRetainInfo implements Serializable { public static WxMaRetainInfo fromJson(String json) { return WxMaGsonBuilder.create().fromJson(json, WxMaRetainInfo.class); }  static WxMaRetainInfo fromJson(String json);  }### Answer:
@Test public void testFromJson() throws Exception { String json = "{\"ref_date\":\"20170313\",\"visit_uv_new\":[{\"key\":0,\"value\":5464}],\"visit_uv\":[{\"key\":0,\"value\":55500}]}\n"; WxMaRetainInfo retainInfo = WxMaRetainInfo.fromJson(json); assertNotNull(retainInfo); assertEquals("20170313", retainInfo.getRefDate()); assertTrue(retainInfo.getVisitUv().containsKey(0)); assertTrue(retainInfo.getVisitUvNew().containsKey(0)); System.out.println(retainInfo); }