先来看看response.getWriter().println()的使用及返回的结果：
@RequestMapping({"/wxLogin"})
public void wxLogin(HttpServletRequest request, HttpServletResponse response)throws
Exception
{
response.setCharacterEncoding("utf-8");
String json = "";
Gson gson = new Gson();
Map<String,Object> map = new HashMap<String,Object>();
PrintWriter out = response.getWriter();
String id="sn258369";
WXInfo wxInfo=wxInfoService.findById(id);
String id2="sn357159";
User user=userService.findById(id2);
map.put("wxInfo", wxInfo);
map.put("user",user);
json=gson.toJson(map);
out.print(json);
out.flush();
out.close();
}返回结果如下：
{"wxInfo":{"id":"189e725696fb44cd8f8c1519deb40148","nickName":"@\"nickname\" : @\"你你若安好111\"\"","sex":"1","country":"China","province":"Guangdong","city":"Shenzhen","unionId":"oWuV20tjS-8h12xxxc","openId":"oca0s6LxxxAU","avatarUrl":"http://thirdwx.qeUribdzW3GSQj2Q/132","mobilePhone":"139xxxxx802","subscribe":0,"createdDate":"2019-09-11 14:09:11.0","updatedDate":"2019-12-24 11:11:57"},"user":{"userId":"727","userName":"139xxxxx802","name":"Daniel","birthday":"1990-01-14 17:18:16.0","sex":"1","mobilePhone":"139xxxxx802","registerTime":"2019-06-05 18:02:11.0"},"status":2}
可以看到各个属性均有值，没有出现值为null的属性。再来看看使用@Responsebody的写法和返回结果：
@RequestMapping("/wxLogin")
@ResponseBody
public Map<String, Object> wxLogin(HttpServletRequest request,HttpServletResponse response)throws Exception{
response.setCharacterEncoding("utf-8");
int status=0;
Gson gson=new Gson();
Map<String, Object>map=new HashMap<String, Object>();
String id="sn258369";
WXInfo wxInfo=wxInfoService.findById(id);
String id2="sn357159";
User user=userService.findById(id2);
map.put("wxInfo", wxInfo);
map.put("user",user);
return map;
}返回结果如下：
{
"wxInfo": {
"id": "189e7256deb40148",
"nickName": "@\"nickname\" : @\"你你若安好111安\"\"",
"sex": "1",
"country": "China",
"province": "Guangdong",
"city": "Shenzhen",
"userId": null,
"unionId": "oWuV20tjxxxDxc",
"openId": "oca0s6xxxxeIH3AU",
"avatarUrl": "http://thirdwx.qlogo.cn/2Q/132",
"mobilePhone": "139xxxxx802",
"subscribe": 0,
"createdDate": "2019-09-11 14:09:11",
"updatedDate": "2019-12-24 13:22:23"
},
"user": {
"userId": "727",
"userName": "139xxxxx802",
"password": "",
"name": "Daniel",
"birthday": "1990-01-14",
"sex": "1",
"bloodType": null,
"email": "",
"height": null,
"weight": null,
"qqNum": null,
"weChat": null,
"weiBo": null,
"homePhone": null,
"mobilePhone": "1319xxxxx802",
"officePhone": null,
"country": null,
"ctyId": null,
"province": null,
"city": null,
"district": null,
"address": null,
"allergy": null,
"remark": null,
"dataURL": null,
"registerTime": "2019-06-05 18:02:11.0",
"ssuppliercode": null
},
"status": 2
}
可以看到，在返回user对象的时候，出现很多值为null的属性，这些属性均为user中的属性，但数据库查询到的值为null。
这是两种推送JSON方式，返回结果的差异，Gson已屏蔽掉值为null的属性，而@ResponseBody则根据对象的所有属性原原本本地返回。
