使用GSON从网络服务故障检索数据 [英] Trouble retrieving data from web service using GSON

问题描述

我已经尝试了很多关于GSON和样品和教程如何事情会使用它，如工作：

I have tried a lot of samples and tutorials about GSON and how things would work using it such as:

• 的http://www.softwarepassion.com/android-series-parsing-json-data-with-gson/

的http：// androidsmith。 COM / 2011/07 /使用-GSON到语法分析JSON-上的Andr​​oid /

等

我的问题是，我有这个返回值的JSON我的的http：//本地主机：3000 /用户/ 1.json ，它是：

My problem is that I have this json value returned by my http://localhost:3000/users/1.json, which is:

{
  "created_at": "2012-09-20T01:43:15Z",
  "id": 1,
  "name": "kevin",
  "updated_at": "2012-09-20T01:43:15Z"
} 

还有一个就是在这个网址的http：//本地主机：3000 / users.json 里面有一个JSON值

[ {
    "created_at": "2012-09-20T01:43:15Z",
    "id": 1,
    "name": "kevin",
    "updated_at": "2012-09-20T01:43:15Z"
  }, {
    "created_at": "2012-09-20T01:43:33Z",
    "id": 2,
    "name": "pineda",
    "updated_at": "2012-09-20T01:43:33Z"
  }, {
    "created_at": "2012-09-20T01:46:08Z",
    "id": 3,
    "name": "raphael",
    "updated_at": "2012-09-20T01:46:08Z"
  }, {
    "created_at": "2012-09-20T16:13:42Z",
    "id": 4,
    "name": null,
    "updated_at": "2012-09-20T16:13:42Z"
  }, {
    "created_at": "2012-09-20T16:18:03Z",
    "id": 5,
    "name": null,
    "updated_at": "2012-09-20T16:18:03Z"
  }, {
    "created_at": "2012-09-20T16:19:23Z",
    "id": 6,
    "name": null,
    "updated_at": "2012-09-20T16:19:23Z"
  }, {
    "created_at": "2012-09-20T16:20:41Z",
    "id": 7,
    "name": null,
    "updated_at": "2012-09-20T16:20:41Z"
  } 
]

我有一点很难解析这些数据和得到它存储的目的。

I am having a bit of a hard time parsing such data and getting it for storage purposes.

推荐答案

为了解析您的JSON，首先需要创建一个类来的包的数据。你的情况：

In order to parse your JSON, you first need to create a class to wrap your data. In your case:

public class Item {
  @SerializedName("created_at")
  private String createdAt;
  @SerializedName("id")
  private int id;
  @SerializedName("name")
  private String name;
  @SerializedName("updated_at")
  private String updatedAt;
  //getters and setters
}

然后，为了解析您的 1 JSON效应初探，你只需要做的：

Then, in order to parse your 1st JSON reponse, you just have to do:

Gson gson = new Gson();
Item item = gson.fromJson(your1stJsonString, Item.class);

您的第二 JSON的反应是比较麻烦一些，因为它是一个数组。问题是，你不能简单地做：

Your 2nd JSON response is a bit more tricky, because it's an array. The problem is that you can't simply do:

List<Item> item = gson.fromJson(your1stJsonString, List<Item>.class); //wrong!

因为Java不知道班级清单1所述的previous code失败;项目＆GT; 因的 类型擦除 。

所以，你必须做这种方式：

So you have to do it this way:

Type itemListType = new TypeToken<List<Item>>() {}.getType();
List<User> itemList = gson.fromJson(your2stJsonString, itemListType);

而这一切，一旦你解析你的目标你的JSON响应（或对象列表），您可以访问所有的数据检索和往常一样：

And that's all, once you have parsed your JSON response in your object (or list of objects) you can access all the retrieved data as usual:

String name = itemList.get(i).getName();

---

的注1 的：请注意，我已经设置了类型的属性created_at和的updated_at刚才字符串，因为它使事情变得更加容易。我通常做这种方式，然后我解析日期或任何其他的 confictive 的类型。无论如何，如果你想直接解析的日期，我想你可以使用自定义解串器下的 GSON的用户指南 。

---

Note 1: Notice that I've set the types of attributes created_at and updated_at as just String, because it makes things easier. I usually do it this way, and then I parse the Date or any other confictive type. Anyway, if you want to directly parse the dates, I think you can use a Custom Deserializer following Gson's User Guide.

的注2 的：使用注释 @SerializedName 的有趣的是，一个字段的名称中的JSON响应，并在您的应用程序分开，为了遵循Java的命名约定...

Note2: The use of the annotation @SerializedName is interesting to separate the name of a field in the JSON response and in your app, in order to follow Java naming conventions...

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