java - Gson 将新对象数组附加到现有 JSON 文件

Question

我需要一些帮助将新数组附加到现有文件中。我有一个像这样的 JSON 文件:

[
  {
    "name": "any",
    "address": {
      "street": "xxxx",
      "number": 1
    },
    "email": "<a href="https://stackoverflow.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="e99d8c9a9d8ca98e84888085c78a8684" rel="noreferrer noopener nofollow">[email protected]</a>"
  }
]

我想插入新数组，所以我的文件将如下所示:

[
      {
        "name": "any",
        "address": {
          "street": "xxxx",
          "number": 1
        },
        "email": "<a href="https://stackoverflow.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="3c48594f487c5b515d5550125f5351" rel="noreferrer noopener nofollow">[email protected]</a>"
      },
      {
        "name": "any2",
        "address": {
          "street": "yyyyy",
          "number": 2
        },
        "email": "<a href="https://stackoverflow.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="483c2d3b3c7a082f25292124662b2725" rel="noreferrer noopener nofollow">[email protected]</a>"
      }
]

这是我的代码:

Gson gson = new GsonBuilder().setPrettyPrinting().create();    
ArrayList<Person> ps = new ArrayList<Person>();

//  .... reading entries...

ps.add(new Person(name, address, email));
String JsonPerson = gson.toJson(ps);

File f = new File("jsonfile");
if (f.exists() && !f.isDirectory()) { 
    JsonReader jsonfile = new JsonReader(new FileReader("jsonfile"));
    JsonParser parser = new JsonParser();
    JsonElement element = parser.parse(jsonfile);
    //here goes the new entry?

    try (FileWriter file = new FileWriter("pessoas.json")) {
        file.write(JsonPessoa);
        file.close();
    } catch (Exception e) {
        e.printStackTrace();
    }

那么，最好的方法是什么？ 提前致谢。

Answer 1

Gson 与 Pojos 结合时确实很出色，所以我的建议是使用映射的 pojos。考虑下面两个类。

public class Contact {

    @SerializedName("address")
    private Address mAddress;
    @SerializedName("email")
    private String mEmail;
    @SerializedName("name")
    private String mName;

    // getters and setters...

}

public class Address {

    @SerializedName("number")
    private Long mNumber;
    @SerializedName("street")
    private String mStreet;

    // getters and setters...

}

读取 JSON 并添加新联系人并将其转换回 JSON，它也可以无缝地用于其他方式。同样，您可以使用这种方法来解决许多用例。通过从文件读取或使用类似的方式传递 json 数组字符串，之后

Gson gson = new Gson();

List<Contact> contacts = gson.fromJson("JSON STRING", new TypeToken<List<Contact>>() {}.getType());

Contact newContact = new Contact();
// set properties
contacts.add(newContact);

String json = gson.toJson(contacts);

有像this one这样的工具从 JSON 创建 pojo。