如何使用gson处理动态响应数据？ （json到java对象）

这是Json的用户列表：

{ 'response': { 'result': { 'users': [{ name: "ABC", age: "20", gender: "F" }, { name: "cbd", age: "23", gender: "M" }] } } } 

有时会像这样回来

 { 'response': { 'result': { 'users': { name: "ABC", age: "20", gender: "F" } } } } 

当它返回单个用户时，我可以使用以下java类将json转换为java

 class Data{ private response response; class response{ private result result; class result{ private users users; class users{ private String name; private String age; private String gender; } } } } 

但如果返回用户列表，我会得到Exception。 我该怎么处理？

Answer 1

要执行您想要的操作，您必须将users更改为List 并编写（简单）自定义反序列化程序。 没有自定义反序列化器，Gson将不会解析，除非您将用户切换到Object （但在这种情况下，它将返回一个映射列表）。

在向您展示可以在IDE中复制和运行的完整示例之前，请注意两个注释。 用户“而不是”作为字符串分隔符并遵循Java命名约定 。类必须至少以大写字母开头。放置小写不会改变Gson行为，因为它查看类字段名称而不是类名。

 package stackoverflow.questions.q19124387; import java.lang.reflect.Type; import java.util.*; import com.google.gson.*; import com.google.gson.reflect.TypeToken; public class Q19124387 { public static class User { private String name; private String age; private String gender; @Override public String toString() { return "User [name=" + name + ", age=" + age + ", gender=" + gender + "]"; } } public static class Result { private List users = new ArrayList(); } public static class Response { private Result result; } public static class Data { private Response response; } public static class CustomDeserializer implements JsonDeserializer { public Result deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException { Result r = null; JsonElement usersField = json.getAsJsonObject().get("users"); if (usersField.isJsonNull() || usersField.isJsonPrimitive()) ; // if is null or is a primitive type will return an empty result else if (usersField.isJsonObject()) { r = new Result(); r.users.add((User) context.deserialize(usersField, User.class)); } else if (usersField.isJsonArray()) { Type listOfUserType = new TypeToken>() {}.getType(); r = new Result(); r.users.addAll((Collection) context.deserialize(usersField, listOfUserType)); } return r; } } /** * @param args */ public static void main(String[] args) { String json1 = " {\"response\": { \"result\": { \"users\": [{ name: \"ABC\", age: \"20\", gender: \"F\" }, { name: \"cbd\", age: \"23\", gender: \"M\" }] } } }"; String json2 = "{\"response\": { \"result\": {\"users\": { name: \"ABC\", age: \"20\",gender: \"F\" } } } } "; Gson g = new Gson(); try { Data d1 = g.fromJson(json1, Data.class); System.out.println("Parsed json1, list of users"); } catch (Exception e) { System.out.println("Cannot parse json1, list of users"); } try { Data d2 = g.fromJson(json2, Data.class); System.out.println("Parsed json2, single user"); } catch (Exception e) { System.out.println("Cannot parse json2, single user"); } GsonBuilder gb = new GsonBuilder(); gb.registerTypeAdapter(Result.class, new CustomDeserializer()); Gson g2 = gb.create(); Data d1 = g2.fromJson(json1, Data.class); Data d2 = g2.fromJson(json2, Data.class); System.out.println("Second user of json1 is " + d1.response.result.users.get(1)); System.out.println("First user of json2 is " + d2.response.result.users.get(0)); } } 

这是代码的执行：

 Parsed json1, list of user Cannot parse json2, single user Second user of json1 is User [name=cbd, age=23, gender=M] First user of json2 is User [name=ABC, age=20, gender=F]