gson 自定义特定的序列化的方式

Question

有一个 Student 类，包含了 id 和 name 两个属性，使用 SpringMVC 和 gson 整合，默认 gson 将该实体会序列化为：

{
    "id" : 1,
    "name" : "StuName"
}

目前希望将 Student 序列化为：

{
    "Type" : "Student",
    "Property": {
        "id" : 1,
        "name" : "StuName"
    }
}

请问大家该如何做呢？（gson 版本为 2.8.0，使用 TypeAdapter 我一直得不到想要的效果。使用 Jackson 的时候，可以直接定义一个 JsonSerializer 并将其使用 @JsonSerialize(using = xxx.class) 注解来自定义序列化的格式，不知道在 gson 中有没有提供的方式）

Answer 1

用：JsonSerializer/JsonDeserializer public static class StudentJsonSerializer implements JsonSerializer<Student> { @Override public JsonElement serialize(Student src, Type typeOfSrc, JsonSerializationContext context) { final JsonObject propEle = new JsonObject(); propEle.addProperty("id", src.getId()); propEle.addProperty("name", src.getName()); final JsonObject root = new JsonObject(); root.addProperty("Type", "Student"); root.add("Property", propEle); return root; } } public static class StudentJsonDeserializer implements JsonDeserializer<Student> { public Student deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException { final JsonObject root = json.getAsJsonObject(); JsonObject propEle = root.getAsJsonObject("Property"); Student student = new Student(); student.setId(propEle.get("id").getAsInt()); student.setName(propEle.get("name").getAsString()); return student; } } @Test public void test_1010000010436869() { Gson gson = new GsonBuilder().registerTypeAdapter(Student.class, new StudentJsonSerializer()) .registerTypeAdapter(Student.class, new StudentJsonDeserializer()).create(); Student student = new Student(); student.setId(1); student.setName("StuName"); String json = gson.toJson(student); System.out.println(json); Student student2 = gson.fromJson(json, Student.class); System.out.println(student2); }

Answer 2

通过继承 GsonHttpMessageConverter 并覆写 writeInternal 方法达到了想要的效果，但不知道有没有更加优雅的方法。 public class MyGsonHttpMessageConverter extends GsonHttpMessageConverter { @Override protected void writeInternal(Object o, Type type, HttpOutputMessage outputMessage) throws IOException, HttpMessageNotWritableException { if (o instanceof Student) { Student s = (Student) o; JsonObject stuObj = new JsonObject(); stuObj.addProperty("id", s.getId()); stuObj.addProperty("name", s.getName()); JsonObject entity = new JsonObject(); entity.addProperty("Type", "Student"); entity.add("property", stuObj); try (OutputStreamWriter writer = new OutputStreamWriter(outputMessage.getBody(), DEFAULT_CHARSET)) { Gson gson = super.getGson(); gson.toJson(entity, writer); } catch (JsonIOException ex) { throw new HttpMessageNotWritableException("Could not write JSON: " + ex.getMessage(), ex); } } else { super.writeInternal(o, type, outputMessage); } } }