GSON 'nested' 个反序列化器

Question

我对以下 json 样本的 'nested' gson 反序列化器有问题。我卡了好几天了。

这里我为 dept、contact、role 使用了 3 个反序列化器。 dept 和 role 处于同一层级。 contact 在 dept 里面。问题是我无法提取内部 contact.

的内容

{
  "depts": {
    "dept": [
      {
        "name": "IT1",
        "contacts": {
          "contact": [
            {
              "name": "CCC11"
            },
            {
              "name": "CCC12"
            }
          ]
        }
      },
      {
        "name": "IT2",
        "contacts": {
          "contact": [
            {
              "name": "CCC21"
            }
          ]
        }
      }
    ]
  },
  "roles": {
    "role": [
      {
        "name": "ADMIN"
      },
      {
        "name": "MANAGER"
      }
    ]
  }
}

public class D_result {
  public D_depts depts;
  public D_roles roles;
}

public class D_depts {

  // fixme: choose either (A) or (B)

  // region - (A) not using deserializer
//
//  public D_dept[] dept;
//
  // endregion - (A) not using deserializer

  // region - (B) using deserializer

  private static final String TAG_dept = "dept";
  public D_dept mD_dept;
  public D_dept[] mD_deptList;

  public void setD_dept(D_dept d_dept) {
    mD_dept = d_dept;
  }

  public void setD_deptList(D_dept[] d_deptList) {
    mD_deptList = d_deptList;
  }

  public static class D_deptsDeserializer implements JsonDeserializer<D_depts> {
    @Override
    public D_depts deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {

      D_depts depts = new Gson().fromJson(json, D_depts.class);

      JsonObject jsonObject = json.getAsJsonObject();

      if (jsonObject.has(TAG_dept)) {

        JsonElement jsonElement = jsonObject.get(TAG_dept);
        if (jsonElement.isJsonArray()) {

          JsonArray array = jsonElement.getAsJsonArray();
          D_dept[] values = new Gson().fromJson(array, D_dept[].class);
          depts.setD_deptList(values);

        } else if (jsonElement.isJsonObject()) {

          JsonObject object = jsonElement.getAsJsonObject();
          D_dept value = new Gson().fromJson(object, D_dept.class);
          depts.setD_dept(value);

        } else {

        }
      }
      return depts;
    }
  }

  // endregion - (B) using deserializer

}

public class D_dept {
  public String name;
  public D_contacts contacts;
}

public class D_contacts {

  // fixme: choose either (A) or (B)

//  // region - (A) not using deserializer
//
//  public D_contact[] contact;
//
//  // endregion - (A) not using deserializer

  // region - (B) using deserializer

  private static final String TAG_contact = "contact";
  public D_contact mD_contact;
  public D_contact[] mD_contactList;

  public void setD_contact(D_contact d_contact) {
    mD_contact = d_contact;
  }

  public void setD_contactList(D_contact[] d_contactList) {
    mD_contactList = d_contactList;
  }

  public static class D_contactsDeserializer implements JsonDeserializer<D_contacts> {
    @Override
    public D_contacts deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {

      D_contacts contacts = new Gson().fromJson(json, D_contacts.class);

      JsonObject jsonObject = json.getAsJsonObject();

      if (jsonObject.has(TAG_contact)) {

        JsonElement jsonElement = jsonObject.get(TAG_contact);
        if (jsonElement.isJsonArray()) {

          JsonArray array = jsonElement.getAsJsonArray();
          D_contact[] values = new Gson().fromJson(array, D_contact[].class);
          contacts.setD_contactList(values);

        } else if (jsonElement.isJsonObject()) {

          JsonObject object = jsonElement.getAsJsonObject();
          D_contact value = new Gson().fromJson(object, D_contact.class);
          contacts.setD_contact(value);

        } else {

        }
      }
      return contacts;
    }
  }

  // endregion - (B) using deserializer

}

public class D_contact {
  public String name;
}

public class D_roles {

  // fixme: choose either (A) or (B)

//  // region - (A) not using deserializer
//
//  public D_role[] role;
//
//  // endregion - (A) not using deserializer

  // region - (B) using deserializer

  private static final String TAG_role = "role";
  public D_role mD_role;
  public D_role[] mD_roleList;

  public void setD_role(D_role d_role) {
    mD_role = d_role;
  }

  public void setD_roleList(D_role[] d_roleList) {
    mD_roleList = d_roleList;
  }

  public static class D_rolesDeserializer implements JsonDeserializer<D_roles> {
    @Override
    public D_roles deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {

      D_roles roles = new Gson().fromJson(json, D_roles.class);

      JsonObject jsonObject = json.getAsJsonObject();

      if (jsonObject.has(TAG_role)) {

        JsonElement jsonElement = jsonObject.get(TAG_role);
        if (jsonElement.isJsonArray()) {

          JsonArray array = jsonElement.getAsJsonArray();
          D_role[] values = new Gson().fromJson(array, D_role[].class);
          roles.setD_roleList(values);

        } else if (jsonElement.isJsonObject()) {

          JsonObject object = jsonElement.getAsJsonObject();
          D_role value = new Gson().fromJson(object, D_role.class);
          roles.setD_role(value);

        } else {

        }
      }
      return roles;
    }
  }

  // endregion - (B) using deserializer

}

public class D_role {
  public String name;
}

  private static String sJsonString = "{\"depts\":{\"dept\":[{\"name\":\"IT1\",\"contacts\":{\"contact\":[{\"name\":\"CCC11\"},{\"name\":\"CCC12\"}]}},{\"name\":\"IT2\",\"contacts\":{\"contact\":[{\"name\":\"CCC21\"}]}}]},\"roles\":{\"role\":[{\"name\":\"ADMIN\"},{\"name\":\"MANAGER\"}]}}";

  private void vTest() {

    GsonBuilder gsonBuilder = new GsonBuilder();
    gsonBuilder.registerTypeAdapter(D_depts.class, new D_depts.D_deptsDeserializer());
    gsonBuilder.registerTypeAdapter(D_roles.class, new D_roles.D_rolesDeserializer());
    gsonBuilder.registerTypeAdapter(D_contacts.class, new D_contacts.D_contactsDeserializer());

    Gson gson = gsonBuilder.create();

    D_result result = gson.fromJson(sJsonString, D_result.class);

//    D_dept[] dDepts = result.depts.dept;  // not using deserializer
    D_dept[] dDepts = result.depts.mD_deptList;  // using deserializer
    if (dDepts != null) {
      for (D_dept dept : dDepts) {
        Log.d(TAG, dept.name);

        D_contacts dContacts = dept.contacts;
//        if (dContacts != null && dContacts.contact != null) {  // not using deserializer
        if (dContacts != null && dContacts.mD_contactList != null) {  // using deserializer
//          for (D_contact contact : dContacts.contact) {  // not using deserializer
          for (D_contact contact : dContacts.mD_contactList) {  // using deserializer
            Log.d(TAG+"dbg", dept.name + " " + contact.name);
          }
        }
        else {
          Log.d(TAG+"dbg", "Contacts unavailable");
        }
      }
    }
//    D_role[] dRoles = result.roles.role;  // not using deserializer
    D_role[] dRoles = result.roles.mD_roleList;  // using deserializer
    if (dRoles != null) {
      for (D_role role : dRoles) {
        Log.d(TAG, role.name);
      }
    }
  }

Logcat of NG result:
--------------------
D/DBG: IT1
D/DBGdbg: Contacts unavailable
D/DBG: IT2
D/DBGdbg: Contacts unavailable
D/DBG: ADMIN
D/DBG: MANAGER

Logcat of OK result:
--------------------
D/DBG: IT1
D/DBGdbg: IT1 CCC11
D/DBGdbg: IT1 CCC12
D/DBG: IT2
D/DBGdbg: IT2 CCC21
D/DBG: ADMIN
D/DBG: MANAGER

结果：

出于分析目的，提供的源代码能够 enable/disable comment/uncomment 使用反序列化器。此处NG表示'no good'，无法提取contact内容。

对于以下这些组合，我的结果是 NG：

所有 dept、role、contact 反序列化器都处于活动状态。
只有 dept、contact 反序列化器处于活动状态。

对于以下这些组合，我的结果还可以：

只有 role、contact 反序列化器处于活动状态，禁用 dept 反序列化器。
只有 role、dept 反序列化器处于活动状态，contact 反序列化器已禁用。

结果分析：

5.1。 contact 解串器在启用 dept 解串器时出现错误。参见 (1),(2)。

5.2。当 dept 反序列化器被禁用时，contact 反序列化器正常。见(3).

5.3。同一层次结构级别的多个反序列化器是可以的。见(4).

问题：

6.1。为什么 contact 内容在启用 dept 解串器时不可用？

6.2。需要进行哪些修改才能使所有 3 个反序列化器正常工作？

谢谢。

解决方案：

非常感谢 Gurgen Gevondov 提供的解决方案。问题是内部反序列化器 contact 的错误放置。搜索 fixme 以获取更新的代码。添加了额外的测试用例。现在能够解析 dept、contact 它们是 JsonArray 还是 JsonObject。

public class D_depts {

  // fixme: choose either (A) or (B)

  // region - (A) not using deserializer
//
//  public D_dept[] dept;
//
  // endregion - (A) not using deserializer

  // region - (B) using deserializer

  private static final String TAG_dept = "dept";
  public D_dept mD_dept;
  public D_dept[] mD_deptList;

  public void setD_dept(D_dept d_dept) {
    mD_dept = d_dept;
  }

  public void setD_deptList(D_dept[] d_deptList) {
    mD_deptList = d_deptList;
  }

  public static class D_deptsDeserializer implements JsonDeserializer<D_depts> {
    @Override
    public D_depts deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {

      D_depts depts = new Gson().fromJson(json, D_depts.class);

      //fixme-add
      Gson gson = new GsonBuilder()
          .registerTypeAdapter(D_contacts.class, new D_contacts.D_contactsDeserializer())
          .create();

      JsonObject jsonObject = json.getAsJsonObject();

      if (jsonObject.has(TAG_dept)) {

        JsonElement jsonElement = jsonObject.get(TAG_dept);
        if (jsonElement.isJsonArray()) {

          JsonArray array = jsonElement.getAsJsonArray();
//          D_dept[] values = new Gson().fromJson(array, D_dept[].class);  //fixme:del
          D_dept[] values = gson.fromJson(array, D_dept[].class);  //fixme:add
          depts.setD_deptList(values);

        } else if (jsonElement.isJsonObject()) {

          JsonObject object = jsonElement.getAsJsonObject();
//          D_dept value = new Gson().fromJson(object, D_dept.class);  //fixme:del
          D_dept value = gson.fromJson(object, D_dept.class);  //fixme:add
          depts.setD_dept(value);

        } else {

        }
      }
      return depts;
    }
  }

  // endregion - (B) using deserializer

}

  private static String sJsonString1 = "{\"depts\":{\"dept\":[{\"name\":\"IT1\",\"contacts\":{\"contact\":[{\"name\":\"CCC11\"},{\"name\":\"CCC12\"}]}},{\"name\":\"IT2\",\"contacts\":{\"contact\":[{\"name\":\"CCC21\"}]}}]},\"roles\":{\"role\":[{\"name\":\"ADMIN\"},{\"name\":\"MANAGER\"}]}}";
  private static String sJsonString2 = "{\"depts\":{\"dept\":[{\"name\":\"IT1\",\"contacts\":{\"contact\":[{\"name\":\"CCC11\"},{\"name\":\"CCC12\"}]}},{\"name\":\"IT2\",\"contacts\":{\"contact\":{\"name\":\"CCC21_obj\"}}}]},\"roles\":{\"role\":[{\"name\":\"ADMIN\"},{\"name\":\"MANAGER\"}]}}";
  private static String sJsonString3 = "{\"depts\":{\"dept\":{\"name\":\"IT3_obj\",\"contacts\":{\"contact\":[{\"name\":\"CCC31\"},{\"name\":\"CCC32\"}]}}},\"roles\":{\"role\":[{\"name\":\"ADMIN\"},{\"name\":\"MANAGER\"}]}}";
  private static String sJsonString4 = "{\"depts\":{\"dept\":{\"name\":\"IT4_obj\",\"contacts\":{\"contact\":{\"name\":\"CCC41_obj\"}}}},\"roles\":{\"role\":[{\"name\":\"ADMIN\"},{\"name\":\"MANAGER\"}]}}";

  private static final String[] sJsonStrings = new String[] {
      sJsonString1   // dept as array, contact as array
      ,sJsonString2  // dept as array, contact as object
      ,sJsonString3  // dept as object, contact as array
      ,sJsonString4  // dept as object, contact as object
  };

  private void vTests() {
    for (String s : sJsonStrings) {
      Log.d(TAG, "--------------------");
      vTest(s);
    }
    Log.d(TAG, "--------------------");
  }

  private void vTest(String jsonString) {

    GsonBuilder gsonBuilder = new GsonBuilder();
    gsonBuilder.registerTypeAdapter(D_depts.class, new D_depts.D_deptsDeserializer());
    gsonBuilder.registerTypeAdapter(D_roles.class, new D_roles.D_rolesDeserializer());
//    gsonBuilder.registerTypeAdapter(D_contacts.class, new D_contacts.D_contactsDeserializer());  //fixme:del

    Gson gson = gsonBuilder.create();

    D_result result = gson.fromJson(jsonString, D_result.class);

    if (result.depts.mD_deptList != null) {
      for (D_dept dept : result.depts.mD_deptList) {
        Log.d(TAG, dept.name);
        vShowContacts(dept.contacts, dept);
      }
    } else if (result.depts.mD_dept != null) {
      D_dept dept = result.depts.mD_dept;
      Log.d(TAG, dept.name);
      vShowContacts(dept.contacts, dept);
    }

    D_role[] dRoles = result.roles.mD_roleList;
    if (dRoles != null) {
      for (D_role role : dRoles) {
        Log.d(TAG, role.name);
      }
    }
  }

  private void vShowContacts(D_contacts contacts, D_dept dept) {
    if (contacts.mD_contactList != null) {
      for (D_contact contact : contacts.mD_contactList) {
        Log.d(TAG+"dbgL", dept.name + " " + contact.name);
      }
    } else if (contacts.mD_contact != null) {
      D_contact contact = contacts.mD_contact;
      Log.d(TAG+"dbg1", dept.name + " " + contact.name);
    }
  }

Answer 1

问题是您每次都在创建新的 Gson 对象来解析 D_dept 数组，键 dept in D_depts.D_deptsDeserializer class 和这个新的创建的 Gson 对象对 D_contacts.D_contactsDeserializer 一无所知。要解决此问题，您需要删除

gsonBuilder.registerTypeAdapter(D_contacts.class, new D_contacts.D_contactsDeserializer());

从您的 vTest 方法开始并创建 Gson 对象以使用此代码解析 D_dept：

private Gson gson = new GsonBuilder()
        .registerTypeAdapter(D_contacts.class, new D_contacts.D_contactsDeserializer())
        .create();

并更改此行（在 D_depts.D_deptsDeserializer#deserialize 方法中）

D_dept[] values = new Gson().fromJson(array, D_dept[].class);

到

D_dept[] values = gson.fromJson(array, D_dept[].class);

GSON 'nested' 个反序列化器

GSON 'nested' deserializers

android

json

gson

结果：

结果分析：

问题：

解决方案：