面對一些不規範的json,我們的gson解析經常會丟擲各種異常導致app崩潰,這裡可以採取一些措施來避免

關於陣列型別的欄位解析異常,我嘗試了一些方案,但最後都存在問題,如果大家有好的解決方案,希望能貼在下面.不甚感激.
異常示例=>正常json:

{
    "code":0,
    "msg":"ok",
    "data":[    //約定為陣列
      {
        "id":5638,
        "newsId":5638
      }
      ]
}

異常json:

{
    "code":0,
    "msg":"ok",
    "data
 
":{}    //返回為物件或者空字串
}

Json異常情況

先來看一個後臺返回的json
正常情況下json:

{
    "code":0,
    "msg":"ok",
    "data":{
        "id":5638,
        "newsId":5638
    }
}

data部分對應的實體類:

public class JsonBean {
    private int id;
    private int newsId;

    public int getId() {
        return id;
    }

    public void
 
 setId(int id) {
        this.id = id;
    }

    public int getNewsId() {
        return newsId;
    }

    public void setNewsId(int newsId) {
        this.newsId = newsId;
    }
}

異常情況json(後臺資料庫newsId欄位未查詢到對應資料):

{
    "code":0,
    "msg":"ok",
    "data":{
        "id":5638,
        "newsId":""
    
 
}
}

這樣Gson在解析時就會丟擲解析錯誤的異常,app崩潰,原因是無法將”“轉化為int

json異常的處理

我們期望在後臺返回的json異常時,也能解析成功,空值對應的轉換為預設值,如:newsId=0;
這裡排除掉後臺開發人員輸出時給你做矯正,還是得靠自己啊—

我們寫一個針對int值的型別轉換器,需要實現Gson的JsonSerializer<T>介面和JsonDeserializer<T>,即序列化和反序列化介面

public class IntegerDefault0Adapter implements JsonSerializer<Integer>, JsonDeserializer<Integer> {
    @Override
    public Integer deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
            throws JsonParseException {
        try {
            if (json.getAsString().equals("") || json.getAsString().equals("null")) {//定義為int型別,如果後臺返回""或者null,則返回0
                return 0;
            }
        } catch (Exception ignore) {
        }
        try {
            return json.getAsInt();
        } catch (NumberFormatException e) {
            throw new JsonSyntaxException(e);
        }
    }

    @Override
    public JsonElement serialize(Integer src, Type typeOfSrc, JsonSerializationContext context) {
        return new JsonPrimitive(src);
    }
}

同理Long及Double型別

double=>

public class DoubleDefault0Adapter implements JsonSerializer<Double>, JsonDeserializer<Double> {
    @Override
    public Double deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {
        try {
            if (json.getAsString().equals("") || json.getAsString().equals("null")) {//定義為double型別,如果後臺返回""或者null,則返回0.00
                return 0.00;
        }
            } catch (Exception ignore) {
        }
        try {
            return json.getAsDouble();
        } catch (NumberFormatException e) {
            throw new JsonSyntaxException(e);
        }
    }

    @Override
    public JsonElement serialize(Double src, Type typeOfSrc, JsonSerializationContext context) {
        return new JsonPrimitive(src);
    }
}

long=>

public class LongDefault0Adapter implements JsonSerializer<Long>, JsonDeserializer<Long> {
    @Override
    public Long deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
        throws JsonParseException {
        try {
            if (json.getAsString().equals("") || json.getAsString().equals("null")) {//定義為long型別,如果後臺返回""或者null,則返回0
                    return 0l;
                }
            } catch (Exception ignore) {
        }
        try {
            return json.getAsLong();
        } catch (NumberFormatException e) {
            throw new JsonSyntaxException(e);
        }
    }

    @Override
    public JsonElement serialize(Long src, Type typeOfSrc, JsonSerializationContext context) {
        return new JsonPrimitive(src);
    }
}

所以使用是這樣的:

return new Retrofit.Builder()
       .client(okHttpClient)//設定網路訪問框架
       .addConverterFactory(GsonConverterFactory.create(buildGson()))//新增json轉換框架
       .addCallAdapterFactory(RxJavaCallAdapterFactory.create())//讓Retrofit支援RxJava
       .baseUrl(baseUrl)
       .build();

/**
 * 增加後臺返回""和"null"的處理
 * 1.int=>0
 * 2.double=>0.00
 * 3.long=>0L
 *
 * @return
 */
public static Gson buildGson() {
    if (gson == null) {
        gson = new GsonBuilder()
                .registerTypeAdapter(Integer.class, new IntegerDefault0Adapter())
                .registerTypeAdapter(int.class, new IntegerDefault0Adapter())
                .registerTypeAdapter(Double.class, new DoubleDefault0Adapter())
                .registerTypeAdapter(double.class, new DoubleDefault0Adapter())
                .registerTypeAdapter(Long.class, new LongDefault0Adapter())
                .registerTypeAdapter(long.class, new LongDefault0Adapter())
                .create();
    }
    return gson;
}

再也不會因為後臺json欄位為空的情況崩潰了