Retrofit自定義GsonConverter處理請求錯誤異常處理
阿新 • • 發佈：2018-12-31
通常從服務端拿到的JSON資料格式大概如下:
{
"code":1,
"message":"查詢成功",
"detail":{"aa":"123","bb":"123","cc":"123"}
}因此通常我們會定義一個實體類來解析對應的json:
public class Response {
@SerializedName("code")
private int code;
@SerializedName("message")
private String message;
@SerializedName("detail" 其中的code欄位表示狀態,比如以下值可能代表了不同的含義
- code = 1, 表示成功, 不等於1代表錯誤
- code = -101, 表示token過期
- code = -102, 表示手機號碼已經註冊
- 等等等
如果我們按照正常的Retrofit+RxJava邏輯來處理,寫出來的程式碼如下所示:
//ApiService.java
public interface ApiService {
String ENDPOINT = Constants.END_POINT;
@POST("app/api")
Observable<Response1> request1(@Body 使用的時候:
ApiService mApiService = ApiService.Factory.createService();
mApiService.request1(request)
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new Subscriber<Response1>() {
@Override
public void onCompleted() {
}
@Override
public void onError(Throwable e) {
}
@Override
public void onNext(Response1 response) {
int code = response.getCode();
switch (code) {
case 1: //do something
break;
case -101://do something
break;
case -102: //do something
break;
default:
break;
}
}
});如果對每一個請求都這麼做,那不是寫死個人嗎, 萬一哪天這些值變了, 比如從-102 變成了 -105 , 那你不是每個地方全部都得改, 想想就可怕!
解決辦法
Retrofit retrofit =
new Retrofit.Builder().baseUrl(ApiService.ENDPOINT)
.client(client)
.addConverterFactory(GsonConverterFactory.create())
.addCallAdapterFactory(RxJavaCallAdapterFactory.create())
.build();addConverterFactory(GsonConverterFactory.create()) 這句程式碼是為了用Gson把服務端返回的json資料解析成實體的, 那就從這裡入手,可以自己定義一個GsonConverter,擴充套件一下原來的功能
先分析一下預設的GsonConverter怎麼寫的, 由三個類組成:
- GsonConverterFactory // GsonConverter 工廠類, 用來建立GsonConverter
- GsonResponseBodyConverter // 處理ResponseBody
- GsonRequestBodyConverter // 處理RequestBody
從名字就很容易看出每個類是幹嘛的, GsonResponseBodyConverter這個類肯定是關鍵, 看一下這個類:
final class GsonResponseBodyConverter<T> implements Converter<ResponseBody, T> {
private final Gson gson;
private final TypeAdapter<T> adapter;
GsonResponseBodyConverter(Gson gson, TypeAdapter<T> adapter) {
this.gson = gson;
this.adapter = adapter;
}
@Override public T convert(ResponseBody value) throws IOException {
JsonReader jsonReader = gson.newJsonReader(value.charStream());
try {
return adapter.read(jsonReader);
} finally {
value.close();
}
}
}你沒有看錯,就是這麼幾行程式碼… 這個convert()方法就是要擴充套件的地方了,
只需要在原來的邏輯上面新增上處理code ! = 1 的情況, 如果code ! = 1,就丟擲異常,
先直接上程式碼:
//CustomGsonConverterFactory.java
public class CustomGsonConverterFactory extends Converter.Factory {
private final Gson gson;
private CustomGsonConverterFactory(Gson gson) {
if (gson == null) throw new NullPointerException("gson == null");
this.gson = gson;
}
public static CustomGsonConverterFactory create() {
return create(new Gson());
}
public static CustomGsonConverterFactory create(Gson gson) {
return new CustomGsonConverterFactory(gson);
}
@Override
public Converter<ResponseBody, ?> responseBodyConverter(Type type, Annotation[] annotations,Retrofit retrofit) {
TypeAdapter<?> adapter = gson.getAdapter(TypeToken.get(type));
return new CustomGsonResponseBodyConverter<>(gson, adapter);
}
@Override
public Converter<?, RequestBody> requestBodyConverter(Type type,Annotation[] parameterAnnotations, Annotation[] methodAnnotations, Retrofit retrofit) {
TypeAdapter<?> adapter = gson.getAdapter(TypeToken.get(type));
return new CustomGsonRequestBodyConverter<>(gson, adapter);
}
}//CustomGsonRequestBodyConverter.java
final class CustomGsonRequestBodyConverter<T> implements Converter<T, RequestBody> {
private static final MediaType MEDIA_TYPE = MediaType.parse("application/json; charset=UTF-8");
private static final Charset UTF_8 = Charset.forName("UTF-8");
private final Gson gson;
private final TypeAdapter<T> adapter;
CustomGsonRequestBodyConverter(Gson gson, TypeAdapter<T> adapter) {
this.gson = gson;
this.adapter = adapter;
}
@Override
public RequestBody convert(T value) throws IOException {
Buffer buffer = new Buffer();
Writer writer = new OutputStreamWriter(buffer.outputStream(), UTF_8);
JsonWriter jsonWriter = gson.newJsonWriter(writer);
adapter.write(jsonWriter, value);
jsonWriter.close();
return RequestBody.create(MEDIA_TYPE, buffer.readByteString());
}
}//CustomGsonResponseBodyConverter.java
final class CustomGsonResponseBodyConverter<T> implements Converter<ResponseBody, T> {
private final Gson gson;
private final TypeAdapter<T> adapter;
CustomGsonResponseBodyConverter(Gson gson, TypeAdapter<T> adapter) {
this.gson = gson;
this.adapter = adapter;
}
@Override
public T convert(ResponseBody value) throws IOException {
String response = value.string();
HttpStatus httpStatus = gson.fromJson(response, HttpStatus.class);
if (httpStatus.isCodeInvalid()) {
value.close();
throw new ApiException(httpStatus.getCode(), httpStatus.getMessage());
}
MediaType contentType = value.contentType();
Charset charset = contentType != null ? contentType.charset(UTF_8) : UTF_8;
InputStream inputStream = new ByteArrayInputStream(response.getBytes());
Reader reader = new InputStreamReader(inputStream, charset);
JsonReader jsonReader = gson.newJsonReader(reader);
try {
return adapter.read(jsonReader);
} finally {
value.close();
}
}
}他兩個類和預設的一樣的, 只看第三個類CustomGsonResponseBodyConverter
這裡自定義了兩個類,一個是HttpStatus和ApiException,下面是這兩個類:
//HttpStatus.java
public class HttpStatus {
@SerializedName("code")
private int mCode;
@SerializedName("message")
private String mMessage;
public int getCode() {
return mCode;
}
public String getMessage() {
return mMessage;
}
/**
* API是否請求失敗
*
* @return 失敗返回true, 成功返回false
*/
public boolean isCodeInvalid() {
return mCode != Constants.WEB_RESP_CODE_SUCCESS;
}
}//ApiException.java
public class ApiException extends RuntimeException {
private int mErrorCode;
public ApiException(int errorCode, String errorMessage) {
super(errorMessage);
mErrorCode = errorCode;
}
/**
* 判斷是否是token失效
*
* @return 失效返回true, 否則返回false;
*/
public boolean isTokenExpried() {
return mErrorCode == Constants.TOKEN_EXPRIED;
}
}很通俗易懂, 解釋一下其中關鍵的幾行程式碼
String response = value.string(); //把responsebody轉為string
// 這裡只是為了檢測code是否==1,所以只解析HttpStatus中的欄位,因為只要code和message就可以了
HttpStatus httpStatus = gson.fromJson(response, HttpStatus.class);
if (httpStatus.isCodeInvalid()) {
value.close();
//丟擲一個RuntimeException, 這裡丟擲的異常會到Subscriber的onError()方法中統一處理
throw new ApiException(httpStatus.getCode(), httpStatus.getMessage());
}這裡有個關於ResponseBody的坑, 如果有人遇到過這個異常的肯定就知道
java.lang.IllegalStateException: closed
at com.squareup.okhttp.internal.http.HttpConnection$FixedLengthSource.read(HttpConnection.java:455)
at okio.Buffer.writeAll(Buffer.java:594)
at okio.RealBufferedSource.readByteArray(RealBufferedSource.java:87)
at com.squareup.okhttp.ResponseBody.bytes(ResponseBody.java:56)
at com.squareup.okhttp.ResponseBody.string(ResponseBody.java:82)因為你只能對ResponseBody讀取一次 , 如果你呼叫了response.body().string()兩次或者response.body().charStream()兩次就會出現這個異常, 先呼叫string()再呼叫charStream()也不可以.
所以通常的做法是讀取一次之後就儲存起來,下次就不從ResponseBody裡讀取.
使用方法
先建立一個BaseSubscriber
//BaseSubscriber.java
public class BaseSubscriber<T> extends Subscriber<T> {
protected Context mContext;
public BaseSubscriber(Context context) {
this.mContext = context;
}
@Override
public void onCompleted() {
}
@Override
public void onError(final Throwable e) {
Log.w("Subscriber onError", e);
if (e instanceof HttpException) {
// We had non-2XX http error
Toast.makeText(mContext, mContext.getString(R.string.server_internal_error), Toast.LENGTH_SHORT).show();
} else if (e instanceof IOException) {
// A network or conversion error happened
Toast.makeText(mContext, mContext.getString(R.string.cannot_connected_server), Toast.LENGTH_SHORT).show();
} else if (e instanceof ApiException) {
ApiException exception = (ApiException) e;
if (exception.isTokenExpried()) {
//處理token失效對應的邏輯
} else {
Toast.makeText(mContext, e.getMessage(), Toast.LENGTH_SHORT).show();
}
}
}
@Override
public void onNext(T t) {
}
}請求介面
ApiService mApiService = ApiService.Factory.createService();
mApiService.request1(request)
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new BaseSubscriber<Response1>() {
@Override
public void onCompleted() {
super.onCompleted();
}
@Override
public void onError(Throwable e) {
super.onError(e); //這裡就全部交給基類來處理了
}
@Override
public void onNext(Response1 response) {
super.onNext(response);
}
});