Retrofit自定义GsonConverter处理请求错误异常处理
通常从服务端拿到的JSON数据格式大概如下:
{
"code":1,
"message":"查询成功",
"detail":{"aa":"123","bb":"123","cc":"123"}
}因此通常我们会定义一个实体类来解析对应的json:
public class Response {
@SerializedName("code")
private int code;
@SerializedName("message")
private String message;
@SerializedName("detail")
private DetailBean detail;
//省略getter和setter方法...
public static class DetailBean {
@SerializedName("aa")
private String aa;
@SerializedName("bb")
private String bb;
@SerializedName("cc")
private String cc;
//省略getter和setter方法...
}
}其中的code字段表示状态,比如以下值可能代表了不同的含义
- code = 1, 表示成功, 不等于1代表错误
- code = -101, 表示token过期
- code = -102, 表示手机号码已经注册
- 等等等
如果我们按照正常的Retrofit+RxJava逻辑来处理,写出来的代码如下所示:
//ApiService.java
public interface ApiService {
String ENDPOINT = Constants.END_POINT;
@POST("app/api")
Observable<Response1> request1(@Body Request1 request);
@POST("app/api")
Observable<Response2> request2(@Body Request2 request);
/**
* Create a new ApiService
*/
class Factory {
private Factory() { }
public static ApiService createService( ) {
OkHttpClient.Builder builder = new OkHttpClient().newBuilder();
builder.readTimeout(10, TimeUnit.SECONDS);
builder.connectTimeout(9, TimeUnit.SECONDS);
if (BuildConfig.DEBUG) {
HttpLoggingInterceptor interceptor = new HttpLoggingInterceptor();
interceptor.setLevel(HttpLoggingInterceptor.Level.BODY);
builder.addInterceptor(interceptor);
}
builder.addInterceptor(new HeaderInterceptor());
OkHttpClient client = builder.build();
Retrofit retrofit =
new Retrofit.Builder().baseUrl(ApiService.ENDPOINT)
.client(client)
.addConverterFactory(GsonConverterFactory.create())
.addCallAdapterFactory(RxJavaCallAdapterFactory.create())
.build();
return retrofit.create(ApiService.class);
}
}
}使用的时候:
ApiService mApiService = ApiService.Factory.createService();
mApiService.request1(request)
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new Subscriber() {
@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;
}
}
}); 如果对每一个请求都这么做,那不是写死个人吗, 万一哪天这些值变了, 比如从-102 变成了 -105 , 那你不是每个地方全部都得改, 想想就可怕!
解决办法
Retrofit retrofit =
new Retrofit.Builder().baseUrl(ApiService.ENDPOINT)
.client(client)
.addConverterFactory(GsonConverterFactory.create())
.addCallAdapterFactory(RxJavaCallAdapterFactory.create())
.build();addConverterFactory(GsonConverterFactory.create()) 这句代码是为了用Gson把服务端返回的json数据解析成实体的, 那就从这里入手,可以自己定义一个GsonConverter,扩展一下原来的功能
先分析一下默认的GsonConverter怎么写的, 由三个类组成:
- GsonConverterFactory // GsonConverter 工厂类, 用来创建GsonConverter
- GsonResponseBodyConverter // 处理ResponseBody
- GsonRequestBodyConverter // 处理RequestBody
从名字就很容易看出每个类是干嘛的, GsonResponseBodyConverter这个类肯定是关键, 看一下这个类:
final class GsonResponseBodyConverter<T> implements Converter<ResponseBody, T> {
private final Gson gson;
private final TypeAdapter adapter;
GsonResponseBodyConverter(Gson gson, TypeAdapter 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();
}
}
} 你没有看错,就是这么几行代码… 这个convert()方法就是要扩展的地方了,
只需要在原来的逻辑上面添加上处理code ! = 1 的情况, 如果code ! = 1,就抛出异常,
先直接上代码:
//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 responseBodyConverter(Type type, Annotation[] annotations,Retrofit retrofit) {
TypeAdapter adapter = gson.getAdapter(TypeToken.get(type));
return new CustomGsonResponseBodyConverter<>(gson, adapter);
}
@Override
public Converter 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 adapter;
CustomGsonRequestBodyConverter(Gson gson, TypeAdapter 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 adapter;
CustomGsonResponseBodyConverter(Gson gson, TypeAdapter 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();
}
}
} 他两个类和默认的一样的, 只看第三个类CustomGsonResponseBodyConverter
这里自定义了两个类,一个是HttpStatus和ApiException,下面是这两个类:
//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是否请求失败
*
* @return 失败返回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;
}
/**
* 判断是否是token失效
*
* @return 失效返回true, 否则返回false;
*/
public boolean isTokenExpried() {
return mErrorCode == Constants.TOKEN_EXPRIED;
}
}很通俗易懂, 解释一下其中关键的几行代码
String response = value.string(); //把responsebody转为string
// 这里只是为了检测code是否==1,所以只解析HttpStatus中的字段,因为只要code和message就可以了
HttpStatus httpStatus = gson.fromJson(response, HttpStatus.class);
if (httpStatus.isCodeInvalid()) {
value.close();
//抛出一个RuntimeException, 这里抛出的异常会到Subscriber的onError()方法中统一处理
throw new ApiException(httpStatus.getCode(), httpStatus.getMessage());
}这里有个关于ResponseBody的坑, 如果有人遇到过这个异常的肯定就知道
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)因为你只能对ResponseBody读取一次 , 如果你调用了response.body().string()两次或者response.body().charStream()两次就会出现这个异常, 先调用string()再调用charStream()也不可以.
所以通常的做法是读取一次之后就保存起来,下次就不从ResponseBody里读取.
使用方法
先建立一个BaseSubscriber
//BaseSubscriber.java
public class BaseSubscriber extends Subscriber {
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()) {
//处理token失效对应的逻辑
} else {
Toast.makeText(mContext, e.getMessage(), Toast.LENGTH_SHORT).show();
}
}
}
@Override
public void onNext(T t) {
}
} 请求接口
ApiService mApiService = ApiService.Factory.createService();
mApiService.request1(request)
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new BaseSubscriber() {
@Override
public void onCompleted() {
super.onCompleted();
}
@Override
public void onError(Throwable e) {
super.onError(e); //这里就全部交给基类来处理了
}
@Override
public void onNext(Response1 response) {
super.onNext(response);
}
}); 来自简书：http://www.jianshu.com/p/5b8b1062866b