改造 2 自定義 Xml 轉換器

將依賴項新增到 build.gradle 檔案中。

dependencies {
    ....
    compile 'com.squareup.retrofit2:retrofit:2.1.0'
    compile ('com.thoughtworks.xstream:xstream:1.4.7') {
        exclude group: 'xmlpull', module: 'xmlpull'
    }
    ....
}

然後建立 Converter Factory

public class XStreamXmlConverterFactory extends Converter.Factory {

    /** Create an instance using a default {@link com.thoughtworks.xstream.XStream} instance for conversion. */
    public static XStreamXmlConverterFactory create() {
        return create(new XStream());
    }

    /** Create an instance using {@code xStream} for conversion. */
    public static XStreamXmlConverterFactory create(XStream xStream) {
        return new XStreamXmlConverterFactory(xStream);
    }

    private final XStream xStream;

    private XStreamXmlConverterFactory(XStream xStream) {
        if (xStream == null) throw new NullPointerException("xStream == null");
        this.xStream = xStream;
    }

    @Override
    public Converter<ResponseBody, ?> responseBodyConverter(Type type, Annotation[] annotations, Retrofit retrofit) {

        if (!(type instanceof Class)) {
            return null;
        }

        Class<?> cls = (Class<?>) type;

        return new XStreamXmlResponseBodyConverter<>(cls, xStream);
    }

    @Override
    public Converter<?, RequestBody> requestBodyConverter(Type type,
          Annotation[] parameterAnnotations, Annotation[] methodAnnotations, Retrofit retrofit) {

        if (!(type instanceof Class)) {
            return null;
        }

        return new XStreamXmlRequestBodyConverter<>(xStream);
    }
}

建立一個類來處理 body 請求。

final class XStreamXmlResponseBodyConverter <T> implements Converter<ResponseBody, T> {

    private final Class<T> cls;
    private final XStream xStream;

    XStreamXmlResponseBodyConverter(Class<T> cls, XStream xStream) {
        this.cls = cls;
        this.xStream = xStream;
    }

    @Override
    public T convert(ResponseBody value) throws IOException {

        try {

            this.xStream.processAnnotations(cls);
            Object object =  this.xStream.fromXML(value.byteStream());
            return (T) object;

        }finally {
            value.close();
        }
    }
}

建立一個類來處理身體反應。

final class XStreamXmlRequestBodyConverter<T> implements Converter<T, RequestBody> {

    private static final MediaType MEDIA_TYPE = MediaType.parse("application/xml; charset=UTF-8");
    private static final String CHARSET = "UTF-8";

    private final XStream xStream;

    XStreamXmlRequestBodyConverter(XStream xStream) {
        this.xStream = xStream;
    }

    @Override
    public RequestBody convert(T value) throws IOException {

        Buffer buffer = new Buffer();

        try {
            OutputStreamWriter osw = new OutputStreamWriter(buffer.outputStream(), CHARSET);
            xStream.toXML(value, osw);
            osw.flush();
        } catch (Exception e) {
            throw new RuntimeException(e);
        }

        return RequestBody.create(MEDIA_TYPE, buffer.readByteString());
    }
}

所以，這一點我們可以傳送和接收任何 XML，我們只需要為實體建立 XStream Annotations。

然後建立一個 Retrofit 例項：

XStream xs = new XStream(new DomDriver());
xs.autodetectAnnotations(true);

Retrofit retrofit = new Retrofit.Builder()
    .baseUrl("http://example.com/")
    .addConverterFactory(XStreamXmlConverterFactory.create(xs))
    .client(client)
    .build();