Open Feign form encoder
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Artem Labazin Artem Labazin
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README.md

Form Encoder

build_status maven_central

This module adds support for encoding application/x-www-form-urlencoded and multipart/form-data forms.

Add dependency

Include the dependency to your project's pom.xml file:

<dependencies>
    ...
    <dependency>
        <groupId>io.github.openfeign.form</groupId>
        <artifactId>feign-form</artifactId>
        <version>3.4.0</version>
    </dependency>
    ...
</dependencies>

Usage

Add FormEncoder to your Feign.Builder like so:

SomeApi github = Feign.builder()
                     .encoder(new FormEncoder())
                     .target(SomeApi.class, "http://api.some.org");

Moreover, you can decorate the existing encoder, for example JsonEncoder like this:

SomeApi github = Feign.builder()
                     .encoder(new FormEncoder(new JacksonEncoder()))
                     .target(SomeApi.class, "http://api.some.org");

And use them together:

interface SomeApi {

    @RequestLine("POST /json")
    @Headers("Content-Type: application/json")
    void json (Dto dto);

    @RequestLine("POST /form")
    @Headers("Content-Type: application/x-www-form-urlencoded")
    void from (@Param("field1") String field1, @Param("field2") String field2);

}

You can specify two types of encoding forms by Content-Type header.

application/x-www-form-urlencoded

interface SomeApi {

    ...

    @RequestLine("POST /authorization")
    @Headers("Content-Type: application/x-www-form-urlencoded")
    void authorization (@Param("email") String email, @Param("password") String password);

    ...

}

multipart/form-data

interface SomeApi {

    ...

    // File parameter
    @RequestLine("POST /send_photo")
    @Headers("Content-Type: multipart/form-data")
    void sendPhoto (@Param("is_public") Boolean isPublic, @Param("photo") File photo);

    // byte[] parameter
    @RequestLine("POST /send_photo")
    @Headers("Content-Type: multipart/form-data")
    void sendPhoto (@Param("is_public") Boolean isPublic, @Param("photo") byte[] photo);

    // FormData parameter
    @RequestLine("POST /send_photo")
    @Headers("Content-Type: multipart/form-data")
    void sendPhoto (@Param("is_public") Boolean isPublic, @Param("photo") FormData photo);
    ...

}

In the example above, the sendPhoto method uses the photo parameter using three different supported types.

  • File will use the File's extension to detect the Content-Type.
  • byte[] will use application/octet-stream as Content-Type.
  • FormData will use the FormData's Content-Type and fileName.

FormData is custom object that wraps a byte[] and defines a Content-Type and fileName like this:

    FormData formData = new FormData("image/png", "filename.png", myDataAsByteArray);
    someApi.sendPhoto(true, formData);

Spring MultipartFile and Spring Cloud Netflix @FeignClient support

You can also use Form Encoder with Spring MultipartFile and @FeignClient.

Include the dependencies to your project's pom.xml file:

<dependencies>
    ...
    <dependency>
        <groupId>io.github.openfeign.form</groupId>
        <artifactId>feign-form</artifactId>
        <version>3.4.0</version>
    </dependency>
    <dependency>
        <groupId>io.github.openfeign.form</groupId>
        <artifactId>feign-form-spring</artifactId>
        <version>3.4.0</version>
    </dependency>
    ...
</dependencies>
@FeignClient(name = "file-upload-service", configuration = FileUploadServiceClient.MultipartSupportConfig.class)
public interface FileUploadServiceClient extends IFileUploadServiceClient {

    public class MultipartSupportConfig {

        @Autowired
        private ObjectFactory<HttpMessageConverters> messageConverters;

        @Bean
        public Encoder feignFormEncoder() {
            return new SpringFormEncoder(new SpringEncoder(messageConverters));
        }
    }
}

Or, if you don't need Spring's standard encoder:

@FeignClient(name = "file-upload-service", configuration = FileUploadServiceClient.MultipartSupportConfig.class)
public interface FileUploadServiceClient extends IFileUploadServiceClient {

    public class MultipartSupportConfig {

        @Bean
        public Encoder feignFormEncoder() {
            return new SpringFormEncoder();
        }
    }
}

Thanks to tf-haotri-pham for his featur, which makes use of Apache commons-fileupload library, which handles the parsing of the multipart response. The body data parts are held as byte arrays in memory.

To use this feature, include SpringManyMultipartFilesReader in the list of message converters for the Decoder and have the Feign client return an array of MultipartFile:

@FeignClient(
        name = "${feign.name}",
        url = "${feign.url}"
        configuration = DownloadClient.ClientConfiguration.class)
public interface DownloadClient {

    @RequestMapping(
            value = "/multipart/download/{fileId}",
            method = GET)
    MultipartFile[] download(@PathVariable("fileId") String fileId);

    class ClientConfiguration {

        @Autowired
        private ObjectFactory<HttpMessageConverters> messageConverters;

        @Bean
        public Decoder feignDecoder () {
            final List<HttpMessageConverter<?>> springConverters = messageConverters.getObject().getConverters();
            final List<HttpMessageConverter<?>> decoderConverters
                    = new ArrayList<HttpMessageConverter<?>>(springConverters.size() + 1);

            decoderConverters.addAll(springConverters);
            decoderConverters.add(new SpringManyMultipartFilesReader(4096));
            final HttpMessageConverters httpMessageConverters = new HttpMessageConverters(decoderConverters);

            return new SpringDecoder(new ObjectFactory<HttpMessageConverters>() {
                @Override
                public HttpMessageConverters getObject() {
                    return httpMessageConverters;
                }
            });
        }
    }
}