Reactive Spring WebClient - Making a SOAP call

Question

I am looking to make a SOAP call from spring reactive webclient. I couldn't find any documentation for it. Wondering what would the approach. Right now I am thinking

1. Construct the SOAP message using JAXB on a separate thread pool
2. Make the call by converting it to string via webclient
3. Do convert back into java using jaxb on the way back on separate tp.

What are the downsides and any other approaches?

Answer 1

You need to generate SOAP client as the stub classes with methods for asynchronous. JAX-WS API supports asynchronous invocation. Use wsiimport with enableAsyncMapping for generating method operationAsync(Input request, AsyncHandler asyncHandler);

AsyncHandler create using Mono.create()

Service service = new Service();
ServicePortType portType = service.getPortType();

public Mono<Output> operation(Input input) {
            return Mono.create(sink ->
               portType.operation(input, outputFuture -> {
                   try {
                       sink.success(outputFuture.get());
                   } catch (Exception e) {
                       sink.error(e);
                   }
               })
            );
        }

and you get Mono reactivly

I have found suggest in the post https://blog.godatadriven.com/jaxws-reactive-client

Answer 2

Here is a working example with Spring Reactor: https://github.com/gungor/spring-webclient-soap

You need to enclose your generated JAXB classes in a soap envelope with a custom encoder as below then add it to WebClient's exchange strategies.

package webclient.soap.encoding;

import org.reactivestreams.Publisher;
import org.springframework.core.ResolvableType;
import org.springframework.core.codec.CodecException;
import org.springframework.core.codec.Encoder;
import org.springframework.core.codec.EncodingException;
import org.springframework.core.io.buffer.DataBuffer;
import org.springframework.core.io.buffer.DataBufferFactory;
import org.springframework.core.io.buffer.DataBufferUtils;
import org.springframework.core.io.buffer.PooledDataBuffer;
import org.springframework.util.ClassUtils;
import org.springframework.util.MimeType;
import org.springframework.util.MimeTypeUtils;
import org.springframework.ws.WebServiceMessage;
import org.springframework.ws.WebServiceMessageFactory;
import org.springframework.ws.client.core.WebServiceTemplate;
import org.springframework.ws.support.DefaultStrategiesHelper;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.MarshalException;
import javax.xml.bind.Marshaller;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlType;
import java.io.OutputStream;
import java.nio.charset.StandardCharsets;
import java.util.Arrays;
import java.util.List;
import java.util.Map;

public class Jaxb2SoapEncoder implements Encoder<Object> {

    private final JaxbContextContainer jaxbContexts = new JaxbContextContainer();

    @Override
    public boolean canEncode(ResolvableType elementType, MimeType mimeType) {
        Class<?> outputClass = elementType.toClass();
        return (outputClass.isAnnotationPresent(XmlRootElement.class) ||
                    outputClass.isAnnotationPresent(XmlType.class));

    }

    @Override
    public Flux<DataBuffer> encode(Publisher<?> inputStream, DataBufferFactory bufferFactory, ResolvableType elementType, MimeType mimeType, Map<String, Object> hints) {
        return Flux.from(inputStream)
                .take(1)
                .concatMap(value -> encode(value, bufferFactory, elementType, mimeType, hints))
                .doOnDiscard(PooledDataBuffer.class, PooledDataBuffer::release);
    }

    @Override
    public List<MimeType> getEncodableMimeTypes() {
        return Arrays.asList( MimeTypeUtils.TEXT_XML );
    }



    private Flux<DataBuffer> encode(Object value ,
                                    DataBufferFactory bufferFactory,
                                    ResolvableType type,
                                    MimeType mimeType,
                                    Map<String, Object> hints){

        return Mono.fromCallable(() -> {
            boolean release = true;
            DataBuffer buffer = bufferFactory.allocateBuffer(1024);
            try {
                OutputStream outputStream = buffer.asOutputStream();
                Class<?> clazz = ClassUtils.getUserClass(value);
                Marshaller marshaller = initMarshaller(clazz);

                // here should be optimized
                DefaultStrategiesHelper helper = new DefaultStrategiesHelper(WebServiceTemplate.class);
                WebServiceMessageFactory messageFactory = helper.getDefaultStrategy(WebServiceMessageFactory.class);
                WebServiceMessage message = messageFactory.createWebServiceMessage();

                marshaller.marshal(value, message.getPayloadResult());
                message.writeTo(outputStream);

                release = false;
                return buffer;
            }
            catch (MarshalException ex) {
                throw new EncodingException(
                        "Could not marshal " + value.getClass() + " to XML", ex);
            }
            catch (JAXBException ex) {
                throw new CodecException("Invalid JAXB configuration", ex);
            }
            finally {
                if (release) {
                    DataBufferUtils.release(buffer);
                }
            }
        }).flux();
    }


    private Marshaller initMarshaller(Class<?> clazz) throws JAXBException {
        Marshaller marshaller = this.jaxbContexts.createMarshaller(clazz);
        marshaller.setProperty(Marshaller.JAXB_ENCODING, StandardCharsets.UTF_8.name());
        return marshaller;
    }
}

WebClient config

@Bean
    public WebClient webClient(){
        TcpClient tcpClient = TcpClient.create();

        tcpClient
                .option(ChannelOption.CONNECT_TIMEOUT_MILLIS, 5000)
                .doOnConnected(connection -> {
                    connection.addHandlerLast(new ReadTimeoutHandler(5000, TimeUnit.MILLISECONDS));
                    connection.addHandlerLast(new WriteTimeoutHandler(5000, TimeUnit.MILLISECONDS));
                });

        ExchangeStrategies exchangeStrategies = ExchangeStrategies.builder().codecs( clientCodecConfigurer -> {
            clientCodecConfigurer.customCodecs().encoder(new Jaxb2SoapEncoder());
        }).build();

        WebClient webClient = WebClient.builder()
                .clientConnector(new ReactorClientHttpConnector(HttpClient.from(tcpClient).wiretap(true)))
                .exchangeStrategies( exchangeStrategies )
                .build();

        return webClient;
    }

WebClient

public void call(GetCountryRequest getCountryRequest) throws SOAPException, ParserConfigurationException, IOException {

        webClient.post()
                .uri( soapServiceUrl )
                .contentType(MediaType.TEXT_XML)
                .body( Mono.just(getCountryRequest) , GetCountryRequest.class  )
                .retrieve()
                .onStatus(
                        HttpStatus::isError,
                        clientResponse ->
                                clientResponse
                                        .bodyToMono(String.class)
                                        .flatMap(
                                                errorResponseBody ->
                                                        Mono.error(
                                                                new ResponseStatusException(
                                                                        clientResponse.statusCode(),
                                                                        errorResponseBody))))

                .bodyToMono(GetCountryResponse.class)
                .doOnSuccess( (GetCountryResponse response) -> {
                    //handle success
                })
                .doOnError(ResponseStatusException.class, error -> {
                    //handle error
                })
                .subscribe();

    }