How to transform byte array to a MultipartFile resource in Java?

Let's assume you have a backend api and it accept MultipartFile as the request body. How can the client send a MultipartFile object in its body if client only has the bytes rather than a Resource? implement MultipartFile interface A representation of an uploaded file received in a multipart request. The file contents are either stored in memory or temporarily on disk. In either case, the user is responsible for copying file contents to a session-level or persistent store as and if desired. T

Post, Code and Quiet Time. How to transform byte array to a MultipartFile resource in Java? By Errong Leng – 25 Feb 2023 – View online → Photo by Andrey Metelev / Unsplash Let's assume you have a backend api and it accept MultipartFile as the request body. How can the client send a MultipartFile object in its body if client only has the bytes rather than a Resource? implement MultipartFile interface A representation of an uploaded file received in a multipart request. The file contents are either stored in memory or temporarily on disk. In either case, the user is responsible for copying file contents to a session-level or persistent store as and if desired. The temporary storage will be cleared at the end of request processing. The below sample code implement a PDF MultipartFile. public class PdfMultipartFile implements MultipartFile { private byte[] input; private String name; public PdfMultipartFile(byte[] input, String name) { this.input = input; this.name = name; } @Override public String getName() { return name; } @Override public String getOriginalFilename() { return name + ".pdf"; } @Override public String getContentType() { return MediaType.APPLICATION_PDF_VALUE; } @Override public boolean isEmpty() { return input == null || input.length == 0; } @Override public long getSize() { return input.length; } @Override public byte[] getBytes() throws IOException { return input; } @Override public InputStream getInputStream() throws IOException { return new ByteArrayInputStream(input); } @Override public void transferTo(File destination) throws IOException, IllegalStateException { try(FileOutputStream fos = new FileOutputStream(destination)) { fos.write(input); } } } MultipartFile.#transferTo(java.io.File) Transfer the received file to the given destination file. This may either move the file in the filesystem, copy the file in the filesystem, or save memory-held contents to the destination file. If the destination file already exists, it will be deleted first. If the target file has been moved in the filesystem, this operation cannot be invoked again afterwards. Therefore, call this method just once in order to work with any storage mechanism. NOTE: Depending on the underlying provider, temporary storage may be container-dependent, including the base directory for relative destinations specified here (e.g. with Servlet multipart handling). For absolute destinations, the target file may get renamed/moved from its temporary location or newly copied, even if a temporary copy already exists. The good part with MultipartFile is you can verify the bytes your received or send out is the exactly file you want to transmit by transfer the bytes to a MultipartFile instance. with the help of MultipartFile::transferTo method, you can save the bytes into a file. Post, Code and Quiet Time. © 2023 – Unsubscribe

How to parse Multiparts response body from client side in Spring Boot?

Default HttpMessageReader for parsing "multipart/form-data" requests to a stream of Parts. In default, non-streaming mode, this message reader stores the contents of parts smaller than maxInMemorySize in memory, and parts larger than that to a temporary file in fileStorageDirectory. This reader can be provided to MultipartHttpMessageReader in order to aggregate all parts into a Map. use toEntityFlux and DefaultPartHttpMessageReader for Reactive stack Variant of toEntityFlux(Class) with a Bo

Post, Code and Quiet Time. How to parse Multiparts response body from client side in Spring Boot? By Errong Leng – 25 Feb 2023 – View online → Photo by Edgar Chaparro / Unsplash Default HttpMessageReader for parsing "multipart/form-data" requests to a stream of Parts. In default, non-streaming mode, this message reader stores the contents of parts smaller than maxInMemorySize in memory, and parts larger than that to a temporary file in fileStorageDirectory. This reader can be provided to MultipartHttpMessageReader in order to aggregate all parts into a Map. use toEntityFlux and DefaultPartHttpMessageReader for Reactive stack Variant of toEntityFlux(Class) with a BodyExtractor. Params: bodyExtractor – the BodyExtractor that reads from the response Type parameters: – the body element type Returns: the ResponseEntity Since: 5.3.2 webclient.get() .uri(...uri) .headers(...headers) .retrieve() .toEntityFlux((inputMessage, context) -> partReader.read(ResolvableType.forType(byte[].class), inputMessage, Map.of())) .map(ResponseEntity::getBody) .flatMap(parts -> parts.reduce(MixedResponse.builder(), (body, part) -> { if (part.headers().getContentType().equals(MediaType.APPLICATION_JSON)) { val json = DataBufferUtils.join(part.content()) .map(buffer -> { byte[] bytes = new byte[buffer.readableByteCount()]; buffer.read(bytes); DataBufferUtils.release(buffer); return jsonValueSerializer.deserializeValue(new String(bytes), JSON.class); }); body.json(json); } if (part.headers().getContentType().equals(MediaType.APPLICATION_PDF)) { var pdf = DataBufferUtils.join(part.content()) .map(buffer -> buffer.asByteBuffer().array()); body.pdf(pdf); } return body; }) .map(body -> body.build())); NOTE that the body contents must be completely consumed, relayed, or released to avoid memory leaks. custom HttpMessageConverter for the RestTemplate You might have to custom your own HttpMessageConverter and add into the RestTemplate message converters. RestTemplate restTemplate = new RestTemplate(); restTemplate.getMessageConverters().add(new MultiPartMessageConverter(objectMapper)); final ResponseEntity<ResultModel> responseEntity = restTemplate.getForEntity("http://localhost:" + randomServerPort + "/test", ResultModel.class); final ResultModel resultModel = responseEntity.getBody(); Assertions.assertNotNull(resultModel); Assertions.assertEquals(2, resultModel.secondModel.size()); Assertions.assertEquals("Param1.Value", resultModel.firstModel.param1); Assertions.assertEquals("Param2.Value", resultModel.firstModel.param2); References HttpMessageConverter (Spring Framework 6.0.5 API) declaration: package: org.springframework.http.converter, interface: HttpMessageConverter https://stackoverflow.com/questions/65762857/resttemplate-multipart-form-data-response Post, Code and Quiet Time. © 2023 – Unsubscribe

How to Prepare a multipart body of a response in Sprint Boot

use PartEvent for Reactive Stack To stream multipart data sequentially, you can provide multipart content through PartEvent objects. Form fields can be created via FormPartEvent::create. File uploads can be created via FilePartEvent::create. You can concatenate the streams returned from methods via Flux::concat, and create a request for the WebClient. For instance, this sample will POST a multipart form containing a form field and a file. return Flux.concat( FormPartEvent.creat

Post, Code and Quiet Time. How to Prepare a multipart body of a response in Sprint Boot By Errong Leng – 25 Feb 2023 – View online → use PartEvent for Reactive Stack To stream multipart data sequentially, you can provide multipart content through PartEvent objects. Form fields can be created via FormPartEvent::create. File uploads can be created via FilePartEvent::create. You can concatenate the streams returned from methods via Flux::concat, and create a request for the WebClient. For instance, this sample will POST a multipart form containing a form field and a file. return Flux.concat( FormPartEvent.create("field", "field value"), FilePartEvent.create("file", resource) ); PS: FormPartEvent are only available since Spring-Web version 6.0. use MultiValueMap<String, HttpEntity> for Serverlet Stack MultiValueMap<String, HttpEntity<?>> mixParts = new LinkedMultiValueMap<>(); HttpHeaders jsonHeaders = new HttpHeaders(); jsonHeaders.setContentType(MediaType.APPLICATION_JSON); try { mixParts.add("metadata", new HttpEntity<>(objectMapper.writeValueAsString(response), jsonHeaders)); } catch (JsonProcessingException e) { log.error("Oops!", e); } HttpHeaders pdfHeaders = new HttpHeaders(); pdfHeaders.setContentType(MediaType.APPLICATION_PDF); mixParts.add("pdf", new HttpEntity<>(new ClassPathResource("contract_unsigned.pdf"), pdfHeaders)); return new ResponseEntity<>(mixParts, HttpStatus.OK); References PartEvent (Spring Framework 6.0.5 API) declaration: package: org.springframework.http.codec.multipart, interface: PartEvent Post, Code and Quiet Time. © 2023 – Unsubscribe

How to Prepare the body of a multipart request in Sprint Boot

Prepare the body of a multipart request, resulting in a MultiValueMap<String, HttpEntity>. Parts may be concrete values or via asynchronous types such as Reactor Mono, Flux, and others registered in the ReactiveAdapterRegistry. This builder is intended for use with the reactive WebClient. For multipart requests with the RestTemplate, simply create and populate a MultiValueMap<String, HttpEntity> as shown in the Javadoc for FormHttpMessageConverter and in the reference docs. use MultipartBodyB

Post, Code and Quiet Time. How to Prepare the body of a multipart request in Sprint Boot By Errong Leng – 25 Feb 2023 – View online → Photo by Koen Speelman / Unsplash Prepare the body of a multipart request, resulting in a MultiValueMap<String, HttpEntity>. Parts may be concrete values or via asynchronous types such as Reactor Mono, Flux, and others registered in the ReactiveAdapterRegistry. This builder is intended for use with the reactive WebClient. For multipart requests with the RestTemplate, simply create and populate a MultiValueMap<String, HttpEntity> as shown in the Javadoc for FormHttpMessageConverter and in the reference docs. use MultipartBodyBuilder for WebClient assume you need to post a pdf file and submit some extra information in json together in a single request, you can create the multi part body like below: webclient.post() .uri(...) .headers(...) .accept(MediaType.APPLICATION_JSON) .bodyValue(createMultiPartBody()) .retrieve().bodyToMono(SendSignedAgreementResponse.class); } private MultiValueMap<String, HttpEntity<?>> createMultiPartRelatedBody() { MultipartBodyBuilder builder = new MultipartBodyBuilder(); builder.part("json", json, MediaType.APPLICATION_JSON); builder.part("pdf", new MultipartFile().getResource(), MediaType.APPLICATION_PDF); return builder.build(); } PS: remember set right content type header, or you might got 415 unsupported media type response error. .header(HttpHeaders.CONTENT_TYPE, MediaType.MULTIPART_MIXED_VALUE) .header(HttpHeaders.CONTENT_TYPE, MediaType.MULTIPART_FORM_VALUE) .header(HttpHeaders.CONTENT_TYPE, MediaType.MULTIPART_RELATED_VALUE) the above code is equal to below POST raw log use MultiValueMap<String, HttpEntity> for the RestTemplate MultiValueMap<String, HttpEntity<?>> mixParts = new LinkedMultiValueMap<>(); HttpHeaders jsonHeaders = new HttpHeaders(); jsonHeaders.setContentType(MediaType.APPLICATION_JSON); try { mixParts.add("metadata", new HttpEntity<>(objectMapper.writeValueAsString(response), jsonHeaders)); } catch (JsonProcessingException e) { log.error("Oops!", e); } HttpHeaders pdfHeaders = new HttpHeaders(); pdfHeaders.setContentType(MediaType.APPLICATION_PDF); mixParts.add("pdf", new HttpEntity<>(new ClassPathResource("contract_unsigned.pdf"), pdfHeaders)); Response res = restTemplate.exchange(...url, HttpMethod.POST, mixParts, Response.class); References MultipartBodyBuilder (Spring Framework 6.0.5 API) declaration: package: org.springframework.http.client, class: MultipartBodyBuilder Web on Reactive Stack Web on Servlet Stack Post, Code and Quiet Time. © 2023 – Unsubscribe