Shulou(Shulou.com)06/02 Report--

This article mainly introduces "how Feign solves the problem of transferring files, list,map and objects between services". In daily operation, I believe that many people have doubts about how Feign solves the problems of transferring files, list,map and objects between services. The editor has consulted all kinds of materials and sorted out simple and useful operation methods. I hope to answer "how to transfer files and list between services by Feign." Doubts about map, objects, etc., are helpful! Next, please follow the editor to study!

Let's first talk about the background. Some time ago, there was a requirement that a file generated by Service A should be passed to Service B and handed over to Service B for processing. Spring-cloud-starter-openfeign, which was used at the beginning, found that this piece was not supported, and then io.github.openfeign.form was introduced to solve the problem, but there were new requirements after a period of time. While transferring the file, it also passed the object and some other parameters. At this time, I found that feign was a little bad. At this time, feign-httpclient was introduced to solve the problem temporarily. After a period of time, there were some problems such as data loss when large files were found. There are all kinds of other pitfalls, all of which are solved by upgrading versions and introducing other jar, but the problem of data loss in large files has not been good all the time.

Previously used maven important coordinates

Io.github.openfeign.form feign-form ${feign-form-version} io.github.openfeign.form feign-form-spring ${feign-form-version} io.github.openfeign feign-httpclient ${feign-httpclient}

Decide to solve this, first of all, talk about the version used, this is very important, very important!

Version used:

Springboot 2.0.3.RELEASE

Springcloud Finchley.RELEASE

Replace with the maven below. The maven addresses above are unnecessary.

2.0.8 8.17.0 org.springframework.cloud spring-cloud-starter-openfeign com.netflix.feign feign-core ${netflix.feign-version} com.netflix.feign feign-jackson ${netflix.feign-version} com.netflix.feign feign-slf4j ${netflix.feign-version} org.springframework spring-mock ${spring-mock-version}

Note that I have tested openfeign and feign-httpclient, if using these versions does not solve the problem of file transfer, although you can receive the file, but the file is incomplete, be sure to replace it with the maven above.

The core idea is: to rewrite the encoder, the principle of Encoder is to serialize each parameter json, set requestHeader to Multipart/form-data, and use the form request to request the interface provided by the generator. This method can send multiple entity files and an array of MultipartFile [] at the same time.

First rewrite the encoder

Import feign.RequestTemplate;import feign.codec.EncodeException;import feign.codec.Encoder;import org.springframework.core.io.InputStreamResource;import org.springframework.core.io.Resource;import org.springframework.http.HttpEntity;import org.springframework.http.HttpHeaders;import org.springframework.http.HttpOutputMessage;import org.springframework.http.MediaType;import org.springframework.http.converter.HttpMessageConverter;import org.springframework.util.LinkedMultiValueMap;import org.springframework.web.client.RestTemplate;import org.springframework.web.multipart.MultipartFile;import java.io.ByteArrayOutputStream Import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;import java.lang.reflect.Type;import java.nio.charset.Charset;import java.util.Arrays;import java.util.List;import java.util.Map;import java.util.Map.Entry;/** * @ author: LX * creation time: 2020-10-14. 15:06 * place: Guangzhou * purpose: custom form encoder. Feign implements multi-pojo transmission and MultipartFile upload encoder. You need to enable feign with its own annotations * used to support the upload of multiple objects and files * * the principle of Encoder is to serialize each parameter json, set requestHeader to Multipart/form-data, and use the form request to request the interface provided by the generator. * this method can send multiple entity files and an array of MultipartFile [] at the same time. * * reference: * https://github.com/pcan/feign-client-test * remarks: * / public class FeignSpringFormEncoder implements Encoder {private final List requestType = value.getClass (); MediaType requestContentType = requestHeaders.getContentType () For (HttpMessageConverter messageConverter: converters) {if (messageConverter.canWrite (requestType, requestContentType)) {((HttpMessageConverter) messageConverter) .write (value, requestContentType, dummyRequest); break;} catch (IOException e) {throw new EncodeException ("cannot encode the request:", e) } HttpHeaders headers = dummyRequest.getHeaders (); if (headers! = null) {for (Entry entry: headers.entrySet ()) {template.header (entry.getKey (), entry.getValue ());}} / * Please use the template output stream. If the file is too large, this will cause problems because the entire request will be in memory. * / template.body (outputStream.toByteArray (), UTF_8);} / * is encoded as a json object * @ param obj * @ return * / private HttpEntity encodeJsonObject (Object obj) {HttpHeaders jsonPartHeaders = new HttpHeaders (); jsonPartHeaders.setContentType (MediaType.APPLICATION_JSON); return new HttpEntity (obj, jsonPartHeaders) } / * encode the MultipartFile file, convert it to HttpEntity, and set Content-type to application/octet-stream * @ param map current request map. Name of * @ param name array field * @ param fileList file to be processed * / private void encodeMultipartFiles (LinkedMultiValueMap map, String name, List)

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