使用feign發(fā)送http請(qǐng)求解析報(bào)錯(cuò)的問(wèn)題

更新時(shí)間：2022年03月16日 08:54:45 作者：yangchuanan

這篇文章主要介紹了使用feign發(fā)送http請(qǐng)求解析報(bào)錯(cuò)的問(wèn)題，具有很好的參考價(jià)值，希望對(duì)大家有所幫助。如有錯(cuò)誤或未考慮完全的地方，望不吝賜教

錯(cuò)誤如下

發(fā)送請(qǐng)求開(kāi)始

-----
[ChannelFeign#formRecog] ---> END HTTP (304117-byte body)

發(fā)送請(qǐng)求結(jié)束

返回開(kāi)始

[ChannelFeign#formRecog] <--- HTTP/1.1 200 OK (4948ms)
[ChannelFeign#formRecog] content-length: 5207
[ChannelFeign#formRecog] content-type: text/json;charset=UTF-8
[ChannelFeign#formRecog] date: Mon, 08 Oct 2018 10:47:03 GMT
[ChannelFeign#formRecog] x-vcap-request-id: c323f65a-12e6-4604-7393-a4bf0ca403d5
[ChannelFeign#formRecog]?
[ChannelFeign#formRecog] {json格式的數(shù)據(jù)}
[ChannelFeign#formRecog] <--- END HTTP (5207-byte body)

返回結(jié)束

ERROR org.apache.catalina.core.ContainerBase.[Tomcat].[localhost].[/].[dispatcherServlet] : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is feign.codec.DecodeException: Could not extract response: no suitable HttpMessageConverter found for response type [channel.domain.ChannelResponse<TableData>] and content type [text/json;charset=UTF-8]] with root cause
org.springframework.web.client.RestClientException: Could not extract response: no suitable HttpMessageConverter found for response type [channel.domain.ChannelResponse<TableData>] and content type [text/json;charset=UTF-8]
   at org.springframework.web.client.HttpMessageConverterExtractor.extractData(HttpMessageConverterExtractor.java:110) ~[spring-web-4.3.13.RELEASE.jar:4.3.13.RELEASE]
   at org.springframework.cloud.netflix.feign.support.SpringDecoder.decode(SpringDecoder.java:59) ~[spring-cloud-netflix-core-1.3.6.RELEASE.jar:1.3.6.RELEASE]
   at org.springframework.cloud.netflix.feign.support.ResponseEntityDecoder.decode(ResponseEntityDecoder.java:47) ~[spring-cloud-netflix-core-1.3.6.RELEASE.jar:1.3.6.RELEASE]
   at feign.SynchronousMethodHandler.decode(SynchronousMethodHandler.java:165) ~[feign-core-9.5.0.jar:?]
   at feign.SynchronousMethodHandler.executeAndDecode(SynchronousMethodHandler.java:133) ~[feign-core-9.5.0.jar:?]
   at feign.SynchronousMethodHandler.invoke(SynchronousMethodHandler.java:76) ~[feign-core-9.5.0.jar:?]
   at feign.ReflectiveFeign$FeignInvocationHandler.invoke(ReflectiveFeign.java:103) ~[feign-core-9.5.0.jar:?]

org.springframework.web.client.RestClientException: Could not extract response: no suitable HttpMessageConverter found for response type [channel.domain.ChannelResponse<TableData>] and content type [text/json;charset=UTF-8]

可以看到返回的類(lèi)型為[ChannelFeign#formRecog] content-type: text/json;charset=UTF-8

錯(cuò)誤原因

接口返回為JSON格式數(shù)據(jù)但卻將數(shù)據(jù)表示為了[text/json]導(dǎo)致Feign沒(méi)有采用JSON解析器來(lái)解析，從而無(wú)法將響應(yīng)數(shù)據(jù)轉(zhuǎn)化為對(duì)應(yīng)的POJO對(duì)象；

源碼分析

feign客戶(hù)端發(fā)送請(qǐng)求入口函數(shù)invoke()

? ? @Override
? ? public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
? ? ? if ("equals".equals(method.getName())) {
? ? ? ? try {
? ? ? ? ? Object
? ? ? ? ? ? ? otherHandler =
? ? ? ? ? ? ? args.length > 0 && args[0] != null ? Proxy.getInvocationHandler(args[0]) : null;
? ? ? ? ? return equals(otherHandler);
? ? ? ? } catch (IllegalArgumentException e) {
? ? ? ? ? return false;
? ? ? ? }
? ? ? } else if ("hashCode".equals(method.getName())) {
? ? ? ? return hashCode();
? ? ? } else if ("toString".equals(method.getName())) {
? ? ? ? return toString();
? ? ? }
? ? ? // 分發(fā)請(qǐng)求
? ? ? return dispatch.get(method).invoke(args);
? ? }

decode()返回請(qǐng)求的解碼函數(shù)

? Object decode(Response response) throws Throwable {
? ? try {
? ? ? return decoder.decode(response, metadata.returnType());
? ? } catch (FeignException e) {
? ? ? throw e;
? ? } catch (RuntimeException e) {
? ? ? throw new DecodeException(e.getMessage(), e);
? ? }
? }

進(jìn)入decode.decode()，提取數(shù)據(jù)

@Override
?? ?@SuppressWarnings({"unchecked", "rawtypes", "resource"})
?? ?public T extractData(ClientHttpResponse response) throws IOException {
?? ??? ?MessageBodyClientHttpResponseWrapper responseWrapper = new MessageBodyClientHttpResponseWrapper(response);
?? ??? ?if (!responseWrapper.hasMessageBody() || responseWrapper.hasEmptyMessageBody()) {
?? ??? ??? ?return null;
?? ??? ?}
?? ??? ?MediaType contentType = getContentType(responseWrapper);
?
?? ??? ?for (HttpMessageConverter<?> messageConverter : this.messageConverters) {
?? ??? ??? ?if (messageConverter instanceof GenericHttpMessageConverter) {
?? ??? ??? ??? ?GenericHttpMessageConverter<?> genericMessageConverter =
?? ??? ??? ??? ??? ??? ?(GenericHttpMessageConverter<?>) messageConverter;
?? ??? ??? ??? ?if (genericMessageConverter.canRead(this.responseType, null, contentType)) {
?? ??? ??? ??? ??? ?if (logger.isDebugEnabled()) {
?? ??? ??? ??? ??? ??? ?logger.debug("Reading [" + this.responseType + "] as \"" +
?? ??? ??? ??? ??? ??? ??? ??? ?contentType + "\" using [" + messageConverter + "]");
?? ??? ??? ??? ??? ?}
?? ??? ??? ??? ??? ?return (T) genericMessageConverter.read(this.responseType, null, responseWrapper);
?? ??? ??? ??? ?}
?? ??? ??? ?}
?? ??? ??? ?if (this.responseClass != null) {
?? ??? ??? ??? ?if (messageConverter.canRead(this.responseClass, contentType)) {
?? ??? ??? ??? ??? ?if (logger.isDebugEnabled()) {
?? ??? ??? ??? ??? ??? ?logger.debug("Reading [" + this.responseClass.getName() + "] as \"" +
?? ??? ??? ??? ??? ??? ??? ??? ?contentType + "\" using [" + messageConverter + "]");
?? ??? ??? ??? ??? ?}
?? ??? ??? ??? ??? ?return (T) messageConverter.read((Class) this.responseClass, responseWrapper);
?? ??? ??? ??? ?}
?? ??? ??? ?}
?? ??? ?}
?
?? ??? ?throw new RestClientException("Could not extract response: no suitable HttpMessageConverter found " +
?? ??? ??? ??? ?"for response type [" + this.responseType + "] and content type [" + contentType + "]");
?? ?}

進(jìn)入genericMessageConverter.canRead(this.responseType, null, contentType)

?? ?protected boolean canRead(MediaType mediaType) {
?? ??? ?if (mediaType == null) {
?? ??? ??? ?return true;
?? ??? ?}
?? ??? ?for (MediaType supportedMediaType : getSupportedMediaTypes()) {
?? ??? ??? ?if (supportedMediaType.includes(mediaType)) {
?? ??? ??? ??? ?return true;
?? ??? ??? ?}
?? ??? ?}
?? ??? ?return false;
?? ?}

通過(guò)斷點(diǎn)發(fā)現(xiàn)mediaType為接口返回的content-type：text/json類(lèi)型。而supportedMediaType為application/json，所以返回false，找不到合適的轉(zhuǎn)換器。

解決方案一

替代Feign的解碼器，使json解析器同時(shí)解析[text/plain]的數(shù)據(jù)

// 創(chuàng)建一個(gè)新的轉(zhuǎn)換器 解析微信的 [text/plain]?
public class WxMessageConverter extends MappingJackson2HttpMessageConverter {
? ? public WxMessageConverter(){
? ? ? ? List<MediaType> mediaTypes = new ArrayList<>();
? ? ? ? mediaTypes.add(MediaType.TEXT_PLAIN);
? ? ? ? setSupportedMediaTypes(mediaTypes);
? ? }
}

注入新的Decoder Feign將自動(dòng) 替換

// 解決微信返回參數(shù)為[text/plain] 無(wú)法轉(zhuǎn)化為json
@Bean
public Decoder feignDecoder(){
? ? WxMessageConverter wxConverter = new WxMessageConverter();
? ? ObjectFactory<HttpMessageConverters> objectFactory = () -> new HttpMessageConverters(wxConverter);
? ? return new SpringDecoder(objectFactory);
}

解決方案二

對(duì)返回的json字符串使用fastjosn轉(zhuǎn)換

? ? ? ? String result = channelFeign.formRecogTest(channelRequest);
? ? ? ? ChannelResponse<TableData> hello = JSONObject.parseObject(result,
? ? ? ? ? ? ? ? new TypeReference<ChannelResponse<TableData>>() {
? ? ? ? ? ? ? ? });

錯(cuò)誤2

發(fā)送請(qǐng)求時(shí)對(duì)象轉(zhuǎn)換json會(huì)自動(dòng)將屬性的首字母小寫(xiě)

解決方法：

//@Data
public class ChannelRequest {
? ? //@JSONField(name="Header")
? ? @JsonProperty
? ? private ChannelReqHead Header;
? ? //@JSONField(name="Body")
? ? @JsonProperty
? ? private ChannelReqBody Body;
? ??
? ? // 如果get方法上不加JsonIgnore，jason化時(shí)小寫(xiě)header也會(huì)出現(xiàn)
? ? @JsonIgnore
? ? public ChannelReqHead getHeader() {
? ? ? ? return Header;
? ? }
? ? @JsonIgnore
? ? public void setHeader(ChannelReqHead header) {
? ? ? ? Header = header;
? ? }
? ? @JsonIgnore
? ? public ChannelReqBody getBody() {
? ? ? ? return Body;
? ? }
? ? @JsonIgnore
? ? public void setBody(ChannelReqBody body) {
? ? ? ? Body = body;
? ? }? ??
}

使用jsonField不起作用，不使用jsonIgnore會(huì)生成大寫(xiě)和小寫(xiě)

如：{“Header”:xxx,"header":xxx}

以上為個(gè)人經(jīng)驗(yàn)，希望能給大家一個(gè)參考，也希望大家多多支持腳本之家。

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