可考慮修改 feign 接口，如下，使用注解 @ResponseBody、@RequestBody

@FeignClient("gulimall-order")
public interface OrderFeignService {
    @RequestMapping("/order/order/listWithItem")
    @ResponseBody
    R listWithItem(@RequestBody Map<String, Object> params);
}

報錯信息

在使用 RestTemplate請求調(diào)用的時候，程序報錯

報錯信息如下：

org.springframework.web.client.RestClientException: Could not extract response: no suitable HttpMessageConverter found for response type [class afei.common.utils.R] and content type [text/html;charset=UTF-8]
	at org.springframework.web.client.HttpMessageConverterExtractor.extractData(HttpMessageConverterExtractor.java:121) ~[spring-web-5.1.9.RELEASE.jar:5.1.9.RELEASE]
	at org.springframework.cloud.openfeign.support.SpringDecoder.decode(SpringDecoder.java:59) ~[spring-cloud-openfeign-core-2.1.3.RELEASE.jar:2.1.3.RELEASE]
	at org.springframework.cloud.openfeign.support.ResponseEntityDecoder.decode(ResponseEntityDecoder.java:62) ~[spring-cloud-openfeign-core-2.1.3.RELEASE.jar:2.1.3.RELEASE]
	at feign.optionals.OptionalDecoder.decode(OptionalDecoder.java:36) ~[feign-core-10.2.3.jar:na]

錯誤信息是未知的ContentType，這個ContentType就是第三方接口返回時候在HTTP頭中的Content-Type，如果通過其他工具查看這個接口返回的HTTP頭，會發(fā)現(xiàn)他的值是 text/html，通常我們見的都是 application/json 類型。（微信接口返回的是text/plain），由于內(nèi)部沒有 HttpMessageConverter 能處理text/html的數(shù)據(jù)，沒有一個實現(xiàn)類的 canRead() 返回 true，所以最后報錯

源碼分析

public T extractData(ClientHttpResponse response) throws IOException {
    MessageBodyClientHttpResponseWrapper responseWrapper = new MessageBodyClientHttpResponseWrapper(response);
    if (responseWrapper.hasMessageBody() && !responseWrapper.hasEmptyMessageBody()) {
        MediaType contentType = this.getContentType(responseWrapper);
        try {
        	//拿到messageConverters的迭代器
            Iterator var4 = this.messageConverters.iterator();
            while(var4.hasNext()) {
            	//下一個HttpMessageConverter
                HttpMessageConverter<?> messageConverter = (HttpMessageConverter)var4.next();
                //如果是GenericHttpMessageConverter接口的實例，繼承AbstractHttpMessageConverter會走這個if。
                if (messageConverter instanceof GenericHttpMessageConverter) {
                    GenericHttpMessageConverter<?> genericMessageConverter = (GenericHttpMessageConverter)messageConverter;
                    //判斷這個轉(zhuǎn)換器能不能轉(zhuǎn)換這個contentType類型
                    if (genericMessageConverter.canRead(this.responseType, (Class)null, contentType)) {
                        if (this.logger.isDebugEnabled()) {
                            ResolvableType resolvableType = ResolvableType.forType(this.responseType);
                            this.logger.debug("Reading to [" + resolvableType + "]");
                        }
                        //走到這代表當前的HttpMessageConverter能進行轉(zhuǎn)換，則調(diào)用read并返回
                        return genericMessageConverter.read(this.responseType, (Class)null, responseWrapper);
                    }
                }
                //還是判斷這個轉(zhuǎn)換器能不能進行contentType轉(zhuǎn)換
                if (this.responseClass != null && messageConverter.canRead(this.responseClass, contentType)) {
                    if (this.logger.isDebugEnabled()) {
                        String className = this.responseClass.getName();
                        this.logger.debug("Reading to [" + className + "] as \"" + contentType + "\"");
                    }
                    //走到這代表當前的HttpMessageConverter能進行轉(zhuǎn)換，則調(diào)用read并返回
                    return messageConverter.read(this.responseClass, responseWrapper);
                }
            }
        } catch (HttpMessageNotReadableException | IOException var8) {
            throw new RestClientException("Error while extracting response for type [" + this.responseType + "] and content type [" + contentType + "]", var8);
        }
        //走到這拋出異常，所有的消息轉(zhuǎn)換器都不能進行處理。
        throw new UnknownContentTypeException(this.responseType, contentType, response.getRawStatusCode(), response.getStatusText(), response.getHeaders(), getResponseBody(response));
    } else {
        return null;
    }
}

messageConverters 集合中就保存著
在 RestTemplate 構(gòu)造方法中添加的 HttpMessageConverter 實現(xiàn)類

解決方法

修改 mappingJackson2HttpMessageConverter 配置

重新設(shè)置 MappingJackson2HttpMessageConverter 能處理的 MediaType

@Bean
public RestTemplate restTemplate(){
    RestTemplate restTemplate = new RestTemplate();
    MappingJackson2HttpMessageConverter mappingJackson2HttpMessageConverter = new MappingJackson2HttpMessageConverter();
    mappingJackson2HttpMessageConverter.setSupportedMediaTypes(Arrays.asList(MediaType.TEXT_HTML));
    restTemplate.getMessageConverters().add(mappingJackson2HttpMessageConverter);
    return  restTemplate;
}

MappingJackson2HttpMessageConverter 也是一個 HttpMessageConverter 轉(zhuǎn)換類，但是他不能處理 text/html 的數(shù)據(jù)，原因是他的父類 AbstractHttpMessageConverter 中的 supportedMediaTypes 集合中沒有 text/html 類型，如果有的話就能處理了，通過 setSupportedMediaTypes 可以給他指定一個新的 MediaType 集合

上面的寫法會導(dǎo)致 MappingJackson2HttpMessageConverter 只能處理 text/html 類型的數(shù)據(jù)

繼承 mappingJackson2HttpMessageConverter

使用MappingJackson2HttpMessageConverter，只需要給他能處理的MediaType

public class QQHttpMessageConverter extends MappingJackson2HttpMessageConverter {
    public QQHttpMessageConverter() {
        setSupportedMediaTypes(Arrays.asList(MediaType.TEXT_HTML));
    }
}

然后將這個消息轉(zhuǎn)換器追加到RestTemplate中的 messageConverters

@Bean
public RestTemplate restTemplate() {
    RestTemplate restTemplate = new RestTemplate();
    restTemplate.getMessageConverters().add(new QQHttpMessageConverter());  // 兼容 text/plain
    return restTemplate;
}

實現(xiàn) HttpMessageConverter

直接繼承HttpMessageConverter（當然更推薦的是繼承 Abstract HttpMessageConverter）來實現(xiàn)

public interface HttpMessageConverter<T> {
    /**
     * 根據(jù)mediaType判斷clazz是否可讀
     */
    boolean canRead(Class<?> clazz, @Nullable MediaType mediaType);

    /**
     * 根據(jù)mediaType判斷clazz是否可寫
     */
    boolean canWrite(Class<?> clazz, @Nullable MediaType mediaType);

    /**
     * 獲取支持的mediaType
     */
    List<MediaType> getSupportedMediaTypes();

    /**
     * 將HttpInputMessage流中的數(shù)據(jù)綁定到clazz中
     */
    T read(Class<? extends T> clazz, HttpInputMessage inputMessage)
			throws IOException, HttpMessageNotReadableException;

    /**
     * 將t對象寫入到HttpOutputMessage流中
     */
    void write(T t, @Nullable MediaType contentType, HttpOutputMessage outputMessage)
			throws IOException, HttpMessageNotWritableException;
}

canWrite，write方式是不需要處理的，只管canRead和read就行

在 canRead 方法中判斷了是不是 text/html 類型，是的話就會返回true，Spring 就會調(diào)用 read，用來將字節(jié)流中的數(shù)據(jù)轉(zhuǎn)換成具體實體，aClass就是我們最終想要得到的實例對象的Class

StreamUtils 這個工具類是SpringBoot自帶的一個，用來讀取InputStream中的數(shù)據(jù)并返回String字符串，SpringBoott內(nèi)部很多地方都用到了這個工具類

import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.http.HttpInputMessage;
import org.springframework.http.HttpOutputMessage;
import org.springframework.http.MediaType;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.converter.HttpMessageNotReadableException;
import org.springframework.http.converter.HttpMessageNotWritableException;
import org.springframework.util.StreamUtils;

import java.io.IOException;
import java.nio.charset.Charset;
import java.util.Arrays;
import java.util.List;

public class QQHttpMessageConverter implements HttpMessageConverter<Object> {
    @Override
    public boolean canRead(Class<?> aClass, MediaType mediaType) {
        if (mediaType != null) {
            return mediaType.isCompatibleWith(MediaType.TEXT_HTML);
        }
        return false;
    }

    @Override
    public boolean canWrite(Class<?> aClass, MediaType mediaType) {
        return false;
    }

    @Override
    public List<MediaType> getSupportedMediaTypes() {
        return Arrays.asList(MediaType.TEXT_HTML);
    }

    @Override
    public Object read(Class<?> aClass, HttpInputMessage httpInputMessage) throws IOException, HttpMessageNotReadableException {
        String json = StreamUtils.copyToString(httpInputMessage.getBody(), Charset.forName("UTF-8"));
        ObjectMapper objectMapper = new ObjectMapper();
        objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
        return objectMapper.readValue(json, aClass);
    }

    @Override
    public void write(Object o, MediaType mediaType, HttpOutputMessage httpOutputMessage) throws IOException, HttpMessageNotWritableException {

    }
}

最后需要要進行配置，getMessageConverters() 會返回現(xiàn)有的 HttpMessageConverter 集合，我們在這個基礎(chǔ)上加入我們自定義的 HttpMessageConverter 即可文章來源地址http://www.zghlxwxcb.cn/news/detail-477165.html

@Bean
public RestTemplate restTemplate(){
    RestTemplate restTemplate = new RestTemplate();
    restTemplate.getMessageConverters().add(new QQHttpMessageConverter());
    return  restTemplate;
}

繼承 AbstractHttpMessageConverter

public class QQHttpMessageConverter extends AbstractHttpMessageConverter<Object> {
    public QQHttpMessageConverter() {
        super(MediaType.TEXT_HTML);
    }
    @Override
    protected boolean supports(Class<?> aClass) {
        return true;
    }
    @Override
    protected Object readInternal(Class<?> aClass, HttpInputMessage httpInputMessage) throws IOException, HttpMessageNotReadableException {
        String json = StreamUtils.copyToString(httpInputMessage.getBody(), Charset.forName("UTF-8"));
        ObjectMapper objectMapper = new ObjectMapper();
        objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
        return objectMapper.readValue(json, aClass);
    }
    @Override
    protected void writeInternal(Object o, HttpOutputMessage httpOutputMessage) throws IOException, HttpMessageNotWritableException {
    }
}

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