Feign - Error while extracting response for type [class java.lang.String]

定义Feign接口

  @RequestMapping(produces = MediaType.APPLICATION_JSON_UTF8_VALUE, method = RequestMethod.GET,
            value = "/temp/test/data")
    String testData(@RequestParam("data") String data);

调用Feign接口

  @GetMapping("/internal/test/data")
    public String testData(@RequestParam("data") String data){
        return facadeFeignClient.testData(data);
    }

调用feign接口报错

Caused by: org.springframework.web.client.RestClientException: Error while extracting response for type [class java.lang.String] and content type [application/json;charset=UTF-8]; nested exception is org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: Unrecognized token 'adsf22': was expecting ('true', 'false' or 'null'); nested exception is com.fasterxml.jackson.core.JsonParseException: Unrecognized token 'adsf22': was expecting ('true', 'false' or 'null')
 at [Source: (PushbackInputStream); line: 1, column: 13]
	at org.springframework.web.client.HttpMessageConverterExtractor.extractData(HttpMessageConverterExtractor.java:117)
	at org.springframework.cloud.openfeign.support.SpringDecoder.decode(SpringDecoder.java:59)
	at org.springframework.cloud.openfeign.support.ResponseEntityDecoder.decode(ResponseEntityDecoder.java:62)
	at feign.optionals.OptionalDecoder.decode(OptionalDecoder.java:36)
	at feign.SynchronousMethodHandler.decode(SynchronousMethodHandler.java:176)
	... 79 more

Caused by: org.springframework.web.client.RestClientException: Error while extracting response for type [class java.lang.String] and content type [application/json;charset=UTF-8]; nested exception is org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: Unrecognized token 'adsf22': was expecting ('true', 'false' or 'null'); nested exception is com.fasterxml.jackson.core.JsonParseException: Unrecognized token 'adsf22': was expecting ('true', 'false' or 'null')
 at [Source: (PushbackInputStream); line: 1, column: 13]
	at org.springframework.web.client.HttpMessageConverterExtractor.extractData(HttpMessageConverterExtractor.java:117)
	at org.springframework.cloud.openfeign.support.SpringDecoder.decode(SpringDecoder.java:59)
	at org.springframework.cloud.openfeign.support.ResponseEntityDecoder.decode(ResponseEntityDecoder.java:62)
	at feign.optionals.OptionalDecoder.decode(OptionalDecoder.java:36)
	at feign.SynchronousMethodHandl

问题分析

跟踪代码发现，这里的messageConverter只有一个，没有对应的String的converter.

正确的Converter

问题根源

项目中HttpMessageConverters这个bean被重写了，且只定义了一个MappingJackson2HttpMessageConverter

    @Bean
    public HttpMessageConverters customConverters() {
        return new HttpMessageConverters(false, Arrays.asList(new MappingJackson2HttpMessageConverter()));
    }

解决方法

删除项目中重写的HttpMessageConverters这个Bean方法