在生产环境使用feign调用外部接口时，偶尔会出现下面错误
2020-10-15 11:00:18,535 [] ERROR com.shein.abc.rmp.controller.RecExplainConfigController - rec_explain_query.fail f feign.codec.DecodeException: Error while extracting response for type [class com.alibaba.fastjson.JSONObject] and content type [application/json;charset=UTF-8]; nested exception is org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: Unexpected end-of-input in field name; nested exception is com.fasterxml.jackson.core.io.JsonEOFException: Unexpected end-of-input in field name at [Source: (PushbackInputStream); line: 1, column: 108927] at feign.SynchronousMethodHandler.decode(SynchronousMethodHandler.java:169) at feign.SynchronousMethodHandler.executeAndDecode(SynchronousMethodHandler.java:133) at feign.SynchronousMethodHandler.invoke(SynchronousMethodHandler.java:76) Caused by: org.springframework.web.client.RestClientException: Error while extracting response for type [class com.alibaba.fastjson.JSONObject] and content type [application/json;charset=UTF-8]; nested exception is org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: Unexpected end-of-input in field name; nested exception is com.fasterxml.jackson.core.io.JsonEOFException: Unexpected end-of-input in field name at [Source: (PushbackInputStream); line: 1, column: 108927] at org.springframework.web.client.HttpMessageConverterExtractor.extractData(HttpMessageConverterExtractor.java:115) at org.springframework.cloud.openfeign.support.SpringDecoder.decode(SpringDecoder.java:60) at org.springframework.cloud.openfeign.support.ResponseEntityDecoder.decode(ResponseEntityDecoder.java:45) at feign.SynchronousMethodHandler.decode(SynchronousMethodHandler.java:165) ... 112 common frames omitted C Caused by: org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: Unexpected end-of-input in field name; nested exception is com.fasterxml.jackson.core.io.JsonEOFException: Unexpected end-of-input in field name at [Source: (PushbackInputStream); line: 1, column: 108927] at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.readJavaType(AbstractJackson2HttpMessageConverter.java:243) at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.read(AbstractJackson2HttpMessageConverter.java:225) at org.springframework.web.client.HttpMessageConverterExtractor.extractData(HttpMessageConverterExtractor.java:100) ... 115 common frames omitted C Caused by: com.fasterxml.jackson.core.io.JsonEOFException: Unexpected end-of-input in field name at [Source: (PushbackInputStream); line: 1, column: 108927] at com.fasterxml.jackson.core.base.ParserMinimalBase._reportInvalidEOF(ParserMinimalBase.java:618) at com.fasterxml.jackson.core.json.UTF8StreamJsonParser.parseEscapedName(UTF8StreamJsonParser.java:1962) at com.fasterxml.jackson.core.json.UTF8StreamJsonParser.slowParseName(UTF8StreamJsonParser.java:1867) at com.fasterxml.jackson.core.json.UTF8StreamJsonParser._parseName(UTF8StreamJsonParser.java:1651) at com.fasterxml.jackson.core.json.UTF8StreamJsonParser.nextFieldName(UTF8StreamJsonParser.java:1005) at com.fasterxml.jackson.databind.deser.std.UntypedObjectDeserializer$Vanilla.mapObject(UntypedObjectDeserializer.java:896) at com.fasterxml.jackson.databind.deser.std.UntypedObjectDeserializer$Vanilla.deserialize(UntypedObjectDeserializer.java:654) ... 117 common frames omitted
这个很明显是json反序列化失败，根据提示json字符串不全，根据上面的报错，分别预估了几个可能原因，并针对性的排查。 1、feign中是否有拦截器，截取了响应结果 排查结果：无
2、是否服务端响应的结果就不全 经过排查，服务端响应结果没问题，并支持gzip压缩
3、打印feign的debug日志，并查询出header中的content-length是否与响应结果不一致，这里不了解content-length的可以参考下面链接： Content-Length是如何工作的 HTTP 协议中的 Transfer-Encoding 这两篇文章中有详细的描述，当实际响应结果比content-length大时会被截取
既然服务端支持gzip压缩，且请求结果返回值比较大，这时我们是否考虑feign开启gzip压缩
feign: compression: request: # 开启请求压缩 enabled: true # 配置压缩的 MIME TYPE mime-types: text/xml,application/xml,application/json # 配置压缩数据大小的下限 min-request-size: 2048 response: # 开启响应压缩 enabled: true
开启压缩后重新请求，报下面的错误
feign.codec.DecodeException: Error while extracting response for type [class com.alibaba.fastjson.JSONObject] and content type [application/json;charset=UTF-8]; nested exception is org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: Illegal character ((CTRL-CHAR, code 31)): only regular white space (\r, \n, \t) is allowed between tokens; nested exception is com.fasterxml.jackson.core.JsonParseException: Illegal character ((CTRL-CHAR, code 31)): only regular white space (\r, \n, \t) is allowed between tokens at [Source: (PushbackInputStream); line: 1, column: 2] at feign.SynchronousMethodHandler.decode(SynchronousMethodHandler.java:169) at feign.SynchronousMethodHandler.executeAndDecode(SynchronousMethodHandler.java:133) Caused by: org.springframework.web.client.RestClientException: Error while extracting response for type [class com.alibaba.fastjson.JSONObject] and content type [application/json;charset=UTF-8]; nested exception is org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: Illegal character ((CTRL-CHAR, code 31)): only regular white space (\r, \n, \t) is allowed between tokens; nested exception is com.fasterxml.jackson.core.JsonParseException: Illegal character ((CTRL-CHAR, code 31)): only regular white space (\r, \n, \t) is allowed between tokens at [Source: (PushbackInputStream); line: 1, column: 2] at org.springframework.web.client.HttpMessageConverterExtractor.extractData(HttpMessageConverterExtractor.java:115) at org.springframework.cloud.openfeign.support.SpringDecoder.decode(SpringDecoder.java:60) at org.springframework.cloud.openfeign.support.ResponseEntityDecoder.decode(ResponseEntityDecoder.java:45) at feign.SynchronousMethodHandler.decode(SynchronousMethodHandler.java:165) ... 114 common frames omitted Caused by: org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: Illegal character ((CTRL-CHAR, code 31)): only regular white space (\r, \n, \t) is allowed between tokens; nested exception is com.fasterxml.jackson.core.JsonParseException: Illegal character ((CTRL-CHAR, code 31)): only regular white space (\r, \n, \t) is allowed between tokens at [Source: (PushbackInputStream); line: 1, column: 2] at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.readJavaType(AbstractJackson2HttpMessageConverter.java:243) at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.read(AbstractJackson2HttpMessageConverter.java:225) at org.springframework.web.client.HttpMessageConverterExtractor.extractData(HttpMessageConverterExtractor.java:100) ... 117 common frames omitted Caused by: com.fasterxml.jackson.core.JsonParseException: Illegal character ((CTRL-CHAR, code 31)): only regular white space (\r, \n, \t) is allowed between tokens at [Source: (PushbackInputStream); line: 1, column: 2] at com.fasterxml.jackson.core.JsonParser._constructError(JsonParser.java:1804) at com.fasterxml.jackson.core.base.ParserMinimalBase._reportError(ParserMinimalBase.java:693) at com.fasterxml.jackson.core.base.ParserMinimalBase._throwInvalidSpace(ParserMinimalBase.java:644) at com.fasterxml.jackson.core.json.UTF8StreamJsonParser._skipWSOrEnd(UTF8StreamJsonParser.java:2951) at com.fasterxml.jackson.core.json.UTF8StreamJsonParser.nextToken(UTF8StreamJsonParser.java:691) at com.fasterxml.jackson.databind.ObjectMapper._initForReading(ObjectMapper.java:4142) at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4001) at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3085) at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.readJavaType(AbstractJackson2HttpMessageConverter.java:237) ... 119 common frames omitted
这个报错比较明显了，反序列化解析出问题，经过排查发现是HttpURLConnection不支持gzip反序列化，SpringCloud需要升级到Hoxton才能解决该问题：
https://github.com/spring-cloud/spring-cloud-openfeign/pull/230
还有一种方案是将httpclient换成okhttp，如下配置变更：
feign: okhttp: enabled: true httpclient: enabled: false
pom中增加相关依赖
<!-- okhttp --> <dependency> <groupid>io.github.openfeign</groupid> <artifactid>feign-okhttp</artifactid> </dependency>
配置后重新启动，不再报错。
参考链接：
https://www.jianshu.com/p/df37eb5f2169
https://blog.csdn.net/wo18237095579/article/details/83344529
https://imququ.com/post/transfer-encoding-header-in-http.html
https://blog.piaoruiqing.com/2019/09/08/do-you-know-content-length/
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