Spring Boot REST服務：JSON反序列化不起作用

Question

我正在使用spring-boot和Kotlin開發REST服務。 （我要提到它的同時使用我的第一次。）我遇到了麻煩傑克遜使用此代碼從POST請求反序列化JSON：

@RequestMapping("cloudservice/login/{uuid}", method = arrayOf(RequestMethod.POST)) 
fun login(@PathVariable(value="uuid")uuid: String, @RequestBody user: CloudServiceUser) : ResponseEntity<CloudServiceUser> { 

    val cloudServiceFactory : Class<CloudServiceFactory> = cloudServiceRepository.cloudServiceExtensions[UUID.fromString(uuid)] ?: throw InvalidPathVariableException("Invalid UUID.") 
    var token : String 
    try { 
     token = cloudServiceFactory.newInstance().authenticationService.login(user.userId, user.password) 
    } catch (e:Exception){ 
     throw CloudServiceException(e.message) 
    } 

    return ResponseEntity(CloudServiceUser(userId=user.userId, password = "", token = token),HttpStatus.OK) 
} 

用戶對象很簡單：

data class CloudServiceUser(val userId: String, val password:String, val token:String) 

我得到了錯誤

org.springframework.http.converter.HttpMessageNotReadableException: Could not read document: Can not construct instance of com.irotsoma.cloudbackenc.cloudservice.CloudServiceUser: no suitable constructor found, can not deserialize from Object value (missing default constructor or creator, or perhaps need to add/enable type information?) 
at [Source: java.io.PushbackInputStream@682b15d6; line: 1, column: 2]; nested exception is com.fasterxml.jackson.databind.JsonMappingException: Can not construct instance of com.irotsoma.cloudbackenc.cloudservice.CloudServiceUser: no suitable constructor found, can not deserialize from Object value (missing default constructor or creator, or perhaps need to add/enable type information?) 
at [Source: java.io.PushbackInputStream@682b15d6; line: 1, column: 2] 
    at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.readJavaType(AbstractJackson2HttpMessageConverter.java:229) ~[spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
    at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.read(AbstractJackson2HttpMessageConverter.java:213) ~[spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
    at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodArgumentResolver.readWithMessageConverters(AbstractMessageConverterMethodArgumentResolver.java:197) ~[spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
    at org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.readWithMessageConverters(RequestResponseBodyMethodProcessor.java:147) ~[spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
    at org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.resolveArgument(RequestResponseBodyMethodProcessor.java:125) ~[spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
    at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:99) ~[spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
    at org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:161) [spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:128) [spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:110) [spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:832) [spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:743) [spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85) [spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:961) [spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:895) [spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:967) [spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:869) [spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:648) [tomcat-embed-core-8.0.33.jar:8.0.33] 
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:843) [spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) [tomcat-embed-core-8.0.33.jar:8.0.33] 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:292) [tomcat-embed-core-8.0.33.jar:8.0.33] 
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) [tomcat-embed-core-8.0.33.jar:8.0.33] 
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) [tomcat-embed-websocket-8.0.33.jar:8.0.33] 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) [tomcat-embed-core-8.0.33.jar:8.0.33] 
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) [tomcat-embed-core-8.0.33.jar:8.0.33] 
    at org.springframework.boot.actuate.autoconfigure.EndpointWebMvcAutoConfiguration$ApplicationContextHeaderFilter.doFilterInternal(EndpointWebMvcAutoConfiguration.java:261) [spring-boot-actuator-1.3.5.RELEASE.jar:1.3.5.RELEASE] 
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) [tomcat-embed-core-8.0.33.jar:8.0.33] 
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) [tomcat-embed-core-8.0.33.jar:8.0.33] 
    at org.springframework.boot.actuate.trace.WebRequestTraceFilter.doFilterInternal(WebRequestTraceFilter.java:115) [spring-boot-actuator-1.3.5.RELEASE.jar:1.3.5.RELEASE] 
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) [tomcat-embed-core-8.0.33.jar:8.0.33] 
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) [tomcat-embed-core-8.0.33.jar:8.0.33] 
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) [spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) [tomcat-embed-core-8.0.33.jar:8.0.33] 
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) [tomcat-embed-core-8.0.33.jar:8.0.33] 
    at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:87) [spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) [tomcat-embed-core-8.0.33.jar:8.0.33] 
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) [tomcat-embed-core-8.0.33.jar:8.0.33] 
    at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77) [spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) [tomcat-embed-core-8.0.33.jar:8.0.33] 
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) [tomcat-embed-core-8.0.33.jar:8.0.33] 
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:121) [spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) [tomcat-embed-core-8.0.33.jar:8.0.33] 
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) [tomcat-embed-core-8.0.33.jar:8.0.33] 
    at org.springframework.boot.actuate.autoconfigure.MetricsFilter.doFilterInternal(MetricsFilter.java:103) [spring-boot-actuator-1.3.5.RELEASE.jar:1.3.5.RELEASE] 
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) [tomcat-embed-core-8.0.33.jar:8.0.33] 
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) [tomcat-embed-core-8.0.33.jar:8.0.33] 
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:212) [tomcat-embed-core-8.0.33.jar:8.0.33] 
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106) [tomcat-embed-core-8.0.33.jar:8.0.33] 
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502) [tomcat-embed-core-8.0.33.jar:8.0.33] 
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:141) [tomcat-embed-core-8.0.33.jar:8.0.33] 
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) [tomcat-embed-core-8.0.33.jar:8.0.33] 
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88) [tomcat-embed-core-8.0.33.jar:8.0.33] 
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:522) [tomcat-embed-core-8.0.33.jar:8.0.33] 
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1095) [tomcat-embed-core-8.0.33.jar:8.0.33] 
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:672) [tomcat-embed-core-8.0.33.jar:8.0.33] 
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1502) [tomcat-embed-core-8.0.33.jar:8.0.33] 
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1458) [tomcat-embed-core-8.0.33.jar:8.0.33] 
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_92] 
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_92] 
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-8.0.33.jar:8.0.33] 
    at java.lang.Thread.run(Thread.java:745) [na:1.8.0_92] 
Caused by: com.fasterxml.jackson.databind.JsonMappingException: Can not construct instance of com.irotsoma.cloudbackenc.cloudservice.CloudServiceUser: no suitable constructor found, can not deserialize from Object value (missing default constructor or creator, or perhaps need to add/enable type information?) 
at [Source: java.io.PushbackInputStream@682b15d6; line: 1, column: 2] 
    at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:261) ~[jackson-databind-2.8.0.jar:2.8.0] 
    at com.fasterxml.jackson.databind.DeserializationContext.instantiationException(DeserializationContext.java:1420) ~[jackson-databind-2.8.0.jar:2.8.0] 
    at com.fasterxml.jackson.databind.DeserializationContext.handleMissingInstantiator(DeserializationContext.java:1011) ~[jackson-databind-2.8.0.jar:2.8.0] 
    at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromObjectUsingNonDefault(BeanDeserializerBase.java:1201) ~[jackson-databind-2.8.0.jar:2.8.0] 
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:314) ~[jackson-databind-2.8.0.jar:2.8.0] 
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:148) ~[jackson-databind-2.8.0.jar:2.8.0] 
    at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3789) ~[jackson-databind-2.8.0.jar:2.8.0] 
    at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2913) ~[jackson-databind-2.8.0.jar:2.8.0] 
    at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.readJavaType(AbstractJackson2HttpMessageConverter.java:226) ~[spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE] 
    ... 66 common frames omitted 

但是，return語句中的序列化工作很好，可以很好地序列化爲一個JSON對象併發送響應。這只是反序列化不起作用。

如果我將主體變量更改爲字符串並手動創建映射器，它也可以正常工作。像這樣：

@RequestMapping("cloudservice/login/{uuid}", method = arrayOf(RequestMethod.POST)) 
fun login(@PathVariable(value="uuid")uuid: String, @RequestBody user: String) : ResponseEntity<CloudServiceUser> { 

    val mapper = ObjectMapper().registerModule(KotlinModule()) 
    val mapperData: CloudServiceUser = mapper.readValue(user) 


    val cloudServiceFactory : Class<CloudServiceFactory> = cloudServiceRepository.cloudServiceExtensions[UUID.fromString(uuid)] ?: throw InvalidPathVariableException("Invalid UUID.") 
    var token : String 
    try { 
     token = cloudServiceFactory.newInstance().authenticationService.login(mapperData.userId, mapperData.password) 
    } catch (e:Exception){ 
     throw CloudServiceException(e.message) 
    } 

    return ResponseEntity(CloudServiceUser(userId=mapperData.userId, password = "", token = token),HttpStatus.OK) 
} 

任何想法？

這是一個開源項目，如果您需要更多信息，請隨時瀏覽它：https://github.com/irotsoma/cloudbackenc。請注意，目前它處於非常早期的狀態。

編輯：只是想在集成測試中添加一個關於我的麻煩的註釋，正如在接受的答案上的註釋中指出的那樣。我最終沒有得到集成測試能夠反序列化響應（雖然REST控制器方面的工作很好，就像在生產中一樣）。所以我找到了一個使用Map對象的解決方法，出於某種原因，它能夠反序列化，然後手動處理它，而不是使用類對象。由於這只是測試的問題，而不是測試代碼，這對我來說很好。

val returnValue = template.postForEntity("REQUEST URL", httpEntity, Map::class.java) 

Answer 1

您需要幫助Jackson反序列化數據類，如錯誤消息中所示。您可以通過註冊jackson-module-kotlin在ObjectMapper做到像這樣：

val mapper = ObjectMapper().registerModule(KotlinModule()) 

告訴春天你自己定製的ObjectMapperdefine a @Bean and mark it as @Primary：

@Configuration 
open class ObjectMapperConfiguration { 
    @Bean 
    @Primary 
    open fun objectMapper() = ObjectMapper().apply { 
    registerModule(KotlinModule()) 
    } 
} 

延伸閱讀：

• How to use jackson to deserialize to Kotlin collections
• How do I deserialize JSON into a List<SomeType> with Kotlin + Jackson