【问题标题】：JSON error: Cannot construct instance of class name?JSON 错误：无法构造类名的实例？
【发布时间】：2021-10-06 09:01:53
【问题描述】：

当我试图通过邮递员使用 rest api 传递一个 json 请求时，我遇到了一个错误，这里是错误日志的下方，我很想知道这里出了什么问题，我怀疑这是构造函数知道我的问题使用 AllArgsConstructor 和 NoArgsConstructor 注释编写了所有参数构造函数和默认构造函数，或者我在某处遗漏了一些注释，但老实说我不确定我哪里出错了。


2021-07-30 14:46:04.363 ERROR 7576 --- [nio-8080-exec-6] o.s.d.r.w.RepositoryRestExceptionHandler : JSON parse error: Cannot construct instance of `org.sid.cinema.entities.Categorie` (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value ('http://localhost:8080/categories/1'); nested exception is com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot construct instance of `org.sid.cinema.entities.Categorie` (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value ('http://localhost:8080/categories/1')
 at [Source: (org.apache.catalina.connector.CoyoteInputStream); line: 5, column: 17] (through reference chain: org.sid.cinema.entities.Film["categorie"])

org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: Cannot construct instance of `org.sid.cinema.entities.Categorie` (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value ('http://localhost:8080/categories/1'); nested exception is com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot construct instance of `org.sid.cinema.entities.Categorie` (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value ('http://localhost:8080/categories/1')
 at [Source: (org.apache.catalina.connector.CoyoteInputStream); line: 5, column: 17] (through reference chain: org.sid.cinema.entities.Film["categorie"])
    at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.readJavaType(AbstractJackson2HttpMessageConverter.java:389) ~[spring-web-5.3.8.jar:5.3.8]
    at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.readInternal(AbstractJackson2HttpMessageConverter.java:350) ~[spring-web-5.3.8.jar:5.3.8]
    at org.springframework.http.converter.AbstractHttpMessageConverter.read(AbstractHttpMessageConverter.java:199) ~[spring-web-5.3.8.jar:5.3.8]
    at org.springframework.data.rest.webmvc.config.PersistentEntityResourceHandlerMethodArgumentResolver.read(PersistentEntityResourceHandlerMethodArgumentResolver.java:246) ~[spring-data-rest-webmvc-3.5.2.jar:3.5.2]
    at org.springframework.data.rest.webmvc.config.PersistentEntityResourceHandlerMethodArgumentResolver.lambda$read$6(PersistentEntityResourceHandlerMethodArgumentResolver.java:202) ~[spring-data-rest-webmvc-3.5.2.jar:3.5.2]
    at java.util.Optional.orElseGet(Optional.java:267) ~[na:1.8.0_191]
    at org.springframework.data.rest.webmvc.config.PersistentEntityResourceHandlerMethodArgumentResolver.read(PersistentEntityResourceHandlerMethodArgumentResolver.java:202) ~[spring-data-rest-webmvc-3.5.2.jar:3.5.2]
    at org.springframework.data.rest.webmvc.config.PersistentEntityResourceHandlerMethodArgumentResolver.resolveArgument(PersistentEntityResourceHandlerMethodArgumentResolver.java:132) ~[spring-data-rest-webmvc-3.5.2.jar:3.5.2]
    at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:121) ~[spring-web-5.3.8.jar:5.3.8]
    at org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:170) ~[spring-web-5.3.8.jar:5.3.8]
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:137) ~[spring-web-5.3.8.jar:5.3.8]
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:106) ~[spring-webmvc-5.3.8.jar:5.3.8]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:894) ~[spring-webmvc-5.3.8.jar:5.3.8]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808) ~[spring-webmvc-5.3.8.jar:5.3.8]
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.3.8.jar:5.3.8]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1063) ~[spring-webmvc-5.3.8.jar:5.3.8]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:963) ~[spring-webmvc-5.3.8.jar:5.3.8]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) [spring-webmvc-5.3.8.jar:5.3.8]
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909) [spring-webmvc-5.3.8.jar:5.3.8]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:681) [tomcat-embed-core-9.0.48.jar:4.0.FR]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) [spring-webmvc-5.3.8.jar:5.3.8]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:764) [tomcat-embed-core-9.0.48.jar:4.0.FR]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:228) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:163) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) [tomcat-embed-websocket-9.0.48.jar:9.0.48]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:190) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:163) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) [spring-web-5.3.8.jar:5.3.8]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) [spring-web-5.3.8.jar:5.3.8]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:190) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:163) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) [spring-web-5.3.8.jar:5.3.8]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) [spring-web-5.3.8.jar:5.3.8]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:190) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:163) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) [spring-web-5.3.8.jar:5.3.8]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) [spring-web-5.3.8.jar:5.3.8]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:190) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:163) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:357) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:382) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:893) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1723) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_191]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_191]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at java.lang.Thread.run(Thread.java:748) [na:1.8.0_191]
Caused by: com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot construct instance of `org.sid.cinema.entities.Categorie` (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value ('http://localhost:8080/categories/1')
 at [Source: (org.apache.catalina.connector.CoyoteInputStream); line: 5, column: 17] (through reference chain: org.sid.cinema.entities.Film["categorie"])
    at com.fasterxml.jackson.databind.exc.MismatchedInputException.from(MismatchedInputException.java:63) ~[jackson-databind-2.12.3.jar:2.12.3]
    at com.fasterxml.jackson.databind.DeserializationContext.reportInputMismatch(DeserializationContext.java:1588) ~[jackson-databind-2.12.3.jar:2.12.3]
    at com.fasterxml.jackson.databind.DeserializationContext.handleMissingInstantiator(DeserializationContext.java:1213) ~[jackson-databind-2.12.3.jar:2.12.3]
    at com.fasterxml.jackson.databind.deser.std.StdDeserializer._deserializeFromString(StdDeserializer.java:311) ~[jackson-databind-2.12.3.jar:2.12.3]
    at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromString(BeanDeserializerBase.java:1495) ~[jackson-databind-2.12.3.jar:2.12.3]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer._deserializeOther(BeanDeserializer.java:207) ~[jackson-databind-2.12.3.jar:2.12.3]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:197) ~[jackson-databind-2.12.3.jar:2.12.3]
    at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:129) ~[jackson-databind-2.12.3.jar:2.12.3]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:402) ~[jackson-databind-2.12.3.jar:2.12.3]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:195) ~[jackson-databind-2.12.3.jar:2.12.3]
    at com.fasterxml.jackson.databind.deser.DefaultDeserializationContext.readRootValue(DefaultDeserializationContext.java:322) ~[jackson-databind-2.12.3.jar:2.12.3]
    at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4593) ~[jackson-databind-2.12.3.jar:2.12.3]
    at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3601) ~[jackson-databind-2.12.3.jar:2.12.3]
    at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.readJavaType(AbstractJackson2HttpMessageConverter.java:378) ~[spring-web-5.3.8.jar:5.3.8]
    ... 54 common frames omitted

2021-07-30 14:46:04.415  WARN 7576 --- [nio-8080-exec-6] .m.m.a.ExceptionHandlerExceptionResolver : Resolved [org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: Cannot construct instance of `org.sid.cinema.entities.Categorie` (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value ('http://localhost:8080/categories/1'); nested exception is com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot construct instance of `org.sid.cinema.entities.Categorie` (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value ('http://localhost:8080/categories/1')
 at [Source: (org.apache.catalina.connector.CoyoteInputStream); line: 5, column: 17] (through reference chain: org.sid.cinema.entities.Film["categorie"])]
2021-07-30 16:16:53.003  WARN 7576 --- [nio-8080-exec-2] tion$ResourceSupportHttpMessageConverter : Failed to evaluate Jackson deserialization for type [[simple type, class org.springframework.data.rest.webmvc.PersistentEntityResource]]: java.lang.NullPointerException
2021-07-30 16:21:05.694  WARN 7576 --- [nio-8080-exec-8] tion$ResourceSupportHttpMessageConverter : Failed to evaluate Jackson deserialization for type [[simple type, class org.springframework.data.rest.webmvc.PersistentEntityResource]]: java.lang.NullPointerException
2021-07-30 16:21:06.306 ERROR 7576 --- [nio-8080-exec-8] o.s.d.r.w.RepositoryRestExceptionHandler : JSON parse error: Cannot construct instance of `org.sid.cinema.entities.Categorie` (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value ('http://localhost:8080/categories/2'); nested exception is com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot construct instance of `org.sid.cinema.entities.Categorie` (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value ('http://localhost:8080/categories/2')
 at [Source: (org.apache.catalina.connector.CoyoteInputStream); line: 5, column: 17] (through reference chain: org.sid.cinema.entities.Film["categorie"])

org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: Cannot construct instance of `org.sid.cinema.entities.Categorie` (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value ('http://localhost:8080/categories/2'); nested exception is com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot construct instance of `org.sid.cinema.entities.Categorie` (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value ('http://localhost:8080/categories/2')
 at [Source: (org.apache.catalina.connector.CoyoteInputStream); line: 5, column: 17] (through reference chain: org.sid.cinema.entities.Film["categorie"])
    at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.readJavaType(AbstractJackson2HttpMessageConverter.java:389) ~[spring-web-5.3.8.jar:5.3.8]
    at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.readInternal(AbstractJackson2HttpMessageConverter.java:350) ~[spring-web-5.3.8.jar:5.3.8]
    at org.springframework.http.converter.AbstractHttpMessageConverter.read(AbstractHttpMessageConverter.java:199) ~[spring-web-5.3.8.jar:5.3.8]
    at org.springframework.data.rest.webmvc.config.PersistentEntityResourceHandlerMethodArgumentResolver.read(PersistentEntityResourceHandlerMethodArgumentResolver.java:246) ~[spring-data-rest-webmvc-3.5.2.jar:3.5.2]
    at org.springframework.data.rest.webmvc.config.PersistentEntityResourceHandlerMethodArgumentResolver.lambda$read$6(PersistentEntityResourceHandlerMethodArgumentResolver.java:202) ~[spring-data-rest-webmvc-3.5.2.jar:3.5.2]
    at java.util.Optional.orElseGet(Optional.java:267) ~[na:1.8.0_191]
    at org.springframework.data.rest.webmvc.config.PersistentEntityResourceHandlerMethodArgumentResolver.read(PersistentEntityResourceHandlerMethodArgumentResolver.java:202) ~[spring-data-rest-webmvc-3.5.2.jar:3.5.2]
    at org.springframework.data.rest.webmvc.config.PersistentEntityResourceHandlerMethodArgumentResolver.resolveArgument(PersistentEntityResourceHandlerMethodArgumentResolver.java:132) ~[spring-data-rest-webmvc-3.5.2.jar:3.5.2]
    at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:121) ~[spring-web-5.3.8.jar:5.3.8]
    at org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:170) ~[spring-web-5.3.8.jar:5.3.8]
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:137) ~[spring-web-5.3.8.jar:5.3.8]
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:106) ~[spring-webmvc-5.3.8.jar:5.3.8]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:894) ~[spring-webmvc-5.3.8.jar:5.3.8]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808) ~[spring-webmvc-5.3.8.jar:5.3.8]
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.3.8.jar:5.3.8]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1063) ~[spring-webmvc-5.3.8.jar:5.3.8]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:963) ~[spring-webmvc-5.3.8.jar:5.3.8]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) [spring-webmvc-5.3.8.jar:5.3.8]
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909) [spring-webmvc-5.3.8.jar:5.3.8]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:681) [tomcat-embed-core-9.0.48.jar:4.0.FR]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) [spring-webmvc-5.3.8.jar:5.3.8]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:764) [tomcat-embed-core-9.0.48.jar:4.0.FR]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:228) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:163) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) [tomcat-embed-websocket-9.0.48.jar:9.0.48]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:190) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:163) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) [spring-web-5.3.8.jar:5.3.8]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) [spring-web-5.3.8.jar:5.3.8]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:190) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:163) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) [spring-web-5.3.8.jar:5.3.8]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) [spring-web-5.3.8.jar:5.3.8]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:190) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:163) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) [spring-web-5.3.8.jar:5.3.8]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) [spring-web-5.3.8.jar:5.3.8]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:190) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:163) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:357) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:382) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:893) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1723) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_191]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_191]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.48.jar:9.0.48]
    at java.lang.Thread.run(Thread.java:748) [na:1.8.0_191]
Caused by: com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot construct instance of `org.sid.cinema.entities.Categorie` (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value ('http://localhost:8080/categories/2')
 at [Source: (org.apache.catalina.connector.CoyoteInputStream); line: 5, column: 17] (through reference chain: org.sid.cinema.entities.Film["categorie"])
    at com.fasterxml.jackson.databind.exc.MismatchedInputException.from(MismatchedInputException.java:63) ~[jackson-databind-2.12.3.jar:2.12.3]
    at com.fasterxml.jackson.databind.DeserializationContext.reportInputMismatch(DeserializationContext.java:1588) ~[jackson-databind-2.12.3.jar:2.12.3]
    at com.fasterxml.jackson.databind.DeserializationContext.handleMissingInstantiator(DeserializationContext.java:1213) ~[jackson-databind-2.12.3.jar:2.12.3]
    at com.fasterxml.jackson.databind.deser.std.StdDeserializer._deserializeFromString(StdDeserializer.java:311) ~[jackson-databind-2.12.3.jar:2.12.3]
    at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromString(BeanDeserializerBase.java:1495) ~[jackson-databind-2.12.3.jar:2.12.3]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer._deserializeOther(BeanDeserializer.java:207) ~[jackson-databind-2.12.3.jar:2.12.3]

这是我在邮递员中使用以下 url 作为 json 请求写的：http://localhost:8080/films 使用 post 方法

{
   "titre": "my titre8",
    "description": "my descr8",
    "realisateur": "realisateur8",
    "categorie":"http://localhost:8080/categories/1"
   
}

这里是电影课

package org.sid.cinema.entities;

import java.util.Collection;
import java.util.Date;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.ManyToOne;
import javax.persistence.OneToMany;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.ToString;
@Entity
@Data @AllArgsConstructor @NoArgsConstructor @ToString
public class Film {
    @Id @GeneratedValue(strategy= GenerationType.IDENTITY)
    private Long id;
    private String titre;
    private String description;
    private String realisateur;
    private Date dateSortie;
    private double duree;
    private String photo;
    @OneToMany(mappedBy="film")
    private Collection<Projection> projections;
    @ManyToOne
    private Categorie categorie;
    

}

这里是分类类

package org.sid.cinema.entities;

import java.util.Collection;
import java.util.Date;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToMany;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.ToString;
@Entity
@Data @AllArgsConstructor @NoArgsConstructor @ToString
public class Categorie {
    @Id @GeneratedValue(strategy= GenerationType.IDENTITY)
    private Long id;
    @Column(length=75) // par defaut length=255
    private String name ;
    @OneToMany(mappedBy="categorie")
    private Collection<Film> films;

}

【问题讨论】：

标签： java json spring spring-boot rest

【解决方案1】：

您的 json 请求正在尝试将类别写入 String

{
   "titre": "my titre8",
    "description": "my descr8",
    "realisateur": "realisateur8",
    "categorie":"http://localhost:8080/categories/1"
   
}
---

"categorie":"http://localhost:8080/categories/1"

当你的电影课期望 Catagorie 是一个课时。

public class Film {
    @Id @GeneratedValue(strategy= GenerationType.IDENTITY)
    private Long id;
    private String titre;
    private String description;
    private String realisateur;
    private Date dateSortie;
    private double duree;
    private String photo;
    @OneToMany(mappedBy="film")
    private Collection<Projection> projections;
    @ManyToOne
    private Categorie categorie;
   
}

您可以将json对象以Catagorie的形式传递到json请求中，也可以添加它可以使用的字符串参数构造函数。

org.sid.cinema.entities.Categorie (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value

创建一个接受字符串的构造函数

public class Catagorie {

    public Catagorie(String initStringUrl) {
     // handle url
}
}

【讨论】：

Sam Orozco 我已经在 json 请求中传递了一个 json 对象，我不明白表单的类别形式是什么意思，不知道我如何添加字符串参数构造函数跨度>
Catagorie 是一个类，有很多字段，您试图将其作为字符串传递。您需要创建一个构造函数是 Catagorie 类，它只接受一个字符串 OR 您需要在请求对象中传递一个对象。
Sam Orozco 我如何创建一个构造函数是 Catagorie 类，它只接受一个字符串或者我如何在我的请求中传递一个对象
您正在向您的服务器发送一个 Film 对象 json 请求。服务器无法反序列化 json，因为您将 catagorie 字段作为字符串发送，在 File 对象上它是一个 catagorie 对象。所以服务器不知道如何将字符串反序列化为对象。如果您创建一个接受字符串的构造函数然后相应地处理或在您的电影请求中传递一个 json 对象，服务器将知道如何反序列化。
Sam Orozco 我理解这个问题，但仍然不知道如何创建一个接受字符串的构造函数，你能告诉我