java 杰克逊：获得反序列化的空引用
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/45918309/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
提示：将鼠标放在中文语句上可以显示对应的英文。显示中英文
时间：2020-11-03 08:59:23 来源:igfitidea点击:
Hymanson: get a null reference on deserializing
提问by
I'm using spring-mvc for a restfulservice. By adding the dependency, my rest controllers automatically generate jsonfrom my response entities.
我正在使用 spring-mvc 作为restful服务。通过添加依赖项，我的休息控制器会自动generate json从我的response entities.
Dependency
依赖
Hymanson = '2.9.0'
compile "com.fasterxml.Hymanson.core:Hymanson-databind:$Hymanson"
Objects
对象
@Getter @Setter
public final class UserDTO {
[...]
private int id;
private Set<ActivityDTO> activities = Sets.newHashSet();
}
@Getter @Setter
public final class ActivityDTO {
[...]
private int id;
private Set<ActivityDTO> subActivities;
}
Problem
问题
Problems come in special cases. For example, I want to add an activityto an user. The following user-json worksgood, Hymanson converts it without error.
问题进来了special cases。例如，我想activity在一个user. 下面的user-jsonworks不错，Hymanson converts it without error.
{
"id": 1,
"activities": [
{
"id": 1,
"subActivities": null,
}
]
}
But if I add an activity with sub activities, it crashes!
但是如果我添加一个带有子活动的活动，它就会崩溃！
{
"id": 6,
"activities": [
{
"id": 19,
"subActivities": [
{
"id": 20,
"subActivities": [
{
"id": 24,
"subActivities": null
},
{
"id": 21,
"subActivities": [
{
"id": 23,
"subActivities": null
},
{
"id": 22,
"subActivities": null
}
]
}
]
}
],
}
]
}
Indeed, Hymanson can't deserializethis json and I don't understand why. I get the following error.. Any idea?
确实，Hyman逊can't deserialize这个json，我不明白为什么。我收到以下错误.. 知道吗？
13:45:56.890 [http-nio-8080-exec-1] DEBUG org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod - Failed to resolve argument 0 of type 'com.ortec.gta.database.model.dto.UserDTO'
org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: (was java.lang.NullPointerException); nested exception is com.fasterxml.Hymanson.databind.JsonMappingException: (was java.lang.NullPointerException) (through reference chain: com.ortec.gta.database.model.dto.UserDTO["activities"]->java.util.HashSet[2]->com.ortec.gta.database.model.dto.ActivityDTO["subActivities"]->java.util.HashSet[0]->com.ortec.gta.database.model.dto.ActivityDTO["subActivities"])
at org.springframework.http.converter.json.AbstractHymanson2HttpMessageConverter.readJavaType(AbstractHymanson2HttpMessageConverter.java:238)
at org.springframework.http.converter.json.AbstractHymanson2HttpMessageConverter.read(AbstractHymanson2HttpMessageConverter.java:223)
at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodArgumentResolver.readWithMessageConverters(AbstractMessageConverterMethodArgumentResolver.java:201)
at org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.readWithMessageConverters(RequestResponseBodyMethodProcessor.java:150)
at org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.resolveArgument(RequestResponseBodyMethodProcessor.java:128)
at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:121)
at org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:158)
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:128)
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:97)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738)
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:967)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:901)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
at org.springframework.web.servlet.FrameworkServlet.doPut(FrameworkServlet.java:883)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:664)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330)
at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:118)
at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:84)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:113)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:103)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:113)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:154)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:45)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.oauth2.provider.authentication.OAuth2AuthenticationProcessingFilter.doFilter(OAuth2AuthenticationProcessingFilter.java:176)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:110)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.header.HeaderWriterFilter.doFilterInternal(HeaderWriterFilter.java:57)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:87)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:50)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:192)
at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:160)
at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:346)
at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:262)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at com.ortec.gta.configuration.ServletInitializer$CorsFilter.doFilter(ServletInitializer.java:78)
at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:346)
at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:262)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:478)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:80)
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:624)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:799)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1455)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)
Caused by: com.fasterxml.Hymanson.databind.JsonMappingException: (was java.lang.NullPointerException) (through reference chain: com.ortec.gta.database.model.dto.UserDTO["activities"]->java.util.HashSet[2]->com.ortec.gta.database.model.dto.ActivityDTO["subActivities"]->java.util.HashSet[0]->com.ortec.gta.database.model.dto.ActivityDTO["subActivities"])
at com.fasterxml.Hymanson.databind.JsonMappingException.wrapWithPath(JsonMappingException.java:391)
at com.fasterxml.Hymanson.databind.JsonMappingException.wrapWithPath(JsonMappingException.java:351)
at com.fasterxml.Hymanson.databind.deser.BeanDeserializerBase.wrapAndThrow(BeanDeserializerBase.java:1689)
at com.fasterxml.Hymanson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:370)
at com.fasterxml.Hymanson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:159)
at com.fasterxml.Hymanson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:285)
at com.fasterxml.Hymanson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:244)
at com.fasterxml.Hymanson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:27)
at com.fasterxml.Hymanson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:127)
at com.fasterxml.Hymanson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:368)
at com.fasterxml.Hymanson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:159)
at com.fasterxml.Hymanson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:285)
at com.fasterxml.Hymanson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:244)
at com.fasterxml.Hymanson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:27)
at com.fasterxml.Hymanson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:127)
at com.fasterxml.Hymanson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:368)
at com.fasterxml.Hymanson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:159)
at com.fasterxml.Hymanson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4001)
at com.fasterxml.Hymanson.databind.ObjectMapper.readValue(ObjectMapper.java:3072)
at org.springframework.http.converter.json.AbstractHymanson2HttpMessageConverter.readJavaType(AbstractHymanson2HttpMessageConverter.java:235)
... 77 common frames omitted
Caused by: java.lang.NullPointerException: null
at com.fasterxml.Hymanson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:271)
at com.fasterxml.Hymanson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:244)
at com.fasterxml.Hymanson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:27)
at com.fasterxml.Hymanson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:127)
at com.fasterxml.Hymanson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:368)
... 93 common frames omitted
Here the objects with all fields, maybe related to my error?
这里所有字段的对象，可能与我的错误有关？
@Getter @Setter
public final class ActivityDTO {
private int id;
private String name;
private long creationDate;
private long modificationDate;
private long deletionDate;
@JsonIgnoreProperties(value = {"activities"})
private UserDTO lastEditor;
@JsonIgnoreProperties(value = {"subActivities", "users", "parentActivity"})
private ActivityDTO parentActivity;
@JsonIgnoreProperties(value = {"parentActivity"})
private Set<ActivityDTO> subActivities;
@JsonIgnoreProperties(value = {"activities"})
private Set<UserDTO> users;
private String code;
private boolean active;
}
@Getter @Setter
public final class UserDTO {
private int id;
private String username;
private String name;
private String lastname;
private byte[] avatar;
private String email;
@JsonIgnoreProperties(value = {"activities", "activities"})
private UserDTO superior;
private Set<RoleDTO> roles;
@JsonIgnoreProperties(value = {"users", "parentActivity"})
private Set<ActivityDTO> activities;
}
@Getter @Setter
public final class RoleDTO {
private Integer id;
private String name;
}
采纳答案by chimmi
First of all, this definetely looks like a bug in Hymanson since error only appears in version 2.8.0and later.
首先，这绝对看起来像是 Hymanson 中的一个错误，因为错误只出现在版本2.8.0和更高版本中。
As to the source of the error, it appears that the reason for it is your configuration for ActivityDTO, specifically this annotation:
至于错误的来源，看来是你对 的配置ActivityDTO，特别是这个注解：
@JsonIgnoreProperties(value = {"parentActivity"})
private Set<ActivityDTO> subActivities;
So you have 3 options:
所以你有3个选择：
- Rollback to Hymanson 2.7.9
- Make custom deserializer for this case
- Remove this annotation and use custom serializer (if needed)
- 回滚到 Hymanson 2.7.9
- 为这种情况制作自定义解串器
- 删除此注释并使用自定义序列化程序（如果需要）
回答by Damian Kober
When I found this error it was because I was using primitive types as you
当我发现这个错误是因为我像你一样使用原始类型
Try using nullable properties instead
尝试改用可为空的属性
@Getter @Setter
public final class ActivityDTO {
private Integer id;
private String name;
private Long creationDate;
private Long modificationDate;
private Long deletionDate;
回答by Andrei
It is because you have an extra "," character, which makes your json invalid. It's towards the end of your json : ],. Remove the "," and it should work.
这是因为您有一个额外的“，”字符，这使您的 json 无效。快到 json 的结尾了：],。删除“，”，它应该可以工作。
回答by boukobba adil
@Bean
public ObjectMapper objectMapper() {
ObjectMapper objectMapper = new ObjectMapper();
return objectMapper;
}
add this bean to your config file and add
将此bean添加到您的配置文件并添加
@JsonIgnoreProperties(ignoreUnknown=true)
to your pojo classes;
到您的 pojo 课程；
