春天和杰克逊整合

Question

我在使用JacksonMapper在JSON对象上返回Java类时遇到此异常。

org.codehaus.jackson.map.JsonMappingException：没有找到类$ Proxy57的序列化器，也没有发现创建BeanSerializer的属性（为了避免异常，禁用SerializationConfig.Feature.FAIL_ON_EMPTY_BEANS））（通过引用链：java.util.HashMap [ “异常”] - GT; org.springframework.core.convert.ConversionFailedException [ “TARGETTYPE”] - ＆GT; org.springframework.core.convert.TypeDescriptor [ “注释”]）

at org.codehaus.jackson.map.ser.StdSerializerProvider$1.serialize(StdSerializerProvider.java:55)

at org.codehaus.jackson.map.ser.ArraySerializers$ObjectArraySerializer.serialize(ArraySerializers.java:66)

at org.codehaus.jackson.map.ser.ArraySerializers$ObjectArraySerializer.serialize(ArraySerializers.java:35)

at org.codehaus.jackson.map.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:218)

at org.codehaus.jackson.map.ser.BeanSerializer.serialize(BeanSerializer.java:122)

at org.codehaus.jackson.map.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:218)

at org.codehaus.jackson.map.ser.BeanSerializer.serialize(BeanSerializer.java:122)

at org.codehaus.jackson.map.ser.MapSerializer.serializeEntries(MapSerializer.java:131)

at org.codehaus.jackson.map.ser.MapSerializer.serialize(MapSerializer.java:74)

at org.codehaus.jackson.map.ser.MapSerializer.serialize(MapSerializer.java:19)

at org.codehaus.jackson.map.ser.StdSerializerProvider._serializeValue(StdSerializerProvider.java:260)

at org.codehaus.jackson.map.ser.StdSerializerProvider.serializeValue(StdSerializerProvider.java:212)

at org.codehaus.jackson.map.ObjectMapper.writeValue(ObjectMapper.java:694)

at org.springframework.web.servlet.view.json.MappingJacksonJsonView.renderMergedOutputModel(MappingJacksonJsonView.java:151)

at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:250)

at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1063)

at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:801)

at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:719)

at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:644)

at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:549)

at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)

at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)

at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77)

at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)

at com.opensymphony.sitemesh.webapp.SiteMeshFilter.obtainContent(SiteMeshFilter.java:129)

at com.opensymphony.sitemesh.webapp.SiteMeshFilter.doFilter(SiteMeshFilter.java:77)

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)

at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:343)

at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:109)

at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:83)

at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:355)

at org.springframework.security.oauth.provider.OAuthProviderProcessingFilter.doFilter(OAuthProviderProcessingFilter.java:173)

at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:355)

at org.springframework.security.oauth.provider.OAuthProviderProcessingFilter.doFilter(OAuthProviderProcessingFilter.java:193)

at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:355)

at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:187)

at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:355)

at org.springframework.security.oauth.provider.OAuthProviderProcessingFilter.doFilter(OAuthProviderProcessingFilter.java:193)

at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:355)

at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:97)

at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:355)

at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:100)

at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:355)

at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:78)

at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:355)

at org.springframework.security.web.authentication.rememberme.RememberMeAuthenticationFilter.doFilter(RememberMeAuthenticationFilter.java:112)

at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:355)

at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:54)

at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:355)

at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:35)

at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:355)

at org.springframework.security.web.authentication.www.BasicAuthenticationFilter.doFilter(BasicAuthenticationFilter.java:177)

at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:355)

at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:187)

at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:355)

at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:105)

at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:355)

at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:79)

at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:355)

at org.springframework.security.web.session.ConcurrentSessionFilter.doFilter(ConcurrentSessionFilter.java:109)

at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:355)

at org.springframework.security.web.access.channel.ChannelProcessingFilter.doFilter(ChannelProcessingFilter.java:109)

at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:355)

at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:149)

at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:237)

at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:167)

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)

at net.bull.javamelody.MonitoringFilter.doFilter(MonitoringFilter.java:206)

at net.bull.javamelody.MonitoringFilter.doFilter(MonitoringFilter.java:179)

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
at org.apache.jk.server.JkCoyoteHandler.invoke(JkCoyoteHandler.java:190)
at org.apache.jk.common.HandlerRequest.invoke(HandlerRequest.java:291)
at org.apache.jk.common.ChannelSocket.invoke(ChannelSocket.java:776)
at org.apache.jk.common.ChannelSocket.processConnection(ChannelSocket.java:705)
at org.apache.jk.common.ChannelSocket$SocketConnection.runIt(ChannelSocket.java:898)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:690)
at java.lang.Thread.run(Thread.java:662)

我想知道Spring创建了哪个类$ Proxy57对象，以便我可以调试我的代码，而且我很少在服务器上发现此错误。所以我没有得到正确的理由。此异常导致我的服务器有时崩溃。

先谢谢，

Answer 1

当您使用ORM时，它会从您持久存储的对象创建代理对象。这样它就可以通过该代理延迟加载（即仅在需要时加载）信息。杰克逊不知道如何序列化这些代理，只是普通的POJO。通常，当您将对象传递给jackson时，ORM会话已经关闭，延迟加载尝试失败。我确信您尝试序列化ORM代理对象的事实是您的问题的根本原因。

一种解决方案是在ORM中禁用延迟加载。当然，您将失去延迟加载的所有好处。仔细考虑你加载的内容以及你不使用的内容（如果你使用JPA，我强烈建议，明确注释你的POJO关系）。

另一种解决方案是编写一个知道如何序列化这类对象的自定义Jackson序列化程序。

我遇到了与hibernate相同的问题，而little module就是这样做的：我的Jackson现在序列化了Hibernate特定的对象和数据类型。