Why is the following Spring Boot + HATEOAS with mongodb not working (MarshalException)?

I am attempting to use spring-data-mongodb with the spring-hateoas and am getting a javax.xml.bind.MarshalException exception through testing. How can I get around this issue? Are there annotations or other steps I am missing? my pom: ``` <dependency> <groupId>org.springframework.hateoas</groupId> <artifactId>spring-hateoas</artifactId> </dependency> <dependency> <groupId>org.springframework.plugin</groupId> <artifactId>spring-plugin-core</artifactId> <version>1.0.0.RELEASE</version> </dependency> ``` My "UserResourceAssembler.java": ``` @Component class UserResourceAssembler implements ResourceAssembler<User, Resource<User>> { String customersRel = "customers"; @Override public Resource<User> toResource(MyObj u) { try { User user = new User("John"); Collection<Link> links = new ArrayList<Link>(); return new Resource<User>(user, links); } catch (Exception throwable) { throw new RuntimeException(throwable); } } } ``` My "User.java" representing a mongodb document: ``` @Document @XmlRootElement(name="user") public class User { @Id private String id; private String occupation; public User() {} public User(String occupation) { this.occupation = occupation; } @Override public String toString() { return String.format( "{id:%s, occupation='%s'}", ttid, occupation); } } ``` My "UserController.java": ``` @RestController @ExposesResourceFor(User.class) @RequestMapping(value = "/users") public class UserController { @Autowired UserResourceAssembler userResourceAssembler; @RequestMapping(method = RequestMethod.GET, value = "/name/{user}") Resource<User> testUser(@PathVariable String user) { return userResourceAssembler.toResource(new User("Teenager")); } } ``` In my Application.java I included the following annotation: ``` @EnableHypermediaSupport(type = EnableHypermediaSupport.HypermediaType.HAL) ``` My issue is why am I getting error when I visit: ``` http://localhost:8080/users/name/doesnotmatterrightnow ``` The problem based on the error message is with the line: ``` return userResourceAssembler.toResource(new User("Teenager")); ``` The following is the full error: ``` HTTP Status 500 - Could not marshal [Resource { content: {id:null, occupation='Teenager'}, links: [] }]: null; nested exception is javax.xml.bind.MarshalException type Exception report message Could not marshal [Resource { content: {id:null, occupation='Teenager'}, links: [] }]: null; nested exception is javax.xml.bind.MarshalException description The server encountered an internal error that prevented it from fulfilling this request. exception org.springframework.http.converter.HttpMessageNotWritableException: Could not marshal [Resource { content: {id:null, occupation='Teenager'}, links: [] }]: null; nested exception is javax.xml.bind.MarshalException - with linked exception: [com.sun.istack.internal.SAXException2: class sample.User nor any of its super class is known to this context. javax.xml.bind.JAXBException: class sample.User nor any of its super class is known to this context.] org.springframework.http.converter.xml.Jaxb2RootElementHttpMessageConverter.writeToResult(Jaxb2RootElementHttpMessageConverter.java:138) org.springframework.http.converter.xml.AbstractXmlHttpMessageConverter.writeInternal(AbstractXmlHttpMessageConverter.java:66) org.springframework.http.converter.AbstractHttpMessageConverter.write(AbstractHttpMessageConverter.java:207) org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:148) org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:90) org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.handleReturnValue(RequestResponseBodyMethodProcessor.java:193) org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:71) org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:122) org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:749) org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:689) org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:83) org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:938) org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:870) org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:961) org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:852) javax.servlet.http.HttpServlet.service(HttpServlet.java:620) org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:837) javax.servlet.http.HttpServlet.service(HttpServlet.java:727) org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77) org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:108) root cause javax.xml.bind.MarshalException - with linked exception: [com.sun.istack.internal.SAXException2: class sample.User nor any of its super class is known to this context. javax.xml.bind.JAXBException: class sample.User nor any of its super class is known to this context.] com.sun.xml.internal.bind.v2.runtime.MarshallerImpl.write(MarshallerImpl.java:311) com.sun.xml.internal.bind.v2.runtime.MarshallerImpl.marshal(MarshallerImpl.java:236) org.springframework.http.converter.xml.Jaxb2RootElementHttpMessageConverter.writeToResult(Jaxb2RootElementHttpMessageConverter.java:135) org.springframework.http.converter.xml.AbstractXmlHttpMessageConverter.writeInternal(AbstractXmlHttpMessageConverter.java:66) org.springframework.http.converter.AbstractHttpMessageConverter.write(AbstractHttpMessageConverter.java:207) org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:148) org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:90) org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.handleReturnValue(RequestResponseBodyMethodProcessor.java:193) org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:71) org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:122) org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:749) org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:689) org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:83) org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:938) org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:870) org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:961) org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:852) javax.servlet.http.HttpServlet.service(HttpServlet.java:620) org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:837) javax.servlet.http.HttpServlet.service(HttpServlet.java:727) org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77) org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:108) root cause com.sun.istack.internal.SAXException2: class sample.User nor any of its super class is known to this context. javax.xml.bind.JAXBException: class sample.User nor any of its super class is known to this context. com.sun.xml.internal.bind.v2.runtime.XMLSerializer.reportError(XMLSerializer.java:235) com.sun.xml.internal.bind.v2.runtime.XMLSerializer.reportError(XMLSerializer.java:250) com.sun.xml.internal.bind.v2.runtime.property.SingleReferenceNodeProperty.serializeBody(SingleReferenceNodeProperty.java:102) com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeBody(ClassBeanInfoImpl.java:343) com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsSoleContent(XMLSerializer.java:582) com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeRoot(ClassBeanInfoImpl.java:325) com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsRoot(XMLSerializer.java:483) com.sun.xml.internal.bind.v2.runtime.MarshallerImpl.write(MarshallerImpl.java:308) com.sun.xml.internal.bind.v2.runtime.MarshallerImpl.marshal(MarshallerImpl.java:236) org.springframework.http.converter.xml.Jaxb2RootElementHttpMessageConverter.writeToResult(Jaxb2RootElementHttpMessageConverter.java:135) org.springframework.http.converter.xml.AbstractXmlHttpMessageConverter.writeInternal(AbstractXmlHttpMessageConverter.java:66) org.springframework.http.converter.AbstractHttpMessageConverter.write(AbstractHttpMessageConverter.java:207) org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:148) org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:90) org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.handleReturnValue(RequestResponseBodyMethodProcessor.java:193) org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:71) org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:122) org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:749) org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:689) org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:83) org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:938) org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:870) org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:961) org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:852) javax.servlet.http.HttpServlet.service(HttpServlet.java:620) org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:837) javax.servlet.http.HttpServlet.service(HttpServlet.java:727) org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77) org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:108) root cause javax.xml.bind.JAXBException: class sample.User nor any of its super class is known to this context. com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.getBeanInfo(JAXBContextImpl.java:572) com.sun.xml.internal.bind.v2.runtime.property.SingleReferenceNodeProperty.serializeBody(SingleReferenceNodeProperty.java:94) com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeBody(ClassBeanInfoImpl.java:343) com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsSoleContent(XMLSerializer.java:582) com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeRoot(ClassBeanInfoImpl.java:325) com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsRoot(XMLSerializer.java:483) com.sun.xml.internal.bind.v2.runtime.MarshallerImpl.write(MarshallerImpl.java:308) com.sun.xml.internal.bind.v2.runtime.MarshallerImpl.marshal(MarshallerImpl.java:236) org.springframework.http.converter.xml.Jaxb2RootElementHttpMessageConverter.writeToResult(Jaxb2RootElementHttpMessageConverter.java:135) org.springframework.http.converter.xml.AbstractXmlHttpMessageConverter.writeInternal(AbstractXmlHttpMessageConverter.java:66) org.springframework.http.converter.AbstractHttpMessageConverter.write(AbstractHttpMessageConverter.java:207) org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:148) org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:90) org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.handleReturnValue(RequestResponseBodyMethodProcessor.java:193) org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:71) org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:122) org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:749) org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:689) org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:83) org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:938) org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:870) org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:961) org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:852) javax.servlet.http.HttpServlet.service(HttpServlet.java:620) org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:837) javax.servlet.http.HttpServlet.service(HttpServlet.java:727) org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77) org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:108) ```