我对Hibernate相当新，并且我一直试图将实体保存到与另一个实体具有ManyToOne关系的数据库中已经有一段时间了。问题是我在保存实体时没有城市的ID或公司的ID，我只有城市的名称和公司的名称。我有一个班级用户：
@Entity
@Table(name = "users")
public class User {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "id")
private int id;
@Column(name = "email")
private String email;
@Column(name = "password")
private String password;
@Column(name = "first_name")
private String firstName;
@Column(name = "last_name")
private String lastName;
@Column(name = "description")
private String description;
@ManyToOne
@JoinColumn(name = "id", insertable = false, updatable = false)
private City city;
@Column(name = "github_username")
private String githubUsername;
@Column(name = "personal_site")
private String personalSite;
@Column(name = "unemployed")
private boolean unemployed;
@Column(name = "degree")
private String degree;
@ManyToOne
@JoinColumn(name = "id", insertable = false, updatable = false)
private Company employer;
// getters and setters...
}
这是City类：
@Entity
@Table(name = "cities")
public class City {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "id")
private int id;
@Column(name = "name")
private String name;
@OneToMany(mappedBy="employer")
private List<User> users = new ArrayList<User>();
// getters and setters...
}
因此，当我尝试将具有session.save（）的新用户保存到数据库时，抛出以下异常：
org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: squadknowhow.dbmodels.City
at org.hibernate.engine.internal.ForeignKeys.getEntityIdentifierIfNotUnsaved(ForeignKeys.java:279) ~[hibernate-core-5.2.14.Final.jar:5.2.14.Final]
at org.hibernate.type.EntityType.getIdentifier(EntityType.java:488) ~[hibernate-core-5.2.14.Final.jar:5.2.14.Final]
at org.hibernate.type.ManyToOneType.isDirty(ManyToOneType.java:287) ~[hibernate-core-5.2.14.Final.jar:5.2.14.Final]
at org.hibernate.type.ManyToOneType.isDirty(ManyToOneType.java:298) ~[hibernate-core-5.2.14.Final.jar:5.2.14.Final]
at org.hibernate.type.TypeHelper.findDirty(TypeHelper.java:308) ~[hibernate-core-5.2.14.Final.jar:5.2.14.Final]
at org.hibernate.persister.entity.AbstractEntityPersister.findDirty(AbstractEntityPersister.java:4222) ~[hibernate-core-5.2.14.Final.jar:5.2.14.Final]
at org.hibernate.event.internal.DefaultFlushEntityEventListener.dirtyCheck(DefaultFlushEntityEventListener.java:538) ~[hibernate-core-5.2.14.Final.jar:5.2.14.Final]
at org.hibernate.event.internal.DefaultFlushEntityEventListener.isUpdateNecessary(DefaultFlushEntityEventListener.java:215) ~[hibernate-core-5.2.14.Final.jar:5.2.14.Final]
at org.hibernate.event.internal.DefaultFlushEntityEventListener.onFlushEntity(DefaultFlushEntityEventListener.java:142) ~[hibernate-core-5.2.14.Final.jar:5.2.14.Final]
at org.hibernate.event.internal.AbstractFlushingEventListener.flushEntities(AbstractFlushingEventListener.java:216) ~[hibernate-core-5.2.14.Final.jar:5.2.14.Final]
at org.hibernate.event.internal.AbstractFlushingEventListener.flushEverythingToExecutions(AbstractFlushingEventListener.java:85) ~[hibernate-core-5.2.14.Final.jar:5.2.14.Final]
at org.hibernate.event.internal.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:38) ~[hibernate-core-5.2.14.Final.jar:5.2.14.Final]
at org.hibernate.internal.SessionImpl.doFlush(SessionImpl.java:1436) ~[hibernate-core-5.2.14.Final.jar:5.2.14.Final]
at org.hibernate.internal.SessionImpl.managedFlush(SessionImpl.java:493) ~[hibernate-core-5.2.14.Final.jar:5.2.14.Final]
at org.hibernate.internal.SessionImpl.flushBeforeTransactionCompletion(SessionImpl.java:3206) ~[hibernate-core-5.2.14.Final.jar:5.2.14.Final]
at org.hibernate.internal.SessionImpl.beforeTransactionCompletion(SessionImpl.java:2412) ~[hibernate-core-5.2.14.Final.jar:5.2.14.Final]
at org.hibernate.engine.jdbc.internal.JdbcCoordinatorImpl.beforeTransactionCompletion(JdbcCoordinatorImpl.java:473) ~[hibernate-core-5.2.14.Final.jar:5.2.14.Final]
at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl.beforeCompletionCallback(JdbcResourceLocalTransactionCoordinatorImpl.java:156) ~[hibernate-core-5.2.14.Final.jar:5.2.14.Final]
at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl.access$100(JdbcResourceLocalTransactionCoordinatorImpl.java:38) ~[hibernate-core-5.2.14.Final.jar:5.2.14.Final]
at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl$TransactionDriverControlImpl.commit(JdbcResourceLocalTransactionCoordinatorImpl.java:231) ~[hibernate-core-5.2.14.Final.jar:5.2.14.Final]
at org.hibernate.engine.transaction.internal.TransactionImpl.commit(TransactionImpl.java:68) ~[hibernate-core-5.2.14.Final.jar:5.2.14.Final]
at squadknowhow.services.DbRegistrationService.attemptRegister(DbRegistrationService.java:53) ~[main/:na]
at squadknowhow.controllers.RegistrationController.register(RegistrationController.java:32) ~[main/:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_161]
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[na:1.8.0_161]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[na:1.8.0_161]
at java.lang.reflect.Method.invoke(Unknown Source) ~[na:1.8.0_161]
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:209) ~[spring-web-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136) ~[spring-web-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:102) ~[spring-webmvc-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:870) ~[spring-webmvc-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:776) ~[spring-webmvc-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:991) ~[spring-webmvc-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:925) ~[spring-webmvc-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:978) ~[spring-webmvc-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:881) ~[spring-webmvc-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:661) ~[tomcat-embed-core-8.5.28.jar:8.5.28]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:855) ~[spring-webmvc-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:742) ~[tomcat-embed-core-8.5.28.jar:8.5.28]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-8.5.28.jar:8.5.28]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.28.jar:8.5.28]
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) ~[tomcat-embed-websocket-8.5.28.jar:8.5.28]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.28.jar:8.5.28]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.28.jar:8.5.28]
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) ~[spring-web-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.28.jar:8.5.28]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.28.jar:8.5.28]
at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:109) ~[spring-web-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.28.jar:8.5.28]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.28.jar:8.5.28]
at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:81) ~[spring-web-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.28.jar:8.5.28]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.28.jar:8.5.28]
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200) ~[spring-web-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.0.4.RELEASE.jar:5.0.4.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.28.jar:8.5.28]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.28.jar:8.5.28]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199) ~[tomcat-embed-core-8.5.28.jar:8.5.28]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-8.5.28.jar:8.5.28]
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:496) [tomcat-embed-core-8.5.28.jar:8.5.28]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) [tomcat-embed-core-8.5.28.jar:8.5.28]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81) [tomcat-embed-core-8.5.28.jar:8.5.28]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) [tomcat-embed-core-8.5.28.jar:8.5.28]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342) [tomcat-embed-core-8.5.28.jar:8.5.28]
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:803) [tomcat-embed-core-8.5.28.jar:8.5.28]
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-8.5.28.jar:8.5.28]
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:790) [tomcat-embed-core-8.5.28.jar:8.5.28]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1459) [tomcat-embed-core-8.5.28.jar:8.5.28]
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-8.5.28.jar:8.5.28]
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) [na:1.8.0_161]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) [na:1.8.0_161]
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-8.5.28.jar:8.5.28]
at java.lang.Thread.run(Unknown Source) [na:1.8.0_161]
是否有办法使用城市名称和公司名称设置保存新用户实体？ 提前谢谢。
答案 0 :(得分：0)
City和User是不同的实体。
当您实例化User对象并为其分配新的City时，Hibernate不会自动将新的City对象保存到数据库。您需要先将新的City对象保存到数据库，然后将该对象附加到新的User对象。
如果您想在创建新City时自动保留User，那么您还可以在@ManyToOne注释中添加cascade = CascadeType.PERSIST。这告诉hibernate也将City保存到数据库。
答案 1 :(得分：0)
这是因为您要添加数据库中不可用的user和city id。
如果您在数据库中提供了ID为1,2,3的城市，并且您正在后端获得下面提到的请求。
{city:{"id":4}在这里，你传递的是id为4的城市，实体中不存在。
确保您在后端获得正确的city id。