Question

我有两个问题阻碍了我的开发一段时间：

当我在我的控制器中执行此操作时，仅当我在子类中的父类引用上执行Jackson（com.fasterxml.jackson）@JsonIgnore时才有效：

为什么会出现这种行为？这是应该预料到的吗？

@RequestMapping(value = "/get", method = RequestMethod.POST)
@ResponseBody
public Tenant data(@RequestParam("id") Long id) {
    return tenantRepo.get(id);
}

（如果我不给@JsonIgnore，它会进入一个孩子内部父类的infinte循环并抛出错误）

2。现在我将这个json传递给下面的控制器端点：

{
  "type": "Student",
  "numOfPeople": "1",
  "tenantMembers": [
    {
      "firstName": "Chris",
      "lastName": "C"
    }
  ],
  "tenantDetails": {
    "firstName": "John",
    "lastName": "J",
    "email" "xyz@gmail.com"
  }
}

 @RequestMapping(value = "/set", method = RequestMethod.POST, consumes = MediaType.APPLICATION_JSON_VALUE)
        @ResponseBody
        public Tenant test(@RequestBody Tenant tenant) {
            return tenantRepo.save(tenant);
        }

（我得到了SQLERROR。我尝试删除外键约束，但仍然是同样的问题。）

我的父类：

@Entity
@Table(name = "tenant")
public class Tenant {

@GeneratedValue
@Id
private Long id;

private String type;

@Column(name = "num_of_people")
private String numOfPeople;

@OneToMany(mappedBy = "tenant", cascade = CascadeType.ALL, fetch = FetchType.LAZY)
private List<TenantMember> tenantMembers;

@OneToOne(mappedBy = "tenant", cascade = CascadeType.ALL)
private TenantDetails tenantDetails;

TenantMember儿童班：

@Entity
@Table(name = "tenant_member")
public class TenantMember {
@GeneratedValue
@Id
private Long id;

@ManyToOne
@JoinColumn(name = "tenant_id")
@JsonIgnore
private Tenant tenant;

@Column(name = "first_name")
private String firstName;

@Column(name = "last_name")
private String lastName;

TenanatDetails子类：

@Entity
@Table(name="tenant_details")
public class TenantDetails {
@GeneratedValue
@Id
private Long id;

@OneToOne
@JoinColumn(name = "tenant_id")
@JsonIgnore
private Tenant tenant;

@Column(name = "first_name")
private String firstName;

@Column(name = "last_name")
private String lastName;

private String email;

这是我的Hibernate配置：

@Configuration
@EnableTransactionManagement
public class HibernateConfig {

    @Value("${jdbc.driverClassName}")
    private String driverClassName;
    @Value("${jdbc.url}")
    private String url;
    @Value("${jdbc.username}")
    private String username;
    @Value("${jdbc.password}")
    private String password;

    @Value("${hibernate.dialect}")
    private String hibernateDialect;
    @Value("${hibernate.show_sql}")
    private String hibernateShowSql;
    @Value("${hibernate.format_sql}")
    private String hibernateFormatSql;


    @Bean
    public SessionFactory sessionFactory() {
        LocalSessionFactoryBuilder builder = new LocalSessionFactoryBuilder(dataSource());
        builder.scanPackages(new String[]{"com.example.demo.core.db.models"})
                .addProperties(hibernateProperties());
        return builder.buildSessionFactory();
    }

    @Bean
    public DataSource dataSource() {
        DriverManagerDataSource dataSource = new DriverManagerDataSource();
        dataSource.setDriverClassName(driverClassName);
        dataSource.setUrl(url);
        dataSource.setUsername(username);
        dataSource.setPassword(password);
        return dataSource;
    }

    private Properties hibernateProperties() {
        Properties properties = new Properties();
        //properties.put("hibernate.dialect", hibernateDialect);
        properties.put("hibernate.show_sql", hibernateShowSql);
        properties.put("hibernate.format_sql", hibernateFormatSql);
        return properties;
    }

    @Bean
    public HibernateTransactionManager transactionManager(SessionFactory sessionFactory) {
        return new HibernateTransactionManager(sessionFactory);
    }
}

问题1的堆栈跟踪：

org.springframework.http.converter.HttpMessageNotWritableException: Could not write content: failed to lazily initialize a collection of role: com.example.demo.core.db.models.Tenant.tenantMembers, could not initialize proxy - no Session (through reference chain: com.example.demo.core.db.models.Tenant[&quot;tenantMembers&quot;]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: failed to lazily initialize a collection of role: com.example.demo.core.db.models.Tenant.tenantMembers, could not initialize proxy - no Session (through reference chain: com.example.demo.core.db.models.Tenant[&quot;tenantMembers&quot;])
    org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.writeInternal(AbstractJackson2HttpMessageConverter.java:272)
    org.springframework.http.converter.AbstractGenericHttpMessageConverter.write(AbstractGenericHttpMessageConverter.java:100)
    org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:222)
    org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:153)
    org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.handleReturnValue(RequestResponseBodyMethodProcessor.java:165)
    org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:80)
    org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:126)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:817)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:731)
    org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
    org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:959)
    org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893)
    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:968)
    org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:870)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:648)
    org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:844)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.example.demo.core.db.models.Tenant.tenantMembers, could not initialize proxy - no Session
    org.hibernate.collection.internal.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:579)
    org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:203)
    org.hibernate.collection.internal.AbstractPersistentCollection.readSize(AbstractPersistentCollection.java:144)
    org.hibernate.collection.internal.PersistentBag.size(PersistentBag.java:261)
    com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:102)
    com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:25)
    com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:672)
    com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:678)
    com.fasterxml.jackson.databind.ser.std.BeanSerializerBase._serializeWithObjectId(BeanSerializerBase.java:600)
    com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:148)
    com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:130)
    com.fasterxml.jackson.databind.ObjectWriter$Prefetch.serialize(ObjectWriter.java:1428)
    com.fasterxml.jackson.databind.ObjectWriter.writeValue(ObjectWriter.java:930)
    org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.writeInternal(AbstractJackson2HttpMessageConverter.java:265)
    org.springframework.http.converter.AbstractGenericHttpMessageConverter.write(AbstractGenericHttpMessageConverter.java:100)
    org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:222)
    org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:153)
    org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.handleReturnValue(RequestResponseBodyMethodProcessor.java:165)
    org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:80)
    org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:126)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:817)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:731)
    org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
    org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:959)
    org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893)
    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:968)
    org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:870)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:648)
    org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:844)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

问题2的堆栈跟踪:(已编辑）

org.hibernate.exception.ConstraintViolationException: could not execute statement
    org.hibernate.exception.internal.SQLExceptionTypeDelegate.convert(SQLExceptionTypeDelegate.java:59)
    org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:42)
    org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:111)
    org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:97)
    org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:207)
    org.hibernate.dialect.identity.GetGeneratedKeysDelegate.executeAndExtract(GetGeneratedKeysDelegate.java:57)
    org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:42)
    org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2827)
    org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:3398)
    org.hibernate.action.internal.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:81)
    org.hibernate.engine.spi.ActionQueue.execute(ActionQueue.java:597)
    org.hibernate.engine.spi.ActionQueue.addResolvedEntityInsertAction(ActionQueue.java:232)
    org.hibernate.engine.spi.ActionQueue.addInsertAction(ActionQueue.java:213)
    org.hibernate.engine.spi.ActionQueue.addAction(ActionQueue.java:256)
    org.hibernate.event.internal.AbstractSaveEventListener.addInsertAction(AbstractSaveEventListener.java:318)
    org.hibernate.event.internal.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:275)
    org.hibernate.event.internal.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:182)
    org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:113)
    org.hibernate.event.internal.DefaultMergeEventListener.saveTransientEntity(DefaultMergeEventListener.java:254)
    org.hibernate.event.internal.DefaultMergeEventListener.entityIsTransient(DefaultMergeEventListener.java:234)
    org.hibernate.event.internal.DefaultMergeEventListener.onMerge(DefaultMergeEventListener.java:172)
    org.hibernate.internal.SessionImpl.fireMerge(SessionImpl.java:853)
    org.hibernate.internal.SessionImpl.merge(SessionImpl.java:835)
    org.hibernate.engine.spi.CascadingActions$6.cascade(CascadingActions.java:260)
    org.hibernate.engine.internal.Cascade.cascadeToOne(Cascade.java:391)
    org.hibernate.engine.internal.Cascade.cascadeAssociation(Cascade.java:316)
    org.hibernate.engine.internal.Cascade.cascadeProperty(Cascade.java:155)
    org.hibernate.engine.internal.Cascade.cascadeCollectionElements(Cascade.java:424)
    org.hibernate.engine.internal.Cascade.cascadeCollection(Cascade.java:356)
    org.hibernate.engine.internal.Cascade.cascadeAssociation(Cascade.java:319)
    org.hibernate.engine.internal.Cascade.cascadeProperty(Cascade.java:155)
    org.hibernate.engine.internal.Cascade.cascade(Cascade.java:104)
    org.hibernate.event.internal.AbstractSaveEventListener.cascadeAfterSave(AbstractSaveEventListener.java:445)
    org.hibernate.event.internal.DefaultMergeEventListener.entityIsTransient(DefaultMergeEventListener.java:238)
    org.hibernate.event.internal.DefaultMergeEventListener.onMerge(DefaultMergeEventListener.java:172)
    org.hibernate.event.internal.DefaultMergeEventListener.onMerge(DefaultMergeEventListener.java:68)
    org.hibernate.internal.SessionImpl.fireMerge(SessionImpl.java:843)
    org.hibernate.internal.SessionImpl.merge(SessionImpl.java:825)
    org.hibernate.internal.SessionImpl.merge(SessionImpl.java:830)
    com.example.demo.core.db.repos.base.impl.BaseRepoImpl.save(BaseRepoImpl.java:80)
    sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    java.lang.reflect.Method.invoke(Method.java:606)
    org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:302)
    org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:190)
    org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)
    org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:99)
    org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:281)
    org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)
    org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:208)
    com.sun.proxy.$Proxy48.save(Unknown Source)
    com.example.demo.web.controllers.TenantsController.test(TenantsController.java:30)
    sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    java.lang.reflect.Method.invoke(Method.java:606)
    org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:221)
    org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136)
    org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:110)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:817)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:731)
    org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
    org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:959)
    org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893)
    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:968)
    org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:870)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:648)
    org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:844)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)


com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Column 'tenant_id' cannot be null
    sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
    sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    java.lang.reflect.Constructor.newInstance(Constructor.java:526)
    com.mysql.jdbc.Util.handleNewInstance(Util.java:404)
    com.mysql.jdbc.Util.getInstance(Util.java:387)
    com.mysql.jdbc.SQLError.createSQLException(SQLError.java:932)
    com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3878)
    com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3814)
    com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2478)
    com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2625)
    com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2551)
    com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1861)
    com.mysql.jdbc.PreparedStatement.executeUpdateInternal(PreparedStatement.java:2073)
    com.mysql.jdbc.PreparedStatement.executeUpdateInternal(PreparedStatement.java:2009)
    com.mysql.jdbc.PreparedStatement.executeLargeUpdate(PreparedStatement.java:5094)
    com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:1994)
    org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:204)
    org.hibernate.dialect.identity.GetGeneratedKeysDelegate.executeAndExtract(GetGeneratedKeysDelegate.java:57)
    org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:42)
    org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2827)
    org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:3398)
    org.hibernate.action.internal.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:81)
    org.hibernate.engine.spi.ActionQueue.execute(ActionQueue.java:597)
    org.hibernate.engine.spi.ActionQueue.addResolvedEntityInsertAction(ActionQueue.java:232)
    org.hibernate.engine.spi.ActionQueue.addInsertAction(ActionQueue.java:213)
    org.hibernate.engine.spi.ActionQueue.addAction(ActionQueue.java:256)
    org.hibernate.event.internal.AbstractSaveEventListener.addInsertAction(AbstractSaveEventListener.java:318)
    org.hibernate.event.internal.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:275)
    org.hibernate.event.internal.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:182)
    org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:113)
    org.hibernate.event.internal.DefaultMergeEventListener.saveTransientEntity(DefaultMergeEventListener.java:254)
    org.hibernate.event.internal.DefaultMergeEventListener.entityIsTransient(DefaultMergeEventListener.java:234)
    org.hibernate.event.internal.DefaultMergeEventListener.onMerge(DefaultMergeEventListener.java:172)
    org.hibernate.internal.SessionImpl.fireMerge(SessionImpl.java:853)
    org.hibernate.internal.SessionImpl.merge(SessionImpl.java:835)
    org.hibernate.engine.spi.CascadingActions$6.cascade(CascadingActions.java:260)
    org.hibernate.engine.internal.Cascade.cascadeToOne(Cascade.java:391)
    org.hibernate.engine.internal.Cascade.cascadeAssociation(Cascade.java:316)
    org.hibernate.engine.internal.Cascade.cascadeProperty(Cascade.java:155)
    org.hibernate.engine.internal.Cascade.cascadeCollectionElements(Cascade.java:424)
    org.hibernate.engine.internal.Cascade.cascadeCollection(Cascade.java:356)
    org.hibernate.engine.internal.Cascade.cascadeAssociation(Cascade.java:319)
    org.hibernate.engine.internal.Cascade.cascadeProperty(Cascade.java:155)
    org.hibernate.engine.internal.Cascade.cascade(Cascade.java:104)
    org.hibernate.event.internal.AbstractSaveEventListener.cascadeAfterSave(AbstractSaveEventListener.java:445)
    org.hibernate.event.internal.DefaultMergeEventListener.entityIsTransient(DefaultMergeEventListener.java:238)
    org.hibernate.event.internal.DefaultMergeEventListener.onMerge(DefaultMergeEventListener.java:172)
    org.hibernate.event.internal.DefaultMergeEventListener.onMerge(DefaultMergeEventListener.java:68)
    org.hibernate.internal.SessionImpl.fireMerge(SessionImpl.java:843)
    org.hibernate.internal.SessionImpl.merge(SessionImpl.java:825)
    org.hibernate.internal.SessionImpl.merge(SessionImpl.java:830)
    com.example.demo.core.db.repos.base.impl.BaseRepoImpl.save(BaseRepoImpl.java:80)
    sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    java.lang.reflect.Method.invoke(Method.java:606)
    org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:302)
    org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:190)
    org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)
    org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:99)
    org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:281)
    org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)
    org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:208)
    com.sun.proxy.$Proxy48.save(Unknown Source)
    com.example.demo.web.controllers.TenantsController.test(TenantsController.java:30)
    sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    java.lang.reflect.Method.invoke(Method.java:606)
    org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:221)
    org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136)
    org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:110)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:817)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:731)
    org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
    org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:959)
    org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893)
    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:968)
    org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:870)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:648)
    org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:844)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

Answer 1

问题1：以下内容并不完全适合您使用@JsonIgnore作为Tenant的子引用。

但它解释了为什么你会得到我认为的第一个例外。

您正在从控制器返回租户实例。 Tenant.tenantMembers是一个懒惰的集合。当您从tenantRepo中读取Tenant时，Tenant.tenantMembers集合未加载，因为它很懒。 Spring在输入tenantRepo.get（id）之前打开一个事务，然后在它之后关闭它。当事务关闭时，hibernate会话也会关闭，并且无法加载空集合Tenant.tenantMembers。杰克逊试图将租户转换为JSON并尝试阅读Tenant.tenantMembers。因为没有会话，所以抛出异常

com.example.demo.core.db.models.Tenant.tenantMembers, could not initialize proxy - no Session

当您在tenantMembers上添加@JsonIgnore时，Jackson不会触及该字段，您也不会获得例外。

要解决这个问题，你必须获取Tenant.tenantMembers EAGER，而不是LAZY。这不会使您的应用程序变慢，因为您必须阅读整个集合，以将其作为JSON返回。实现这一目标的最简单方法是改变

@OneToMany(mappedBy = "tenant", cascade = CascadeType.ALL, fetch =    
FetchType.EAGER)
private List<TenantMember> tenantMembers;

但如果你想在其他情况下获取LAZY，这可能不是你想要的。您还可以使用方法get（Long id）创建TenatService，并注释ax @Transactional。你可以在get（..）方法中进行

租户租户= tenantRepo.get（id）; 。tenant.getTenantMembers（）大小（）;

当您输入get（..）方法时，spring会打开一个新事务（因为@Transactional），从同一事务中的存储库中读取。在集合上调用size（）将加载它，因为事务仍处于打开状态，所以hibernate会这样做。当get（..）离开时，spring关闭事务，但这没有问题，因为集合已经初始化。多数民众赞成。

问题2 在提供的代码中，我找不到该异常的原因。我建议在

设置一个断点

  com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2551)

看看到底发生了什么。在那里，或者在堆栈中你会看到hibernate想要编写的实体。通常情况下，这会为您提供有关出错的更多信息。在堆栈跟踪中，您会看到ActionQueue，hibernate在事务结束时使用它来写入数据库。这种情况发生在交易关闭时，而不是在执行保存（..）时直接发生。希望有所帮助。

关于评论：@Transactional，并调用size（）但它不起作用 - 得到了相同的错误。（在调用size（）之前抛出的异常）...

嗨kukkuz，可能有理由获得异常，但是你得到相同的HttpMessageNotWritableException听起来不太可能。序列化将在很晚之后发生，因此在调用.size（）之前接近该异常几乎是不可能的。

实际上堆栈跟踪显示，当请求离开控制器方法并且spring尝试将结果序列化为JSON时抛出异常。

您必须在注释为transactional的服务方法中调用.size（）。在那里设置一个断点，你应该在调用服务方法之前在stacktrace中看到一个spring代理。如果不是，则表明您的事务管理不起作用。您还可能必须使用服务接口，具体取决于配置/版本spring将仅创建接口的代理。请发布该异常的堆栈跟踪以找到确切原因。

关于评论：对于问题2，已更新堆栈跟踪....

在堆栈跟踪中，您会看到hibernate尝试保存一对一的关系：

org.hibernate.engine.internal.Cascade.cascadeToOne(Cascade.java:391)

所以问题一定是这种关系错误的定义：

@OneToMany(mappedBy = "tenant", cascade = CascadeType.ALL, fetch = FetchType.LAZY)

私人名单租户成员;

我认为你的mappedBy在错误的一端。

来自jpa one to one：

如果关系是双向的，则非拥有方必须使用mappedBy

你拥有非自有的一面。

父类选择查询错误+一起插入父/子：Spring 4 Hibernate ORM

1 个答案: