插入数据时外键约束失败如何解决答案

【问题标题】：how to solve foreign key constraint fails when inserting data插入数据时外键约束失败如何解决
【发布时间】：2020-12-20 09:27:20
【问题描述】：

我创建了一个简单的在线购物网站。后端使用 Spring Boot 和 MySQL 数据库开发。在那里，有两张桌子。那些是购物车和购物车项目。 Cart 基本上有一个 Id，它是 Cart 的主键，并且 Cart 有一个 CartItems 列表。所以每个 CartItem 都有一个属性，即购物车 id，它是购物车项目表中的外键。

所以问题是当我尝试向 Cart 表添加新记录时，它不起作用并引发错误

无法添加或更新子行：外键约束失败（test.cartitem, CONSTRAINT FK_CART_ID FOREIGN KEY (fkcartid) REFERENCES cart (id)）

这是我的表结构

create table cart(
    
    id int AUTO_INCREMENT,
    totalprice double,
    itemcount int,
    CONSTRAINT PK_CART_ID PRIMARY KEY (id)
)

create table cartitem(
    
    id int AUTO_INCREMENT,
    fkcartid int,
    productname text,
    qty int,
    totalprice double,
    CONSTRAINT PK_CARTITEM_ID PRIMARY KEY (id),
    CONSTRAINT FK_CART_ID FOREIGN KEY (fkcartid) REFERENCES cart(id)
    
    
)

这是我在项目中的模型

@Entity
@Table(name = "cart")
public class Cart {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;

    private double totalprice;

    private int itemcount;

    @OneToMany(cascade=CascadeType.ALL)
    @JoinColumn(name = "cart_id", referencedColumnName = "id",insertable = false,updatable = false)
    private List<Cartitem> cartitems;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public double getTotalprice() {
        return totalprice;
    }

    public void setTotalprice(double totalprice) {
        this.totalprice = totalprice;
    }

    public List<Cartitem> getCartitemtests() {
        return cartitems;
    }

    public void setCartitemtests(List<Cartitem> cartitems) {
        this.cartitems = cartitems;
    }

    public int getItemcount() {
        return itemcount;
    }

    public void setItemcount(int itemcount) {
        this.itemcount = itemcount;
    }

    public List<Cartitem> getCartitems() {
        return cartitems;
    }

    public void setCartitems(List<Cartitem> cartitems) {
        this.cartitems = cartitems;
    }
}

        @Entity
@Table(name = "cartitem")
public class Cartitem {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private  int id;

    private int fkcartid;

    private String productname;

    private int qty;

    private double totalprice;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public int getFkcartid() {
        return fkcartid;
    }

    public void setFkcartid(int fkcartid) {
        this.fkcartid = fkcartid;
    }

    public String getProductname() {
        return productname;
    }

    public void setProductname(String productname) {
        this.productname = productname;
    }

    public int getQty() {
        return qty;
    }

    public void setQty(int qty) {
        this.qty = qty;
    }

    public double getTotalprice() {
        return totalprice;
    }

    public void setTotalprice(double totalprice) {
        this.totalprice = totalprice;
    }
}

这是存储库类

@Repository
public interface CartRepo extends CrudRepository<Cart,Integer> {
}

@Repository
public interface CartItemrepo extends CrudRepository<Cartitem,Integer> {
}

这是控制器类

@RestController
public class homecontroller {

    @Autowired
    basicService basicServiceobj;

   
    @PostMapping(value = "/product")
    public Cart addproduct(@RequestBody Cart cart){
        return basicServiceobj.additems(cart);
    }
}

这是服务类

@Service
public class basicService {

    @Autowired
    AddressRepo addressRepo;
    @Autowired
    CityRepo cityRepo;

    @Autowired
    CartRepo cartRepo;

    public Cart additems(Cart cart){
        return cartRepo.save(cart);
    }

}

这是轨迹

java.sql.SQLIntegrityConstraintViolationException: Cannot add or update a child row: a foreign key constraint fails (`test`.`cartitem`, CONSTRAINT `FK_CART_ID` FOREIGN KEY (`fkcartid`) REFERENCES `cart` (`id`))
at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:117) ~[mysql-connector-java-8.0.22.jar:8.0.22]
at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:97) ~[mysql-connector-java-8.0.22.jar:8.0.22]
at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:122) ~[mysql-connector-java-8.0.22.jar:8.0.22]
at com.mysql.cj.jdbc.ClientPreparedStatement.executeInternal(ClientPreparedStatement.java:953) ~[mysql-connector-java-8.0.22.jar:8.0.22]
at com.mysql.cj.jdbc.ClientPreparedStatement.executeUpdateInternal(ClientPreparedStatement.java:1092) ~[mysql-connector-java-8.0.22.jar:8.0.22]
at com.mysql.cj.jdbc.ClientPreparedStatement.executeUpdateInternal(ClientPreparedStatement.java:1040) ~[mysql-connector-java-8.0.22.jar:8.0.22]
at com.mysql.cj.jdbc.ClientPreparedStatement.executeLargeUpdate(ClientPreparedStatement.java:1347) ~[mysql-connector-java-8.0.22.jar:8.0.22]
at com.mysql.cj.jdbc.ClientPreparedStatement.executeUpdate(ClientPreparedStatement.java:1025) ~[mysql-connector-java-8.0.22.jar:8.0.22]
at com.zaxxer.hikari.pool.ProxyPreparedStatement.executeUpdate(ProxyPreparedStatement.java:61) ~[HikariCP-3.4.5.jar:na]
at com.zaxxer.hikari.pool.HikariProxyPreparedStatement.executeUpdate(HikariProxyPreparedStatement.java) ~[HikariCP-3.4.5.jar:na]
at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:197) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.dialect.identity.GetGeneratedKeysDelegate.executeAndExtract(GetGeneratedKeysDelegate.java:57) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:43) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:3199) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:3805) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.action.internal.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:84) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.engine.spi.ActionQueue.execute(ActionQueue.java:645) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.engine.spi.ActionQueue.addResolvedEntityInsertAction(ActionQueue.java:282) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.engine.spi.ActionQueue.addInsertAction(ActionQueue.java:263) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.engine.spi.ActionQueue.addAction(ActionQueue.java:317) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.event.internal.AbstractSaveEventListener.addInsertAction(AbstractSaveEventListener.java:330) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.event.internal.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:287) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.event.internal.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:193) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:123) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.event.internal.DefaultPersistEventListener.entityIsTransient(DefaultPersistEventListener.java:185) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:128) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.event.service.internal.EventListenerGroupImpl.fireEventOnEachListener(EventListenerGroupImpl.java:113) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.internal.SessionImpl.firePersist(SessionImpl.java:744) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:712) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.engine.spi.CascadingActions$7.cascade(CascadingActions.java:298) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.engine.internal.Cascade.cascadeToOne(Cascade.java:492) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.engine.internal.Cascade.cascadeAssociation(Cascade.java:416) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.engine.internal.Cascade.cascadeProperty(Cascade.java:218) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.engine.internal.Cascade.cascadeCollectionElements(Cascade.java:525) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.engine.internal.Cascade.cascadeCollection(Cascade.java:456) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.engine.internal.Cascade.cascadeAssociation(Cascade.java:419) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.engine.internal.Cascade.cascadeProperty(Cascade.java:218) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.engine.internal.Cascade.cascade(Cascade.java:151) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.event.internal.AbstractSaveEventListener.cascadeAfterSave(AbstractSaveEventListener.java:459) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.event.internal.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:293) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.event.internal.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:193) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:123) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.event.internal.DefaultPersistEventListener.entityIsTransient(DefaultPersistEventListener.java:185) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:128) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:55) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.event.service.internal.EventListenerGroupImpl.fireEventOnEachListener(EventListenerGroupImpl.java:102) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.internal.SessionImpl.firePersist(SessionImpl.java:720) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:706) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_261]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_261]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_261]
at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_261]
at org.springframework.orm.jpa.ExtendedEntityManagerCreator$ExtendedEntityManagerInvocationHandler.invoke(ExtendedEntityManagerCreator.java:362) ~[spring-orm-5.3.2.jar:5.3.2]
at com.sun.proxy.$Proxy79.persist(Unknown Source) ~[na:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_261]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_261]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_261]
at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_261]
at org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:311) ~[spring-orm-5.3.2.jar:5.3.2]
at com.sun.proxy.$Proxy79.persist(Unknown Source) ~[na:na]
at org.springframework.data.jpa.repository.support.SimpleJpaRepository.save(SimpleJpaRepository.java:557) ~[spring-data-jpa-2.4.2.jar:2.4.2]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_261]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_261]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_261]
at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_261]
at org.springframework.data.repository.core.support.RepositoryMethodInvoker$RepositoryFragmentMethodInvoker.lambda$new$0(RepositoryMethodInvoker.java:289) ~[spring-data-commons-2.4.2.jar:2.4.2]
at org.springframework.data.repository.core.support.RepositoryMethodInvoker.doInvoke(RepositoryMethodInvoker.java:137) ~[spring-data-commons-2.4.2.jar:2.4.2]
at org.springframework.data.repository.core.support.RepositoryMethodInvoker.invoke(RepositoryMethodInvoker.java:121) ~[spring-data-commons-2.4.2.jar:2.4.2]
at org.springframework.data.repository.core.support.RepositoryComposition$RepositoryFragments.invoke(RepositoryComposition.java:524) ~[spring-data-commons-2.4.2.jar:2.4.2]
at org.springframework.data.repository.core.support.RepositoryComposition.invoke(RepositoryComposition.java:285) ~[spring-data-commons-2.4.2.jar:2.4.2]
at org.springframework.data.repository.core.support.RepositoryFactorySupport$ImplementationMethodExecutionInterceptor.invoke(RepositoryFactorySupport.java:531) ~[spring-data-commons-2.4.2.jar:2.4.2]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.3.2.jar:5.3.2]
at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.doInvoke(QueryExecutorMethodInterceptor.java:156) ~[spring-data-commons-2.4.2.jar:2.4.2]
at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.invoke(QueryExecutorMethodInterceptor.java:131) ~[spring-data-commons-2.4.2.jar:2.4.2]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.3.2.jar:5.3.2]
at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:123) ~[spring-tx-5.3.2.jar:5.3.2]
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:388) ~[spring-tx-5.3.2.jar:5.3.2]
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:119) ~[spring-tx-5.3.2.jar:5.3.2]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.3.2.jar:5.3.2]
at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:137) ~[spring-tx-5.3.2.jar:5.3.2]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.3.2.jar:5.3.2]
at org.springframework.data.jpa.repository.support.CrudMethodMetadataPostProcessor$CrudMethodMetadataPopulatingMethodInterceptor.invoke(CrudMethodMetadataPostProcessor.java:174) ~[spring-data-jpa-2.4.2.jar:2.4.2]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.3.2.jar:5.3.2]
at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:97) ~[spring-aop-5.3.2.jar:5.3.2]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.3.2.jar:5.3.2]
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:215) ~[spring-aop-5.3.2.jar:5.3.2]
at com.sun.proxy.$Proxy86.save(Unknown Source) ~[na:na]
at com.test.addressmapping.demo.basicService.additems(basicService.java:28) ~[classes/:na]
at com.test.addressmapping.demo.homecontroller.addproduct(homecontroller.java:32) ~[classes/:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_261]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_261]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_261]
at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_261]
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:197) ~[spring-web-5.3.2.jar:5.3.2]
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:141) ~[spring-web-5.3.2.jar:5.3.2]
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:106) ~[spring-webmvc-5.3.2.jar:5.3.2]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:894) ~[spring-webmvc-5.3.2.jar:5.3.2]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808) ~[spring-webmvc-5.3.2.jar:5.3.2]
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.3.2.jar:5.3.2]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1061) ~[spring-webmvc-5.3.2.jar:5.3.2]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:961) ~[spring-webmvc-5.3.2.jar:5.3.2]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.3.2.jar:5.3.2]
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909) ~[spring-webmvc-5.3.2.jar:5.3.2]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:652) ~[tomcat-embed-core-9.0.41.jar:4.0.FR]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.3.2.jar:5.3.2]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:733) ~[tomcat-embed-core-9.0.41.jar:4.0.FR]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-9.0.41.jar:9.0.41]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.41.jar:9.0.41]
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.41.jar:9.0.41]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.41.jar:9.0.41]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.41.jar:9.0.41]
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.3.2.jar:5.3.2]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.2.jar:5.3.2]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.41.jar:9.0.41]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.41.jar:9.0.41]
at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.3.2.jar:5.3.2]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.2.jar:5.3.2]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.41.jar:9.0.41]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.41.jar:9.0.41]
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.3.2.jar:5.3.2]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.2.jar:5.3.2]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.41.jar:9.0.41]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.41.jar:9.0.41]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) ~[tomcat-embed-core-9.0.41.jar:9.0.41]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97) [tomcat-embed-core-9.0.41.jar:9.0.41]
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542) [tomcat-embed-core-9.0.41.jar:9.0.41]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143) [tomcat-embed-core-9.0.41.jar:9.0.41]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.41.jar:9.0.41]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78) [tomcat-embed-core-9.0.41.jar:9.0.41]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) [tomcat-embed-core-9.0.41.jar:9.0.41]
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:374) [tomcat-embed-core-9.0.41.jar:9.0.41]
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) [tomcat-embed-core-9.0.41.jar:9.0.41]
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:888) [tomcat-embed-core-9.0.41.jar:9.0.41]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1597) [tomcat-embed-core-9.0.41.jar:9.0.41]
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.41.jar:9.0.41]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_261]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_261]
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.41.jar:9.0.41]
at java.lang.Thread.run(Thread.java:748) [na:1.8.0_261]

在此处输入代码

所有存储库都由 CrudRepository 接口 spring boot 版本（2.4.1）扩展 java版本（8）

如何解决这个问题

【问题讨论】：

您似乎尝试多次保留同一个购物车。定义看起来不错。你能edit这个问题包含更多代码和堆栈跟踪吗？
好的，我会这样做的
另外，我们通常在 JPA 实体中嵌入由外键引用的对象。所以private int fkcartid 真的应该是一个@ManyToOne-annotated Cart-field。
我确实编辑了问题并包含了您提出的所有问题。你能用代码解释一下吗？
啊，我想我看到了问题所在。由于Cartitem中的外键值fkcartid设置不正确，fkcartid的值很可能是0，并且对于第一个持久化，不存在Cart和id 0。反过来，这会导致对外键约束的约束违反。正如我在上一条评论中所建议的那样，当您在Cartitem 中使用@ManyToOne-relation 时，问题应该会自行解决。您能否验证这是否解决了问题？

标签： java spring-boot spring-data-jpa

【解决方案1】：

有很多事情是错误的。我会尽量解决它。首先，为了将来的目的，最好通过在 application.properties 中执行以下操作来查看执行的 sql 查询

# Hibernate ddl auto (create, create-drop, update)
spring.jpa.properties.hibernate.hbm2ddl.auto=update
spring.jpa.properties.hibernate.show_sql=true
spring.jpa.properties.hibernate.format_sql=true

其次，据我了解，从您建立关系的方式来看，您似乎正在建立一个双向的一对多映射。如果是这样，我建议在子实体中添加 @ManyToOne。此外，您需要添加一个实用程序方法来同步此双向映射。正如 cmets 中所指出的，外键值将为 0，因为您使用原始类型作为“id”字段。所以，设置变成了以下

购物车实体

public class Cart implements Serializable {
    
    /**
     * 
     */
    private static final long serialVersionUID = 8155938349165825920L;

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    
    private int totalPrice;
    
    private int itemCount;
    
    @OneToMany(mappedBy = "cart", cascade = CascadeType.ALL, orphanRemoval = true)
    private List<CartItem> cartItems;
    
    public void setCart(CartItem cartItem) {
        cartItem.setCart(this);
    }   
  // setters/getters removed for brevity
}

CartItem 实体

public class CartItem {
    
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    
    private String productName;
    
    private int qty;
    
    private double totalPrice;
    
    @ManyToOne(fetch = FetchType.LAZY)
    @JsonIgnore
    private Cart cart;
  // setters/getters removed for brevity    
}

购物车服务实现

public interface ICartService {
    
    Cart addCart(Cart cart);
    
}


@Service
public class CartServiceImpl implements ICartService {

    @Autowired
    private CartRepository cartRepository;
    
    @Override
    public Cart addCart(Cart cart) {
        cart.getCartItems().forEach(item -> cart.setCart(item));
        return cartRepository.save(cart);
    }
}

除此之外，id 最好使用对象类型而不是原始类型。为什么？因为根据“null”值检查实体的持久性是有意义的，否则，在持久化“id”字段之前，该值将具有“0”作为值（不是 null）。

【讨论】：