如何使用休眠方式保存ManyToOne关系

Question

我有以下User实体。

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name="user_id")
    private int id;

    @Embedded
    private Person person;

    @Column(columnDefinition = "VARCHAR(255)")
    private String image;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name="user_group_id")
    private UserGroup userGroup;
    
    // Some getters and setters ommitted

    public int getId() {
        return id;
    }

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

    public UserGroup getUserGroup() {
        return userGroup;
    }

    public void setUserGroup(UserGroup userGroup) {
        this.userGroup = userGroup;
    }

以及以下可嵌入的Person实体。

    @NotNull
    @Column(name="firstname", nullable = false, columnDefinition = "VARCHAR(32)")
    private String firstName;

    @NotNull
    @Column(name="lastname", nullable = false, columnDefinition = "VARCHAR(32)")
    private String lastName;

    @NotNull
    @Column(nullable = false, columnDefinition = "VARCHAR(96)")
    private String email;

    @NotNull
    @Column(nullable = false, columnDefinition = "VARCHAR(24)")
    private String telephone;

    @NotNull
    @Column(nullable = false, columnDefinition = "VARCHAR(255)")
    private String password;

    @Column(nullable = false, columnDefinition = "TINYINT(1) DEFAULT 1")
    private boolean status;

    @Column(name = "date_added", nullable = false, updatable=false, columnDefinition = "DATETIME DEFAULT CURRENT_TIMESTAMP")
    @Temporal(value = TemporalType.TIMESTAMP)
    private Date dateAdded;

以及以下UserGroup实体。

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name="user_group_id")
    private int id;

    @NotNull
    @Column(nullable = false, columnDefinition = "VARCHAR(20)")
    private String name;

    @NotNull
    @Column(nullable = false, columnDefinition = "TEXT")
    private String permission;

    @OneToMany(mappedBy="userGroup",
    cascade={CascadeType.PERSIST, CascadeType.MERGE},
    fetch = FetchType.LAZY)
    private List<User> users = new ArrayList<User>();
    
    // Getters and Setters ommitted

我已经在数据库中建立了几个用户组。添加新用户时，我检索了一个特定的组，并希望将其分配给新用户。我使用以下代码来做到这一点。

        Session session = HibernateHelper.getSessionFactory().openSession();
        UserGroup userGroup = (UserGroup) session.createQuery("FROM UserGroup UG WHERE UG.id = :user_group_id")
                .setParameter("user_group_id",Integer.parseInt(group))
                .getSingleResult();

        Transaction tx = session.getTransaction();
        tx.begin();

        User user = new User();
        user.setPerson(new Person());
        user.getPerson().setFirstName(firstName);
        user.getPerson().setLastName(lastName);
        user.getPerson().setEmail(email);
        user.getPerson().setTelephone(telephone);
        user.getPerson().setPassword(hashedPassword);

        user.setUserGroup(userGroup); // Assign the new user this group

        session.save(user);
        tx.commit();
        session.close();

但是我得到了例外：org.hibernate.exception.ConstraintViolationException 正确的方法是什么？

我正在使用在wildfly服务器上运行的servlet开发Web应用。

错误堆栈跟踪：

org.hibernate.exception.ConstraintViolationException: could not execute statement
    at deployment.shopping_cart.war//org.hibernate.exception.internal.SQLExceptionTypeDelegate.convert(SQLExceptionTypeDelegate.java:59)
    at deployment.shopping_cart.war//org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:42)
    at deployment.shopping_cart.war//org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:113)
    at deployment.shopping_cart.war//org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:99)
    at deployment.shopping_cart.war//org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:200)
    at deployment.shopping_cart.war//org.hibernate.dialect.identity.GetGeneratedKeysDelegate.executeAndExtract(GetGeneratedKeysDelegate.java:57)
    at deployment.shopping_cart.war//org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:43)
    at deployment.shopping_cart.war//org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:3153)
    at deployment.shopping_cart.war//org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:3759)
    at deployment.shopping_cart.war//org.hibernate.action.internal.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:84)
    at deployment.shopping_cart.war//org.hibernate.engine.spi.ActionQueue.execute(ActionQueue.java:645)
    at deployment.shopping_cart.war//org.hibernate.engine.spi.ActionQueue.addResolvedEntityInsertAction(ActionQueue.java:282)
    at deployment.shopping_cart.war//org.hibernate.engine.spi.ActionQueue.addInsertAction(ActionQueue.java:263)
    at deployment.shopping_cart.war//org.hibernate.engine.spi.ActionQueue.addAction(ActionQueue.java:317)
    at deployment.shopping_cart.war//org.hibernate.event.internal.AbstractSaveEventListener.addInsertAction(AbstractSaveEventListener.java:330)
    at deployment.shopping_cart.war//org.hibernate.event.internal.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:287)
    at deployment.shopping_cart.war//org.hibernate.event.internal.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:193)
    at deployment.shopping_cart.war//org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:123)
    at deployment.shopping_cart.war//org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:194)
    at deployment.shopping_cart.war//org.hibernate.event.internal.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:38)
    at deployment.shopping_cart.war//org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:179)
    at deployment.shopping_cart.war//org.hibernate.event.internal.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:32)
    at deployment.shopping_cart.war//org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:75)
    at deployment.shopping_cart.war//org.hibernate.event.service.internal.EventListenerGroupImpl.fireEventOnEachListener(EventListenerGroupImpl.java:102)
    at deployment.shopping_cart.war//org.hibernate.internal.SessionImpl.fireSave(SessionImpl.java:634)
    at deployment.shopping_cart.war//org.hibernate.internal.SessionImpl.save(SessionImpl.java:627)
    at deployment.shopping_cart.war//org.hibernate.internal.SessionImpl.save(SessionImpl.java:622)
    at deployment.shopping_cart.war//controllers.UserCreate.doPost(UserCreate.java:51)
    at javax.servlet.api@2.0.0.Final//javax.servlet.http.HttpServlet.service(HttpServlet.java:523)
    at javax.servlet.api@2.0.0.Final//javax.servlet.http.HttpServlet.service(HttpServlet.java:590)
    at io.undertow.servlet@2.1.3.Final//io.undertow.servlet.handlers.ServletHandler.handleRequest(ServletHandler.java:74)
    at io.undertow.servlet@2.1.3.Final//io.undertow.servlet.handlers.security.ServletSecurityRoleHandler.handleRequest(ServletSecurityRoleHandler.java:62)
    at io.undertow.servlet@2.1.3.Final//io.undertow.servlet.handlers.ServletChain$1.handleRequest(ServletChain.java:68)
    at io.undertow.servlet@2.1.3.Final//io.undertow.servlet.handlers.ServletDispatchingHandler.handleRequest(ServletDispatchingHandler.java:36)
    at org.wildfly.extension.undertow@20.0.1.Final//org.wildfly.extension.undertow.security.SecurityContextAssociationHandler.handleRequest(SecurityContextAssociationHandler.java:78)
    at io.undertow.core@2.1.3.Final//io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
    at io.undertow.servlet@2.1.3.Final//io.undertow.servlet.handlers.RedirectDirHandler.handleRequest(RedirectDirHandler.java:68)
    at io.undertow.servlet@2.1.3.Final//io.undertow.servlet.handlers.security.SSLInformationAssociationHandler.handleRequest(SSLInformationAssociationHandler.java:132)
    at io.undertow.servlet@2.1.3.Final//io.undertow.servlet.handlers.security.ServletAuthenticationCallHandler.handleRequest(ServletAuthenticationCallHandler.java:57)
    at io.undertow.core@2.1.3.Final//io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
    at io.undertow.core@2.1.3.Final//io.undertow.security.handlers.AbstractConfidentialityHandler.handleRequest(AbstractConfidentialityHandler.java:46)
    at io.undertow.servlet@2.1.3.Final//io.undertow.servlet.handlers.security.ServletConfidentialityConstraintHandler.handleRequest(ServletConfidentialityConstraintHandler.java:64)
    at io.undertow.core@2.1.3.Final//io.undertow.security.handlers.AuthenticationMechanismsHandler.handleRequest(AuthenticationMechanismsHandler.java:60)
    at io.undertow.servlet@2.1.3.Final//io.undertow.servlet.handlers.security.CachedAuthenticatedSessionHandler.handleRequest(CachedAuthenticatedSessionHandler.java:77)
    at io.undertow.core@2.1.3.Final//io.undertow.security.handlers.NotificationReceiverHandler.handleRequest(NotificationReceiverHandler.java:50)
    at io.undertow.core@2.1.3.Final//io.undertow.security.handlers.AbstractSecurityContextAssociationHandler.handleRequest(AbstractSecurityContextAssociationHandler.java:43)
    at io.undertow.core@2.1.3.Final//io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
    at org.wildfly.extension.undertow@20.0.1.Final//org.wildfly.extension.undertow.security.jacc.JACCContextIdHandler.handleRequest(JACCContextIdHandler.java:61)
    at io.undertow.core@2.1.3.Final//io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
    at org.wildfly.extension.undertow@20.0.1.Final//org.wildfly.extension.undertow.deployment.GlobalRequestControllerHandler.handleRequest(GlobalRequestControllerHandler.java:68)
    at io.undertow.core@2.1.3.Final//io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
    at io.undertow.servlet@2.1.3.Final//io.undertow.servlet.handlers.ServletInitialHandler.handleFirstRequest(ServletInitialHandler.java:269)
    at io.undertow.servlet@2.1.3.Final//io.undertow.servlet.handlers.ServletInitialHandler.access$100(ServletInitialHandler.java:78)
    at io.undertow.servlet@2.1.3.Final//io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:133)
    at io.undertow.servlet@2.1.3.Final//io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:130)
    at io.undertow.servlet@2.1.3.Final//io.undertow.servlet.core.ServletRequestContextThreadSetupAction$1.call(ServletRequestContextThreadSetupAction.java:48)
    at io.undertow.servlet@2.1.3.Final//io.undertow.servlet.core.ContextClassLoaderSetupAction$1.call(ContextClassLoaderSetupAction.java:43)
    at org.wildfly.extension.undertow@20.0.1.Final//org.wildfly.extension.undertow.security.SecurityContextThreadSetupAction.lambda$create$0(SecurityContextThreadSetupAction.java:105)
    at org.wildfly.extension.undertow@20.0.1.Final//org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction.lambda$create$0(UndertowDeploymentInfoService.java:1530)
    at org.wildfly.extension.undertow@20.0.1.Final//org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction.lambda$create$0(UndertowDeploymentInfoService.java:1530)
    at org.wildfly.extension.undertow@20.0.1.Final//org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction.lambda$create$0(UndertowDeploymentInfoService.java:1530)
    at org.wildfly.extension.undertow@20.0.1.Final//org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction.lambda$create$0(UndertowDeploymentInfoService.java:1530)
    at io.undertow.servlet@2.1.3.Final//io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:249)
    at io.undertow.servlet@2.1.3.Final//io.undertow.servlet.handlers.ServletInitialHandler.access$000(ServletInitialHandler.java:78)
    at io.undertow.servlet@2.1.3.Final//io.undertow.servlet.handlers.ServletInitialHandler$1.handleRequest(ServletInitialHandler.java:99)
    at io.undertow.core@2.1.3.Final//io.undertow.server.Connectors.executeRootHandler(Connectors.java:370)
    at io.undertow.core@2.1.3.Final//io.undertow.server.HttpServerExchange$1.run(HttpServerExchange.java:830)
    at org.jboss.threads@2.3.3.Final//org.jboss.threads.ContextClassLoaderSavingRunnable.run(ContextClassLoaderSavingRunnable.java:35)
    at org.jboss.threads@2.3.3.Final//org.jboss.threads.EnhancedQueueExecutor.safeRun(EnhancedQueueExecutor.java:1982)
    at org.jboss.threads@2.3.3.Final//org.jboss.threads.EnhancedQueueExecutor$ThreadBody.doRunTask(EnhancedQueueExecutor.java:1486)
    at org.jboss.threads@2.3.3.Final//org.jboss.threads.EnhancedQueueExecutor$ThreadBody.run(EnhancedQueueExecutor.java:1377)
    at java.base/java.lang.Thread.run(Thread.java:832)
Caused by: java.sql.SQLIntegrityConstraintViolationException: Column 'date_added' cannot be null
    at deployment.shopping_cart.war//com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:117)
    at deployment.shopping_cart.war//com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:97)
    at deployment.shopping_cart.war//com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:122)
    at deployment.shopping_cart.war//com.mysql.cj.jdbc.ClientPreparedStatement.executeInternal(ClientPreparedStatement.java:953)
    at deployment.shopping_cart.war//com.mysql.cj.jdbc.ClientPreparedStatement.executeUpdateInternal(ClientPreparedStatement.java:1092)
    at deployment.shopping_cart.war//com.mysql.cj.jdbc.ClientPreparedStatement.executeUpdateInternal(ClientPreparedStatement.java:1040)
    at deployment.shopping_cart.war//com.mysql.cj.jdbc.ClientPreparedStatement.executeLargeUpdate(ClientPreparedStatement.java:1347)
    at deployment.shopping_cart.war//com.mysql.cj.jdbc.ClientPreparedStatement.executeUpdate(ClientPreparedStatement.java:1025)
    at deployment.shopping_cart.war//org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:197)
    ... 67 more

Answer 1

拥有字段时

@Column(name = "date_added", nullable = false, updatable=false, columnDefinition = "DATETIME DEFAULT CURRENT_TIMESTAMP")
@Temporal(value = TemporalType.TIMESTAMP)
private Date dateAdded;

未将dateAdded设置为适当的值（因此将其保留为null）会导致ConstraintViolationException。因此，在初始化用户时，您需要设置dateAdded，这通常是在构造函数中或通过JPA批注进行的，但您也可以手动进行设置：

[...]
user.getPerson().setDateAdded(new Date());
user.setUserGroup(userGroup); // Assign the new user this group
[...]

编辑：

因为我很懒，我想使事情自动化，所以我主要使用注释来自动更新日期。我特别不喜欢特定于供应商的解决方案，因此我通常使用JPA：

public class Person {
    // ...
    
    @PrePersist
    public void prePersist() {
        dateAdded = new Date();
    }
}

尽管那里有针对Hibernate或Spring的更复杂的解决方案，但效果始终是相同的：使用基于注释的机制，您不再需要手动设置dateAdded。