使用hibernate和JPA实现一对一外键的正确方法

Question

所以我有2个对象，User和LastFm帐户。现在，用户可能没有LastFm帐户，但每个LastFm帐户将只映射到一个用户。现在您对问题空间了解不多，这就是问题：每当我保存LastFm帐户时，我都会遇到异常。这是例外：

Hibernate: insert into LAST_FM_ACCOUNT (LAST_FM_PASSWORD, LAST_FM_USERNAME, USER_ID) values (?, ?, ?)
Exception in thread "main" org.hibernate.exception.ConstraintViolationException: Cannot add or update a child row: a foreign key constraint fails (`mobsterdb`.`LAST_FM_ACCOUNT`, CONSTRAINT `USER_ID_FK` FOREIGN KEY (`USER_ID`) REFERENCES `MOBSTER_USER` (`USER_ID`) ON DELETE NO ACTION ON UPDATE NO ACTION)
    at org.hibernate.exception.internal.SQLExceptionTypeDelegate.convert(SQLExceptionTypeDelegate.java:74)
    at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:49)
    at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:125)
    at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:110)
    at org.hibernate.engine.jdbc.internal.proxy.AbstractStatementProxyHandler.continueInvocation(AbstractStatementProxyHandler.java:129)
    at org.hibernate.engine.jdbc.internal.proxy.AbstractProxyHandler.invoke(AbstractProxyHandler.java:81)
    at $Proxy17.executeUpdate(Unknown Source)
    at org.hibernate.id.IdentityGenerator$GetGeneratedKeysDelegate.executeAndExtract(IdentityGenerator.java:96)
    at org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:58)
    at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2767)
    at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:3278)
    at org.hibernate.action.internal.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:81)
    at org.hibernate.engine.spi.ActionQueue.execute(ActionQueue.java:362)
    at org.hibernate.engine.spi.ActionQueue.addResolvedEntityInsertAction(ActionQueue.java:203)
    at org.hibernate.engine.spi.ActionQueue.addInsertAction(ActionQueue.java:183)
    at org.hibernate.engine.spi.ActionQueue.addAction(ActionQueue.java:167)
    at org.hibernate.event.internal.AbstractSaveEventListener.addInsertAction(AbstractSaveEventListener.java:320)
    at org.hibernate.event.internal.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:287)
    at org.hibernate.event.internal.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:193)
    at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:126)
    at org.hibernate.ejb.event.EJB3SaveEventListener.saveWithGeneratedId(EJB3SaveEventListener.java:71)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:204)
    at org.hibernate.event.internal.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:55)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:189)
    at org.hibernate.event.internal.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:49)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:90)
    at org.hibernate.internal.SessionImpl.fireSave(SessionImpl.java:757)
    at org.hibernate.internal.SessionImpl.save(SessionImpl.java:749)
    at org.hibernate.internal.SessionImpl.save(SessionImpl.java:745)
    at mobster.persistence.dao.generic.MobsterBaseHibernateDAO.create(MobsterBaseHibernateDAO.java:22)
    at cc.main(cc.java:35)
Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Cannot add or update a child row: a foreign key constraint fails (`mobsterdb`.`LAST_FM_ACCOUNT`, CONSTRAINT `USER_ID_FK` FOREIGN KEY (`USER_ID`) REFERENCES `MOBSTER_USER` (`USER_ID`) ON DELETE NO ACTION ON UPDATE NO ACTION)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
    at java.lang.reflect.Constructor.newInstance(Unknown Source)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
    at com.mysql.jdbc.Util.getInstance(Util.java:386)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1040)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4074)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4006)
    at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2468)
    at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2629)
    at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2719)
    at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2155)
    at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2450)
    at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2371)
    at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2355)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.hibernate.engine.jdbc.internal.proxy.AbstractStatementProxyHandler.continueInvocation(AbstractStatementProxyHandler.java:122)
    ... 26 more

以下是两个实体类：

@Entity
@Table(name = "LAST_FM_ACCOUNT")
public final class LastFmAccount implements Serializable {

private static final long serialVersionUID = 1L;

@Id
@GeneratedValue(generator = "system-id")
@GenericGenerator(name = "system-id", strategy = "identity")
@Column(name = "LAST_FM_ACCOUNT_ID", unique = true)
private int id;

@NotNull
@Column(name = "LAST_FM_USERNAME")
@Type(type = "encryptedString")
private String lastFmUserName;

@NotNull
@Column(name = "LAST_FM_PASSWORD")
@Type(type = "encryptedString")
private String lastFmPassword;

@OneToOne
@JoinColumn(name = "USER_ID")
private MobsterUser user;

public LastFmAccount() {
    /* null op */
}

public LastFmAccount(String lastFmUserName, String lastFmPassword,
        MobsterUser user) {
    super();
    this.lastFmUserName = lastFmUserName;
    this.lastFmPassword = lastFmPassword;
    this.user = user;
}

public int getId() {
    return id;
}

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

public String getLastFmUserName() {
    return lastFmUserName;
}

public void setLastFmUserName(String lastFmUserName) {
    this.lastFmUserName = lastFmUserName;
}

public String getLastFmPassword() {
    return lastFmPassword;
}

public void setLastFmPassword(String lastFmPassword) {
    this.lastFmPassword = lastFmPassword;
}

public MobsterUser getUser() {
    return user;
}

public void setUser(MobsterUser user) {
    this.user = user;
}

@Override
public int hashCode() {
    final int prime = 31;
    int result = 1;
    result = prime * result + id;
    result = prime * result
            + ((lastFmPassword == null) ? 0 : lastFmPassword.hashCode());
    result = prime * result
            + ((lastFmUserName == null) ? 0 : lastFmUserName.hashCode());
    result = prime * result + ((user == null) ? 0 : user.hashCode());
    return result;
}

@Override
public boolean equals(Object obj) {
    if (this == obj)
        return true;
    if (obj == null)
        return false;
    if (getClass() != obj.getClass())
        return false;
    LastFmAccount other = (LastFmAccount) obj;
    if (id != other.id)
        return false;
    if (lastFmPassword == null) {
        if (other.lastFmPassword != null)
            return false;
    } else if (!lastFmPassword.equals(other.lastFmPassword))
        return false;
    if (lastFmUserName == null) {
        if (other.lastFmUserName != null)
            return false;
    } else if (!lastFmUserName.equals(other.lastFmUserName))
        return false;
    if (user == null) {
        if (other.user != null)
            return false;
    } else if (!user.equals(other.user))
        return false;
    return true;
}

@Override
public String toString() {
    return "LastFmAccount [id=" + id + ", lastFmUserName=" + lastFmUserName
            + ", lastFmPassword=" + lastFmPassword + ", user=" + user + "]";
} 
}
//New Table
@Entity @Table(name = "MOBSTER_USER")
public final class MobsterUser implements Serializable {
private static final long serialVersionUID = 1L;
private String userId, email, password, firstName, lastName;
private char gender;
private Date birthday;

public MobsterUser() {

}

public MobsterUser(String email, String password,
        String firstName, String lastName, char gender, Date birthday) {
    this.email = email;
    this.password = password;
    this.firstName = firstName;
    this.lastName = lastName;
    this.gender = gender;
    this.birthday = birthday;
}

@Id
@GeneratedValue(generator="system-uuid")
@GenericGenerator(name="system-uuid", strategy = "uuid")
@Column(name = "USER_ID", unique = true)
public String getUserId() {
    return userId;
}

public void setUserId(String userId) {
    this.userId = userId;
}

@Column(name = "EMAIL", unique = true)
@NotNull
public String getEmail() {
    return email;
}

public void setEmail(String email) {
    this.email = email;
}

@Column(name = "PASSWORD")
@NotNull
@Type(type="encryptedString")
public String getPassword() {
    return password;
}

public void setPassword(String password) {
    this.password = password;
}

@Column(name = "FIRST_NAME")    
@NotNull
public String getFirstName() {
    return firstName;
}

public void setFirstName(String firstName) {
    this.firstName = firstName;
}

@Column(name = "LAST_NAME")
@NotNull
public String getLastName() {
    return lastName;
}

public void setLastName(String lastName) {
    this.lastName = lastName;
}

@Column(name = "GENDER")
@NotNull
public char getGender() {
    return gender;
}

public void setGender(char gender) {
    this.gender = gender;
}

@Column(name = "BIRTHDATE")
@Temporal(TemporalType.DATE)
public Date getBirthday() {
    return birthday;
}

public void setBirthday(Date birthday) {
    this.birthday = birthday;
}

@Override
public String toString() {
    return "MobsterUser [userId=" + userId + ", email=" + email
            + ", password=" + password + ", firstName=" + firstName
            + ", lastName=" + lastName + ", gender=" + gender
            + ", birthday=" + birthday + "]";
}

}

现在我知道有几个关于基本相同问题的帖子，但是有人看到我在这里做错了吗？