Hibernate持久化ArrayList-问题


问题内容

遇到一些麻烦。我正在创建一个带有锦标赛的网站,用户可以注册。比赛将列出注册会员。它不保存用户对象,而只保存用户电子邮件地址,这始终是用户表的关键。我想以这样的方式存储数组列表:我将拥有多个比赛ID的副本,但每个比赛ID仅一个用户名实例。

例如T_ID用户名1 Tom 1 Mike 1 John 2 Tom 2 Chris 2 Timmy 3 Timmy 3 Chris

等等

这是表的SQL。

DROP TABLE IF EXISTS `mtc`.`tournament` ;

CREATE TABLE IF NOT EXISTS `mtc`.`tournament` (
  `id` INT NOT NULL,
  `tournamentName` VARCHAR(100) NULL,
  `tournamentGender` VARCHAR(45) NULL,
  `tournamentType` VARCHAR(45) NULL,
  `tournamentCategory` VARCHAR(45) NULL,
  `tournamentStyle` VARCHAR(45) NULL,
  PRIMARY KEY (`id`))
ENGINE = InnoDB;


-- -----------------------------------------------------
-- Table `mtc`.`tournament_eligible`
-- -----------------------------------------------------
DROP TABLE IF EXISTS `mtc`.`tournament_eligible` ;

CREATE TABLE IF NOT EXISTS `mtc`.`tournament_eligible` (
  `id` INT NOT NULL,
  `username` VARCHAR(45) NULL,
  PRIMARY KEY (`id`),
  CONSTRAINT `fk_tournament_eligible_tournament1`
    FOREIGN KEY (`id`)
    REFERENCES `mtc`.`tournament` (`id`)
    ON DELETE NO ACTION
    ON UPDATE NO ACTION)
ENGINE = InnoDB;

我有两节课。

Tournament.java

    @Entity
    @Table(name = "tournament")
    public class Tournament implements Event {

        @Id
        @GeneratedValue
        private int id;

        @OneToMany
        @JoinColumn(name = "id")
        private List<User> eligible; // Contains a list of eligible members

        @Size(min = 5, max = 45, message = "Tournament Name must be between 5 and 60 characters", groups = {
                PersistenceValidationGroup.class, FormValidationGroup.class })
        private String tournamentName; // Specified the name of the tournament

        private String tournamentGender = "MIXED"; // Specifies where a tournament
                                                    // is M(ale), F(emale) or MIXED;

        private String tournamentType = "S"; // Specifies S(ingles) or D(oubles)

        private String tournamentCategory = "O"; // Specifies Member_Type to be
                                                    // S(enior) only, J(unior) only,
                                                    // or O(pen) Tournament

        private String tournamentStyle = "L"; // Specfies type of Tournament to be
                                                // (L)adder/(L)eague, (B)ucket or
                                                // (G)roup - Probably change this to
                                                // a class later on.

        public Tournament() {
            this.eligible = new ArrayList<User>();
        }

// getters and setters

寄存器类

    @Entity
    @Table(name="tournament_eligible")
    public class Registered {


        @Id
        @Column(name="id")
        private int tournamentID;

        @Column(name="username")
        private String username;

        @OneToMany(mappedBy="tournament")
        private List<String> registered;

// getter and setters

我使用的是正确的javax。*注释,而不是Hibernate的注释。

当前错误:由以下原因引起:org.hibernate.AnnotationException:events.tournaments.Tournament.eligible上的@OneToOne或@ManyToOne引用了一个未知实体:java.util.List

我确实设置了Hibernate配置,以使用Register实体在程序包中查找。

<beans profile="production">
        <jee:jndi-lookup jndi-name="jdbc/mtc" id="dataSource"
            expected-type="javax.sql.DataSource">
        </jee:jndi-lookup>
        <bean id="transactionManager"
            class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
            <property name="dataSource" ref="dataSource"></property>
        </bean>
        <tx:annotation-driven />
        <bean id="sessionFactory"
            class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean">
            <property name="dataSource" ref="dataSource"></property>
            <property name="hibernateProperties">
                <props>
                    <prop key="hibernate.dialect">org.hibernate.dialect.MySQL5Dialect</prop>
                </props>
            </property>
            <property name="packagesToScan">
                <list>
                    <value>users</value>
                    <value>dao</value>
                    <value>events.tournaments</value>
                </list>
            </property>
        </bean>
        <bean id="exceptionTranslator"
            class="org.springframework.dao.annotation.PersistenceExceptionTranslationPostProcessor">
        </bean>
    </beans>

问题答案:

在您的Register课程中,您尝试映射一个字符串列表,就好像它们是实体一样:

    @OneToMany(mappedBy="tournament")
    private List<String> registered;

@OneToMany仅用于实体之间的关系。无论是List也不String是实体。如果要将Collection基本值(如String)映射到表,请查看@CollectionTable批注