Question

我有一个映射的POJO，我需要坚持。在那个POJO中我有另一个POJO，用外键绑定现在，当我创建一个新对象并使用Hibernate持久化时，Hibernate是否仍然存在嵌入式POJO，或者我必须手动执行它？基本上问题是关于“反向级联”。

在我的情况下，这不会发生，如果我事先没有保留嵌入式POJO，我会收到异常。

编辑：这里有一些代码，我省略了一些细节（setter＆amp; getters）：这是Person类，如您所见，它有一个嵌入在其中的Address类。

@Entity
public class Person {

    protected Address address;
    protected String privateName;
    ...
    /* More members */

    @ManyToOne
    @JoinColumn(name = "address_id", nullable = false, unique = true)
    public Address getAddress() {
        return this.address;
    }

    public void setAddress(Address address) {
        this.address = address;
    }

    @Column(name = "private_name", nullable = false, length = 45)
    public String getPrivateName() {
        return this.privateName;
    }

    public void setPrivateName(String privateName) {
        this.privateName = privateName;
    }
}

这是地址类：

@JsonIgnoreProperties({ "hibernateLazyInitializer", "handler" })
@SuppressWarnings("serial")
@Entity
@Table(name = "address")
public class Address implements java.io.Serializable {

    private Integer id; 
    private Country country;
    private State state;
    private String city;
    private String street;
    private String number;
    private String postcode;
    private float longitude;
    private float latitude;

    public Address() {
    }

    public Address(Integer id, Country countries, String city, String street,
        String number, String postcode, float longitude, float latitude) {
    this.id = id;
    this.country = countries;
    this.city = city;
    this.street = street;
    this.number = number;
    this.postcode = postcode;
    this.longitude = longitude;
    this.latitude = latitude;
    }

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "id", unique = true, nullable = false)
    public Integer getId() {
    return this.id;
    }

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

    @ManyToOne
    @JoinColumn(name = "state")
    public State getState() {
    return this.state;
    }

    public void setState(State state) {
    this.state = state;
    }

    @ManyToOne
    @JoinColumn(name = "country", nullable = false)
    public Country getCountry() {
    return this.country;
    }  
}

这是我在Spring中使用的Hibernate配置：

<bean id="dataSource"
        class="org.springframework.jdbc.datasource.DriverManagerDataSource">
        <property name="driverClassName" value="org.h2.Driver" />
        <property name="url" value="jdbc:h2:mem:my_db;INIT=CREATE SCHEMA IF NOT EXISTS my_db;DB_CLOSE_DELAY=-1" />

    </bean>

    <bean id="sessionFactory"
        class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean">
        <property name="dataSource">
            <ref bean="dataSource" />
        </property>
        <property name="packagesToScan" value="com.tra.la.bla" />

        <property name="hibernateProperties">
            <props>
                <prop key="hibernate.dialect">org.hibernate.dialect.H2Dialect</prop>
                <prop key="hibernate.hbm2ddl.auto">create</prop>
                <prop key="hibernate.show_sql">true</prop>
            </props>
        </property>
    </bean>

    <bean id="transactionManager"
        class="org.springframework.orm.hibernate3.HibernateTransactionManager">
        <property name="sessionFactory">
            <ref bean="sessionFactory" />
        </property>
    </bean>

Answer 1

不，除非你告诉Hibernate使用

，否则不会级联

@ManyToOne(cascade = CascadeType.PERSIST)

请参阅http://docs.jboss.org/hibernate/core/3.6/reference/en-US/html_single/#objectstate-transitive

Answer 2

@ManyToOne(cascade = CascadeType.DETACH)
@JoinColumn(name = "address_id", nullable = false, unique = true)
public Address getAddress() {
    return this.address;
}

也许上面的代码解决了你的问题

您可以使用上面的一些代码来说明hibernate如何对连接的POJO起作用。

我希望它有所帮助

基本的休眠持久性

2 个答案: