如何使用我的persistence.xml创建我的EntityManagerFactory的实例？

• Z时代
• 2024-01-10
• 分类：问答

我正在使用Spring，Hibernate和JPA创建后端应用程序。 目前应用程序测试通过，但我收到警告： 警告：HHH000436：实体管理器工厂名称（JpaPersistenceUnit）已注册。如何使用我的persistence.xml创建我的EntityManagerFactory的实例？

我认为这样做的原因是我在persistence.xml中定义了我的JpaPersistenceUnit，并且我也在我的dao类中创建了一个。如果是这种情况，我需要找到一种方法从persistence.xml中获取我的JpaPersistenceUnit，而不必再次创建它。但我不知道怎么...

这是我的persistence.xml：

<?xml version="1.0" encoding="UTF-8"?> 
<persistence xmlns="http://java.sun.com/xml/ns/persistence" version="2.0"> 
<persistence-unit name="JpaPersistenceUnit" 
        transaction-type="RESOURCE_LOCAL"> 
    <provider>org.hibernate.ejb.HibernatePersistence</provider> 
    <properties> 
     <property name="hibernate.archive.autodetection" value="class, hbm"/> 
     <property name="hibernate.show_sql" value="true"/> 
     <property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver"/> 
     <property name="hibernate.connection.password" value="groepD"/> 
     <property name="hibernate.connection.url" value="jdbc:mysql://localhost/groepd"/> 
     <property name="hibernate.connection.username" value="groepD"/> 
     <property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect"/> 
     <property name="hibernate.hbm2ddl.auto" value="update"/> 
    </properties> 
</persistence-unit> 
</persistence> 

这是我的泛型DAO类：

public interface GenericDao<E, ID extends Serializable> { 
EntityManagerFactory emf = Persistence.createEntityManagerFactory("JpaPersistenceUnit"); 
public void add(E entity); 
public void remove(E entity); 
public void update(E entity); 
public E findById(ID id); 
public List<E> findAll(); 
} 

这是具体的DAO类：

public interface TripDao extends GenericDao<Trip,Integer> { 
} 

这是dao类的实现：

@Repository 
public class TripDaoImpl implements TripDao { 
protected EntityManager entityManager; 
public TripDaoImpl() { 
    entityManager = emf.createEntityManager(); 
} 
@Override 
@Transactional 
public void add(Trip entity) { 
    entityManager.getTransaction().begin(); 
    entityManager.persist(entity); 
    entityManager.getTransaction().commit(); 
} 
.... 
} 

这是实体：

@Entity 
@Table(name = "T_TRIP") 
public class Trip { 
@Id 
@GeneratedValue(strategy = GenerationType.IDENTITY) 
private Integer id; 
@NotNull 
private String name; 
@ManyToMany(cascade = CascadeType.ALL) 
@JoinTable(name="T_TRIP_ADMINS", 
     joinColumns={@JoinColumn(name="tripId")}, 
     inverseJoinColumns={@JoinColumn(name="userId")}) 
private Set<User> admins; 
@ManyToMany(cascade = CascadeType.ALL) 
@JoinTable(name="T_TRIP_PARTICIPANT", 
     joinColumns={@JoinColumn(name="tripId")}, 
     inverseJoinColumns={@JoinColumn(name="userId")}) 
private Set<User> invitedUsers; 
@NotNull 
private Boolean privateTrip; 
@NotNull 
private Boolean published; 
@Enumerated(EnumType.STRING) 
private TripType type; 
@NotNull 
private Integer nrDays; 
@NotNull 
private Integer nrHours; 
@OneToMany(cascade = CascadeType.ALL) 
@JoinColumn(name = "tripId") 
private Set<Stop> stops; 
public Trip(){ 
    initLists(); 
} 
private void initLists(){ 
    this.admins = new HashSet<User>(); 
    this.invitedUsers = new HashSet<User>(); 
    this.stops = new HashSet<Stop>(); 
} 
public void addStop(Stop stop) { 
    stops.add(stop); 
} 
public boolean removeStop(Stop stop) { 
    if (stops.size() > 1 && stops.contains(stop)) { 
     stops.remove(stop); 
     return true; 
    } else { 
     return false; 
    } 
} 
...More getters and setters... 
} 

如果someboby能告诉我该怎么解决，这将是非常有益的警告。

回答：

<bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean"> 
    <property name="dataSource" ref="dataSource"/> 
    <property name="persistenceXmlLocation" 
     value="classpath:persistence.xml"> 
    </property> 
    <property name="jpaVendorAdapter">   
     <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">  
     <property name="databasePlatform" value="org.hibernate.dialect.MySQL5Dialect" /> 
     </bean> 
    </property> 
    <property name="loadTimeWeaver"> <!-- 运行时植入 --> 
     <bean class="org.springframework.instrument.classloading.InstrumentationLoadTimeWeaver" /> 
    </property> 
</bean> 

以上是 如何使用我的persistence.xml创建我的EntityManagerFactory的实例？ 的全部内容， 来源链接： utcz.com/qa/262679.html