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我想知道如何实现temporal tables在带有 EclipseLink 的 JPA 2 中。我所说的时间是指定义有效期的表。
我面临的一个问题是，由于被引用表的性质，现在它们的主键包括有效期，因此引用表不能再对被引用表(临时表)具有外键约束。
@Entity
public class Team implements Serializable {
private Long id;
private String name;
private Integer wins = 0;
private Integer losses = 0;
private Integer draws = 0;
private List<Player> players = new ArrayList<Player>();
public Team() {
}
public Team(String name) {
this.name = name;
}
@Id
@GeneratedValue(strategy=GenerationType.SEQUENCE, generator="SEQTEAMID")
@SequenceGenerator(name="SEQTEAMID", sequenceName="SEQTEAMID", allocationSize=1)
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
@Column(unique=true, nullable=false)
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getWins() {
return wins;
}
public void setWins(Integer wins) {
this.wins = wins;
}
public Integer getLosses() {
return losses;
}
public void setLosses(Integer losses) {
this.losses = losses;
}
public Integer getDraws() {
return draws;
}
public void setDraws(Integer draws) {
this.draws = draws;
}
@OneToMany(mappedBy="team", cascade=CascadeType.ALL)
public List<Player> getPlayers() {
return players;
}
public void setPlayers(List<Player> players) {
this.players = players;
}
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + ((name == null) ? 0 : name.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;
Team other = (Team) obj;
if (name == null) {
if (other.name != null)
return false;
} else if (!name.equals(other.name))
return false;
return true;
}
}
@Entity
@Table(uniqueConstraints={@UniqueConstraint(columnNames={"team_id","number"})})
public class Player implements Serializable {
private Long id;
private Team team;
private Integer number;
private String name;
public Player() {
}
public Player(Team team, Integer number) {
this.team = team;
this.number = number;
}
@Id
@GeneratedValue(strategy=GenerationType.SEQUENCE, generator="SEQPLAYERID")
@SequenceGenerator(name="SEQPLAYERID", sequenceName="SEQPLAYERID", allocationSize=1)
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
@ManyToOne
@JoinColumn(nullable=false)
public Team getTeam() {
return team;
}
public void setTeam(Team team) {
this.team = team;
}
@Column(nullable=false)
public Integer getNumber() {
return number;
}
public void setNumber(Integer number) {
this.number = number;
}
@Column(unique=true, nullable=false)
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + ((number == null) ? 0 : number.hashCode());
result = prime * result + ((team == null) ? 0 : team.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;
Player other = (Player) obj;
if (number == null) {
if (other.number != null)
return false;
} else if (!number.equals(other.number))
return false;
if (team == null) {
if (other.team != null)
return false;
} else if (!team.equals(other.team))
return false;
return true;
}
}
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration({"/META-INF/application-context-root.xml"})
@Transactional
public class TestingDao {
@PersistenceContext
private EntityManager entityManager;
private Team team;
@Before
public void setUp() {
team = new Team();
team.setName("The Goods");
team.setLosses(0);
team.setWins(0);
team.setDraws(0);
Player player = new Player();
player.setTeam(team);
player.setNumber(1);
player.setName("Alfredo");
team.getPlayers().add(player);
player = new Player();
player.setTeam(team);
player.setNumber(2);
player.setName("Jorge");
team.getPlayers().add(player);
entityManager.persist(team);
entityManager.flush();
}
@Test
public void testPersistence() {
String strQuery = "select t from Team t where t.name = :name";
TypedQuery<Team> query = entityManager.createQuery(strQuery, Team.class);
query.setParameter("name", team.getName());
Team persistedTeam = query.getSingleResult();
assertEquals(2, persistedTeam.getPlayers().size());
//Change the player number
Player p = null;
for (Player player : persistedTeam.getPlayers()) {
if (player.getName().equals("Alfredo")) {
p = player;
break;
}
}
p.setNumber(10);
}
}
Player 开始.
Player 的外键约束。表要
Team .问题是您将如何在 Java 和 JPA 中对其进行建模。
最佳答案
我对这个话题很感兴趣。我在开发使用这些模式的应用程序方面工作了几年，这个想法来自我们的德国文凭论文。
我不知道“DAO Fusion”框架，它们提供了有趣的信息和链接，感谢您提供这些信息。特别是pattern page和 aspects page很棒!
对于您的问题:不，我无法指出其他站点、示例或框架。恐怕您必须使用DAO Fusion框架或自己实现此功能。您必须区分您真正需要哪种功能。用“DAO Fusion”框架来说:你需要“有效时间”和“记录时间”吗？当更改应用于您的数据库时记录时间状态(通常用于审计问题)，当更改发生在现实生活中或在现实生活中有效(由应用程序使用)时，有效的时间状态可能与记录时间不同。在大多数情况下，一维就足够了，不需要第二维。
无论如何，时间功能会对您的数据库产生影响。正如您所说:“现在他们的主键包括有效期”。那么如何对实体的身份进行建模呢？我更喜欢 surrogate keys 的用法.在这种情况下，这意味着:
SELECT * FROM Person p, Residence r
WHERE p.ENTITY_ID = r.FK_ENTITY_ID_PERSON // JOIN SELECT * FROM Person p, Residence r
WHERE p.ENTITY_ID = r.FK_ENTITY_ID_PERSON AND
p.recordTo=[infinity] and r.recordTo=[infinity] // only current technical stateSELECT * FROM Person p, Residence r
WHERE p.ENTITY_ID = r.FK_ENTITY_ID_PERSON AND
p.recordTo=[infinity] and r.recordTo=[infinity] AND
p.validFrom <= [now] AND p.validTo > [now] AND // only current valid state person
r.validFrom <= [now] AND r.validTo > [now] // only current valid state residence关于java - 如何使用 JPA 实现时态表？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/9542366/
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4
0
我正在使用斯坦福标记器来确定词性。但是，我想从文本中获取更多信息。是否有可能获得更多信息，例如句子的时态或是否处于主动/被动状态？ 到目前为止，我使用的是非常基本的 PoS 标记方法: List> t
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