集合映射（不太重要）
1 Set
2 List (与Set差不多 多个@OrderBy)
a) @OrderBy 排序
private List<User> users = new ArrayList<User>();
@OneToMany(mappedBy="group",
cascade={CascadeType.ALL}
)
@OrderBy("name ASC")
public List<User> getUsers() {
return users;
}
public void setUsers(List<User> users) {
this.users = users;
}
3 Map
a) @Mapkey
private Map<Integer, User> users = new HashMap<Integer, User>();
@OneToMany(mappedBy="group", cascade=CascadeType.ALL)
@MapKey(name="id")
public Map<Integer, User> getUsers() {
return users;
}
public void setUsers(Map<Integer, User> users) {
this.users = users;
}
@Test
public void testLoadGroup() {
Session s = sessionFactory.getCurrentSession();
s.beginTransaction();
Group g = (Group)s.load(Group.class, 1);
for(Map.Entry<Integer, User> entry : g.getUsers().entrySet()) {
System.out.println(entry.getValue().getName());
}
s.getTransaction().commit();
}
继承映射（不太重要）
一 三种方式
a) 一张总表SINGLE_TABLE（数据库中生成一张表）
@Entity
@Inheritance(strategy=InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name="discriminator", discriminatorType=DiscriminatorType.STRING)
@DiscriminatorValue("person")
public class Person {
private int id;
private String name;
@Id
@GeneratedValue
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
@Entity
@DiscriminatorValue("student")
public class Student extends Person {
private int score;
public int getScore() {
return score;
}
public void setScore(int score) {
this.score = score;
}
}
@Entity
@DiscriminatorValue("teacher")
public class Teacher extends Person {
private String title;
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
}
@Test
public void testSave() {
Student s = new Student();
s.setName("s1");
s.setScore(80);
Teacher t = new Teacher();
t.setName("t1");
t.setTitle("中级");
Session session = sessionFactory.openSession();
session.beginTransaction();
session.save(s);
session.save(t);
session.getTransaction().commit();
session.close();
}
@Test
public void testLoad() {
testSave();
Session session = sessionFactory.openSession();
session.beginTransaction();
Student s = (Student)session.load(Student.class, 1);
System.out.println(s.getScore());
Person p = (Person)session.load(Person.class, 2);
System.out.println(p.getName());
session.getTransaction().commit();
session.close();
}
b) 每个类分别一张表TABLE_PER_CLASS
@Entity
@Inheritance(strategy=InheritanceType.TABLE_PER_CLASS)
@TableGenerator(
name="t_gen",
table="t_gen_table",
pkColumnName="t_pk",
valueColumnName="t_value",
pkColumnValue="person_pk",
initialValue=1,
allocationSize=1
)
public class Person {
private int id;
private String name;
@Id
@GeneratedValue(generator="t_gen", strategy=GenerationType.TABLE)
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
@Entity
public class Student extends Person {
private int score;
public int getScore() {
return score;
}
public void setScore(int score) {
this.score = score;
}
}
@Entity
public class Teacher extends Person {
private String title;
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
}
c) 每个子类一张表jOINED
父类上加注解@Inheritance(strategy=InheritanceType.JOINED)
@Entity
@Inheritance(strategy=InheritanceType.JOINED)
public class Person {
private int id;
private String name;
@Id
@GeneratedValue
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
时间： 2024-10-06 06:55:59