Hibernate的那些事-manyToOne诠注映射(List集合)

Hibernate的那些事-manyToOne注解映射(List集合)
1:定义一个Group类，在映射关系中为一的一方：

package collections.list;import java.util.ArrayList;import java.util.List;import javax.persistence.CascadeType;import javax.persistence.Entity;import javax.persistence.GeneratedValue;import javax.persistence.Id;import javax.persistence.OneToMany;import javax.persistence.OrderBy;import javax.persistence.Table;@Entity@Table(name = "t_list_group")public class Group { private int id; private String name; private List<User> users = new ArrayList<User>(); @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; } @OneToMany(mappedBy = "group", cascade = { CascadeType.ALL }) @OrderBy("name ASC") public List<User> getUsers() {  return users; } public void setUsers(List<User> users) {  this.users = users; }}

2:定义一个User类，映射中多的一方：

package collections.list;import javax.persistence.CascadeType;import javax.persistence.Entity;import javax.persistence.GeneratedValue;import javax.persistence.Id;import javax.persistence.ManyToOne;import javax.persistence.Table;@Entity@Table(name = "t_list_user")public class User { private int id; private String name; private Group group; @ManyToOne(cascade = CascadeType.ALL) public Group getGroup() {  return group; } public void setGroup(Group group) {  this.group = group; } @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; }}

在hibernate.cfg.xml中添加对实体的映射：

<mapping />
  <mapping />

这里我们使用的是注解映射，要特别与使用映射文件的映射公开来;

同时也要注意一个问题(在hibernate.cfg.xml文件中不能将两种混用，否则会出错)



3：使用Junit对这个映射进行测试：

package collections.list;import org.hibernate.Session;import org.hibernate.SessionFactory;import org.hibernate.cfg.AnnotationConfiguration;import org.hibernate.tool.hbm2ddl.SchemaExport;import org.junit.AfterClass;import org.junit.BeforeClass;import org.junit.Test;public class TestListJunit { /**  * @param args  */ private static SessionFactory sessionFactory; @BeforeClass public static void beforClass() {  new SchemaExport(new AnnotationConfiguration().configure()).create(    false, true);  sessionFactory = new AnnotationConfiguration().configure()    .buildSessionFactory(); } @AfterClass public static void afterClass() {  if (sessionFactory != null) {   sessionFactory.close();  } } @Test public void testSavaEntity() {  Session session = sessionFactory.getCurrentSession();  session.beginTransaction();  Group group = new Group();  group.setName("animal");  User user = new User();  user.setName("little dog");  user.setGroup(group);  User user1 = new User();  user1.setName("little cat");  user1.setGroup(group);  group.getUsers().add(user);  group.getUsers().add(user1);  session.save(group);  session.save(user);  session.save(user1);  session.getTransaction().commit(); } public static void main(String[] args) {  beforClass(); }}

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