hibernate3 一对多多对一单向关联级联增删改查
hibernate中如何对一对多，多对一的单向关联进行级联的crud操作呢，主要使用cascade与fetch
例子如下：
首先是@OneToMany跟@ManyToOne中cascade属性的设置，查看hibernate annotation
文档可以看到cascade属性有几个取值，我们使用ALL来操作，cascade={CascadeType.ALL}
表示对级联的对象进行cud操作时候都进行级联操作(PS:进行读取操作的时候不级联)，
进行读取操作的时候要设置fetch的属性,fetch=FetchType.EAGER,onetomany这方默认是LAZY，
manytoone这方默认是EAGER。
－－－－－－－－－－Group类如下：
import java.util.HashSet;
import java.util.Set;
import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToMany;
import javax.persistence.Table;
@Entity
@Table(name="t_group")
public class Group {
?private int id;
?private String name;
?private Set<User> users = new HashSet<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}
?????//fetch=FetchType.EAGER
??)
?
?public Set<User> getUsers() {
??return users;
?}
?public void setUsers(Set<User> users) {
??this.users = users;
?}
}
－－－－－－－－－－－－－－－User类如下：
import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.ManyToOne;
import javax.persistence.Table;
@Entity
@Table(name="t_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;
?}
}
－－－－－－－－－－－－－－hibernate.cfg.xml配置文件如下：
<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
????????"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
????????"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
????<session-factory>
????????
????????<property name="connection.driver_class">com.mysql.jdbc.Driver</property>
????????<property name="connection.url">jdbc:mysql://localhost/hibernate</property>
????????<property name="connection.username">root</property>
????????<property name="connection.password">heavenlin1</property>
????????<property name="dialect">org.hibernate.dialect.MySQLDialect</property>
???????<!--
????????<property name="connection.driver_class">oracle.jdbc.driver.OracleDriver</property>
????????<property name="connection.url">jdbc:oracle:thin:@localhost:1521:SXT</property>
????????<property name="connection.username">scott</property>
????????<property name="connection.password">tiger</property>
???????<property name="dialect">org.hibernate.dialect.OracleDialect</property>
???????-->
????????<!-- JDBC connection pool (use the built-in) -->
????????<property name="connection.pool_size">1</property>
?
????????<!-- Enable Hibernate's automatic session context management -->
????????<property name="current_session_context_class">thread</property>
????????<!-- Disable the second-level cache??-->
????????<property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>
????????<!-- Echo all executed SQL to stdout -->
????????<property name="show_sql">true</property>
????????<property name="format_sql">true</property>
????????<!-- Drop and re-create the database schema on startup
????????<property name="hbm2ddl.auto">update</property>
???-->
??<mapping class="com.bjsxt.hibernate.Group"/>
??<mapping class="com.bjsxt.hibernate.User"/>
??
????</session-factory>
</hibernate-configuration>
－－－－－－－－－－－－－－－－－－测试类代码如下：
package com.bjsxt.hibernate;
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 HibernateORMappingTest {
?private static SessionFactory sessionFactory;
?
?@BeforeClass
?public static void beforeClass() {
??new SchemaExport(new AnnotationConfiguration().configure()).create(false, true);
??sessionFactory = new AnnotationConfiguration().configure().buildSessionFactory();
?}
?@AfterClass
?public static void afterClass() {
??sessionFactory.close();
?}
?
?@Test
?public void testSaveUser() {
??User u = new User();
??u.setName("u1");
??Group g = new Group();
??g.setName("g1");
??u.setGroup(g);
??Session s = sessionFactory.getCurrentSession();
??s.beginTransaction();
??//s.save(g);
??s.save(u);
??s.getTransaction().commit();
?}
?
?@Test
?public void testSaveGroup() {
??User u1 = new User();
??u1.setName("u1");
??User u2 = new User();
??u2.setName("u2");
??Group g = new Group();
??g.setName("g1");
??g.getUsers().add(u1);
??g.getUsers().add(u2);
??u1.setGroup(g);
??u2.setGroup(g);
??Session s = sessionFactory.getCurrentSession();
??s.beginTransaction();
??//s.save(g);
??s.save(g);
??s.getTransaction().commit();
?}
?
?@Test
?public void testGetUser() {
??
??testSaveGroup();
??
??Session s = sessionFactory.getCurrentSession();
??s.beginTransaction();
??User u = (User)s.get(User.class, 1);
??System.out.println(u.getGroup().getName());
??s.getTransaction().commit();
??
?}
?
?@Test
?public void testLoadUser() {
??
??testSaveGroup();
??
??Session s = sessionFactory.getCurrentSession();
??s.beginTransaction();
??User u = (User)s.load(User.class, 1);
??System.out.println(u.getGroup().getName());
??s.getTransaction().commit();
??
?}
?
?@Test
?public void testDeleteUser() {
??
??testSaveGroup();
??
??Session s = sessionFactory.getCurrentSession();
??s.beginTransaction();
??//User u = (User)s.load(User.class, 1);
??//u.setGroup(null);
??//s.delete(u);
??s.createQuery("delete from User u where u.id = 1").executeUpdate();
??s.getTransaction().commit();
??
?}
?
?@Test
?public void testDeleteGroup() {
??
??testSaveGroup();
??
??Session s = sessionFactory.getCurrentSession();
??s.beginTransaction();
??//User u = (User)s.load(User.class, 1);
??//u.setGroup(null);
??//s.delete(u);
??Group g = (Group)s.load(Group.class, 1);
??s.delete(g);
??//s.createQuery("delete from User u where u.id = 1").executeUpdate();
??s.getTransaction().commit();
??
?}
?
?@Test
?public void testUpdateUser() {
??
??testSaveGroup();
??
??Session s = sessionFactory.getCurrentSession();
??s.beginTransaction();
??User u = (User)s.get(User.class, 1);
??
??s.getTransaction().commit();
??
??u.setName("user");
??u.getGroup().setName("group");
??
??Session s2 = sessionFactory.getCurrentSession();
??s2.beginTransaction();
??s2.update(u);
??
??s2.getTransaction().commit();
?}
?
?
?
?@Test
?public void testGetGroup() {
??
??testSaveGroup();
??
??Session s = sessionFactory.getCurrentSession();
??s.beginTransaction();
??Group g = (Group)s.get(Group.class, 1);
??s.getTransaction().commit();
??for(User u : g.getUsers()) {
???System.out.println(u.getName());
??}
?}
?
?@Test
?public void testSchemaExport() {
??new SchemaExport(new AnnotationConfiguration().configure()).create(false, true);
?}
?
?public static void main(String[] args) {
??beforeClass();
?}
}
