关联关系一对多映射

1. Junit4方法详解

setUpBeforeClass() 类初始化前调用;
tearDownAfterClass() 类初始化后调用;
setUp() 在测试方法前调用;
tearDown() 在测试方法后调用;

JunitTest.java

package com.andrew.service;
import org.junit.After;
import org.junit.AfterClass;
import org.junit.Before;
import org.junit.BeforeClass;
import org.junit.Test;
public class JunitTest {
    @BeforeClass
    public static void setUpBeforeClass() throws Exception {
        System.out.println("类初始化前调用...");
    }
    @AfterClass
    public static void tearDownAfterClass() throws Exception {
        System.out.println("类初始化后调用...");
    }
    @Before
    public void setUp() throws Exception {
        System.out.println("在测试方法前调用...");
    }
    @After
    public void tearDown() throws Exception {
        System.out.println("在测试方法后调用...");
    }
    @Test
    public void test() {
        System.out.println("测试方法");
    }
}

运行结果：
类初始化前调用...
在测试方法前调用...
测试方法
在测试方法后调用...
类初始化后调用...

2. 一对多映射实现(单向)

hibernate.cfg.xml

<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    <session-factory>
        <!-- 数据库连接设置 -->
        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="connection.url">jdbc:mysql://localhost:3306/hibernate4</property>
        <property name="connection.username">root</property>
        <property name="connection.password">root</property>
        <!-- 方言 -->
        <property name="dialect">org.hibernate.dialect.MySQL5Dialect</property>
        <!-- 控制台显示SQL -->
        <property name="show_sql">true</property>
        <!-- 自动更新表结构 -->
        <property name="hbm2ddl.auto">update</property>
        <!-- Mapper -->
        <mapping resource="com/andrew/model/Student.hbm.xml"/>
        <mapping resource="com/andrew/model/Class.hbm.xml"/>
    </session-factory>
</hibernate-configuration>

HibernateUtil.java

package com.andrew.util;
import org.hibernate.SessionFactory;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
public class HibernateUtil {
    private static final SessionFactory sessionFactory = buildSessionFactory();
    private static SessionFactory buildSessionFactory() {
        // 1. 实例化配置文件
        Configuration configuration = new Configuration().configure();
        // 2. 实例化服务登记
        ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder()
                .applySettings(configuration.getProperties()).build();
        // 3. 获取Session工厂
        return configuration.buildSessionFactory(serviceRegistry);
    }
    public static SessionFactory getSessionFactory() {
        return sessionFactory;
    }
}

Class.java

package com.andrew.model;
public class Class {
    private long id;
    private String name;
    public long getId() {
        return id;
    }
    public void setId(long id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
}

Class.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.andrew.model">
    <class name="Class" table="t_class">
        <id column="classId" name="id">
            <generator class="native"/>
        </id>
        <property name="name" column="className"/>
    </class>
</hibernate-mapping>

Student.java

package com.andrew.model;
public class Student {
    private long id;
    private String name;
    private Class c;
    public long getId() {
        return id;
    }
    public void setId(long id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Class getC() {
        return c;
    }
    public void setC(Class c) {
        this.c = c;
    }
    @Override
    public String toString() {
        return "Student [id=" + id + ", name=" + name + ", c=" + c + "]";
    }
}

Student.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.andrew.model">
    <class name="Student" table="t_student">
        <id column="stuId" name="id">
            <generator class="native"/>
        </id>
        <property name="name" column="stuName"/>
        <many-to-one name="c" column="classId" class="com.andrew.model.Class"></many-to-one>
    </class>
</hibernate-mapping>

StudentTest.java

package com.andrew.service;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import com.andrew.model.Class;
import com.andrew.model.Student;
import com.andrew.util.HibernateUtil;
public class StudentTest {
    public static void main(String[] args) {
        SessionFactory sessionFactory = HibernateUtil.getSessionFactory();
        Session session = sessionFactory.openSession(); // 1. 生成一个session
        session.beginTransaction(); // 2. 开启事务
        Class c = new Class();
        c.setName("10级1班");
        session.save(c);
        
        Student s1 = new Student();
        s1.setName("张三");
        s1.setC(c);
        session.save(s1);
        
        Student s2 = new Student();
        s2.setName("李四");
        s2.setC(c);
        session.save(s2);
        session.getTransaction().commit(); // 3. 提交事务
        session.close(); // 4. 关闭session
    }
}

3. 级联保存更新

在<many-to-one>这端，cascade默认是”none”，假如我们希望在持久化多的一端的时候，自动级联保存和更新一的一端，我们可以把cascade设置成”save-update”；

内存空间
临时对象      持久化对象(在session缓存中)
class对象     student1对象
              student2对象

3.1) 不使用级联保存

Student.hbm.xml

<many-to-one name="c" column="classId" class="com.andrew.model.Class"></many-to-one>

StudentJunitTest.java

package com.andrew.service;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import com.andrew.model.Class;
import com.andrew.model.Student;
import com.andrew.util.HibernateUtil;
public class StudentJunitTest {
    private SessionFactory sessionFactory = HibernateUtil.getSessionFactory();
    private Session session;
    @Before
    public void setUp() throws Exception {
        session = sessionFactory.openSession(); // 1. 生成一个session
        session.beginTransaction(); // 2. 开启事务
    }
    @After
    public void tearDown() throws Exception {
        session.getTransaction().commit(); // 3. 提交事务
        session.close(); // 4. 关闭session
    }
    @Test
    public void testSaveClassAndStudent() {
        Class c = new Class();
        c.setName("10级1班");
        session.save(c);
        Student s1 = new Student();
        s1.setName("张三");
        s1.setC(c);
        Student s2 = new Student();
        s2.setName("李四");
        s2.setC(c);
        session.save(s1);
        session.save(s2);
    }
}
运行结果：
Hibernate: insert into t_class (className) values (?)
Hibernate: insert into t_student (stuName, classId) values (?, ?)
Hibernate: insert into t_student (stuName, classId) values (?, ?)

3.2) 使用级联保存

Student.hbm.xml

<many-to-one name="c" column="classId" class="com.andrew.model.Class" cascade="save-update"></many-to-one>

StudentJunitTest.java

package com.andrew.service;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import com.andrew.model.Class;
import com.andrew.model.Student;
import com.andrew.util.HibernateUtil;
public class StudentJunitTest {
    private SessionFactory sessionFactory = HibernateUtil.getSessionFactory();
    private Session session;
    @Before
    public void setUp() throws Exception {
        session = sessionFactory.openSession(); // 1. 生成一个session
        session.beginTransaction(); // 2. 开启事务
    }
    @After
    public void tearDown() throws Exception {
        session.getTransaction().commit(); // 3. 提交事务
        session.close(); // 4. 关闭session
    }
    @Test
    public void testSaveClassAndStudentWithCascade() {
        Class c = new Class();
        c.setName("10级1班");
        Student s1 = new Student();
        s1.setName("张三");
        s1.setC(c);
        Student s2 = new Student();
        s2.setName("李四");
        s2.setC(c);
        session.save(s1);
        session.save(s2);
    }
}
运行结果：
Hibernate: insert into t_class (className) values (?)
Hibernate: insert into t_student (stuName, classId) values (?, ?)
Hibernate: insert into t_student (stuName, classId) values (?, ?)

4) 一对多映射实现(双向)

新建项目Hibernate04-2

hibernate.cfg.xml

<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    <session-factory>
        <!-- 数据库连接设置 -->
        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="connection.url">jdbc:mysql://localhost:3306/hibernate4</property>
        <property name="connection.username">root</property>
        <property name="connection.password">root</property>
        <!-- 方言 -->
        <property name="dialect">org.hibernate.dialect.MySQL5Dialect</property>
        <!-- 控制台显示SQL -->
        <property name="show_sql">true</property>
        <!-- 自动更新表结构 -->
        <property name="hbm2ddl.auto">update</property>
        <!-- Mapper -->
        <mapping resource="com/andrew/model/Student.hbm.xml"/>
        <mapping resource="com/andrew/model/Class.hbm.xml"/>
    </session-factory>
</hibernate-configuration>

HibernateUtil.java

package com.andrew.util;
import org.hibernate.SessionFactory;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
public class HibernateUtil {
    private static final SessionFactory sessionFactory = buildSessionFactory();
    private static SessionFactory buildSessionFactory() {
        // 1. 实例化配置文件
        Configuration configuration = new Configuration().configure();
        // 2. 实例化服务登记
        ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder()
                .applySettings(configuration.getProperties()).build();
        // 3. 获取Session工厂
        return configuration.buildSessionFactory(serviceRegistry);
    }
    public static SessionFactory getSessionFactory() {
        return sessionFactory;
    }
}

Student.java

package com.andrew.model;
public class Student {
    private long id;
    private String name;
    private Class c;
    public long getId() {
        return id;
    }
    public void setId(long id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Class getC() {
        return c;
    }
    public void setC(Class c) {
        this.c = c;
    }
    @Override
    public String toString() {
        return "Student [id=" + id + ", name=" + name + ", c=" + c.getName() + "]";
    }
}

Student.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.andrew.model">
    <class name="Student" table="t_student">
        <id column="stuId" name="id">
            <generator class="native"/>
        </id>
        <property name="name" column="stuName"/>
        <many-to-one name="c" column="classId" class="com.andrew.model.Class" cascade="save-update"></many-to-one>
    </class>
</hibernate-mapping>

Class.java

package com.andrew.model;
import java.util.HashSet;
import java.util.Set;
public class Class {
    private long id;
    private String name;
    private Set<Student> students = new HashSet<Student>();
    public long getId() {
        return id;
    }
    public void setId(long id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Set<Student> getStudents() {
        return students;
    }
    public void setStudents(Set<Student> students) {
        this.students = students;
    }
}

Class.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.andrew.model">
    <class name="Class" table="t_class">
        <id column="classId" name="id">
            <generator class="native"/>
        </id>
        <property name="name" column="className"/>
        <set name="students" cascade="save-update">
            <key column="classId"></key>
            <one-to-many class="com.andrew.model.Student"/>
        </set>
    </class>
</hibernate-mapping>

StudentTest.java

package com.andrew.service;
import java.util.Iterator;
import java.util.Set;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import com.andrew.model.Class;
import com.andrew.model.Student;
import com.andrew.util.HibernateUtil;
public class StudentTest {
    private SessionFactory sessionFactory = HibernateUtil.getSessionFactory();
    private Session session;
    @Before
    public void setUp() throws Exception {
        session = sessionFactory.openSession(); // 1. 生成一个session
        session.beginTransaction(); // 2. 开启事务
    }
    @After
    public void tearDown() throws Exception {
        session.getTransaction().commit(); // 3. 提交事务
        session.close(); // 4. 关闭session
    }
    @Test
    public void testSaveClassAndStudent() {
        Class c = new Class();
        c.setName("10级1班");
        Student s1 = new Student();
        s1.setName("张三");
        Student s2 = new Student();
        s2.setName("李四");
        c.getStudents().add(s1);
        c.getStudents().add(s2);
        session.save(c);
    }
    @Test
    public void getStudentsByClass() {
        Class c = (Class)session.get(Class.class, Long.valueOf(1));
        Set<Student> students = c.getStudents();
        Iterator it = students.iterator();
        while (it.hasNext()) {
            Student s = (Student)it.next();
            System.out.println(s);
        }
    }
}

运行结果：
Hibernate: insert into t_class (className) values (?)
Hibernate: insert into t_student (stuName, classId) values (?, ?)
Hibernate: insert into t_student (stuName, classId) values (?, ?)
Hibernate: update t_student set classId=? where stuId=?
Hibernate: update t_student set classId=? where stuId=?

Hibernate: select class0_.classId as classId1_0_0_, class0_.className as classNam2_0_0_ from t_class class0_ where class0_.classId=?
Hibernate: select students0_.classId as classId3_0_0_, students0_.stuId as stuId1_1_0_, students0_.stuId as stuId1_1_1_, students0_.stuName as stuName2_1_1_, students0_.classId as classId3_1_1_ from t_student students0_ where students0_.classId=?
Student [id=1, name=张三, c=10级1班]
Student [id=2, name=李四, c=10级1班]

5) inverse属性

在多的一端维护一的一端

5.1) 手动实现

StudentTest.java

package com.andrew.service;
import java.util.Iterator;
import java.util.Set;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import com.andrew.model.Class;
import com.andrew.model.Student;
import com.andrew.util.HibernateUtil;
public class StudentTest {
    private SessionFactory sessionFactory = HibernateUtil.getSessionFactory();
    private Session session;
    @Before
    public void setUp() throws Exception {
        session = sessionFactory.openSession(); // 1. 生成一个session
        session.beginTransaction(); // 2. 开启事务
    }
    @After
    public void tearDown() throws Exception {
        session.getTransaction().commit(); // 3. 提交事务
        session.close(); // 4. 关闭session
    }
    @Test
    public void testAdd() {
        Class c = new Class();
        c.setName("10级2班");
        Student s1=new Student();
        s1.setName("王五");
        session.save(c);
        session.save(s1);
    }
    @Test
    public void testInverse() {
        Class c = (Class)session.get(Class.class, Long.valueOf(1));
        Student s = (Student)session.get(Student.class, Long.valueOf(1));
        s.setC(c);
        c.getStudents().add(s);
    }
}

testAdd运行结果：
Hibernate: insert into t_class (className) values (?)
Hibernate: insert into t_student (stuName, classId) values (?, ?)
1    10级2班
1    王五    NULL
testInverse运行结果：
Hibernate: select class0_.classId as classId1_0_0_, class0_.className as classNam2_0_0_ from t_class class0_ where class0_.classId=?
Hibernate: select student0_.stuId as stuId1_1_0_, student0_.stuName as stuName2_1_0_, student0_.classId as classId3_1_0_ from t_student student0_ where student0_.stuId=?
Hibernate: select students0_.classId as classId3_0_0_, students0_.stuId as stuId1_1_0_, students0_.stuId as stuId1_1_1_, students0_.stuName as stuName2_1_1_, students0_.classId as classId3_1_1_ from t_student students0_ where students0_.classId=?
Hibernate: update t_student set stuName=?, classId=? where stuId=?
Hibernate: update t_student set classId=? where stuId=?
1    10级2班
1    王五    1

5.2) 自动实现

Class.hbm.xml

...
<set name="students" cascade="save-update" inverse="true">
    <key column="classId"></key>
    <one-to-many class="com.andrew.model.Student"/>
</set>
...

testAdd运行结果：
Hibernate: insert into t_class (className) values (?)
Hibernate: insert into t_student (stuName, classId) values (?, ?)
1    10级2班
1    王五    NULL
testInverse运行结果：
Hibernate: select class0_.classId as classId1_0_0_, class0_.className as classNam2_0_0_ from t_class class0_ where class0_.classId=?
Hibernate: select student0_.stuId as stuId1_1_0_, student0_.stuName as stuName2_1_0_, student0_.classId as classId3_1_0_ from t_student student0_ where student0_.stuId=?
Hibernate: select students0_.classId as classId3_0_0_, students0_.stuId as stuId1_1_0_, students0_.stuId as stuId1_1_1_, students0_.stuName as stuName2_1_1_, students0_.classId as classId3_1_1_ from t_student students0_ where students0_.classId=?
Hibernate: update t_student set stuName=?, classId=? where stuId=?
1    10级2班
1    王五    1

6) 级联删除

cascade="delete"，危险操作，删除关联表的信息

Class.hbm.xml

<set name="students" cascade="delete" inverse="true">
    <key column="classId"></key>
    <one-to-many class="com.andrew.model.Student"/>
</set>

StudentTest.java

package com.andrew.service;
import java.util.Iterator;
import java.util.Set;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import com.andrew.model.Class;
import com.andrew.model.Student;
import com.andrew.util.HibernateUtil;
public class StudentTest {
    private SessionFactory sessionFactory = HibernateUtil.getSessionFactory();
    private Session session;
    @Before
    public void setUp() throws Exception {
        session = sessionFactory.openSession(); // 1. 生成一个session
        session.beginTransaction(); // 2. 开启事务
    }
    @After
    public void tearDown() throws Exception {
        session.getTransaction().commit(); // 3. 提交事务
        session.close(); // 4. 关闭session
    }
    @Test
    public void testDeleteClassCascade() {
        Class c = (Class)session.get(Class.class, Long.valueOf(1));
        session.delete(c);
    }
}

运行结果：
Hibernate: select class0_.classId as classId1_0_0_, class0_.className as classNam2_0_0_ from t_class class0_ where class0_.classId=?
Hibernate: select students0_.classId as classId3_0_0_, students0_.stuId as stuId1_1_0_, students0_.stuId as stuId1_1_1_, students0_.stuName as stuName2_1_1_, students0_.classId as classId3_1_1_ from t_student students0_ where students0_.classId=?
Hibernate: delete from t_student where stuId=?
Hibernate: delete from t_class where classId=?

7) 一对多双向自身关联关系映射

hibernate.cfg.xml

<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    <session-factory>
        <!-- 数据库连接设置 -->
        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="connection.url">jdbc:mysql://localhost:3306/hibernate4</property>
        <property name="connection.username">root</property>
        <property name="connection.password">root</property>
        <!-- 方言 -->
        <property name="dialect">org.hibernate.dialect.MySQL5Dialect</property>
        <!-- 控制台显示SQL -->
        <property name="show_sql">true</property>
        <!-- 自动更新表结构 -->
        <property name="hbm2ddl.auto">update</property>
        <!-- Mapper -->
        <mapping resource="com/andrew/model/Student.hbm.xml"/>
        <mapping resource="com/andrew/model/Class.hbm.xml"/>
        <mapping resource="com/andrew/model/Node.hbm.xml"/>
    </session-factory>
</hibernate-configuration>

Node.java

package com.andrew.model;
import java.util.HashSet;
import java.util.Set;
public class Node {
    private long id;
    private String name;
    private Node parentNode;
    private Set<Node> childNodes = new HashSet<Node>();
    public long getId() {
        return id;
    }
    public void setId(long id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Node getParentNode() {
        return parentNode;
    }
    public void setParentNode(Node parentNode) {
        this.parentNode = parentNode;
    }
    public Set<Node> getChildNodes() {
        return childNodes;
    }
    public void setChildNodes(Set<Node> childNodes) {
        this.childNodes = childNodes;
    }
}

Node.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.andrew.model">
    <class name="Node" table="t_node">
        <id name="id" column="nodeId">
            <generator class="native"></generator>
        </id>
        <property name="name" column="nodeName"></property>
        <many-to-one name="parentNode" column="parentId" class="com.andrew.model.Node" cascade="save-update"></many-to-one>
        <set name="childNodes"  inverse="true">
            <key column="parentId"></key>
            <one-to-many class="com.andrew.model.Node"/>
        </set>
    </class>
</hibernate-mapping>

NodeTest.java

package com.andrew.service;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import com.andrew.model.Node;
import com.andrew.util.HibernateUtil;
public class NodeTest {
    private SessionFactory sessionFactory = HibernateUtil.getSessionFactory();
    private Session session;
    @Before
    public void setUp() throws Exception {
        session = sessionFactory.openSession(); // 1. 生成一个session
        session.beginTransaction(); // 2. 开启事务
    }
    @After
    public void tearDown() throws Exception {
        session.getTransaction().commit(); // 3. 提交事务
        session.close(); // 4. 关闭session
    }
    @Test
    public void testSaveMenu() {
        Node node = new Node();
        node.setName("根节点");
        Node subNode1 = new Node();
        subNode1.setName("子节点1");
        Node subNode2 = new Node();
        subNode2.setName("子节点2");
        subNode1.setParentNode(node);
        subNode2.setParentNode(node);
        session.save(subNode1);
        session.save(subNode2);
    }
}

运行结果：
Hibernate: insert into t_node (nodeName, parentId) values (?, ?)
Hibernate: insert into t_node (nodeName, parentId) values (?, ?)
Hibernate: insert into t_node (nodeName, parentId) values (?, ?)
1    根节点    NULL
2    子节点1    1
3    子节点2    1