03.Hibernate一对多关联

CREATE TABLE tb_class
(
    id              bigint          NOT NULL    auto_increment          COMMENT ‘ID‘,
    no              varchar(10)     NOT NULL                            COMMENT ‘班级编号‘,
    name            varchar(50)     NOT NULL                            COMMENT ‘班级名称‘,
    PRIMARY KEY (id)
) COMMENT ‘班级信息表‘;
CREATE TABLE  tb_student
(
    id              bigint          NOT NULL    auto_increment          COMMENT ‘ID‘,
    no              varchar(10)     NOT NULL                            COMMENT ‘学号‘,
    name            varchar(50)     NOT NULL                            COMMENT ‘姓名‘,
    sex             char(1)         NOT NULL                            COMMENT ‘性别‘,
    birthday        datetime                                            COMMENT ‘出生日期‘,
    class_id        bigint          NOT NULL                            COMMENT ‘班级ID‘,
    PRIMARY KEY (id)
) COMMENT = ‘学生信息表‘;

ALTER TABLE tb_student ADD CONSTRAINT fk_tb_student_tb_class_1 FOREIGN KEY (class_id) REFERENCES tb_class (id);

package model;
import java.sql.Date;
public class Student
{
	private Long id;
	private String no;
	private String name;
	private String sex;
	private Date birthday;
	private ClassInfo classInfo;
	//省略setter、getter、toString...
}	

<hibernate-mapping package="model">
	<class name="ClassInfo" table="tb_class">
		<id name="id">
			<generator class="native"></generator>
		</id>
		<property name="no" column="no"/>
		<property name="name" column="name"/>
	</class>
</hibernate-mapping>

public static void main(String[] args)
{
    Student student;
    Configuration cfg = new Configuration();
    cfg.configure();
    ServiceRegistry sr = new ServiceRegistryBuilder().applySettings(cfg.getProperties()).buildServiceRegistry();
    SessionFactory sf = cfg.buildSessionFactory(sr);
    System.out.println("连接数据库");
    Session session = sf.openSession();

    student=(Student) session.get(Student.class, new Long(1));
    System.out.println(student);
    System.out.println(student.getClassInfo());

    session.close();
    System.out.println("关闭数据库");
    System.exit(0);
}

<hibernate-configuration>
	<session-factory>
		<!-- 省略其他...，设置实体类到数据库的映射文件 -->
		<mapping resource="model/ClassInfo.hbm.xml"/>
		<mapping resource="model/Student.hbm.xml"/>
	</session-factory>
</hibernate-configuration>

连接数据库
Hibernate: 
    select
        student0_.id as id1_2_0_,
        student0_.no as no2_2_0_,
        student0_.name as name3_2_0_,
        student0_.sex as sex4_2_0_,
        student0_.birthday as birthday5_2_0_,
        student0_.class_id as class_id6_2_0_ 
    from
        tb_student student0_ 
    where
        student0_.id=?
Hibernate: 
    select
        classinfo0_.id as id1_1_0_,
        classinfo0_.no as no2_1_0_,
        classinfo0_.name as name3_1_0_ 
    from
        tb_class classinfo0_ 
    where
        classinfo0_.id=?
Student [id=1, no=000001, name=学生1, sex=男, birthday=2015-01-27]
ClassInfo [id=22, no=000022, name=班级22]
关闭数据库

<hibernate-mapping package="model">
	<class name="Student" table="tb_student">
		<id name="id">
			<generator class="native"></generator>
		</id>
		<property name="no" column="no"/>
		<property name="name" column="name"/>
		<property name="sex" column="sex"/>
		<property name="birthday" column="birthday"/>
	</class>
</hibernate-mapping>

public static void main(String[] args)
{
    ClassInfo classInfo;
    Configuration cfg = new Configuration();
    cfg.configure();
    ServiceRegistry sr = new ServiceRegistryBuilder().applySettings(cfg.getProperties()).buildServiceRegistry();
    SessionFactory sf = cfg.buildSessionFactory(sr);
    System.out.println("连接数据库");
    Session session = sf.openSession();

    classInfo =(ClassInfo) session.get(ClassInfo.class, new Long(1));
    System.out.println(classInfo);
    System.out.println(classInfo.getStudents().size());
    System.out.println(classInfo.getStudents().get(0));

    session.close();
    System.out.println("关闭数据库");
    System.exit(0);
}

连接数据库
Hibernate: 
    select
        classinfo0_.id as id1_1_0_,
        classinfo0_.no as no2_1_0_,
        classinfo0_.name as name3_1_0_ 
    from
        tb_class classinfo0_ 
    where
        classinfo0_.id=?
ClassInfo [id=1, no=000001, name=班级1]
Hibernate: 
    select
        students0_.class_id as class_id6_1_0_,
        students0_.id as id1_2_0_,
        students0_.id as id1_2_1_,
        students0_.no as no2_2_1_,
        students0_.name as name3_2_1_,
        students0_.sex as sex4_2_1_,
        students0_.birthday as birthday5_2_1_,
        students0_.class_id as class_id6_2_1_ 
    from
        tb_student students0_ 
    where
        students0_.class_id=?
35
Student [id=24, no=000024, name=学生24, sex=女, birthday=2015-01-27]
关闭数据库

<hibernate-mapping package="model">
	<class name="Student" table="tb_student">
		<id name="id">
			<generator class="native"></generator>
		</id>
		<property name="no" column="no"/>
		<property name="name" column="name"/>
		<property name="sex" column="sex"/>
		<property name="birthday" column="birthday"/>
		<many-to-one name="classInfo" column="class_id" class="model.ClassInfo" lazy="false"/>
	</class>
</hibernate-mapping>

public static void main(String[] args)
{
    Student student;
    Configuration cfg = new Configuration();
    cfg.configure();
    ServiceRegistry sr = new ServiceRegistryBuilder().applySettings(cfg.getProperties()).buildServiceRegistry();
    SessionFactory sf = cfg.buildSessionFactory(sr);
    System.out.println("连接数据库");
    Session session = sf.openSession();
    
    student=(Student) session.get(Student.class, new Long(1));
    System.out.println(student);
    System.out.println(student.getClassInfo());
    System.out.println(student.getClassInfo().getStudents().size());
    session.close();
    System.out.println("关闭数据库");
    System.exit(0);
}

连接数据库
Hibernate: 
    select
        student0_.id as id1_2_0_,
        student0_.no as no2_2_0_,
        student0_.name as name3_2_0_,
        student0_.sex as sex4_2_0_,
        student0_.birthday as birthday5_2_0_,
        student0_.class_id as class_id6_2_0_ 
    from
        tb_student student0_ 
    where
        student0_.id=?
Hibernate: 
    select
        classinfo0_.id as id1_1_0_,
        classinfo0_.no as no2_1_0_,
        classinfo0_.name as name3_1_0_ 
    from
        tb_class classinfo0_ 
    where
        classinfo0_.id=?
Hibernate: 
    select
        students0_.class_id as class_id6_1_0_,
        students0_.id as id1_2_0_,
        students0_.id as id1_2_1_,
        students0_.no as no2_2_1_,
        students0_.name as name3_2_1_,
        students0_.sex as sex4_2_1_,
        students0_.birthday as birthday5_2_1_,
        students0_.class_id as class_id6_2_1_ 
    from
        tb_student students0_ 
    where
        students0_.class_id=?
Student [id=1, no=000001, name=学生1, sex=男, birthday=2015-01-27]
ClassInfo [id=22, no=000022, name=班级22]
38
关闭数据库

public static void main(String[] args)
{
    ClassInfo classInfoNew;
    ClassInfo classInfo;
    Student studentNew;
    Student student;
    Configuration cfg = new Configuration();
    cfg.configure();
    ServiceRegistry sr = new ServiceRegistryBuilder().applySettings(cfg.getProperties()).buildServiceRegistry();
    SessionFactory sf = cfg.buildSessionFactory(sr);
    System.out.println("连接数据库");
    Session session = sf.openSession();
    Transaction transaction = session.beginTransaction();
    try
    {
        classInfoNew = new ClassInfo();
        classInfoNew.setName("测试Class");
        classInfoNew.setNo("000");
        studentNew = new Student();
        studentNew.setName("测试Student");
        studentNew.setNo("000");
        studentNew.setSex("男");
        studentNew.setBirthday(new Date(1993, 6, 11));
        classInfoNew.getStudents().add(studentNew);
        studentNew.setClassInfo(classInfoNew);
        session.save(classInfoNew);//一定要先保存classInfo不然会报错,因为数据库约束了class_id为NOT NULL
        session.save(studentNew);
        
        student = (Student) session.get(Student.class, new Long(1));
        student.setClassInfo(classInfoNew);//执行update维护关系
        classInfoNew.getStudents().add(student);//执行update维护关系，update语句数受关联对象数影响，此处的update会有重复！
        
        transaction.commit();
    }
    catch (Exception e)
    {
        transaction.rollback();
        System.out.println("错误：" + e);
    }
    finally
    {
        session.close();
        System.out.println("关闭数据库");
    }
    System.exit(0);
}

连接数据库
Hibernate: 
    insert 
    into
        tb_class
        (no, name) 
    values
        (?, ?)
Hibernate: 
    insert 
    into
        tb_student
        (no, name, sex, birthday, class_id) 
    values
        (?, ?, ?, ?, ?)
Hibernate: 
........ 省略若干获取关联对象的查询语句
Hibernate:
    update
        tb_student 
    set
        no=?,
        name=?,
        sex=?,
        birthday=?,
        class_id=? 
    where
        id=?
Hibernate: 
    update
        tb_student 
    set
        class_id=? 
    where
        id=?
Hibernate: 
    update
        tb_student 
    set
        class_id=? 
    where
        id=?
关闭数据库

<bag name="students" lazy="false" inverse="true">
    <key column="class_id"/>
    <one-to-many class="model.Student"/>
</bag>

Hibernate: 
    update
        tb_student 
    set
        no=?,
        name=?,
        sex=?,
        birthday=?,
        class_id=? 
    where
        id=?

<many-to-one name="classInfo" column="class_id" class="model.ClassInfo" lazy="false" cascade="save-update"/>

连接数据库
Hibernate: 
    insert 
    into
        tb_class
        (no, name) 
    values
        (?, ?)
Hibernate: 
    insert 
    into
        tb_student
        (no, name, sex, birthday, class_id) 
    values
        (?, ?, ?, ?, ?)
关闭数据库

<bag name="students" lazy="false" inverse="true" cascade="delete">
    <key column="class_id"/>
    <one-to-many class="model.Student" />
</bag>

Hibernate: 
    delete 
    from
        tb_student 
    where
        id=?
Hibernate: 
    delete 
    from
        tb_class 
    where
        id=?

<bag name="students" lazy="false" inverse="true" cascade="all-delete-orphan">
    <key column="class_id"/>
    <one-to-many class="model.Student" />
</bag>

CREATE TABLE tb_area
(
    id              bigint          NOT NULL    auto_increment          COMMENT ‘ID‘,
    name            varchar(50)     NOT NULL                            COMMENT ‘地区名称‘,
    parent_id       bigint                                              COMMENT ‘所属区域ID‘,
    PRIMARY KEY (id)
) COMMENT = ‘区域信息表‘;
-- 外键约束可续选
ALTER TABLE tb_area ADD CONSTRAINT fk_tb_area_1 FOREIGN KEY (parent_id) REFERENCES tb_area (id); 

package model;
import java.util.Set;
public class Area
{
	private Long id;
	private String name;
	private Area parentArea;
	private Set<Area> childAreas = new HashSet<Area>();
	// 省略setter、getter、toString...
}

<hibernate-mapping package="model">
	<class name="Area" table="tb_area">
		<id name="id">
			<generator class="native"></generator>
		</id>
		<property name="name" column="name"/>
		<many-to-one name="parentArea" column="parent_id" class="model.Area" cascade="save-update"/>
		<set name="childAreas" inverse="true">
			<key column="parent_id"/>
			<one-to-many class="model.Area"/>
		</set>
	</class>
</hibernate-mapping>

public static void main(String[] args)
{
    Configuration cfg = new Configuration();
    cfg.configure();
    ServiceRegistry sr = new ServiceRegistryBuilder().applySettings(cfg.getProperties()).buildServiceRegistry();
    SessionFactory sf = cfg.buildSessionFactory(sr);
    System.out.println("连接数据库");
    Session session = sf.openSession();
    Transaction transaction = session.beginTransaction();
    try
    {
        Area area1=new Area();
        Area area2=new Area();
        Area area3=new Area();
        Area area4=new Area();
        Area area5=new Area();
        
        area1.setName("中国");
        area2.setName("湖北省");
        area3.setName("湖南省");
        area4.setName("武汉市");
        area5.setName("仙桃市");
        
        area2.setParentArea(area1);
        area3.setParentArea(area1);
        area4.setParentArea(area2);
        area5.setParentArea(area2);
        
        session.save(area3);
        session.save(area4);
        session.save(area5);
        transaction.commit();
    }
    catch (Exception e)
    {
        transaction.rollback();
        System.out.println("错误：" + e);
    }
    finally
    {
        session.close();
        System.out.println("关闭数据库");
    }
    System.exit(0);
}

area1.setName("中国");
area2.setName("湖北省");
area2.setParentArea(area1);
area1.getChildAreas().add(area2);

public Area addChildArea(Area area)
{
    if (area != null)
    {
        if (this.childAreas == null)
        {
            this.childAreas = new HashSet<Area>();
        }
        //删除原有的关系
        if (area.getParentArea() != null)
        {
            area.getParentArea().getChildAreas().remove(area);
        }
        //设置当前关系
        this.childAreas.add(area);
        area.setParentArea(this);
    }
    return this;
}

area1.setName("中国");
area2.setName("湖北省");
area3.setName("湖南省");
area1.addChildArea(area2).addChildArea(area3);

1. name:实体类属性名。
   
2. access:默认的实体类属性访问模式，取值为property表示访问getter、setter方法间接访问实体类字段，取值为field表示直接访问实体类字段(类成员变量)。
3. column:对应的数据库字段名，此处的字段是外键字段。
4. class:关联的类的名字，默认是通过反射得到属性类型。
5. property-ref:指定关联类的一个属性，这个属性将会和本外键相对应。如果没有指定，会使用对方关联类的主键。
6. foreign-key:关联的数据库外键名。
7. formula:一个SQL表达式，定义了这个计算属性的值，计算属性没有和它对应的数据库字段。
8. update:在update时是否含有此字段。
9. insert:在insert时是否含有此字段。
10. not-null:字段能否为空。
11. unique:字段是否唯一。
12. unique-key:为此字段创建唯一约束，属性值即为数据库唯一约束名，只影响自动生成的schema脚本。
13. index:为此字段创建索引，属性值即为数据库索引名，只影响自动生成的schema脚本。
14. not-found:指定外键引用的数据不存在时如何处理，ignore会将数据不存在作为关联到一个空对象（null）处理,默认为exception。
15. outer-join:设置Hibernate是否使用外连接获取关联的数据，设置成true可以减少SQL语句的条数。
16. fetch:参数指定了关联对象抓取的方式是select查询还是join查询，默认为select。fetch="join"等同于outer-join="true"，fetch="select"等同于outer-join="false"。
17. lazy:是否采用延迟加载策略。
18. cascade:指明哪些操作会从父对象级联到关联的对象。
19. optimistic-lock:指定这个属性在做更新时是否需要获得乐观锁定，默认为true。
20. embed-xml:如果embed-xml="true"，则对应于被关联实体或值类型的集合的XML树将直接嵌入拥有这些关联的实体的XML树中，默认值为true。
21. entity-name:Hibernate3新增特性，用于动态模型（Dynamic Model）支持。Hibernate3允许一个类进行多次映射(前提是映射到不同的表)。
22. node:配置说明。

<bag name="EntityClassName" 
    access="field|property|ClassName"
    collection-type="collection-type"
    schema="schema"
    catalog="catalog"
    check="arbitrary sql check condition"
    table="TableName"
    subselect="SQL expression"
    where="arbitrary sql where condition"
    optimistic-lock="false|true"
    inverse="false|true"
    fetch="join|select"
    batch-size="5"
    cascade="all|none|save-update|delete"
    lazy="false|true"
    mutable="false|true"
    outer-join="false|true"
    order-by="arbitrary sql order by condition"
    embed-xml="false|true"
    persister="PersisterClass"
    node="element-name"/>

<one-to-many class="ClassName" 
    not-found="exception|ignore"
    embed-xml="true|false"
    entity-name="EntityName"
    node="element-name" />