java Hibernate 学习

导包

hibernate 下载地址 http://hibernate.org/

requir 文件夹为必须要导入的包

• 可选包 有c3p0 包 （数据库连接池）

环境

测试环境

• myeclipse java project

配置

<?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>        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>        <property name="connection.url">jdbc:mysql:///test</property>        <property name="connection.username">root</property>        <property name="connection.password">root</property>        <!-- 方言 -->        <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>        <!-- 数据连接池 -->        <property name="hibernate.c3p0.max_size">2</property>        <property name="hibernate.c3p0.min_size">2</property>        <property name="hibernate.c3p0.timeout">5000</property>        <property name="hibernate.c3p0.max_statements">100</property>        <property name="hibernate.c3p0.idle_test_period">3000</property>        <property name="hibernate.c3p0.acquire_increment">2</property>        <property name="hibernate.c3p0.validate">false</property>        <!-- 其他配置 -->        <property name="hibernate.show_sql">true</property>        <property name="hibernate.current_session_context_class">thread</property>        <!-- 映射文件的配置 -->        <mapping resource="com/norwaya/pojo/User.hbm.xml"/>        <mapping resource="com/norwaya/pojo/Address.hbm.xml"/>    </session-factory></hibernate-configuration>

核心代码

Configuration cfg = new Configuration().configure();        ServiceRegistry serviceRegistry= new                ServiceRegistryBuilder().applySettings(cfg.getProperties()).buildServiceRegistry();         SessionFactory sessionFactory = cfg.buildSessionFactory(serviceRegistry);Session session = sessionFactory.getCurrentSession();//session 是一切操作的核心session.beginTransaction();// CRUD 操作 etc....session.getTransaction().commit();

多对一操作

Address.hbm.xml

<?xml version="1.0" encoding="UTF-8"?><!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.norwaya.pojo">    <class name="Address" table="address">        <id name="id" column="id">            <generator class="native"/>        </id>        <property name="info" />        <many-to-one name="user" class="User" column="user_id"/>    </class></hibernate-mapping>

User.hbm.xml

<?xml version="1.0" encoding="UTF-8"?><!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.norwaya.pojo">    <class name="User" table="User">        <id name="id" column="id">            <generator class="native"/>        </id>        <property name="name" />        <property name="age"/>        <property name="birthday"/>        <set name="set" inverse="true" cascade="delete" fetch="join" order-by="id desc">             <key column="user_id"/>            <one-to-many class="Address"/>        </set>    </class></hibernate-mapping>

fetch ：查询的时候 join 进来 address ，获取address 的时候，不用再次获取
order-by：排序配置
inverse：当自身改变的时候不去更新操作
cascade：值为delete 的时候，级联删除（删除user的时候，会删除address）

---

一对一的数据操作

Card.hbm.xml

<?xml version="1.0" encoding="UTF-8"?><!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.kaishengit.pojo">    <class name="Card" table="t_card">        <id name="id" column="id">            <generator class="foreign">                <param name="property">person</param>            </generator>        </id>        <property name="cardNum"/>        <one-to-one name="person" class="Person"/>    </class></hibernate-mapping>

Person.hbm.xml

<?xml version="1.0" encoding="UTF-8"?><!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.kaishengit.pojo">    <class name="Person" table="t_person">        <id name="id" column="id">            <generator class="native"/>        </id>        <property name="name"/>        <one-to-one name="card"  class="Card" cascade="delete"/>    </class></hibernate-mapping>

当one-to-one 的时候，默认属性为 fetch=”join”

多对一的 特例 （一对一）

<?xml version="1.0" encoding="UTF-8"?><!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.kaishengit.pojo">    <class name="Person" table="t_person">        <id name="id" column="id">            <generator class="native"/>        </id>        <property name="name"/>        <many-to-one name="card"  class="Card" unique="true"/>    </class></hibernate-mapping>

多对多(三张表)

Teacher.hbm.xml

<?xml version="1.0" encoding="UTF-8"?><!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.kaishengit.pojo">    <class name="Teacher" table="t_teacher">        <id name="id" column="id">            <generator class="native"/>        </id>        <property name="name"/>        <set name="studentSet" table="t_teacher_student">            <key column="tea_id"/>            <many-to-many class="Student" column="stu_id"/>        </set>    </class></hibernate-mapping>

Student.hbm.xml

<?xml version="1.0" encoding="UTF-8"?><!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.kaishengit.pojo">    <class name="Student" table="t_student">        <id name="id" column="id">            <generator class="native"/>        </id>        <property name="name"/>        <set name="teacherSet" table="t_teacher_student" inverse="true">            <key column="stu_id"/>            <many-to-many class="Teacher" column="tea_id"/>        </set>    </class></hibernate-mapping>

t_teacher_student 为关系映射表

延迟加载

改变抓取策略 fetch=”join”
关闭延迟加载 lazy=“false”
预加载 Hibernate.initialize（object obj）

解决方案 在spring中实现

注解实现

User.java

import java.util.Date;import java.util.List;import javax.persistence.Entity;import javax.persistence.FetchType;import javax.persistence.GeneratedValue;import javax.persistence.GenerationType;import javax.persistence.Id;import javax.persistence.OneToMany;import javax.persistence.Table;import org.hibernate.annotations.Cascade;import org.hibernate.annotations.CascadeType;@Entity@Table(name = "user")public class User {    private int id;    private String name;    private Date birthday;    private int age;    private List<Address> set;    @OneToMany(fetch = FetchType.EAGER, mappedBy = "user")    // mappedBy address中User 的属性，为use放弃关系维护    @Cascade(value = { CascadeType.SAVE_UPDATE, CascadeType.DELETE_ORPHAN,            CascadeType.ALL })    public List<Address> getSet() {        return set;    }    public void setSet(List<Address> set) {        this.set = set;    }    public User() {    }    @Id    @GeneratedValue(strategy = GenerationType.IDENTITY)    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;    }    public Date getBirthday() {        return birthday;    }    public void setBirthday(Date birthday) {        this.birthday = birthday;    }    public int getAge() {        return age;    }    public void setAge(int age) {        this.age = age;    }}

Address.java

import javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.GeneratedValue;import javax.persistence.GenerationType;import javax.persistence.Id;import javax.persistence.JoinColumn;import javax.persistence.ManyToOne;import javax.persistence.Table;@Entity@Table(name="address")public class Address {    private int id;    private String info;    private User user;    public Address(){       }    @Id    @GeneratedValue(strategy=GenerationType.IDENTITY)    public int getId() {        return id;    }    public void setId(int id) {        this.id = id;    }    @Column(name="info")    public String getInfo() {        return info;    }    public void setInfo(String info) {        this.info = info;    }    @ManyToOne    @JoinColumn(name="user_id")    public User getUser() {        return user;    }    public void setUser(User user) {        this.user = user;    }}

TABLE：使用一个特定的数据库表格来保存主键。
SEQUENCE：根据底层数据库的序列来生成主键，条件是数据库支持序列。
IDENTITY：主键由数据库自动生成（主要是自动增长型）
AUTO：主键由程序控制。

级联删除 我用的是
@Cascade(value = { CascadeType.REMOVE })
还有用下面这个的 他们用的都是
org.hibernate.annotations.CascadeType这个包
@Cascade(value = CascadeType.SAVE_UPDATE, CascadeType.DELETE_ORPHAN,CascadeType.ALL})