hibernate hibernate.cfg.xml component 组件

1.为什么使用component组件？

当一个表的列数目比较多时，可以根据属性分类，将一个java对象拆分为几个对象。

数据库还是一张表，不过有多个对象与之对应。

2.实例

2.1 Java 对象：

public class Person {

    private int id;
    private Name name;
    private Parents parents;

    public Parents getParents() {
        return parents;
    }

    public void setParents(Parents parents) {
        this.parents = parents;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public Name getName() {
        return name;
    }

    public void setName(Name name) {
        this.name = name;
    }
}

public class Parents {
    private Name father;
    private Name mother;

    public Name getFather() {
        return father;
    }

    public void setFather(Name father) {
        this.father = father;
    }

    public Name getMother() {
        return mother;
    }

    public void setMother(Name mother) {
        this.mother = mother;
    }
}

public class Name {
    private String bigName;
    private String nickName;
    private int nameVersion;

    public String getBigName() {
        return bigName;
    }

    public void setBigName(String bigName) {
        this.bigName = bigName;
    }

    public int getNameVersion() {
        return nameVersion;
    }

    public void setNameVersion(int nameVersion) {
        this.nameVersion = nameVersion;
    }

    public String getNickName() {
        return nickName;
    }

    public void setNickName(String nickName) {
        this.nickName = nickName;
    }
}

2.2 Hibernate 配置文件 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>
        <!-- Platform settings -->
        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="connection.url">jdbc:mysql://localhost:3306/test</property>
        <property name="connection.username">root</property>
        <property name="connection.password">123456</property>
        <property name="dialect">org.hibernate.dialect.MySQL5Dialect</property>
        <!-- Miscellaneous Settings -->
        <property name="show_sql">true</property>
        <!--mapping files-->
        <mapping resource="test/com/hibernate/config/hbm/person.hbm.xml"/>
    </session-factory>

</hibernate-configuration>

映射文件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>
    <class name="test.com.hibernate.component.Person" table="person" lazy="false">
        <id name="id" column="id" type="java.lang.Integer">
            <generator class="native"/>
        </id>
        <component name="name" class="test.com.hibernate.component.Name" >
            <property name="bigName" column="bigName" type="string"/>
            <property name="nickName" column="nickName" type="string"/>
            <property name="nameVersion" column="nameVersion" type="integer"/>
        </component>
        <component name="parents" class="test.com.hibernate.component.Parents">
            <component name="father" class="test.com.hibernate.component.Name">
                <property name="bigName" column="f_bigName" type="string"/>
                <property name="nickName" column="f_nickName" type="string"/>
                <property name="nameVersion" column="f_nameVersion" type="integer"/>
            </component>
            <component name="mother" class="test.com.hibernate.component.Name">
                <property name="bigName" column="m_bigName" type="string"/>
                <property name="nickName" column="m_nickName" type="string"/>
                <property name="nameVersion" column="m_nameVersion" type="integer"/>
            </component>
        </component>
    </class>
</hibernate-mapping>

2.3 Hibernate 操作代码：

HibernateUtil.java

public class HibernateUtil {
    static SessionFactory sessionFactory = null;
    static{
        StandardServiceRegistry registry = new StandardServiceRegistryBuilder()
                .configure("test/com/hibernate/config/hibernate.cfg.xml").build();
        MetadataSources sources = new MetadataSources();
        Metadata metadata = sources.buildMetadata(registry);
        sessionFactory = metadata.buildSessionFactory();
    }
    public static Session openSession(){
        if(sessionFactory==null){
            throw new HibernateException("session factory is null!");
        }
        return sessionFactory.openSession();
    }
    public static void destroy() {
        if(sessionFactory!=null){
            sessionFactory.close();
        }
    }
}

Test.java

public class Test {

    public static void main(String[] args) {

        Name name = new Name();
        name.setBigName("Daughter");
        name.setNickName("girl");
        name.setNameVersion(1);
        Person person = new Person();
        person.setName(name);

        Name father = new Name();
        father.setBigName("Father");
        father.setNickName("man");
        father.setNameVersion(1);
        Name mother = new Name();
        mother.setBigName("Mother");
        mother.setNickName("woman");
        mother.setNameVersion(1);

        Parents parents = new Parents();
        parents.setFather(father);
        parents.setMother(mother);

        person.setParents(parents);

        PersonDao.save(person);
    }
}

上述例子使用Hibernate版本为5.2Final，配置文件也可以用以前的Configuration配置。

2.4 运行结果

自动创建一个person表，并插入一条数据