Hibernate的初次使用

Posted 2020-06-30

使用hibernate的四个步骤：
第一：创建一个hibernate.cfg.xml。
<!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<!--声明Hibernate配置文件的开始-->
<hibernate-configuration>
    <session-factory>
            <!--配置链接数据库的基本属性-->
            <property name="connection.url">jdbc:sqlserver://localhost:1433;DatabaseName=Book</property>
            <property name="connection.username">sa</property>
            <property name="connection.password">123456</property>
            <property name="connection.driver_class">com.microsoft.sqlserver.jdbc.SQLServerDriver</property>

            <!--输出sql语句-->
            <property name="show_sql">true</property>

            <!--数据库使用的sql方言-->
            <property name="dialect">org.hibernate.dialect.SQLServerDialect</property>

            <!--是否格式化sql语句-->
            <property name="format_sql">true</property>

            <!--指定自动生成数据表的策略-->
            <!--<property name="hbm2ddl.auto">update</property>-->

            <!--指定需要关联的映射文件-->//注意在最后要加上这个关联的文件，*.hbm.xml文件。
            <mapping resource="NewSpringDAO/Book2.hbm.xml"></mapping>
    </session-factory>
</hibernate-configuration>

第二：写一个持久化类
1：必须有一个无参的构造器。
2：非final类
3：set，get方法。
public class Book2 {

    private int id;
    private String name;
    private double price;
    private String author;
    private int bookCount;

    public Book2(){}

    public Book2(int id,String name,double price,String author,int bookCount){
        this.id=id;
        this.name=name;
        this.price=price;
        this.author=author;
        this.bookCount=bookCount;
    }

    public void setId(int id){this.id=id;}
    public void setName(String name){this.name=name;}
    public void setPrice(double price){this.price=price;}
    public void setAuthor(String author){this.author=author;}
    public void setBookCount(int bookCount){this.bookCount=bookCount;}

    public int getId(){return id;}
    public String getName(){return name;}
    public double getPrice(){return price;}
    public String getAuthor(){return author;}
    public int getBookCount(){return bookCount;}

    @Override
    public String toString() {
        return " "+this.id+" "+this.name+" "+this.price+" "+this.author+" "+this.bookCount;
    }
}

第三：在类路径下创建对应的*.hbm.xml
<?xml version="1.0" encoding=‘UTF-8‘?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD//EN"
        "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
    <class name="NewSpringDAO.Book2" table="Bookimformation">
        <!--主键的方式用id标签。-->
        <id name="id" column="id" type="java.lang.Integer">
            <!--<generator class="native"></generator>--><!-- 这个标签用来定义主键生成策略。
            有这个标签的时候插入会抛出异常，因为表时我自己建的，并不是由Hibernate自动生成的！-->
        </id>

        <property name="name" column="name" type="java.lang.String" not-null="true">
        </property>

        <!--name属性为javaBean相对应的字段，column属性为数据库中的数据表对应的列名，type为数据库中的字段的类型-->
        <property name="author" column="author" type="java.lang.String" not-null="true">
        </property>

        <property name="price" column="price" type="java.lang.Double" not-null="true">
        </property>

        <property name="bookCount" column="bookCount" type="int" not-null="true">
        </property>
    </class>
</hibernate-mapping>

第四步：
在我的创建的一个HibernateUtil的类的前提下，使用hibernate的API。
public class HibernateUtil {
    private static final ThreadLocal<Session>threadLocal=new ThreadLocal<Session>();

    private static SessionFactory sessionFactory=null;

    static {
        try {
            Configuration configuration = new Configuration().configure();

            ServiceRegistry serviceRegistry = new ServiceRegistryBuilder()
                    .applySettings(configuration.getProperties())
                    .buildServiceRegistry();//你麻痹你就不能写个类把这些方法包装起来！！！

            sessionFactory=configuration.buildSessionFactory(serviceRegistry);

        } catch (Exception e) {
            System.out.println("创建会话工厂失败！");
            e.printStackTrace();
        }
    }

    public static Session getSession() throws HibernateException{
        Session session=(Session)threadLocal.get();
        if (session==null||!session.isOpen()) {
            if (sessionFactory == null)
                rebuildSessionFactory();
            session = (sessionFactory != null) ? sessionFactory.openSession() : null;
            threadLocal.set(session);
        }
        return session;
    }

    public static void rebuildSessionFactory(){
        try {
                    Configuration configuration = new Configuration().configure();

                    ServiceRegistry serviceRegistry = new ServiceRegistryBuilder()
                            .applySettings(configuration.getProperties())
                            .buildServiceRegistry();//你麻痹你就不能写个类把这些方法包装起来！！！

                    sessionFactory=configuration.buildSessionFactory(serviceRegistry);

                } catch (Exception e) {
                    System.out.println("创建会话工厂失败！");
                    e.printStackTrace();
                }
    }

    public static SessionFactory getSessionFactory(){
        return sessionFactory;
    }

    public static void closeSession() throws HibernateException{
        Session session=(Session)threadLocal.get();
        threadLocal.set(null);
        if (session!=null)
            session.close();
    }
}
具体使用hibernate的API，参照包Hibernate