Hibernate 入门指南

同时使用面向对象的软件和关系数据库可能既麻烦又耗时。由于对象和关系数据库中数据的表示方式之间存在许多“范式不匹配”​​，因此开发成本显着提高。Hibernate 是 Java 环境的对象/关系映射 (ORM) 解决方案。

本篇讲解xml和注解两种方式，项目结构如下：

 父项目的pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<!--
  ~ Hibernate, Relational Persistence for Idiomatic Java
  ~
  ~ License: GNU Lesser General Public License (LGPL), version 2.1 or later.
  ~ See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
  -->
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <groupId>org.hibernate.tutorials</groupId>
    <artifactId>hibernate-tutorials</artifactId>
    <version>5.4.32.Final</version>
    <packaging>pom</packaging>

    <name>Hibernate Getting Started Guide Tutorials</name>
    <description>Aggregator for the Hibernate tutorials presented in the Getting Started Guide</description>

    <properties>
        <!-- Skip artifact deployment -->
        <maven.deploy.skip>true</maven.deploy.skip>
    </properties>

    <modules>
        <module>basic</module>
        <module>annotations</module>
        <module>entitymanager</module>
        <module>envers</module>
        <module>osgi</module>
    </modules>

    <dependencies>
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-core</artifactId>
            <version>5.4.32.Final</version>
        </dependency>

        <!-- Hibernate uses jboss-logging for logging, for the tutorials we will use the sl4fj-simple backend -->
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-simple</artifactId>
            <version>1.7.5</version>
        </dependency>

        <!-- The tutorials use JUnit test cases to illustrate usage -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>

        <!-- The tutorials use the H2 in-memory database -->
        <dependency>
            <groupId>com.h2database</groupId>
            <artifactId>h2</artifactId>
            <version>1.4.197</version>
        </dependency>
    </dependencies>

    <build>
        <testResources>
            <testResource>
                <filtering>false</filtering>
                <directory>src/test/java</directory>
                <includes>
                    <include>**/*.xml</include>
                </includes>
            </testResource>
            <testResource>
                <directory>src/test/resources</directory>
            </testResource>
        </testResources>
    </build>

</project>

1.XML方式（basic项目）

pom.xml:

<?xml version="1.0"?>
<!--
  ~ Hibernate, Relational Persistence for Idiomatic Java
  ~
  ~ License: GNU Lesser General Public License (LGPL), version 2.1 or later.
  ~ See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
  -->
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <parent>
        <groupId>org.hibernate.tutorials</groupId>
        <artifactId>hibernate-tutorials</artifactId>
        <version>5.4.32.Final</version>
        <relativePath>../pom.xml</relativePath>
    </parent>

    <artifactId>hibernate-tutorial-hbm</artifactId>
    <name>Hibernate hbm.xml Tutorial</name>
    <description>Hibernate tutorial illustrating the use of native APIs and hbm.xml for mapping metadata</description>

    <properties>
        <!-- Skip artifact deployment -->
        <maven.deploy.skip>true</maven.deploy.skip>
    </properties>

</project>

创建实体对象：Event

package org.hibernate.tutorial.hbm;

import java.util.Date;

public class Event {
    private Long id;

    private String title;
    private Date date;

    public Event() {
        // this form used by Hibernate
    }

    public Event(String title, Date date) {
        // for application use, to create new events
        this.title = title;
        this.date = date;
    }

    public Long getId() {
        return id;
    }

    private void setId(Long id) {
        this.id = id;
    }

    public Date getDate() {
        return date;
    }

    public void setDate(Date date) {
        this.date = date;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }
}

创建实体对象对应的XML:Event.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="org.hibernate.tutorial.hbm">

    <class name="Event" table="EVENTS">
        <id name="id" column="EVENT_ID">
            <generator class="increment"/>
        </id>
        <property name="date" type="timestamp" column="EVENT_DATE"/>
        <property name="title"/>
    </class>

</hibernate-mapping>

创建hibernate.cfg.xml配置数据库信息

<?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>

        <!-- Database connection settings -->
        <property name="connection.driver_class">org.h2.Driver</property>
        <property name="connection.url">jdbc:h2:mem:db1;DB_CLOSE_DELAY=-1;MVCC=TRUE</property>
        <property name="connection.username">sa</property>
        <property name="connection.password"/>

        <!-- 连接池大小 -->
        <property name="connection.pool_size">1</property>

        <!-- 方言 -->
        <property name="dialect">org.hibernate.dialect.H2Dialect</property>

        <!-- 缓存  -->
        <property name="cache.provider_class">org.hibernate.cache.internal.NoCacheProvider</property>

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

        <property name="hbm2ddl.auto">create</property>

        <mapping resource="org/hibernate/tutorial/hbm/Event.hbm.xml"/>

    </session-factory>

</hibernate-configuration>

创建测试类：NativeApiIllustrationTest

package org.hibernate.tutorial.hbm;

import java.util.Date;
import java.util.List;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.boot.MetadataSources;
import org.hibernate.boot.registry.StandardServiceRegistry;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;

import junit.framework.TestCase;

public class NativeApiIllustrationTest extends TestCase {
    private SessionFactory sessionFactory;

    @Override
    protected void setUp() throws Exception {
        // 一个应用公用一个SessionFactory
        final StandardServiceRegistry registry = new StandardServiceRegistryBuilder()
                .configure() // 读取hibernate.cfg.xml
                .build();
        try {
            sessionFactory = new MetadataSources( registry ).buildMetadata().buildSessionFactory();
        }
        catch (Exception e) {
            StandardServiceRegistryBuilder.destroy( registry );
        }
    }

    @Override
    protected void tearDown() throws Exception {
        if ( sessionFactory != null ) {
            sessionFactory.close();
        }
    }

    @SuppressWarnings("unchecked")
    public void testBasicUsage() {
        // create a couple of events...
        Session session = sessionFactory.openSession();
        session.beginTransaction();
        session.save( new Event( "第一个event!", new Date() ) );
        session.save( new Event( "第二个event", new Date() ) );
        session.getTransaction().commit();
        session.close();

        session = sessionFactory.openSession();
        session.beginTransaction();
        List result = session.createQuery( "from Event" ).list();
        for ( Event event : (List<Event>) result ) {
            System.out.println( "Event (" + event.getDate() + ") : " + event.getTitle() );
        }
        session.getTransaction().commit();
        session.close();
    }
}

运行testBasicUsage方法：

2.使用注解方式（annotations项目）

pom.xml:

<?xml version="1.0"?>
<!--
  ~ Hibernate, Relational Persistence for Idiomatic Java
  ~
  ~ License: GNU Lesser General Public License (LGPL), version 2.1 or later.
  ~ See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
  -->
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <parent>
        <groupId>org.hibernate.tutorials</groupId>
        <artifactId>hibernate-tutorials</artifactId>
        <version>5.4.32.Final</version>
        <relativePath>../pom.xml</relativePath>
    </parent>

    <artifactId>hibernate-tutorial-annotations</artifactId>
    <name>Hibernate Annotations Tutorial</name>
    <description>Hibernate tutorial illustrating the use of native APIs and annotations for mapping metadata</description>

    <properties>
        <!-- Skip artifact deployment -->
        <maven.deploy.skip>true</maven.deploy.skip>
    </properties>

</project>

创建实体类：Event

package org.hibernate.tutorial.annotations;

import java.util.Date;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;

import org.hibernate.annotations.GenericGenerator;

@Entity
@Table( name = "EVENTS" )
public class Event {
    private Long id;

    private String title;
    private Date date;

    public Event() {
        // this form used by Hibernate
    }

    public Event(String title, Date date) {
        // for application use, to create new events
        this.title = title;
        this.date = date;
    }

    @Id
    @GeneratedValue(generator="increment")
    @GenericGenerator(name="increment", strategy = "increment")
    public Long getId() {
        return id;
    }

    private void setId(Long id) {
        this.id = id;
    }

    @Temporal(TemporalType.TIMESTAMP)
    @Column(name = "EVENT_DATE")
    public Date getDate() {
        return date;
    }

    public void setDate(Date date) {
        this.date = date;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }
}

创建实体类对应的xml：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>

        <!-- Database connection settings -->
        <property name="connection.driver_class">org.h2.Driver</property>
        <property name="connection.url">jdbc:h2:mem:db1;DB_CLOSE_DELAY=-1;MVCC=TRUE</property>
        <property name="connection.username">sa</property>
        <property name="connection.password"></property>

        <!-- JDBC connection pool (use the built-in) -->
        <property name="connection.pool_size">1</property>

        <!-- SQL dialect -->
        <property name="dialect">org.hibernate.dialect.H2Dialect</property>

        <!-- Disable the second-level cache  -->
        <property name="cache.provider_class">org.hibernate.cache.internal.NoCacheProvider</property>

        <!-- Echo all executed SQL to stdout -->
        <property name="show_sql">true</property>

        <!-- Drop and re-create the database schema on startup -->
        <property name="hbm2ddl.auto">create</property>

        <!-- Names the annotated entity class -->
        <mapping class="org.hibernate.tutorial.annotations.Event"/>

    </session-factory>

</hibernate-configuration>

创建测试类：AnnotationsIllustrationTest

package org.hibernate.tutorial.annotations;

import java.util.Date;
import java.util.List;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.boot.MetadataSources;
import org.hibernate.boot.registry.StandardServiceRegistry;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;

import junit.framework.TestCase;

public class AnnotationsIllustrationTest extends TestCase {
    private SessionFactory sessionFactory;

    @Override
    protected void setUp() throws Exception {
        // A SessionFactory is set up once for an application!
        final StandardServiceRegistry registry = new StandardServiceRegistryBuilder()
                .configure() // configures settings from hibernate.cfg.xml
                .build();
        try {
            sessionFactory = new MetadataSources( registry ).buildMetadata().buildSessionFactory();
        }
        catch (Exception e) {
            // The registry would be destroyed by the SessionFactory, but we had trouble building the SessionFactory
            // so destroy it manually.
            StandardServiceRegistryBuilder.destroy( registry );
        }
    }

    @Override
    protected void tearDown() throws Exception {
        if ( sessionFactory != null ) {
            sessionFactory.close();
        }
    }

    @SuppressWarnings({ "unchecked" })
    public void testBasicUsage() {
        // create a couple of events...
        Session session = sessionFactory.openSession();
        session.beginTransaction();
        session.save( new Event( "测试1", new Date() ) );
        session.save( new Event( "测试2", new Date() ) );
        session.getTransaction().commit();
        session.close();

        // now lets pull events from the database and list them
        session = sessionFactory.openSession();
        session.beginTransaction();
        List result = session.createQuery( "from Event" ).list();
        for ( Event event : (List<Event>) result ) {
            System.out.println( "Event (" + event.getDate() + ") : " + event.getTitle() );
        }
        session.getTransaction().commit();
        session.close();
    }
}

运行testBasicUsage方法：