Java Hibernate 之 CRUD 操作

CRUD是指在做计算处理时的增加(Create)、读取(Retrieve)(重新得到数据)、更新(Update)和删除(Delete)几个单词的首字母简写.

下面列举实例来讲解这几个操作:

实体类:

package com.oumyye.model;

public class Student {

    private long id;
    private String name;
    private Class c;

    public long getId() {
        return id;
    }
    public void setId(long id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }

    public Class getC() {
        return c;
    }
    public void setC(Class c) {
        this.c = c;
    }
    @Override
    public String toString() {
        return "Student [id=" + id + ", name=" + name + "]";
    }

}

package com.oumyye.model;

import java.util.HashSet;
import java.util.Set;

public class Class {

    private long id;
    private String name;
    private Set<Student> students=new HashSet<Student>();

    public long getId() {
        return id;
    }
    public void setId(long id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Set<Student> getStudents() {
        return students;
    }
    public void setStudents(Set<Student> students) {
        this.students = students;
    }

}

映射文件:
Student.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="com.oumyye.model">
 <class name="Student" table="t_student">
  <id column="stuId" name="id">
   <generator class="native"/>
  </id>
  <property column="stuName" generated="never" lazy="false" name="name"/>
  <many-to-one cascade="save-update" class="com.oumyye.model.Class"
   column="classId" name="c"/>
 </class>
</hibernate-mapping>

Class.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="com.oumyye.model">
 <class name="Class" table="t_class">
  <id column="classId" name="id">
   <generator class="native"/>
  </id>
  <property column="className" generated="never" lazy="false" name="name"/>
  <set cascade="delete" inverse="true" name="students" sort="unsorted">
   <key column="classId"/>
   <one-to-many class="com.oumyye.model.Student"/>
  </set>
 </class>
</hibernate-mapping>

工具类:可以有myeclipse生成

package com.oumyye.util;

import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.cfg.Configuration;
import org.hibernate.cfg.AnnotationConfiguration;

/**
 * Configures and provides access to Hibernate sessions, tied to the
 * current thread of execution.  Follows the Thread Local Session
 * pattern, see {@link http://hibernate.org/42.html }.
 */
public class HibernateSessionFactory {

    /** 
     * Location of hibernate.cfg.xml file.
     * Location should be on the classpath as Hibernate uses  
     * #resourceAsStream style lookup for its configuration file. 
     * The default classpath location of the hibernate config file is 
     * in the default package. Use #setConfigFile() to update 
     * the location of the configuration file for the current session.   
     */
    private static final ThreadLocal<Session> threadLocal = new ThreadLocal<Session>();
    private static org.hibernate.SessionFactory sessionFactory;

    private static Configuration configuration = new AnnotationConfiguration();    private static String CONFIG_FILE_LOCATION = "/hibernate.cfg.xml";
    private static String configFile = CONFIG_FILE_LOCATION;

    static {
        try {
            configuration.configure(configFile);
            sessionFactory = configuration.buildSessionFactory();
        } catch (Exception e) {
            System.err.println("%%%% Error Creating SessionFactory %%%%");
            e.printStackTrace();
        }
    }
    private HibernateSessionFactory() {
    }

    /**
     * Returns the ThreadLocal Session instance.  Lazy initialize
     * the <code>SessionFactory</code> if needed.
     *
     *  @return Session
     *  @throws HibernateException
     */
    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;
    }

    /**
     *  Rebuild hibernate session factory
     *
     */
    public static void rebuildSessionFactory() {
        try {
            configuration.configure(configFile);
            sessionFactory = configuration.buildSessionFactory();
        } catch (Exception e) {
            System.err.println("%%%% Error Creating SessionFactory %%%%");
            e.printStackTrace();
        }
    }

    /**
     *  Close the single hibernate session instance.
     *
     *  @throws HibernateException
     */
    public static void closeSession() throws HibernateException {
        Session session = (Session) threadLocal.get();
        threadLocal.set(null);

        if (session != null) {
            session.close();
        }
    }

    /**
     *  return session factory
     *
     */
    public static org.hibernate.SessionFactory getSessionFactory() {
        return sessionFactory;
    }

    /**
     *  return session factory
     *
     *    session factory will be rebuilded in the next call
     */
    public static void setConfigFile(String configFile) {
        HibernateSessionFactory.configFile = configFile;
        sessionFactory = null;
    }
    /**
     *  return hibernate configuration
     *
     */
    public static Configuration getConfiguration() {
        return configuration;
    }

}

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>

    <!--数据库连接设置 -->
    <property name="connection.driver_class">
        com.mysql.jdbc.Driver
    </property>
    <property name="connection.url">
        jdbc:mysql://localhost:3306/mytest
    </property>
    <property name="connection.username">root</property>
    <property name="connection.password">root</property>

    <!-- 方言 -->
    <property name="dialect">
        org.hibernate.dialect.MySQL5Dialect
    </property>

    <!-- 控制台显示SQL -->
    <property name="show_sql">true</property>

    <!-- 自动更新表结构 -->
    <property name="hbm2ddl.auto">update</property>
    <mapping resource="com/oumyye/model/Class.hbm.xml" />
    <mapping resource="com/oumyye/model/Student.hbm.xml" />

</session-factory>

</hibernate-configuration>

测试类

package com.oumyye.service;

import java.util.Iterator;
import java.util.Set;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import com.oumyye.model.Class;
import com.oumyye.model.Student;
import com.oumyye.util.HibernateSessionFactory;

public class StudentTest {

    private SessionFactory sessionFactory=HibernateSessionFactory.getSessionFactory();
    private Session session;

    @Before
    public void setUp() throws Exception {
        session=sessionFactory.openSession(); // 生成一个session
        session.beginTransaction(); // 开启事务
    }

    @After
    public void tearDown() throws Exception {
         session.getTransaction().commit(); // 提交事务
         session.close(); // 关闭session
    }

    @Test
    public void testSaveClassAndStudent() {
        Class c=new Class();
        c.setName("08计本");

        Student s1=new Student();
        s1.setName("张三");
        s1.setC(c);

        Student s2=new Student();
        s2.setName("李四");
        s2.setC(c);

        session.save(s1);
        session.save(s2);

    }

    @Test
    public void testLoadClass(){
        // Class c=(Class)session.load(Class.class, Long.valueOf(2));
        Class c=(Class)session.load(Class.class, Long.valueOf(1));
        System.out.println(c.getStudents());
    }

    @Test
    public void testGetClass(){
        // Class c=(Class)session.get(Class.class, Long.valueOf(2));
        Class c=(Class)session.get(Class.class, Long.valueOf(1));
        System.out.println(c.getStudents());
    }

    @Test
    public void testUpdateClass(){
        Session session1=sessionFactory.openSession();
        session1.beginTransaction();
        Class c=(Class)session1.get(Class.class, Long.valueOf(1));
        session1.getTransaction().commit(); // 提交事务
        session1.close();

        Session session2=sessionFactory.openSession();
        session2.beginTransaction();
        c.setName("08计算机本科2");
        session2.update(c);
        session2.getTransaction().commit(); // 提交事务
        session2.close();
    }
    <!--更新-->
    @Test
    public void testSaveOrUpdateClass(){
        Session session1=sessionFactory.openSession();
        session1.beginTransaction();
        Class c=(Class)session1.get(Class.class, Long.valueOf(1));
        session1.getTransaction().commit(); // 提交事务
        session1.close();

        Session session2=sessionFactory.openSession();
        session2.beginTransaction();
        c.setName("08计算机本科3");

        Class c2=new Class();
        c2.setName("09计算机本科3");
        session2.saveOrUpdate(c);
        session2.saveOrUpdate(c2);
        session2.getTransaction().commit(); // 提交事务
        session2.close();
    }

    @Test
    public void testMergeClass(){
        Session session1=sessionFactory.openSession();
        session1.beginTransaction();
        Class c=(Class)session1.get(Class.class, Long.valueOf(1));
        session1.getTransaction().commit(); // 提交事务
        session1.close();

        Session session2=sessionFactory.openSession();
        session2.beginTransaction();

        Class c2=(Class)session2.get(Class.class, Long.valueOf(1));
        c.setName("08计算机本科4");

        session2.merge(c);

        session2.getTransaction().commit(); // 提交事务
        session2.close();
    }
    <!--删除-->
    @Test
    public void testDeleteStudent(){
        Student student=(Student)session.load(Student.class, Long.valueOf(1));
        session.delete(student);
    }
}

Session的入门常用方法

  • Query query = session.createQuery(hql):利用hql查询语句查询;
  • Criteria critera = session.createCriteria(Class clazz);
  • (3)Transaction tx = session.beginTransaction();    
    //开始事务;tx.commit()提交事务;
  • session.close();//关闭Session,此后被session管理的持久化对象变为脱管状态;
  • session.save(Object obj);    //添加
  • 澳门新葡亰3522平台游戏,session.update(Object obj);     //更新
  • session.delete(Object obj);    //删除
  • Object obj = session.get(Class clazz,Serialiazble id);  
     //根据主键查找记录并返回;
  • Object obj = session.load(Class clazz,Serializable id);  
     //和get方法效果一样,但是是懒加载,即在不使用他之前他不会返回对象;