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
- 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；