获得session对象有两种方法：
1)openSession
2)getCurrentSession
如果使用的是getCurrentSession需要在hibernate.cfg.xml文件中进行配置：
如果是本地事务(jdbc事务)，按照如下方法配置：
<property name="hibernate.current_session_context_class">thread</property>
如果是全局事务(jta事务)
<property name="hibernate.current_session_context_class">jta</property>
例子：
先创建java类：
1 package com.imooc.hibernate;
2
3 import java.util.Date;
4
5 public class Students {
6
7 private int sid;
8 private String sname;
9 private String gender;
10 private Date birthday;
11 private String address;
12
13 public Students(int sid, String sname, String gender, Date birthday, String address) {
14 super();
15 this.sid = sid;
16 this.sname = sname;
17 this.gender = gender;
18 this.birthday = birthday;
19 this.address = address;
20 }
21
22 @Override
23 public String toString() {
24 return "Students [sid=" + sid + ", sname=" + sname + ", gender=" + gender + ", birthday=" + birthday
25 + ", address=" + address + "]";
26 }
27
28 public int getSid() {
29 return sid;
30 }
31
32 public void setSid(int sid) {
33 this.sid = sid;
34 }
35
36 public String getSname() {
37 return sname;
38 }
39
40 public void setSname(String sname) {
41 this.sname = sname;
42 }
43
44 public String getGender() {
45 return gender;
46 }
47
48 public void setGender(String gender) {
49 this.gender = gender;
50 }
51
52 public Date getBirthday() {
53 return birthday;
54 }
55
56 public void setBirthday(Date birthday) {
57 this.birthday = birthday;
58 }
59
60 public String getAddress() {
61 return address;
62 }
63
64 public void setAddress(String address) {
65 this.address = address;
66 }
67 }
java类的配置文件
1 <?xml version="1.0"?> 2 <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" 3 "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> 4 <!-- Generated 2017-5-23 0:24:09 by Hibernate Tools 3.5.0.Final --> 5 <hibernate-mapping> 6 <class name="com.imooc.hibernate.Students" table="STUDENTS"> 7 <id name="sid" type="int"> 8 <column name="SID" /> 9 <generator class="assigned" /> 10 </id> 11 <property name="sname" type="java.lang.String"> 12 <column name="SNAME" /> 13 </property> 14 <property name="gender" type="java.lang.String"> 15 <column name="GENDER" /> 16 </property> 17 <property name="birthday" type="java.util.Date"> 18 <column name="BIRTHDAY" /> 19 </property> 20 <property name="address" type="java.lang.String"> 21 <column name="ADDRESS" /> 22 </property> 23 </class> 24 </hibernate-mapping>
hibernate配置文件
<?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>
<property name="connection.username">root</property>
<property name="connection.password">root</property>
<property name="connection.driver_class">com.mysql.jdbc.Driver</property>
<property name="connection.url">jdbc:mysql://localhost:3306/hibernate?useUnicode=true&characterEncoding=UTF-8</property>
<property name="dialect">org.hibernate.dialect.MySQLDialect</property>
<!-- 是否将sql语句打印到控制台，编码阶段便于测试，建议设为true -->
<property name="show_sql">true</property>
<!-- 是否将sql语句进行排版，建议设为true -->
<property name="format_sql">true</property>
<!-- 生成表结构的策略。create是如果之前有表结构，先删除表结构再重建；
update：原有的基础上更新；
create-drop：先删除表结构再重建
validate：与原表进行验证，如果和原表表结构不同，则不进行创建。
一般使用create和update
-->
<property name="hbm2ddl.auto">create</property>
<!-- 使用getCurrentSession方法必须在配置文件中配置 -->
<property name="hibernate.current_session_context_class">thread</property>
<mapping resource="com/imooc/hibernate/Students.hbm.xml"/>
</session-factory>
</hibernate-configuration>
测试类
1 package com.icoom.test;
2
3 import org.hibernate.Session;
4 import org.hibernate.SessionFactory;
5 import org.hibernate.cfg.Configuration;
6 import org.hibernate.service.ServiceRegistry;
7 import org.hibernate.service.ServiceRegistryBuilder;
8 import org.junit.Test;
9
10 public class SessionTest {
11
12 /*
13 * 使用openSession获得session对象
14 */
15 @Test
16 public void testOpenSession() {
17 Configuration config = new Configuration().configure();//获得配置对象（读取hibernate.cfg.xml文件）
18 // 获得服务注册对象
19 ServiceRegistry serviceRegistry = new ServiceRegistryBuilder().applySettings(config.getProperties()).buildServiceRegistry();
20 // 获得sessionFactory对象
21 SessionFactory sessionFactory = config.buildSessionFactory(serviceRegistry);
22 // 获得session对象
23 Session session = sessionFactory.openSession();
24 if (session != null) {
25 System.out.println("session创建成功");
26 } else {
27 System.out.println("session创建失败");
28 }
29 }
30
31 /*
32 * 使用getCurrentSession获得session对象（需要在hibernate配置文件中设置）
33 */
34 @Test
35 public void testGetCurrentSession() {
36 Configuration config = new Configuration().configure();
37 ServiceRegistry serviceRegistry = new ServiceRegistryBuilder().applySettings(config.getProperties()).buildServiceRegistry();
38 SessionFactory sessionFactory = config.buildSessionFactory(serviceRegistry);
39 Session session = sessionFactory.getCurrentSession();
40 if (session != null) {
41 System.out.println("session创建成功！");
42 } else {
43 System.out.println("session创建失败！");
44 }
45 }
46 }
那么，openSession和getCurrentSession有什么区别？
1. getCurrentSession在事务提交或者回滚之后会自动关闭，openSession需要手动关闭。如果使用openSession而没有手动关闭，多次之后会导致连接池溢出。
1 package com.icoom.test;
2
3 import java.sql.Connection;
4 import java.sql.SQLException;
5 import java.util.Date;
6
7 import org.hibernate.Session;
8 import org.hibernate.SessionFactory;
9 import org.hibernate.Transaction;
10 import org.hibernate.cfg.Configuration;
11 import org.hibernate.jdbc.Work;
12 import org.hibernate.service.ServiceRegistry;
13 import org.hibernate.service.ServiceRegistryBuilder;
14 import org.junit.Test;
15
16 import com.imooc.hibernate.Students;
17
18 public class SessionTest {
19
20 @Test
21 public void saveStudentsByOpenSession() {
22
23 // 获取配置对象
24 Configuration configure = new Configuration().configure();
25 // 获得服务注册对象
26 ServiceRegistry serviceRegistry = new ServiceRegistryBuilder().applySettings(configure.getProperties()).buildServiceRegistry();
27 /*
28 * 创建sessionFactory对象。sessionFactory是一种工厂模式，
29 * 目的是返回session，而不必new一个session。这样做比较安全。
30 */
31 SessionFactory sessionFactory = configure.buildSessionFactory(serviceRegistry);
32 // 创建第一个session对象
33 Session session1 = sessionFactory.openSession();
34 // 开启事务
35 Transaction transaction = session1.beginTransaction();
36 // 生成一个学生对象
37 Students s = new Students(1,"张三","男",new Date(),"北京");
38 session1.doWork(new Work() {
39
40 @Override
41 public void execute(Connection connection) throws SQLException {
42 // TODO Auto-generated method stub
43 System.out.println("connection‘s hashCode:" + connection.hashCode());
44 }
45
46 });
47 session1.save(s);
48 // session1.close(); // 不执行close()方法,继续新建session对象
49 transaction.commit();
50
51 // 创建第二个session对象
52 Session session2 = sessionFactory.openSession();
53 transaction = session2.beginTransaction();
54 s = new Students(2,"李四","女",new Date(),"上海");
55 session2.doWork(new Work() {
56
57 @Override
58 public void execute(Connection connection) throws SQLException {
59 // TODO Auto-generated method stub
60 System.out.println("connection‘s hashCode:" + connection.hashCode());
61 }
62
63 });
64 session2.save(s);
65 transaction.commit();
66 }
67 }
控制台打印出两个hashcode值不同，所以使用openSession()方法而不手动关闭，每次创建都会新建一个链接，有可能导致连接池溢出。
再看getCurrentSession()：
1 package com.icoom.test;
2
3 import java.sql.Connection;
4 import java.sql.SQLException;
5 import java.util.Date;
6
7 import org.hibernate.Session;
8 import org.hibernate.SessionFactory;
9 import org.hibernate.Transaction;
10 import org.hibernate.cfg.Configuration;
11 import org.hibernate.jdbc.Work;
12 import org.hibernate.service.ServiceRegistry;
13 import org.hibernate.service.ServiceRegistryBuilder;
14 import org.junit.Test;
15
16 import com.imooc.hibernate.Students;
17
18 public class SessionTest {
19
20 @Test
21 public void saveStudentsByGetCurrentSession() {
22
23 // 获取配置对象
24 Configuration configure = new Configuration().configure();
25 // 获得服务注册对象
26 ServiceRegistry serviceRegistry = new ServiceRegistryBuilder().applySettings(configure.getProperties()).buildServiceRegistry();
27 /*
28 * 创建sessionFactory对象。sessionFactory是一种工厂模式，
29 * 目的是返回session，而不必new一个session。这样做比较安全。
30 */
31 SessionFactory sessionFactory = configure.buildSessionFactory(serviceRegistry);
32 // 创建第一个session对象
33 Session session1 = sessionFactory.getCurrentSession();
34 // 开启事务
35 Transaction transaction = session1.beginTransaction();
36 // 生成一个学生对象
37 Students s = new Students(1,"张三","男",new Date(),"北京");
38 session1.doWork(new Work() {
39
40 @Override
41 public void execute(Connection connection) throws SQLException {
42 // TODO Auto-generated method stub
43 System.out.println("connection‘s hashCode:" + connection.hashCode());
44 }
45
46 });
47 session1.save(s);
48 // session1.close(); // 不执行close()方法,继续新建session对象
49 transaction.commit();
50
51 // 创建第二个session对象
52 Session session2 = sessionFactory.getCurrentSession();
53 transaction = session2.beginTransaction();
54 s = new Students(2,"李四","女",new Date(),"上海");
55 session2.doWork(new Work() {
56
57 @Override
58 public void execute(Connection connection) throws SQLException {
59 // TODO Auto-generated method stub
60 System.out.println("connection‘s hashCode:" + connection.hashCode());
61 }
62
63 });
64 session2.save(s);
65 // session2.close();
66 transaction.commit();
67 }
68 }
两个hashCode一致。
2. openSession每次创建新的session对象，getCurrentSession使用现有的session对象。
1 package com.icoom.test;
2
3 import org.hibernate.Session;
4 import org.hibernate.SessionFactory;
5 import org.hibernate.cfg.Configuration;
6 import org.hibernate.service.ServiceRegistry;
7 import org.hibernate.service.ServiceRegistryBuilder;
8 import org.junit.Test;
9
10 public class SessionTest {
11
12 /*
13 * openSession每次创建新的session对象
14 */
15 @Test
16 public void testOpenSession() {
17 Configuration config = new Configuration().configure();//获得配置对象（读取hibernate.cfg.xml文件）
18 // 获得服务注册对象
19 ServiceRegistry serviceRegistry = new ServiceRegistryBuilder().applySettings(config.getProperties()).buildServiceRegistry();
20 // 获得sessionFactory对象
21 SessionFactory sessionFactory = config.buildSessionFactory(serviceRegistry);
22 // 获得session对象
23 Session session1 = sessionFactory.openSession();
24 Session session2 = sessionFactory.openSession();
25 System.out.println(session1 == session2); // false
26 }
27
28 /*
29 * getCurrentSession使用现有的session对象
30 */
31 @Test
32 public void testGetCurrentSession() {
33 Configuration config = new Configuration().configure();
34 ServiceRegistry serviceRegistry = new ServiceRegistryBuilder().applySettings(config.getProperties()).buildServiceRegistry();
35 SessionFactory sessionFactory = config.buildSessionFactory(serviceRegistry);
36 Session session1 = sessionFactory.getCurrentSession();
37 Session session2 = sessionFactory.getCurrentSession();
38 System.out.println(session1 == session2); // true
39 }
40 }
时间： 2024-07-29 09:48:47