如何在 Hibernate 4.3.4.Final 中配置和获取会话? [英] How to configure and get session in Hibernate 4.3.4.Final?
问题描述
我最近将我的 Hibernate 版本升级到 4.3.4.Final.基于Hibernate的Contextual Sessions配置这个新版本不再基于 ThreadLocal 了. 如果我到目前为止所得到的都是正确的，我是否需要做任何事情来提高效率?如果不正确，我该怎么办?我不知道.
I recently upgraded the version of my Hibernate to 4.3.4.Final. Based on Contextual Sessions configuration of Hibernate this new version is not based on ThreadLocal anymore. If what I have got so far is correct do I need to do anything to make it more efficient? if it is incorrect what should I do? I have no clue.
请注意 文档中提到: Hibernate 提供了三种当前会话跟踪方法.基于线程"的方法不适合生产使用；它仅对诸如此类的原型设计和教程有用.
Please note it is mentioned in documentation that: Hibernate offers three methods of current session tracking. The "thread" based method is not intended for production use; it is merely useful for prototyping and tutorials such as this one.
Hibernate.cfg.xml
<hibernate-configuration>
<session-factory>
<property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
<property name="hibernate.connection.url">jdbc:mysql://localhost/myDB</property>
<property name="hibernate.connection.username">root</property>
<property name="hibernate.connection.password"></property>
<property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
<!-- Enable Hibernate's automatic session context management -->
<property name="current_session_context_class">thread</property>
<!-- Disable the second-level cache -->
<property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>
<property name="show_sql">true</property>
<property name="hibernate.c3p0.min_size">5</property>
<property name="hibernate.c3p0.max_size">20</property>
<property name="hibernate.c3p0.timeout">300</property>
<property name="hibernate.c3p0.max_statements">50</property>
<property name="hibernate.c3p0.idle_test_period">3000</property>
<!-- <property name="hbm2ddl.auto">update</property>-->
<mapping class="com.myProject.entities.users" />
...
当前配置和代码
基于答案爆炸和 这部分文档 mu当前配置是以下:
Based on answers blew and this part of documentation mu current configuration is as following:
public class HibernateUtil {
private static SessionFactory sessionFactory = buildSessionFactory();
private static SessionFactory buildSessionFactory() {
try {
Configuration configuration = new Configuration();
return configuration.configure()
.buildSessionFactory(
new StandardServiceRegistryBuilder()
.applySettings(configuration.getProperties())
.build());
} catch (Throwable ex) {
System.err.println("Initial SessionFactory creation failed." + ex);
throw new ExceptionInInitializerError(ex);
}
}
public static SessionFactory getSessionFactory() {
return sessionFactory;
}
}
代码如下
final Session session = HibernateUtil.getSessionFactory().openSession();
try {
final Transaction tx = session.beginTransaction();
try {
...
之前的配置和代码
public class HibernateUtil {
private static ServiceRegistry serviceRegistry;
private static final ThreadLocal<Session> threadLocal = new ThreadLocal();
private static SessionFactory sessionFactory;
private static SessionFactory configureSessionFactory() {
try {
Configuration configuration = new Configuration();
configuration.configure();
serviceRegistry = new StandardServiceRegistryBuilder()
.applySettings(configuration.getProperties())
.build();
sessionFactory = configuration.buildSessionFactory(serviceRegistry);
return sessionFactory;
} catch (HibernateException e) {
System.out.append("** Exception in SessionFactory **");
e.printStackTrace();
}
return sessionFactory;
}
static {
try {
sessionFactory = configureSessionFactory();
} catch (Exception e) {
System.err.println("%%%% Error Creating SessionFactory %%%%");
e.printStackTrace();
}
}
private HibernateUtil() {
}
public static SessionFactory getSessionFactory() {
return sessionFactory;
}
public static Session getSession() throws HibernateException {
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 {
sessionFactory = configureSessionFactory();
} catch (Exception e) {
System.err.println("%%%% Error Creating SessionFactory %%%%");
e.printStackTrace();
}
}
public static void closeSession() throws HibernateException {
Session session = (Session) threadLocal.get();
threadLocal.set(null);
if (session != null) {
if (session.isOpen()) {
session.close();
}
}
}
}
访问交易和提交命令的代码
Code to access to transactions and submit commands
final Session session = HibernateUtil.getSession();
try {
final Transaction tx = session.beginTransaction();
try {
//Commands related to query go here
if (!tx.wasCommitted()) {
tx.commit();
}
if (session.isOpen()) {
session.close();
}
return true;
} catch (Exception e) {
tx.rollback();
return false;
}
} finally {
HibernateUtil.closeSession();
}
return false;
推荐答案
我会放弃 TreadUtil 类，它让我想起 Spring 1.0 Hibernate 集成风格.如果您打算迁移到 Hibernate 4.
I would drop the TreadUtil class which reminds me of the Spring 1.0 Hibernate integration style. If you plan on moving to Hibernate 4.
除了你应该依赖 Hibernate 4 bootstrap机制，你的代码也存在以下问题:
Beside the fact that you should rely on Hibernate 4 bootstrap mechanism, your code also has the following problems:
会话工厂重建不同步
The session factory rebuilding is not synchronized
synchronized(HibernateUtil.class) {
if (sessionFactory == null) {
rebuildSessionFactory();
}
}
我不明白你为什么需要重建它，因为你从来没有将它设置为 null，会话工厂被初始化为静态块.
I don't see why you need to rebuild it, since you never set it to null, the session factory being initialized static block.
如果您总是需要将您的 Hibernate 代码包装在 HibernateUtil.openSession() try/finally 块中，那么您将在混合业务逻辑和事务逻辑的同时复制大量会话管理逻辑.这打破了单一职责原则.
If you always have to wrap your Hibernate code in the HibernateUtil.openSession() try/finally blocks, you would duplicate a lot of session management logic while mixing business logic with transaction logic. This breaks the single responsibility principle.
如果你还是不想让HibernateUtil去，你至少可以使用类似于JDBCTemplate 在模板方法中抽象会话/事务管理，同时在 Callable 中提供业务代码，对您来说可能看起来像:
If you still don't want to let the HibernateUtil go, you can at least use a mechanism similar to JDBCTemplate to abstract the session/transaction management in a template method, while supplying the business code in a Callable, which for you might look like:
interface SessionCallback<T> {T doInSession(Session session);}
class HibernateUtil {
public T execute(SessionCallback<T> action) {
try{
//open session
//open transcation
T result = action.doInSession(sessionFactory.getCurrentSession());
//commit tx
return result;
}
catch(RuntimeException e) {
//rollback tx
throw e;
}
finally {
//close session
}
}
}
HibernateUtil.execute(new SessionCallback<Void>() {
public Void doInSession(Session session) {
session.createQuery(...);
return null;
}
});
final customerID = ...
Customer customer = HibernateUtil.execute(new SessionCallback<Customer>() {
public Customer doInSession(Session session) {
return (Customer) session.get(Customer.class, customerID);
return null;
}
});
查看您的代码表明您需要具有 session-per-request 访问习惯用法的 JDBC 资源本地事务，这意味着您需要 ThreadLocalSessionContext:
Looking at your code indicates you want JDBC resource local transactions with the session-per-request access idiom, meaning you need the ThreadLocalSessionContext:
hibernate.current_session_context_class=thread
hibernate.transaction.factory_class=JDBCTransactionFactory
额外
您也可以考虑切换到 JPA，并将 Hibernate 属性移动到 persistence.xml.
You might consider switching to JPA as well and moving the Hibernate properties to persistence.xml.
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