接上篇我們看到在spring配置檔案中，配置了事務，這樣在使用getCurrentSession時，只需要在方法上加上@Transcational註解即可，需要注意的是，不管你執行什麼操作，哪怕是查詢，你依然需要事務的控制。這跟上一篇提到的只有進行DDL才需要事務是兩個概念，getCurrentSession是spring管理的物件所共享的，在執行sql時，需要事務保證資料的一致性。這句話另外一層意思是，只有在spring管理的物件中，使用getCurrentSession才能獲取到有效的且是spring控制事務的session。

如果自己new物件，即便你把sessionFactory這個物件傳入物件內部，使用getCurrentSession依然會報錯。如果你根據報錯去搜索，大致會搜尋到這麼一個結論，需要在hibernate.cfg.xml中新增一個屬性

<property name="hibernate.current_session_context_class">thread</property>

一、 不新增hibernate.current_session_context_class屬性，並且在spring管理的物件之外使用getCurrentSession，程式碼及報錯如下：無論get方法有沒有@Transcational註解，都報相同的錯誤，可見@Transcational在這裡並沒有生效

public class Test1Dao {

    private SessionFactory sessionFactory;

    //通過構造器傳入SessionFactory物件
    public Test1Dao(SessionFactory sessionFactory) {
        this.sessionFactory = sessionFactory;
    }

    @Transactional
    public List get() {
        try {
            Session session = sessionFactory.getCurrentSession();
            Transaction transaction = session.beginTransaction();
            List list = sessionFactory.getCurrentSession().createSQLQuery("SELECT  * from test_info").addEntity(TestInfo.class).list();
            transaction.commit();
            return list;
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }
}
 

org.hibernate.HibernateException: Could not obtain transaction-synchronized Session for current thread
	at org.springframework.orm.hibernate4.SpringSessionContext.currentSession(SpringSessionContext.java:134)
	at org.hibernate.internal.SessionFactoryImpl.getCurrentSession(SessionFactoryImpl.java:1014)
	at com.ucredit.test.Test1Dao.get(Test1Dao.java:24)
	at com.ucredit.test.TestController.get(TestController.java:23)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:221)
	at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136)
	at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:114)
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827)
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738)
	at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:963)
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:897)
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:622)
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)

 二、加上hibernate.current_session_context_class屬性，但是去掉Test1Dao中的事務，會發現，getCurrentSession需要事務的支援

public class Test1Dao {

    private SessionFactory sessionFactory;

    //通過構造器傳入SessionFactory物件
    public Test1Dao(SessionFactory sessionFactory) {
        this.sessionFactory = sessionFactory;
    }

    @Transactional
    public List get() {
        try {
            Session session = sessionFactory.getCurrentSession();
//            Transaction transaction = session.beginTransaction();
            List list = sessionFactory.getCurrentSession().createSQLQuery("SELECT  * from test_info").addEntity(TestInfo.class).list();
//            transaction.commit();
            return list;
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }
}

org.hibernate.HibernateException: createSQLQuery is not valid without active transaction
	at org.hibernate.context.internal.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:352)
	at com.sun.proxy.$Proxy88.createSQLQuery(Unknown Source)
	at com.ucredit.test.Test1Dao.get(Test1Dao.java:26)
	at com.ucredit.test.TestController.get(TestController.java:23)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:221)
	at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136)
	at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:114)
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827)
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738)
	at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:963)
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:897)
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:622)
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)

 三、更新操作不生效，這個問題是針對openSession，這種方式獲取的session並不會自動提交，需要執行flush方法才能夠更新資料。

public class Test1Dao {

    private SessionFactory sessionFactory;

    //通過構造器傳入SessionFactory物件
    public Test1Dao(SessionFactory sessionFactory) {
        this.sessionFactory = sessionFactory;
    }

    public void update() {
        Session session = sessionFactory.openSession();
        TestInfo testInfo = (TestInfo) session.createSQLQuery("SELECT  * from test_info").addEntity(TestInfo.class).uniqueResult();
        testInfo.setName("測試");
        session.update(testInfo);
    }
}

Hibernate: SELECT  * from test_info
Hibernate: update test_info set key_id=?, name=? where id=?