Java 休眠对象不刷新

Question

我正在研究Hibernate。我正在测试一个简单的Java，以在2个单独的会话中加载2本书的实体。我加载了第一本书对象，让主线程睡5s，在此期间，我更改了DB中的书名。之后，第二届会议将再次加载本书。但是这本书的名称仍然相同。当预计还会更改时。

请帮忙。我编写了一个servlet程序，但是有同样的问题，更新的数据在DB更改后不会显示。

这是我的代码：

import java.util.Date;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Set;
import org.hibernate.CacheMode;
import org.hibernate.Hibernate;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import org.hibernate.stat.Statistics;
/**
 * @author Guruzu
 * 
 */
public class Launch_3_5 {
    private static SessionFactory sessionFactory;
    public static Session getSession() {
        if (sessionFactory == null) {
            sessionFactory = new Configuration().configure()
                    .buildSessionFactory();
        }
        Session hibernateSession = sessionFactory.openSession();
        return hibernateSession;
    }
    public static SessionFactory getSessionFactory() {
        if (sessionFactory == null) {
            sessionFactory = new Configuration().configure()
                    .buildSessionFactory();
        }
        return sessionFactory;
    }
    public static void main(String[] args) {
        Session session1 = getSessionFactory().openSession();
        try {
            Transaction tx = session1.beginTransaction();
            Book book1 = (Book) session1.get(Book.class, (long) 1);
            System.out.println("Book: " + book1.getName());

        //  session1.flush();
        } finally {
            session1.close();
        }
        try {
            Thread.sleep(5000);
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        Session session2 = getSessionFactory().openSession();
        try {
            Book book2 = (Book) session2.get(Book.class, (long) 1);
            System.out.println("Book: " + book2.getName());
        } finally {
            session2.close();
        }
    }
}

book6_1.hbm.xml

<?xml version="1.0" encoding="UTF-8"?> 
<!DOCTYPE hibernate-mapping PUBLIC 
"-//Hibernate/Hibernate Mapping DTD 3.0//EN" 
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
    <class name="Book" table="Book6_1">
        <id name="book_id" type="long" column="BOOK_ID">
            <generator class="increment">
            </generator>
        </id>
        <property name="isbn" type="string">
            <column name="ISBN" length="50" not-null="true" unique="true" />
        </property>
        <property name="name" type="string">
            <column name="BOOK_NAME" length="100" not-null="true" />
        </property>
        <property name="publishDate" type="date" column="PUBLISH_DATE" />
        <property name="price" type="int" column="PRICE" />

    </class>
</hibernate-mapping> 

hibernate.cfg.xml

<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    <session-factory>
        <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/hibernatetutorial</property>
        <property name="hibernate.connection.username">root</property>
        <property name="hibernate.connection.password">root</property>
        <property name="hibernate.connection.pool_size">10</property>
        <property name="show_sql">true</property>
        <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
        <mapping resource="Book_6_1.hbm.xml" />
    </session-factory>
</hibernate-configuration>

Answer 1

您的第二次会话正在击中第二级缓存。如果您不希望它这样做，则可以在配置文件（use_second_level_cache = false）中完全关闭缓存或映射文件（从hbm.xml中删除'CACE'元素。

）。

或者您可以使用cachemode.refresh

更改查询以始终转到数据库

    Session session2 = getSessionFactory().openSession();
    session2.setCacheMode(CacheMode.REFRESH);
    try {
        Book book2 = (Book) session2.get(Book.class, (long) 1);
    } finally {
        session2.close();
    }