我的Hibernate HQL查询似乎是返回陈旧的数据。Hibernate HQL返回陈旧的数据?
我有一个简单的java类叫做Account,它的实例映射到带有两个varchar列的用户名和姓氏的单个数据库表上。
如果我运行一个HQL查询,如:
List<?> accountList = session.createQuery("from Account where surname is null").list();
我找回帐户对象的列表,如预期(部分在表中的行的确有空姓字段)。
我然后设置姓在返回的对象一定非空值:
Iterator<?> accountIter = accountList.iterator();
while (accountIter.hasNext()) {
Account account = (Account) accountIter.next();
log("Adding surname of Jones to : " + account.getUsername());
account.setSurname("Jones");
}
在这一点上,如果我再次运行HQL查询,我希望要回一个空的列表(如所有的姓都应该是非空的), 但是我回来的时候和第一次运行查询的时候一样。这不是我所期望的。
从Hibernate文档引用:
http://docs.jboss.org/hibernate/orm/4.1/manual/en-US/html_single/
“绝对不存在约当届执行JDBC调用, 只在它们的执行顺序的保证。然而,Hibernate保证, Query.list(..)将永远不会返回陈旧或不正确的数据。
这似乎与我的代码的行为相反。查看下面清单4中的程序输出,SQL Update语句发生在所有select语句之后,所以最后一个select返回不正确的数据。 任何人都可以阐明发生了什么,或者我做错了什么?
如果我用交易包围姓氏的设置,并执行session.saveOrUpdate(account)
这一切都有效,但我认为这不是必需的。
我希望我的代码尽可能只处理域类,并且尽可能免费使用持久性代码 。
我使用Hibernate 4.1.8.Final,与Java 1.6
我完整的代码清单如下:
清单1:Main.java:
package uk.ac.york.cserv.hibernatetest;
import java.util.Iterator;
import java.util.List;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
public class Main {
private static SessionFactory sf;
Session session;
public static void main(String[] args) {
Main main = new Main();
main.doExample();
}
public Main() {
sf = new Configuration()
.configure("hibernate-ora.cfg.xml")
.buildSessionFactory();
session = sf.openSession();
}
public void closeSession() {
session.flush();
session.close();
}
public List<?> getAccountList() {
return session.createQuery("from Account where surname is null").list();
}
public void printAccountList(List<?> accountList) {
Iterator<?> accountIter = accountList.iterator();
while (accountIter.hasNext()) {
System.out.println(accountIter.next());
}
}
public void log(String msg) {
System.out.println(msg);
}
public void doExample() {
log("Print all accounts with null surnames...");
printAccountList(getAccountList());
log("Adding surnames to accounts that have null surnames...");
//session.beginTransaction();
Iterator<?> accountIter = getAccountList().iterator();
while (accountIter.hasNext()) {
Account account = (Account) accountIter.next();
log("Adding surname of Jones to : " + account.getUsername());
account.setSurname("Jones");
//session.saveOrUpdate(account);
}
//session.getTransaction().commit();
log("Again print all accounts that have null surnames (should be none)...");
printAccountList(getAccountList());
closeSession();
}
}
清单2:帐户.java:
package uk.ac.york.cserv.hibernatetest;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;
@Entity
@Table(name="ACCOUNTS")
public class Account {
@Id
@Column(name = "USERNAME", unique = true, nullable = false)
private String username;
@Column(name = "SURNAME")
private String surname;
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getSurname() {
return surname;
}
public void setSurname(String surname) {
this.surname = surname;
}
@Override
public String toString() {
return "Account [username=" + username + ", surname=" + surname + "]";
}
}
清单3:Hibernate-ora.cfg。XML:
<hibernate-configuration>
<session-factory>
<!-- Database connection settings -->
<property name="connection.driver_class">oracle.jdbc.driver.OracleDriver</property>
<property name="connection.url">jdbc:oracle:thin:@testhost:1521:test</property>
<property name="connection.username">testschema</property>
<property name="connection.password">testpassword</property>
<!-- JDBC connection pool (use the built-in) -->
<property name="connection.pool_size">1</property>
<!-- SQL dialect -->
<property name="dialect">org.hibernate.dialect.Oracle10gDialect</property>
<!-- Disable the second-level cache -->
<property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>
<!-- Echo all executed SQL to stdout -->
<property name="show_sql">true</property>
<!-- Names of the annotated classes -->
<mapping class="uk.ac.york.cserv.hibernatetest.Account"/>
</session-factory>
</hibernate-configuration>
清单4:程序的输出:
Print all accounts with null surnames...
Hibernate: select account0_.USERNAME as USERNAME0_, account0_.SURNAME as SURNAME0_ from ACCOUNTS account0_ where account0_.SURNAME is null
Account [username=user2, surname=null]
Adding surnames to accounts that have null surnames...
Hibernate: select account0_.USERNAME as USERNAME0_, account0_.SURNAME as SURNAME0_ from ACCOUNTS account0_ where account0_.SURNAME is null
Adding surname of Jones to : user2
Again print all accounts that have null surnames (should be none)...
Hibernate: select account0_.USERNAME as USERNAME0_, account0_.SURNAME as SURNAME0_ from ACCOUNTS account0_ where account0_.SURNAME is null
Account [username=user2, surname=Jones]
Hibernate: update ACCOUNTS set SURNAME=? where USERNAME=?
感谢您的回复。这真的有帮助。 – user2157387 2013-03-15 15:57:25