3

我刚刚开始研究 java 持久性（目前使用 eclipse 的默认提供程序 eclipselink）。基本上只是创建一个对象并尝试将其持久化到数据库（Oracle）。我的理解是，默认事务性应该在方法返回时将新对象提交到数据库，但似乎没有发生任何事情。有任何想法吗？

@Stateless
public class RegisterUser implements RegisterUserLocal {

 @PersistenceContext
 private EntityManager entityManager;

    public void registerNewUser(String username, String password){
     User user = new User();
     user.setPassword(password);
     user.setUsername(username);
     entityManager.persist(user);
     entityManager.getTransaction().commit();
    }
}

持久性.xml：

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="1.0" xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd">
 <persistence-unit name="SCBCDEntities" transaction-type="RESOURCE_LOCAL">
  <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
  <class>examples.persistence.User</class>
  <properties>
   <property name="eclipselink.target-server" value="WebLogic_10"/>
   <property name="eclipselink.jdbc.driver" value="oracle.jdbc.OracleDriver"/>
   <property name="eclipselink.jdbc.url" value="jdbc:oracle:thin:@localhost:1521:db4"/>
   <property name="eclipselink.jdbc.user" value="SCBCD"/>
   <property name="eclipselink.jdbc.password" value="123456"/>
   <property name="eclipselink.logging.level" value="FINEST"/>
  </properties>
 </persistence-unit>
</persistence>

实体类：

@Entity
@Table(name="USERS")
public class User implements Serializable {
 private static final long serialVersionUID = 1L;

 @Id
 private String username;

 private String password;

    public User() {
    }

 public String getUsername() {
  return this.username;
 }

 public void setUsername(String username) {
  this.username = username;
 }

 public String getPassword() {
  return this.password;
 }

 public void setPassword(String password) {
  this.password = password;
 }

}

此外，为了回应对这个问题的回复，我列出的代码显示了正在执行的提交（为简洁起见，删除了一些细节）

[EL Finest]: 2010-01-05 22:58:07.468--UnitOfWork(25499586)--Thread(Thread[[ACTIVE] ExecuteThread: '0' for queue: 'weblogic.kernel.
Default (self-tuning)',5,Pooled Threads])--PERSIST operation called on: examples.persistence.User@191ed96.
<Jan 5, 2010 10:58:07 PM EST> <Debug> <JTA2PC> <BEA-000000> <BEA1-001959ECF50B251A451D: [EJB examples.session.stateless.RegisterUs
er.registerNewUser(java.lang.String,java.lang.String)]: ServerTransactionImpl.commit()>
<Jan 5, 2010 10:58:07 PM EST> <Debug> <JTA2PC> <BEA-000000> <BEA1-001959ECF50B251A451D: [EJB examples.session.stateless.RegisterUs
er.registerNewUser(java.lang.String,java.lang.String)]: TX[BEA1-001959ECF50B251A451D] active-->pre_preparing
<Jan 5, 2010 10:58:07 PM EST> <Debug> <JTA2PC> <BEA-000000> <SC[mr_domain+AdminServer] active-->pre-preparing
er.registerNewUser(java.lang.String,java.lang.String)]: TX[BEA1-001959ECF50B251A451D] prepared-->committing
<Jan 5, 2010 10:58:07 PM EST> <Debug> <JTA2PC> <BEA-000000> <SC[mr_domain+AdminServer] pre-prepared-->committed
er.registerNewUser(java.lang.String,java.lang.String)]: TX[BEA1-001959ECF50B251A451D] committing-->committed
...
...

但是如果我在持久化之后添加'flush'，我会得到'notransaction'......

[EL Finest]: 2010-01-05 22:44:55.218--UnitOfWork(113017)--Thread(Thread[[ACTIVE] ExecuteThread: '2' for queue: 'weblogic.kernel.De
fault (self-tuning)',5,Pooled Threads])--PERSIST operation called on: examples.persistence.User@1717dea.
<Jan 5, 2010 10:44:55 PM EST> <Info> <EJB> <BEA-010227> <EJB Exception occurred during invocation from home or business: weblogic.
ejb.container.internal.StatelessEJBLocalHomeImpl@1509b8 threw exception: javax.persistence.TransactionRequiredException:
Exception Description: No transaction is currently active>
<Jan 5, 2010 10:44:55 PM EST> <Debug> <JTA2PC> <BEA-000000> <BEA1-001859ECF50B251A451D: [EJB examples.session.stateless.RegisterUs
er.registerNewUser(java.lang.String,java.lang.String)]: TX[BEA1-001859ECF50B251A451D] active-->rolling back
...
...
4

3 回答 3

8

经过大量调查，包括尝试容器管理和用户管理的事务，问题似乎在于事务类型被指定为 RESOURCE_LOCAL。在这种情况下，适用以下规则：

*  You must use the EntityManagerFactory to get an EntityManager
* The resulting EntityManager instance is a PersistenceContext/Cache
* An EntityManagerFactory can be injected via the @PersistenceUnit annotation only (not @PersistenceContext)
* You are not allowed to use @PersistenceContext to refer to a unit of type RESOURCE_LOCAL
* You must use the EntityTransaction API to begin/commit around every call to your EntityManger
* Calling entityManagerFactory.createEntityManager() twice results in two separate EntityManager instances and therefor two separate PersistenceContexts/Caches.
* It is almost never a good idea to have more than one instance of an EntityManager in use (don't create a second one unless you've destroyed the first)

就我而言，我需要使用管理器工厂来访问实体管理器，并使用 persistenceUnit 而不是 persistenceContext。以下代码可以正常工作：

@Stateless
@TransactionManagement(TransactionManagementType.CONTAINER)

public class RegisterUser implements RegisterUserLocal {

 @PersistenceUnit(unitName = "SCBCDEntities")
 private EntityManagerFactory factory;

 public void registerNewUser(String username, String password) {

  EntityManager entityManager = factory.createEntityManager();
  EntityTransaction entityTransaction = entityManager.getTransaction();
  entityTransaction.begin();

  User user = new User();
  user.setPassword(password);
  user.setUsername(username);

  entityManager.persist(user);
  entityTransaction.commit();
 }
}

有关配置事务和persistence.xml 中的设置的其他信息可以在此处找到：http: //openejb.apache.org/3.0/jpa-concepts.html

于 2010-01-06T08:01:57.590 回答
3

您不能使用 EntityTransaction (em.getTransaction())，因为您使用的是容器托管实体管理器（注入），因此您必须依赖容器进行交易。您是否在 XML 中为无状态会话 bean 设置了任何事务设置？如果您还没有，那么它应该可以正常工作，因为默认值应该是“必需的”。您可以尝试使用 @TransactionAttribute(TransactionAttributeType.REQUIRED) 注释“registerNewUser”

或者，您可以在访问 EM 之前创建用户事务，但容器管理事务会更好。

于 2010-01-05T14:16:37.980 回答
1

这可能是因为您尚未开始交易。尝试：

public void registerNewUser(String username, String password){
  entityManager.getTransaction().begin();
  User user = new User();
  user.setPassword(password);
  user.setUsername(username);
  entityManager.persist(user);
  entityManager.getTransaction().commit();
}

虽然我不喜欢以这种方式进行事务处理。相反，我倾向于使用 Spring 的声明式事务，它看起来像这样：

@Transactional
public void registerNewUser(String username, String password){
  User user = new User();
  user.setPassword(password);
  user.setUsername(username);
  entityManager.persist(user);
}

配置时。

编辑：另一种可能性是我曾经在 EclipseLink 中遇到的一个问题，当我在 J2SE 环境中运行它时（一个将一些文件加载​​到数据库中的控制台应用程序），它没有将所有内容都写入数据库。在那种情况下，我必须明确地flush()写下EntityManager所有记录。

于 2010-01-05T07:41:03.787 回答