public class Main { public static void main(String[] args) { EntityManagerFactory factory = Persistence.createEntityManagerFactory("HelloTitan"); EntityManager em = factory.createEntityManager(); Cabin c = new Cabin(); c.setId(0); c.setBedCount(50); c.setDeckLevel(2); c.setName("CabinOne"); c.setShipId(0); em.persist(c); System.out.println( em.contains(c) ); Cabin b = em.find(Cabin.class, 0); System.out.println(b.getName()); em.close(); factory.close(); }}?
问题一：?
Exception in thread "main" javax.persistence.PersistenceException: No Persistence provider for EntityManager named HelloTitan
?at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:56)
?at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:34)
?at Main.main(Main.java:10)
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原因：没有Persistence provider
解决办法：将需要的lib添加到classpath中，Jboss使用的是hibernate实现，这些lib在下面的目录中能找到
jboss-5.0.0.GA\common\lib\
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hibernate-annotations.jar
hibernate-commons-annotations.jar
hibernate-core.jar
hibernate-entitymanager.jar
hibernate-jmx.jar
hibernate-validation.jar
且还依赖 commons-collections.jar
?
问题二：
Exception in thread "main" javax.persistence.PersistenceException: [PersistenceUnit: HelloTitan] Unable to build EntityManagerFactory at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:677) at org.hibernate.ejb.HibernatePersistence.createEntityManagerFactory(HibernatePersistence.java:126) at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:52) at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:34) at Main.main(Main.java:10)Caused by: org.hibernate.HibernateException: Could not find datasource at org.hibernate.connection.DatasourceConnectionProvider.configure(DatasourceConnectionProvider.java:79) at org.hibernate.connection.ConnectionProviderFactory.newConnectionProvider(ConnectionProviderFactory.java:137) at org.hibernate.ejb.InjectionSettingsFactory.createConnectionProvider(InjectionSettingsFactory.java:29) at org.hibernate.cfg.SettingsFactory.buildSettings(SettingsFactory.java:89) at org.hibernate.cfg.Configuration.buildSettings(Configuration.java:2101) at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1325) at org.hibernate.cfg.AnnotationConfiguration.buildSessionFactory(AnnotationConfiguration.java:867) at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:669) ... 4 moreCaused by: javax.naming.NoInitialContextException: Need to specify class name in environment or system property, or as an applet parameter, or in an application resource file: java.naming.factory.initial at javax.naming.spi.NamingManager.getInitialContext(NamingManager.java:645) at javax.naming.InitialContext.getDefaultInitCtx(InitialContext.java:288) at javax.naming.InitialContext.getURLOrDefaultInitCtx(InitialContext.java:325) at javax.naming.InitialContext.lookup(InitialContext.java:392) at org.hibernate.connection.DatasourceConnectionProvider.configure(DatasourceConnectionProvider.java:75) ... 11 more
?
原因：JNDI没有初始化成功
解决办法：?在classpath添加 jnid.properties 文件 （以JBoss为例，配置如下）
java.naming.factory.initial=org.jnp.interfaces.NamingContextFactoryjava.naming.factory.url.pkgs=org.jboss.naming:org.jnp.interfacesjava.naming.provider.url=localhost:1099
?
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问题三：
程序成功运行，但是数据没有写入数据库
原因：没有提交数据
解决办法：em.getTransaction().commit();
?
?
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?其他相关记录：
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?J2SE环境中使用JPA的（Hibernate+MySQL）persistence.xml例子
?如果想使用JNDI的数据源，可以将 non-jta-data-source 这一段的注释去掉，并且注意JNDI的MySqlDS是可访问的！
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<?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="EntityRelationships" transaction-type="RESOURCE_LOCAL"> <provider>org.hibernate.ejb.HibernatePersistence</provider> <!-- <non-jta-data-source>MySqlDS</non-jta-data-source> --> <class>cn.heapstack.jpa.entityrelationships.domain.Customer</class> <class>cn.heapstack.jpa.entityrelationships.domain.Address</class> <class>cn.heapstack.jpa.entityrelationships.domain.CreditCard</class> <class>cn.heapstack.jpa.entityrelationships.domain.Phone</class> <class>cn.heapstack.jpa.entityrelationships.domain.Ship</class> <class>cn.heapstack.jpa.entityrelationships.domain.Cruise</class> <properties> <property name="hibernate.hbm2ddl.auto" value="update" /> <property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver" /> <property name="hibernate.connection.url" value="jdbc:mysql://localhost:3306/ejb3" /> <property name="hibernate.connection.username" value="root" /> <property name="hibernate.connection.password" value="root000" /> <property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect" /> <property name="hibernate.show_sql" value="true" /> <!-- <property name="hibernate.format_sql" value="true" /> --> </properties> </persistence-unit></persistence>
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?
如何在JBoss里配置MySqlDS 数据源？
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?找到这个文件，并且修改 jboss-5.0.0.GA\docs\examples\jca\mysql-ds.xml
?修改完成之后放到 jboss-5.0.0.GA\server\default\deploy 目录下，重启JBoss就可以了
?同时请参看我的另一篇文章： 使用JNDI查找JBOSS内配置好的数据源遇到的问题 ...
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