ClassNotFoundException：尝试将 JPA 与 Derby 结合使用时出现 org.apache.derby.jdbc.EmbeddedDriver

我问的一个相关查询：如何配置和打包简单的 Java 应用程序以使用 JPA https://stackoverflow.com/questions/1892089/how-to-configure-package-a-simple-java-app-to-uss-jpa

我有一个简单的 Derby 数据库，可以通过 WebLogic 中托管的 EJB 连接到该数据库。现在我想使用 JPA 从命令行 Java 应用程序连接到它。

到目前为止，这个 Java 代码 + persistence.xml 文件抛出以下错误。我究竟做错了什么？

我的目录布局：

C:.
│   Registrar.class
│   Registrar.java
│   TxnClient.class
│   TxnClient.java
│
└───META-INF
        persistence.xml

独立客户端：

import javax.persistence.*;

public class TxnClient {
   public static void main(String[] args) throws Exception {
      EntityManagerFactory factory = Persistence.createEntityManagerFactory("SRS-EM");
      EntityManager manager = factory.createEntityManager( );
      try {

      } finally {
         manager.close( );
         factory.close( );
      }
   }
}

持久性.xml

<?xml version="1.0" encoding="windows-1252" ?>
    <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" xmlns="http://java.sun.com/xml/ns/persistence" version="1.0">
    <persistence-unit name="SRS-EM" transaction-type="JTA">
        <class>Registrar</class>
        <properties>
            <property name="openjpa.ConnectionDriverName" 
                          value="org.apache.derby.jdbc.EmbeddedDriver" />
            <property name="openjpa.ConnectionURL"
                          value="jdbc:derby:C:\derby-db-files\MyDB" />
        </properties>
     </persistence-unit>
    </persistence>

C:\temp\jpa>java TxnClient

 80  SRS-EM  INFO   [main] openjpa.Runtime - Starting BEA Kodo 4.2.0load03
221  SRS-EM  INFO   [main] openjpa.jdbc.JDBC - Using dictionary class "org.apache.openjpa.jdbc.sql.DerbyDictionary".
    Exception in thread "main" <openjpa-1.1.0-r422266:657916 nonfatal general error>
     org.apache.openjpa.persistence.PersistenceException: There were errors initializing your configuration: <openjpa-1.1.0-r422266:657916 fatal store error> org.apache.openjpa.util.StoreException: org.apache.derby.jdbc.EmbeddedDriver
            at org.apache.openjpa.jdbc.schema.DataSourceFactory.newDataSource(DataSourceFactory.java:123)
            at org.apache.openjpa.jdbc.conf.JDBCConfigurationImpl.createConnectionFactory(JDBCConfigurationImpl.java:776)
            at org.apache.openjpa.jdbc.conf.JDBCConfigurationImpl.getConnectionFactory(JDBCConfigurationImpl.java:683)
            at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
            at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
            at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
            at java.lang.reflect.Method.invoke(Method.java:597)
            at org.apache.openjpa.lib.conf.ConfigurationImpl.instantiateAll(ConfigurationImpl.java:288)
            at org.apache.openjpa.conf.OpenJPAConfigurationImpl.instantiateAll(OpenJPAConfigurationImpl.java:1409)
            at org.apache.openjpa.kernel.AbstractBrokerFactory.makeReadOnly(AbstractBrokerFactory.java:646)
            at org.apache.openjpa.kernel.AbstractBrokerFactory.newBroker(AbstractBrokerFactory.java:183)
            at org.apache.openjpa.kernel.DelegatingBrokerFactory.newBroker(DelegatingBrokerFactory.java:142)
            at org.apache.openjpa.persistence.EntityManagerFactoryImpl.createEntityManager(EntityManagerFactoryImpl.java:192)
            at org.apache.openjpa.persistence.EntityManagerFactoryImpl.createEntityManager(EntityManagerFactoryImpl.java:145)
            at org.apache.openjpa.persistence.EntityManagerFactoryImpl.createEntityManager(EntityManagerFactoryImpl.java:56)
            at TxnClient.main(TxnClient.java:7)
    Caused by: java.lang.ClassNotFoundException: org.apache.derby.jdbc.EmbeddedDriver
            at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
            at java.security.AccessController.doPrivileged(Native Method)
            at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
            at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
            at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
            at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
            at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)
            at java.lang.Class.forName0(Native Method)
            at java.lang.Class.forName(Class.java:169)
            at org.apache.openjpa.jdbc.schema.DataSourceFactory.newDataSource(DataSourceFactory.java:85)
            ... 15 more 

要使用未随 WebLogic Server 安装的第三方 JDBC 驱动程序，您需要更新 WebLogic Server 的CLASSPATH包括 JDBC 驱动程序类的位置。编辑commEnv.cmd/sh脚本在WL_HOME/common/bin并预习你的课程。

这适用于 Derby 的 JDBC 驱动程序（请参阅第三方驱动程序 http://download.oracle.com/docs/cd/E12840_01/wls/docs103/jdbc_admin/third_party_drivers.html）。如果您不知道将 JAR 放在哪里，请将其放入WL_HOME\server\lib与与 Weblogic 捆绑在一起的其他 JDBC 驱动程序。

PS：我想知道为什么你不使用 Kodo，它是 WebLogic 的默认持久性引擎，但这是另一个故事了。