找不到类 [org.apache.derby.jdbc.ClientDriver].尝试连接到数据库时 [英] Class [org.apache.derby.jdbc.ClientDriver] not found. When trying to connect to db

问题描述

我在 Netbeans 中建立了一个项目，创建了一个脚本，并使用 javadb 创建了一个新数据库.我可以通过 gui 连接到它 - 显示表格内容等，但是当我运行应用程序时:

I have set up a project in Netbeans, created a script, made a new database with javadb. I can connect to it by gui - display the tables contents etc, but when i run an application with:

 EntityManager em = Persistence.createEntityManagerFactory("lab5PU").createEntityManager();

我得到了这个很长的异常:

i get this quite long exception:

[EL Info]: 2013-04-05 21:40:45.554--ServerSession(1198260109)--EclipseLink, version: Eclipse Persistence Services - 2.3.0.v20110604-r9504
[EL Severe]: 2013-04-05 21:40:45.574--ServerSession(1198260109)--Local Exception Stack: 
Exception [EclipseLink-4003] (Eclipse Persistence Services - 2.3.0.v20110604-r9504): org.eclipse.persistence.exceptions.DatabaseException
Exception in thread "AWT-EventQueue-0" javax.persistence.PersistenceException: Exception [EclipseLink-4003] (Eclipse Persistence Services - 2.3.0.v20110604-r9504): org.eclipse.persistence.exceptions.DatabaseException
Exception Description: Configuration error.  Class [org.apache.derby.jdbc.ClientDriver] not found.
Exception Description: Configuration error.  Class [org.apache.derby.jdbc.ClientDriver] not found.
    at org.eclipse.persistence.exceptions.DatabaseException.configurationErrorClassNotFound(DatabaseException.java:82)

我可以在服务的驱动程序部分看到 javadb 驱动程序，所以我不知道可能是什么错误.

I can see the javadb drivers in the driver section in services, so i have no idea what the error might be.

按要求进行persistance.xml:

persistance.xml as requested:

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0" 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_2_0.xsd">
  <persistence-unit name="lab5PU" transaction-type="RESOURCE_LOCAL">
    <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
    <class>lab5.Colleagues</class>
    <properties>
      <property name="javax.persistence.jdbc.url" value="jdbc:derby://localhost:1527/lab5"/>
      <property name="javax.persistence.jdbc.password" value="mypass"/>
      <property name="javax.persistence.jdbc.driver" value="org.apache.derby.jdbc.ClientDriver"/>
      <property name="javax.persistence.jdbc.user" value="admin"/>
      <property name="eclipselink.ddl-generation" value="create-tables"/>
    </properties>
  </persistence-unit>
</persistence>

推荐答案

我认为您遇到的问题是您在项目的类路径中没有 Derby 驱动程序.

I think the problem you have is that you don't have the Derby driver in the classpath of the project.

您可以轻松实现将 JavaDB 库添加到您的项目中:

You can easily achieve that adding the JavaDB library to your project:

• 右键单击项目
• 属性 -> 库
• 添加库 -> JavaDB 驱动程序

这包括项目类路径中的 derby.jar、derbyclient.jar 和 derbynet.jar.

This includes derby.jar, derbyclient.jar and derbynet.jar in your project's classpath.

derbyclient.jar 包含您的代码抱怨的 org.apache.derby.jdbc.ClientDriver 类.

The derbyclient.jar contains the class org.apache.derby.jdbc.ClientDriver your code is complaining about.

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