阿帕奇德比 +杰帕

Question

我嵌入了 derby 数据库，并且使用 jpa。这是我的 persistence.xml：

<?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="pers">

        <class>entities.Leverancier</class>
        <class>entities.Prijsproduct</class>
        <class>entities.Product</class>


    </persistence-unit>
</persistence>

我应该更改或添加什么才能使其正常工作。当我现在运行代码时，我得到以下信息：

Exception in thread "main" javax.persistence.PersistenceException: No Persistence provider for EntityManager named pers
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:55)
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:33)
at test.Test.main(Test.java:19)

Answer 1

您的 persistence.xml 不正确。请看下面的示例：

<persistence-unit name="MyAppPU" transaction-type="RESOURCE_LOCAL">    
    <!-- This is where you mention your JPA runtime provider e.g. it's EclipseLink here -->
    <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>    

    <class>mypkg.MyEntity</class>

    <properties>
      <property name="javax.persistence.jdbc.url" value="jdbc:derby://localhost:1527/my_schema"/>
      <property name="javax.persistence.jdbc.password" value="pass"/>
      <property name="javax.persistence.jdbc.driver" value="org.apache.derby.jdbc.ClientDriver"/>
      <property name="javax.persistence.jdbc.user" value="user"/>
    </properties>

</persistence-unit>

您还必须确保将 JPA 提供程序 jar 文件（以及 derby-client jar）放入类路径中。