使用 Jakarta JPA 3.0 时出现异常

Question

我在基于 Jakarta JPA 3.0 的项目中遇到异常。下面是我的依赖项，persistence.xml 和异常文件。

依赖关系

<groupId>jakarta.persistence</groupId>
  <artifactId>jakarta.persistence-api</artifactId>
  <version>3.0.0</version>
</dependency>

Persistence.xml

<?xml version="1.0" encoding="UTF-8"?>
<persistence xmlns="https://jakarta.ee/xml/ns/persistence"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="https://jakarta.ee/xml/ns/persistence https://jakarta.ee/xml/ns/persistence/persistence_3_0.xsd"
    version="3.0">
    <persistence-unit name="usecase" transaction-type="RESOURCE_LOCAL">
        <exclude-unlisted-classes>false</exclude-unlisted-classes>      
        <properties>
            <property name="jakarta.persistence.jdbc.driver" value="com.mysql.cj.jdbc.Driver" />
            <property name="jakarta.persistence.jdbc.url" value="jdbc:mysql://localhost:3306/usecase" />
            <property name="jakarta.persistence.jdbc.user" value="root" />
            <property name="jakarta.persistence.jdbc.password" value="********" />
        </properties>               
    </persistence-unit>
</persistence>

异常

Feb 16, 2022 1:39:01 PM jakarta.persistence.spi.PersistenceProviderResolverHolder$DefaultPersistenceProviderResolver log
WARNING: jakarta.persistence.spi::No valid providers found.
Exception in thread "main" java.lang.ExceptionInInitializerError
    at za.co.lot24media.usecase.Main.main(Main.java:10)
Caused by: jakarta.persistence.PersistenceException: No Persistence provider for EntityManager named usecase
    at jakarta.persistence.Persistence.createEntityManagerFactory(Persistence.java:86)
    at jakarta.persistence.Persistence.createEntityManagerFactory(Persistence.java:55)
    at za.co.lot24media.usecase.Database.<init>(Database.java:15)
    at za.co.lot24media.usecase.Database.<clinit>(Database.java:9)
    ... 1 more

Answer 1

您只对 Java 持久性 API 有依赖性。但是，要在您的应用程序中使用 JPA 3.0，您需要添加对实现的依赖，例如到 EclipseLink。

为了将 EclipseLink 用作 JPA 提供程序，您必须将相关实现添加为项目的依赖项，例如通过 Maven：

<!-- https://mvnrepository.com/artifact/org.eclipse.persistence/eclipselink -->
<dependency>
    <groupId>org.eclipse.persistence</groupId>
    <artifactId>eclipselink</artifactId>
    <version>3.0.2</version>
</dependency>

请注意，您需要版本 > 3.0.0 才能使用 Jakarta Persistence API 3.0.

然后可以通过 <provider> 标签在 persistence.xml 中指定提供程序（有关详细信息，请参阅 EclipseLink 的 documentation）：

<persistence xmlns="https://jakarta.ee/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="https://jakarta.ee/xml/ns/persistence
    https://jakarta.ee/xml/ns/persistence/persistence_3_0.xsd"
             version="3.0">
    <persistence-unit name="ejblite-pu" transaction-type="JTA">
     <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
    </persistence-unit>
</persistence>

使用 Jakarta JPA 3.0 时出现异常

Exception while using Jakarta JPA 3.0

jpa

jakarta-ee