我有一个项目，我们使用Hibernate-jpa-2.1并以这种方式获得 EntityManager istance
@PersistenceContext(unitName = "common-api")
EntityManager em;
和这个
em = Persistence.createEntityManagerFactory("common-api").createEntityManager();
因为有些类不是 EJB 而其他类是（我猜）。问题是createEntityManagerFactory失败并出现错误：
Caused by: javax.persistence.PersistenceException: Invalid persistence.xml.
Error parsing XML [line : -1, column : -1] : cvc-complex-type.2.4.a: Invalid content was found starting with element 'class'. One of '{"http://xmlns.jcp.org/xml/ns/persistence":validation-mode, "http://xmlns.jcp.org/xml/ns/persistence":properties}' is expected.
at org.hibernate.jpa.boot.internal.PersistenceXmlParser.validate(PersistenceXmlParser.java:357)
at org.hibernate.jpa.boot.internal.PersistenceXmlParser.loadUrl(PersistenceXmlParser.java:290)
at org.hibernate.jpa.boot.internal.PersistenceXmlParser.parsePersistenceXml(PersistenceXmlParser.java:94)
at org.hibernate.jpa.boot.internal.PersistenceXmlParser.doResolve(PersistenceXmlParser.java:84)
at org.hibernate.jpa.boot.internal.PersistenceXmlParser.locatePersistenceUnits(PersistenceXmlParser.java:66)
at org.hibernate.jpa.HibernatePersistenceProvider.getEntityManagerFactoryBuilderOrNull(HibernatePersistenceProvider.java:80)
... 80 more
这是persistence.xml：
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.1" xmlns="http://xmlns.jcp.org/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
<persistence-unit name="common-api" transaction-type="JTA">
<provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
<jta-data-source>(...)</jta-data-source>
<class>(the only entity we have in this Maven module)</class>
<exclude-unlisted-classes>true</exclude-unlisted-classes>
<shared-cache-mode>ENABLE_SELECTIVE</shared-cache-mode>
<validation-mode>NONE</validation-mode>
<properties>
<property name="javax.persistence.validation.mode" value="NONE" />
<property name="hibernate.dialect" value="org.hibernate.dialect.MySQL57InnoDBDialect" />
<property name="hibernate.show_sql" value="false" />
<property name="hibernate.format_sql" value="true" />
<property name="hibernate.order_updates" value="true" />
<property name="hibernate.max_fetch_depth" value="2" />
<property name="hibernate.use_sql_comments" value="true" />
<property name="hibernate.use_identifer_rollback" value="true" />
<property name="hibernate.jdbc.batch_size" value="0" />
<property name="hibernate.jdbc.batch_versioned_data" value="false" />
<property name="hibernate.jdbc.use_get_generated_keys" value="true" />
<property name="hibernate.hbm2ddl.auto" value="none"/>
</properties>
</persistence-unit>
</persistence>
我不明白为什么会发生这种情况，因为我的类在同一个包中，同一个 maven 模块，使用相同的 Hibernate 实体和相同的persistence.xml。
注意：使这个类成为 EJB 不是一种选择。