Hibernate JPA初探的坑

异常

javax.persistence.PersistenceException: No Persistence provider for EntityManager named jpa
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:61)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:39)
    at top.sicso.test.TestApp.<init>(TestApp.java:20)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
    at org.junit.runners.BlockJUnit4ClassRunner.createTest(BlockJUnit4ClassRunner.java:217)
    at org.junit.runners.BlockJUnit4ClassRunner$1.runReflectiveCall(BlockJUnit4ClassRunner.java:266)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.BlockJUnit4ClassRunner.methodBlock(BlockJUnit4ClassRunner.java:263)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:678)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)

控制台

九月 07, 2018 5:17:42 下午 org.hibernate.jpa.boot.internal.PersistenceXmlParser doResolve
INFO: HHH000318: Could not find any META-INF/persistence.xml file in the classpath

测试

    private EntityManagerFactory entityManagerFactory = Persistence.createEntityManagerFactory("jpa");

    @Test
    public void testJpa(){
        EntityManager entityManager = entityManagerFactory.createEntityManager();
        User user = entityManager.find(User.class, "u1");
        entityManager.close();
        System.out.println(user);       
    }

运行时报了异常，将 persistence.xml 文件置于 WebRoot/META-INF 文件夹中。
在网上并没有找到想要的答案，于是进行了尝试。

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 用的hibernate5.2版本,其 Persistence提供者 类为下：

<provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>

persistence.xml

<?xml version="1.0" encoding="UTF-8"?>
<persistence 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"
    version="2.1">

    <persistence-unit name="jpa">
        <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
        <class>entity.User</class>
        <properties>
            <property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver" />
            <property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost:3306/test" />
            <property name="javax.persistence.jdbc.user" value="root" />
            <property name="javax.persistence.jdbc.password" value="1234" />
            <property name="hibernate.show_sql" value="true" />
            <property name="hibernate.format_sql" value="true" />
            <property name="hibernate.hbm2ddl.auto" value="update" />
        </properties>
    </persistence-unit>
</persistence>

---

尝试解决:

 在 src 目录下自行创建一个 META-INF 文件夹，将persistence.xml文件放入。

---

结果&控制台

INFO: HHH000204: Processing PersistenceUnitInfo [
    name: jpa
    ...]

    ...略...

Hibernate: 
select
    user0_.uid as uid1_0_0_,
    user0_.name as name2_0_0_,
    user0_.password as password3_0_0_ 
from
    user user0_ 
where
    user0_.uid=?
User [uid=u1, name=admin, password=admin1]

---

其它
当尝试添加如下属性时

    <!-- 添加 transaction-type 属性 -->
    <persistence-unit name="jpa" transaction-type="JTA">

又出异常，这下有点迷了，由于不是很熟悉JPA，暂时不清楚原因，
可能是 没有配置JTA相关的原因？

javax.persistence.PersistenceException: [PersistenceUnit: jpa] Unable to build Hibernate SessionFactory
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.persistenceException(EntityManagerFactoryBuilderImpl.java:970)
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:895)
    at org.hibernate.jpa.HibernatePersistenceProvider.createEntityManagerFactory(HibernatePersistenceProvider.java:58)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:55)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:39)
    at top.sicso.test.TestApp.<init>(TestApp.java:20)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
    at org.junit.runners.BlockJUnit4ClassRunner.createTest(BlockJUnit4ClassRunner.java:217)
    at org.junit.runners.BlockJUnit4ClassRunner$1.runReflectiveCall(BlockJUnit4ClassRunner.java:266)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.BlockJUnit4ClassRunner.methodBlock(BlockJUnit4ClassRunner.java:263)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:678)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)
Caused by: org.hibernate.HibernateException: DdlTransactionIsolatorJtaImpl could not locate TransactionManager to suspend any current transaction; base JtaPlatform impl (org.h[email protected]319bc845)?
    at org.hibernate.resource.transaction.backend.jta.internal.DdlTransactionIsolatorJtaImpl.<init>(DdlTransactionIsolatorJtaImpl.java:46)
    at org.hibernate.resource.transaction.backend.jta.internal.JtaTransactionCoordinatorBuilderImpl.buildDdlTransactionIsolator(JtaTransactionCoordinatorBuilderImpl.java:46)
    at org.hibernate.tool.schema.internal.HibernateSchemaManagementTool.getDdlTransactionIsolator(HibernateSchemaManagementTool.java:175)
    at org.hibernate.tool.schema.internal.AbstractSchemaMigrator.doMigration(AbstractSchemaMigrator.java:94)
    at org.hibernate.tool.schema.spi.SchemaManagementToolCoordinator.performDatabaseAction(SchemaManagementToolCoordinator.java:183)
    at org.hibernate.tool.schema.spi.SchemaManagementToolCoordinator.process(SchemaManagementToolCoordinator.java:72)
    at org.hibernate.internal.SessionFactoryImpl.<init>(SessionFactoryImpl.java:312)
    at org.hibernate.boot.internal.SessionFactoryBuilderImpl.build(SessionFactoryBuilderImpl.java:462)
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:892)
    ... 26 more

又将其改为

<persistence-unit name="jpa" transaction-type="RESOURCE_LOCAL">

这次运行成功。

由于是初次接触HIbernate的JPA，对其并不熟悉，还是选择了去掉 transaction-type 属性。

官方Persistence Units说明参考

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如若有误，还望指点。