java - 找不到类 : javax. persistence.spi.ProviderUtil

Question

我正在尝试使用 JPA 设置一个简单的 Spring Web 应用程序，但在运行 mvn spring-boot:run 后，我得到了以下堆栈跟踪。当然，我尝试搜索，发现该类不在“类路径”上，但并不真正知道类路径在这种情况下意味着什么，以及如何向其中添加某些内容，以及为什么需要它。因此，提供一点帮助就太好了。

[WARNING]
java.lang.reflect.InvocationTargetException
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at org.springframework.boot.maven.AbstractRunMojo$LaunchRunner.run(AbstractRunMojo.java:506)
        at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.NoClassDefFoundError: javax/persistence/spi/ProviderUtil
        at java.lang.Class.getDeclaredConstructors0(Native Method)
        at java.lang.Class.privateGetDeclaredConstructors(Class.java:2671)
        at java.lang.Class.getConstructor0(Class.java:3075)
        at java.lang.Class.newInstance(Class.java:412)
        at javax.persistence.Persistence.findAllProviders(Persistence.java:112)
        at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:79)
        at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:60)
        at hu.creativetribes.sga.configurations.PersistenceManager.<init>(PersistenceManager.java:13)
        at hu.creativetribes.sga.configurations.PersistenceManager.<clinit>(PersistenceManager.java:8)
        at hu.creativetribes.sga.Application.main(Application.java:18)
        ... 6 more
Caused by: java.lang.ClassNotFoundException: javax.persistence.spi.ProviderUtil
        at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
        ... 16 more

这是我的主要方法，它是持久化对象的测试:

@SpringBootApplication
public class Application {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);

        Partner partner = new Partner("test", "test", "test", "test", "test", "test");

        EntityManager em = PersistenceManager.INSTANCE.getEntityManager();
        em.getTransaction().begin();
        em.persist(partner);
        em.getTransaction().commit();
        em.close();
        PersistenceManager.INSTANCE.close();

    }

}

持久化管理器枚举:

public enum PersistenceManager {
    INSTANCE;

    private EntityManagerFactory emFactory;

    private PersistenceManager() {
        emFactory = Persistence.createEntityManagerFactory("sga-jpa");
    }

    public EntityManager getEntityManager() {
        return emFactory.createEntityManager();
    }

    public void close() {
        emFactory.close();
    }

}

我的 persistence.xml:

<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="sga-jpa" transaction-type="RESOURCE_LOCAL">
        <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
        <properties>
            <property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost/sg_be" />
            <property name="javax.persistence.jdbc.user" value="root" />
            <property name="javax.persistence.jdbc.password" value="" />
            <property name="javax.persistence.jdbc.driver" value="com.mysql.cj.jdbc.Driver" />
            <property name="hibernate.show_sql" value="true" />
            <property name="hibernate.format_sql" value="true" />
            <property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5InnoDBDialect" />
            <property name="hibernate.hbm2ddl.auto" value="validate" />

            <property name="hibernate.c3p0.min_size" value="5" />
            <property name="hibernate.c3p0.max_size" value="20" />
            <property name="hibernate.c3p0.timeout" value="500" />
            <property name="hibernate.c3p0.max_statements" value="50" />
            <property name="hibernate.c3p0.idle_test_period" value="2000" />
        </properties>
    </persistence-unit>
</persistence>

最后是我的 pom.xml:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">


    <modelVersion>4.0.0</modelVersion>
    <groupId>stackoverflow_heplme</groupId>
    <artifactId>sga</artifactId>
    <packaging>war</packaging>
    <version>1.0-VIVALDI</version> <!-- Haha, spring. -->

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.4.1.RELEASE</version>
    </parent>

    <properties>
        <java-version>1.8</java-version>
        <hibernate.version>4.3.6.Final</hibernate.version>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <dependencies>

        <dependency>
            <groupId>com.google.appengine.orm</groupId>
            <artifactId>datanucleus-appengine</artifactId>
            <version>2.1.2</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>javax.persistence</groupId>
            <artifactId>persistence-api</artifactId>
            <version>1.0</version>
        </dependency>

        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-entitymanager</artifactId>
            <version>${hibernate.version}</version>
            <exclusions>
                <exclusion>
                    <groupId>org.hibernate.javax.persistence</groupId>
                    <artifactId>hibernate-jpa-2.1-api</artifactId>
                </exclusion>
            </exclusions>
        </dependency>

        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-c3p0</artifactId>
            <version>${hibernate.version}</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>

        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.11</version>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.hamcrest</groupId>
                    <artifactId>hamcrest-core</artifactId>
                </exclusion>
            </exclusions>
        </dependency>

        <dependency>
            <groupId>org.hamcrest</groupId>
            <artifactId>hamcrest-all</artifactId>
            <version>1.3</version>
            <scope>test</scope>
        </dependency>

    </dependencies>


    <build>
        <finalName>sga</finalName>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>2.5.1</version>
                <configuration>
                    <source>${java.version}</source>
                    <target>${java.version}</target>
                    <compilerArgument>-Xlint:all</compilerArgument>
                    <showWarnings>true</showWarnings>
                    <showDeprecation>true</showDeprecation>

                </configuration>
            </plugin>
        </plugins>
    </build>

</project>

Answer 1

首先，如果您想使用hibernate，则不需要创建entityManager，因为它随springboot bundle 一起提供，并且持久化提供程序在依赖项下生成背景，因此您也不需要persistence.xml，您可以在pom.xml和application.properties上进行管理。

org.springframework.boot spring-boot-starter-data-jpa

将此添加到您的 pom.xml