我使用 JPA 2.0 创建了一个 GAE 1.8.2 项目。当我尝试启动 Junit 测试时，它会引发以下异常：
java.lang.ExceptionInInitializerError
at it.bfm.dbutility.DbAccess.<init>(DbAccess.java:10)
at it.bfm.businesslogic.UtenteImpl.<init>(UtenteImpl.java:16)
at it.bfm.test.UtenteTest.testCreaUtente(UtenteTest.java:13)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
Caused by: javax.persistence.PersistenceException: Explicit persistence provider error(s) occurred for "transactions-optional" after trying the following discovered implementations: org.datanucleus.api.jpa.PersistenceProviderImpl, org.datanucleus.api.jpa.PersistenceProviderImpl from provider: org.datanucleus.api.jpa.PersistenceProviderImpl
at javax.persistence.Persistence.createPersistenceException(Persistence.java:242)
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:184)
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:70)
at it.bfm.dbutility.EntityBfmManager.<clinit>(EntityBfmManager.java:8)
... 26 more
Caused by: org.datanucleus.exceptions.NucleusException: Plugin (Bundle) "org.datanucleus.api.jpa" is already registered. Ensure you dont have multiple JAR versions of the same plugin in the classpath. The URL "file:/Applications/Eclipse/plugins/com.google.appengine.eclipse.sdkbundle_1.8.2/appengine-java-sdk-1.8.2/lib/opt/user/datanucleus/v2/datanucleus-api-jpa-3.1.3.jar" is already registered, and you are trying to register an identical plugin located at URL "file:/Users/Stefano/.m2/repository/org/datanucleus/datanucleus-api-jpa/3.1.3/datanucleus-api-jpa-3.1.3.jar."
at org.datanucleus.plugin.NonManagedPluginRegistry.registerBundle(NonManagedPluginRegistry.java:541)
at org.datanucleus.plugin.NonManagedPluginRegistry.registerBundle(NonManagedPluginRegistry.java:395)
at org.datanucleus.plugin.NonManagedPluginRegistry.registerExtensions(NonManagedPluginRegistry.java:219)
at org.datanucleus.plugin.NonManagedPluginRegistry.registerExtensionPoints(NonManagedPluginRegistry.java:160)
at org.datanucleus.plugin.PluginManager.<init>(PluginManager.java:65)
at org.datanucleus.plugin.PluginManager.createPluginManager(PluginManager.java:427)
at org.datanucleus.api.jpa.JPAEntityManagerFactory.<init>(JPAEntityManagerFactory.java:328)
at org.datanucleus.api.jpa.PersistenceProviderImpl.createEntityManagerFactory(PersistenceProviderImpl.java:91)
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:150)
... 28 more
Persistence.xml 是这样的：
<?xml version="1.0" encoding="UTF-8" ?>
<persistence 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_1_0.xsd" version="1.0">
<persistence-unit name="transactions-optional">
<provider>org.datanucleus.api.jpa.PersistenceProviderImpl</provider>
<properties>
<property name="datanucleus.NontransactionalRead" value="true"/>
<property name="datanucleus.NontransactionalWrite" value="true"/>
<property name="datanucleus.ConnectionURL" value="appengine"/>
<property name="datanucleus.singletonEMFForName" value="true"/>
</properties>
</persistence-unit>
</persistence>
pom.xml 是这样的：
<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/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>it.bfm</groupId>
<artifactId>bfm</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>war</packaging>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
</dependency>
<dependency>
<groupId>javax</groupId>
<artifactId>javaee-api</artifactId>
<version>7.0</version>
</dependency>
<dependency>
<groupId>com.google.appengine</groupId>
<artifactId>appengine-api-1.0-sdk</artifactId>
<version>1.8.2</version>
</dependency>
<dependency>
<groupId>com.google.appengine.orm</groupId>
<artifactId>datanucleus-appengine</artifactId>
<version>2.1.2</version>
</dependency>
<dependency>
<groupId>org.datanucleus</groupId>
<artifactId>datanucleus-core</artifactId>
<version>3.1.3</version>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.datanucleus</groupId>
<artifactId>datanucleus-api-jpa</artifactId>
<version>3.1.3</version>
</dependency>
<!-- <dependency> -->
<!-- <groupId>org.datanucleus</groupId> -->
<!-- <artifactId>datanucleus-api-jdo</artifactId> -->
<!-- <version>3.1.3</version> -->
<!-- </dependency> -->
<dependency>
<groupId>javax.jdo</groupId>
<artifactId>jdo-api</artifactId>
<version>3.0.1</version>
</dependency>
<dependency>
<groupId>org.apache.geronimo.specs</groupId>
<artifactId>geronimo-jpa_2.0_spec</artifactId>
<version>1.0</version>
</dependency>
<dependency>
<groupId>com.google.appengine</groupId>
<artifactId>appengine-jsr107cache</artifactId>
<version>1.8.2</version>
</dependency>
<dependency>
<groupId>com.google.appengine</groupId>
<artifactId>appengine-endpoints</artifactId>
<version>1.8.2</version>
</dependency>
<dependency>
<groupId>net.sf.jsr107cache</groupId>
<artifactId>jsr107cache</artifactId>
<version>1.1</version>
</dependency>
</dependencies>
<build>
<sourceDirectory>${basedir}/src/it/bfm</sourceDirectory>
<testSourceDirectory>${basedir}/src/it/bfm/test</testSourceDirectory>
<outputDirectory>${basedir}/war/WEB-INF/classes</outputDirectory>
<testOutputDirectory>${basedir}/war/WEB-INF/test-classes</testOutputDirectory>
<!-- <resources> -->
<!-- <resource> -->
<!-- <directory>${basedir}/src</directory> -->
<!-- </resource> -->
<!-- </resources> -->
<pluginManagement>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<version>3.1</version>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>1.7</source>
<target>1.7</target>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-war-plugin</artifactId>
<version>2.3</version>
<configuration>
<archiveClasses>true</archiveClasses>
<webResources>
<!-- in order to interpolate version from pom into appengine-web.xml -->
<resource>
<directory>${basedir}/war/WEB-INF</directory>
<filtering>true</filtering>
<targetPath>WEB-INF</targetPath>
</resource>
</webResources>
</configuration>
</plugin>
</plugins>
</pluginManagement>
</build>
</project>
有人能帮助我吗？太感谢了。