没有持久性提供我的AppEngine上后端的EntityManager [英] No persistence provider for my EntityManager in appengine backend
问题描述
我使用的Android Studio和我创建使用Android Studio提供的工具，应用程序引擎的后端。我试图使用JPA /持续性在我的后端模块为我的Android应用程序。
当我尝试我的API来存储一些数据，我得到的异常
java.lang.ExceptionInInitializerError
在be.stece.esocomm.backendApp.EsoCommEndpoint.getEntityManager（EsoCommEndpoint.java:73）
....
javax.persistence.PersistenceException：由没有造成人员对EntityManager的持久性提供者命名esoCommBackendPersistence
在javax.persistence.Persistence.createEntityManagerFactory（Persistence.java:69）
在javax.persistence.Persistence.createEntityManagerFactory（Persistence.java:47）
所以，问题与我的设置或项目结构的地方所在。既然找不到我的持久性提供者。但我不能找出问题的症结所在。
都在这个后端模块的我的build.gradle文件首先我有依赖条件：
编译'的javax.servlet：servlet的API：2.5
编译组：org.hibernate.javax.persistence'，名称：'休眠-JPA-2.0-API，版本：1.0.0.Final
编译org.hibernate作为：休眠-的EntityManager：4.1.7.Final
然后在MyModule中/ src目录/ META_INF / persistence.xml中我已经宣布的一切：
＆LT;？XML版本=1.0编码=UTF-8＆GT？;
＆LT;持久性的xmlns =http://java.sun.com/xml/ns/persistence版本=1.0＆GT;
＆LT;持久性单位名称=esoCommBackendPersistence＆GT;
＆LT;提供商GT; org.datanucleus.api.jpa.PersistenceProviderImpl＆LT; /提供商GT;
＆LT;性状＆gt;
＆LT;属性名=datanucleus.NontransactionalReadVALUE =真/＆GT;
＆LT;属性名=datanucleus.NontransactionalWriteVALUE =真/＆GT;
＆LT;属性名=datanucleus.ConnectionURLVALUE =应用引擎/＆GT;
＆LT;属性名=datanucleus.appengine.datastoreEnableXGTransactions
值=真/＆GT;
＆LT;属性名=datanucleus.appengine.autoCreateDatastoreTxns
值=真/＆GT;
＆LT; /性状＆gt;
＆LT;类别和GT; be.stece.esocomm.backendApp.NewsBean＆LT; /班＆GT;
＆LT; /持久化部＆gt;
＆LT; /持久＆GT;
我不是100％肯定，如果persistence.xml中是在正确的目录。我试过几个选项，比如移动META_INF文件夹复制到/ src目录/主文件夹，而不是只/ src目录。但是，没有什么区别。
要创建我的EntityManager我用正确的持久性名称
公共类MyEntityManagerFactory { 私有静态最后弦乐PERSISTENCE_NAME =esoCommBackendPersistence; 私有静态最后的EntityManagerFactory emfInstance =
Persistence.createEntityManagerFactory（PERSISTENCE_NAME）; 私人MyEntityManagerFactory（）{} 公共静态的EntityManagerFactory的get（）{
返回emfInstance;
}} 私有静态的EntityManager getEntityManager（）{
返回MyEntityManagerFactory.get（）createEntityManager（）。 = GT;该错误是触发这一行
}
好了，我得到它的工作。
我删除了所有休眠和使用持久性的AppEngine按照尼尔·斯托克顿的建议。
{相关性
appengineSdk'com.google.appengine：AppEngine上-Java的SDK：1.8.9
编译com.google.appengine：AppEngine上的端点：1.8.9
编译com.google.appengine：AppEngine上的端点-DEPS：1.8.9
编译'的javax.servlet：servlet的API：2.5 //持久性
编译org.ow2.asm：ASM：4.0
编译org.datanucleus：DataNucleus的-API JPA：3.1.3
编译org.datanucleus：DataNucleus的-API JDO：3.1.3
编译com.google.appengine.orm：DataNucleus的-AppEngine上：2.1.2
编译org.datanucleus：DataNucleus的核心：3.1.3
编译org.apache.geronimo.specs：Geronimo的jpa_2.0_spec：1.0
编译javax.jdo：JDO-API：3.0.1
编译javax.transaction的：JTA：1.1
}
另外现在我跟着以下指南创建端点：<一href=\"https://developers.google.com/appengine/docs/java/datastore/entities#Java_Kinds_and_identifiers\" rel=\"nofollow\">https://developers.google.com/appengine/docs/java/datastore/entities#Java_Kinds_and_identifiers
I'm using Android Studio and I've created an app engine backend with the tools provided by Android Studio. I'm trying to use JPA/Persistence in my backend module for my android application. When I try my API to store some data I get the Exception
java.lang.ExceptionInInitializerError
at be.stece.esocomm.backendApp.EsoCommEndpoint.getEntityManager(EsoCommEndpoint.java:73)
....
Caused by: javax.persistence.PersistenceException: No Persistence provider for EntityManager named esoCommBackendPersistence
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:69)
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:47)
So the problem lies somewhere with my setup or project structure. Since it can't find my persistence provider. But I can't figure out where the problem lies.
First of all in my build.gradle file of this backend module I have the dependecies:
compile 'javax.servlet:servlet-api:2.5'
compile group: 'org.hibernate.javax.persistence', name: 'hibernate-jpa-2.0-api', version: '1.0.0.Final'
compile 'org.hibernate:hibernate-entitymanager:4.1.7.Final'
Then in MyModule/src/META_INF/persistence.xml I have declared everything:
<?xml version="1.0" encoding="UTF-8" ?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence" version="1.0">
<persistence-unit name="esoCommBackendPersistence">
<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.appengine.datastoreEnableXGTransactions"
value="true" />
<property name="datanucleus.appengine.autoCreateDatastoreTxns"
value="true" />
</properties>
<class>be.stece.esocomm.backendApp.NewsBean</class>
</persistence-unit>
</persistence>
I'm not 100% sure if the persistence.xml is in the right directory. I've tried several options, like moving the META_INF folder to the /src/main folder instead of just /src. But no difference.
To create my EntityManager I use the correct Persistence name
public class MyEntityManagerFactory {
private static final String PERSISTENCE_NAME = "esoCommBackendPersistence";
private static final EntityManagerFactory emfInstance =
Persistence.createEntityManagerFactory(PERSISTENCE_NAME);
private MyEntityManagerFactory() {}
public static EntityManagerFactory get() {
return emfInstance;
}
}
private static EntityManager getEntityManager() {
return MyEntityManagerFactory.get().createEntityManager(); => The error is triggered on this line
}
Ok, so I got it to work.
I removed all hibernate and use the appengine persistence as per suggestion of Neil Stockton.
dependencies {
appengineSdk 'com.google.appengine:appengine-java-sdk:1.8.9'
compile 'com.google.appengine:appengine-endpoints:1.8.9'
compile 'com.google.appengine:appengine-endpoints-deps:1.8.9'
compile 'javax.servlet:servlet-api:2.5'
// Persistence
compile 'org.ow2.asm:asm:4.0'
compile 'org.datanucleus:datanucleus-api-jpa:3.1.3'
compile 'org.datanucleus:datanucleus-api-jdo:3.1.3'
compile 'com.google.appengine.orm:datanucleus-appengine:2.1.2'
compile 'org.datanucleus:datanucleus-core:3.1.3'
compile 'org.apache.geronimo.specs:geronimo-jpa_2.0_spec:1.0'
compile 'javax.jdo:jdo-api:3.0.1'
compile 'javax.transaction:jta:1.1'
}
Also now I followed the following guides to create the endpoints: https://developers.google.com/appengine/docs/java/datastore/entities#Java_Kinds_and_identifiers
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