Google Apps Engine Backend - Javax.persistence mis

问题:

I'm trying to migrate to Android studio and my app engine code uses the Entity framework listed below

import javax.persistence.Entity;
import javax.persistence.Id;

@Entity
public class AppVersion {

@Id
private String applicationName;
private int minVersionRequired;

public String getApplicationName() {
    return applicationName;
}
public int getMinVersionRequired() {
    return minVersionRequired;
}
public void setApplicationName(String applicationName) {
    this.applicationName = applicationName;
}
public void setminVersionRequired(int minVersionRequired) {
    this.minVersionRequired = minVersionRequired;
}
}

Just creating a backend in Android Studio (0.5.6) doesn't work, I can't import javax.persistence.*

From this link I discovered that I needed to create a persistence.xml file (this was automatically created in Eclipse). I just can't figure out where in the file structure it is supposed to go. I understand it needs to be in the META-INF folder but I don't know where that corresponds for gradle (or if it has to be created in the gradle build file). Current file structure:

-src
  -main
    -java
      -com.package.test
        class files
    -webapp
      -css
      -js
      -WEB-INF

Gradle build file:

buildscript {
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath 'com.google.appengine:gradle-appengine-plugin:1.9.1'
    }
}

repositories {
    mavenCentral();
}

apply plugin: 'java'
apply plugin: 'war'
apply plugin: 'appengine'

sourceCompatibility = 1.7
targetCompatibility = 1.7

dependencies {
  appengineSdk 'com.google.appengine:appengine-java-sdk:1.9.1'
  compile 'com.google.appengine:appengine-endpoints:1.9.1'
  compile 'com.google.appengine:appengine-endpoints-deps:1.9.1'
  compile 'javax.servlet:servlet-api:2.5'
}

appengine {
  downloadSdk = true
  appcfg {
    oauth2 = true
  }
  endpoints {
    getClientLibsOnBuild = true
    getDiscoveryDocsOnBuild = true
  }
}

回答1:

Android Studio's App Engine samples don't use JPA.

However if you want to use JPA, you need to add the JPA dependencies, this describes where you might find out what those are https://developers.google.com/appengine/docs/java/datastore/jpa/overview-dn2

So these (or some subset of these)

• asm-4.0.jar
• datanucleus-api-jpa-3.1.3.jar
• datanucleus-core-3.1.3.jar
• jdo-api-3.0.1.jar
• datanucleus-api-jdo-3.1.3.jar
• datanucleus-appengine-2.1.2.jar
• geronimo-jpa_2.0_spec-1.0.jar
• jta-1.1.jar

Look on maven.org for those dependencies will reveal how to include them in build.gradle files as compile dependencies:

asm-4.0 :

compile 'org.ow2.asm:asm:4.0'

datanucleus-api-jpa-3.1.3 :

compile 'org.datanucleus:datanucleus-api-jpa:3.1.3'

and so on.

You want the versions to be exactly as they are in the appengine sdk to ensure compatibility. Also make sure you run the enhance task on your project.

回答2:

Try adding following to the build.gradle

compile group: 'javax.persistence', name: 'persistence-api', version: '1.0'