Google App Engine在Hello World应用程序中不起作用

Question

As the name of the post implies, I cannot get a basic Hello World Android app to deploy after modifying my Gradle build scripts to include the Google App Engine. Here is my app's build.gradle file:

apply plugin: 'com.android.application'

android {
    compileSdkVersion 23
    buildToolsVersion "22.0.1"

    defaultConfig {
        applicationId "com.example.tbiegeleisen.myfirstapp"
        minSdkVersion 9
        targetSdkVersion 23
        versionCode 1
        versionName "1.0"
    }
    buildTypes {
        debug {
            debuggable true
        }
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    compile 'com.android.support:appcompat-v7:23.0.0'
    compile 'com.google.appengine:appengine-api-1.0-sdk:1.9.13'
}

And here is my project's build.gradle file:

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

buildscript {
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:1.2.3'
        classpath 'com.google.appengine:gradle-appengine-plugin:1.9.13'
    }
}

dependencies {
    appengineSdk 'com.google.appengine:appengine-java-sdk:1.9.13'
    compile "javax.servlet:servlet-api:3.0"
    compile 'com.google.appengine:appengine-api-1.0-sdk:1.9.13'
}

repositories {
    mavenCentral();
}

appengine {
    downloadSdk = true
    appcfg {
        oauth2 = true
    }
}

allprojects {
    repositories {
        mavenCentral()
    }
}

I am fairly certain that the script is working on some level, because the first time it ran it took a really long time. During this first time, the plugin was being downloaded. When I comment out all of the Google App Engine stuff, then the Hello World app launches with no problems. I have the feeling that Android Studio is trying execute the plugin, but either a dependency is missing, or I have a configuration problem.

When I run the app, Android Studio will spin for around 5-10 minutes, and the die with this error message:

Execution failed for task ':app:preDexDebug'.
\> com.android.ide.common.process.ProcessException:
org.gradle.process.internal.ExecException: Process 'command 'C:\Program
Files\Java\jdk.1.7.0_80\bin\java.exe'' finished with non-zero exit value 3

I don't know whether this error output will be useful, but I am including it anyway.

My hope is that an Android guru on Stack Overflow will be able to help me with this problem. For reference, I need the App Engine because I plan on using geocoding at a later time. I have already been stuck on this for several days now, and I have tried every resource I could find through Google and Stack Overflow.

Answer 1

I think it has something to do with your dependencies. According to Google App Engine documentation, the supported version of Java servlets is 2.5. I don't think Google App Engine supports version 3.0 yet.

Quoting from Google App Engine Java documentation:

App Engine uses the Java Servlet 2.5 standard for web applications. You provide your app's servlet classes, JavaServer Pages (JSPs), static files and data files, along with the deployment descriptor (the web.xml file) and other configuration files, in a standard WAR directory structure. App Engine serves requests by invoking servlets according to the deployment descriptor.

You have to change your dependency to this:

compile "javax.servlet:servlet-api:2.5"