执行com.google.appengine时，缺少必需的类：appengine-maven-plugin：1.9.4

Question

I have just started to learn programming Google App Engine Apps using Java and downloaded an Example from Udacity course ud859-master .when I run the Lesson 2 > helloWorldEndpoit I get this error.

[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 5.808 s
[INFO] Finished at: 2015-07-29T14:08:21+05:00
[INFO] Final Memory: 7M/18M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal com.google.appengine:appengine-maven-plugin:1.9.4:endpoints_get_discovery_doc (default) on project helloworld: Execution default of goal com.google.appengine:appengine-maven-plugin:1.9.4:endpoints_get_discovery_doc failed: A required class was missing while executing com.google.appengine:appengine-maven-plugin:1.9.4:endpoints_get_discovery_doc: com/google/api/server/spi/config/Api
[ERROR] -----------------------------------------------------
[ERROR] realm =    plugin>com.google.appengine:appengine-maven-plugin:1.9.4
[ERROR] strategy = org.codehaus.plexus.classworlds.strategy.SelfFirstStrategy
[ERROR] urls[0] = file:/C:/Users/error/.m2/repository/com/google/appengine/appengine-maven-plugin/1.9.4/appengine-maven-plugin-1.9.4.jar
[ERROR] urls[1] = file:/C:/Users/error/.m2/repository/javax/enterprise/cdi-api/1.0/cdi-api-1.0.jar
[ERROR] urls[2] = file:/C:/Users/error/.m2/repository/javax/annotation/jsr250-api/1.0/jsr250-api-1.0.jar
[ERROR] urls[3] = file:/C:/Users/error/.m2/repository/org/sonatype/sisu/sisu-guice/3.1.0/sisu-guice-3.1.0-no_aop.jar
[ERROR] urls[4] = file:/C:/Users/error/.m2/repository/aopalliance/aopalliance/1.0/aopalliance-1.0.jar
[ERROR] urls[5] = file:/C:/Users/error/.m2/repository/org/eclipse/sisu/org.eclipse.sisu.inject/0.0.0.M2a/org.eclipse.sisu.inject-0.0.0.M2a.jar
[ERROR] urls[6] = file:/C:/Users/error/.m2/repository/asm/asm/3.3.1/asm-3.3.1.jar
[ERROR] urls[7] = file:/C:/Users/error/.m2/repository/org/codehaus/plexus/plexus-interpolation/1.16/plexus-interpolation-1.16.jar
[ERROR] urls[8] = file:/C:/Users/error/.m2/repository/org/codehaus/plexus/plexus-utils/3.0.10/plexus-utils-3.0.10.jar
[ERROR] urls[9] = file:/C:/Users/error/.m2/repository/org/codehaus/plexus/plexus-component-annotations/1.5.5/plexus-component-annotations-1.5.5.jar
[ERROR] urls[10] = file:/C:/Users/error/.m2/repository/org/sonatype/plexus/plexus-sec-dispatcher/1.3/plexus-sec-dispatcher-1.3.jar
[ERROR] urls[11] = file:/C:/Users/error/.m2/repository/org/sonatype/plexus/plexus-cipher/1.4/plexus-cipher-1.4.jar
[ERROR] urls[12] = file:/C:/Users/error/.m2/repository/org/eclipse/aether/aether-util/0.9.0.M2/aether-util-0.9.0.M2.jar
[ERROR] urls[13] = file:/C:/Users/error/.m2/repository/com/google/guava/guava/14.0.1/guava-14.0.1.jar
[ERROR] urls[14] = file:/C:/Users/error/.m2/repository/com/google/appengine/appengine-tools-sdk/1.9.4/appengine-tools-sdk-1.9.4.jar
[ERROR] urls[15] = file:/C:/Users/error/.m2/repository/com/google/appengine/appengine-local-endpoints/1.9.4/appengine-local-endpoints-1.9.4.jar
[ERROR] urls[16] = file:/C:/Users/error/.m2/repository/com/google/appengine/appengine-endpoints/1.9.4/appengine-endpoints-1.9.4.jar
[ERROR] urls[17] = file:/C:/Users/error/.m2/repository/com/google/appengine/appengine-api-1.0-sdk/1.9.4/appengine-api-1.0-sdk-1.9.4.jar
[ERROR] urls[18] = file:/C:/Users/error/.m2/repository/javax/servlet/servlet-api/2.5/servlet-api-2.5.jar
[ERROR] urls[19] = file:/C:/Users/error/.m2/repository/eu/infomas/annotation-detector/3.0.1/annotation-detector-3.0.1.jar
[ERROR] urls[20] = file:/C:/Users/error/.m2/repository/org/slf4j/slf4j-nop/1.7.5/slf4j-nop-1.7.5.jar
[ERROR] urls[21] = file:/C:/Users/error/.m2/repository/org/apache/maven/shared/maven-invoker/2.0.11/maven-invoker-2.0.11.jar
[ERROR] Number of foreign imports: 1
[ERROR] import: Entry[import  from realm ClassRealm[maven.api, parent: null]]
[ERROR] 
[ERROR] -----------------------------------------------------: com.google.api.server.spi.config.Api
[ERROR] -> [Help 1]
[ERROR] 
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/PluginContainerException

I want to know how to solve this issue.

Answer 1

This is for the future folks, I experienced the same error. I followed a few steps -

1. Added these lines of code in my pom.xml

    <pluginRepositories> <pluginRepository> <id>gae-staging1</id> <url>https://oss.sonatype.org/content/repositories/comgoogleappengine- 1293/</url> </pluginRepository> </pluginRepositories> <repositories> <repository> <id>twitter-twttr</id> <url>http://maven.twttr.com/</url> </repository> <repository> <id>gae-staging1</id> <url>https://oss.sonatype.org/content/repositories/comgoogleappengine-1292/</url> </repository> </repositories> 

2. Deleted contents from my C:\\Users\\User\\.m2 directory.

3. Then run these commands mvn package -X , mvn clean package , mvn appengine:run .

Hope this helps !!!