Maven dependency mystery with Google App Engine example

[paul nisset]

Hi,
I am going through a tutorial on Google app engine and running into endless Maven problems.
The latest is a message :

Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:2.5.1:compile (default-compile) on project helloendpoints-war Compilation failure
[ERROR] error: Exception thrown while constructing Processor object: com/google/appengine/tools/compilation/DatastoreCallbacksProcessor : Unsupported major.minor version 51.0

java -version is 1.7.0_45
javac - version is 1.7.0_45

I have no idea of what dependency major.minor version 51.0 is referring to.

Below is the POM .

thanks,
Paul

<?xml version="1.0" encoding="UTF-8"?>
<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>
    <packaging>war</packaging>
    <version>1.0-SNAPSHOT</version>
    <groupId>com.google.devrel.samples.helloendpoints</groupId>
    <artifactId>helloendpoints-war</artifactId>

    <parent>
        <groupId>com.google.devrel.samples.helloendpoints</groupId>
        <artifactId>helloendpoints</artifactId>
        <version>1.0-SNAPSHOT</version>
    </parent>

    <properties>
        <appengine.app.version>1-war</appengine.app.version>
 <appengine.target.version>1.8.8</appengine.target.version>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <dependencies>
        <!-- Compile/runtime dependencies -->
        <dependency>
            <groupId>com.google.appengine</groupId>
            <artifactId>appengine-api-1.0-sdk</artifactId>
            <version>${appengine.target.version}</version>
        </dependency>
       <dependency>
            <groupId>com.google.appengine</groupId>
            <artifactId>appengine-endpoints</artifactId>
            <version>${appengine.target.version}</version>
        </dependency>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>servlet-api</artifactId>
            <version>2.5</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>javax.inject</groupId>
            <artifactId>javax.inject</artifactId>
            <version>1</version>
        </dependency>

        <!-- Test Dependencies -->
        <dependency>
            <groupId>com.google.appengine</groupId>
            <artifactId>appengine-testing</artifactId>
            <version>${appengine.target.version}</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>com.google.appengine</groupId>
            <artifactId>appengine-api-stubs</artifactId>
            <version>${appengine.target.version}</version>
            <scope>test</scope>
        </dependency>
    </dependencies>
      
    <build>
        <outputDirectory>target/${project.artifactId}-${project.version}/WEB-INF/classes</outputDirectory> 
                                   
        <plugins>
                <plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-war-plugin</artifactId>
    <version>2.3</version>
    <configuration>
        <webXml>${project.build.directory}/generated-sources/appengine-endpoints/WEB-INF/web.xml</webXml>
        <webResources>
            <resource>
                <!-- this is relative to the pom.xml directory -->
                <directory>${project.build.directory}/generated-sources/appengine-endpoints</directory>
                <!-- the list has a default value of ** -->
                <includes>
                    <include>WEB-INF/*.discovery</include>
                    <include>WEB-INF/*.api</include>
                </includes>
            </resource>
        </webResources>
    </configuration>
</plugin>
  <plugin>
    <groupId>com.google.appengine</groupId>
    <artifactId>appengine-maven-plugin</artifactId>
    <version>${appengine.target.version}</version>
    <configuration>
        <enableJarClasses>false</enableJarClasses>
    </configuration>
    <executions>
        <execution>
            <goals>
                <goal>endpoints_get_discovery_doc</goal>
            </goals>
        </execution>
    </executions>
</plugin>

        </plugins>
    </build>

</project>

[Greg Charles]

51.0 is the version of Java 7 class files. I think this error indicates that Maven is using an earlier version of Java for compiling. Where are you getting that version information? If you run "mvn -version" from a command line, it should tell you the version that Maven is actually using.