线程“主”中的Py4j异常java.lang.NoClassDefFoundError：py4j / GatewayServer

Question

我希望python使用py4j调用Java方法，当我将Java文件打包为jar并在Windows中运行时，它出错了：

>java -jar spark-1.0-SNAPSHOT.jar

Exception in thread "main" java.lang.NoClassDefFoundError: py4j/GatewayServer
    at com.littlely.AddNum.main(AddNum.java:11)
Caused by: java.lang.ClassNotFoundException: py4j.GatewayServer
    at java.net.URLClassLoader.findClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    ... 1 more

java：

package com.littlely;
import py4j.GatewayServer;

public class AddNum{
    public float add(float a, float b){
        return a + b;
}

    public static void main(String[] args) {
        GatewayServer server = new GatewayServer(new AddNum());
        server.start();
        System.out.println("server started!");
}}

python：

from py4j.java_gateway import JavaGateway

def main():
    jvm = JavaGateway().jvm
    myadd = jvm.com.littlely.AddNum()
    print(myadd.add(40.0, 80.0))


if __name__ == "__main__":
    main()

我已经将主类添加到manifest.MF文件中，这怎么了？我该如何处理它，而我是java的新手，请举个例子。