Currently dubbo support java6, java7 and java8.

All unit test pass in java9, we should consider add official support for java9 and even java10.
Currently travis support java9. java10 is in progress (https://github.com/travis-ci/travis-ci/issues/9368)

As discussed in mail list, the first step is to add java9 in travis ci.
/**
     * get method desc.
     * int do(int arg1) => "do(I)I"
     * void do(String arg1,boolean arg2) => "do(Ljava/lang/String;Z)V"
     *
     * @param m method.
     * @return desc.
     */
    public static String getDesc(final Method m) {
        StringBuilder ret = new StringBuilder(m.getName()).append('(');
        Class<?>[] parameterTypes = m.getParameterTypes();
        for (int i = 0; i < parameterTypes.length; i++)
            ret.append(getDesc(parameterTypes[i]));
        ret.append(')').append(getDesc(m.getReturnType()));
        return ret.toString();
    }
    /**
     * get constructor desc.
     * "()V", "(Ljava/lang/String;I)V"
     *
     * @param c constructor.
     * @return desc
     */
    public static String getDesc(final Constructor<?> c) {
        StringBuilder ret = new StringBuilder("(");
        Class<?>[] parameterTypes = c.getParameterTypes();
        for (int i = 0; i < parameterTypes.length; i++)
            ret.append(getDesc(parameterTypes[i]));
        ret.append(')').append('V');
        return ret.toString();