@Override
    public void setAppDesc(AppDesc appDesc) {
        this.appDesc = appDesc;
    }
Specification: each appconn needs to define a method starting with create
and returning as standard type to initialize the specifications owned by appconn.
dss-appconn/dss-appconn-core/src/main/java/com/webank/wedatasphere/dss/appconn/core/impl/AbstractAppConn.java