want to develop my project on Google App Engine .I want to use google big table as database. For the database I have two options JPA and JDO. Will you guys please suggest me on it? Both are new for me and I need to learn them. So I will be focused on one after your replies.
Since you're using Data Nucleus, see their FAQ on JDO vs JPA. http://www.datanucleus.org/products/accessplatform_3_0/jdo_jpa_faq.html
DataNucleus AccessPlatform supports both JDO and JPA specifications of Java persistence. As such it has no "vested interest" in either technology, believing that it is for users to choose which they like best. There has been much FUD on the web about JDO and JPA, largely perpetrated by RDBMS vendors. This FAQ corrects many of these points