在Play!中提供RMI(通过Spring)

1、SOAP/RPC风格的Webservice(通过XFire)，Hessian, PHPRPC都需要Servlet模型的支持，但是Play!不支持Servlet(或许有变通的方法？)，所以，还是使用RMI这种技术

2、Play！的Model类，不是纯的POJO，继承了JPASupport，作为远程对象传递时，可能会产生

10:38:16,956 ERROR ~ failed to lazily initialize a collection of role: models.User.posts, no session or session was closed
org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: models.User.posts, no session or session was closed

这样的错误，因此，要定义 POJO的VO/DTO对象，做为远程传递对象

3、VO对象，因为要通过RMI传递，必须要实现Serializable接口，并且最好在类中指定serialVersionUID，象这样

private static final long serialVersionUID = 1L;

可以避免Server和Client之间同种对象版本不一样的错误

4、通过Spring封装并提供RMI的服务。需要自定义一个job，随Play!启动而启动，初始化RMI服务，象这样 

//注册RMI
play.modules.spring.Spring.getBean("postServiceRmi");

5、RMI实现类，无法象Play!的Controller类一样，直接调用Model对象，Guillaume Bort的解释是

“I think that the RMI server call your code in a non managed thread.
You need to wrap your code in a play.Invoker.Invocation object. “

需要使用以下的变通方法

So it is almost the same code than Jobs. Btw you could directly use jobs:

public class RetrievePostsByUserJob extends Job<List<PostVO>> {

      private Long id;

      public RetrievePostsByUserJob(Long id) {
          this.id = id;
      }

      public List<PostVO> doJobWithResult() {
          ... your code here
          return list;
      }

}

and then use the job in your RMI server:

public List<PostVO> getPostsByUserId(Long id) {
     return new RetrievePostsByUserJob(id).now().get();

}