[英]Java RMI - Passing Objects
I'm running a Java program on a Raspberry Pi
and an Android-App
on a smartphone. 我正在智能手机上的Raspberry Pi
和Android-App
上运行Java程序。 The app should be able to invoke methods running on the Raspi
. 该应用程序应该能够调用在Raspi
上运行的Raspi
。 Since Android
does not include the standard Java RMI package, I used LipeRMI
: http://lipermi.sourceforge.net/ 由于Android
不包含标准的Java RMI包,我使用了LipeRMI
: http : LipeRMI
So far so good, LipeRMI
does work well for passing primitive data types such as boolean or int. 到目前为止, LipeRMI
确实可以很好地传递原始数据类型,如boolean或int。
What I want to do now is passing an ArrayList<String>
from the Server to the app but every time I run the method, I receive following error: 我现在要做的是将ArrayList<String>
从服务器传递给应用程序,但每次运行该方法时,都会收到以下错误:
LipeRMIException:Class java.util.ArrayList is not assignable from control.ServerInt
at lipermi.handler.CallHandler.exportObject(CallHandler.java:54)
at lipermi.handler.CallHandler.exportObject(CallHandler.java:48)
at control.RMIServer.createServer(RMIServer.java:26)
at control.Main.main(Main.java:17)
I do not understand what I'm doing wrong here. 我不明白我在这里做错了什么。
RMIServer.java RMIServer.java
public class RMIServer implements ServerInt{
private static final long serialVersionUID = 1L;
private ArrayList<String> list;
public RMIServer() {
list = new ArrayList<String>();
list.add("50:25:5:-1");
list.add("99:42:6:4");
createServer();
}
public void createServer() {
try {
CallHandler callHandler = new CallHandler();
callHandler.registerGlobal(ServerInt.class, this);
callHandler.exportObject(ServerInt.class, list);
Server server = new Server();
server.bind(7777, callHandler);
server.addServerListener(new IServerListener() {
@Override
public void clientDisconnected(Socket socket) {}
@Override
public void clientConnected(Socket socket) {}
});
} catch (LipeRMIException | IOException e) {
e.printStackTrace();
}
}
@Override
public ArrayList<String> getPWMLines() {
return list;
}
}
ServerInt.java ServerInt.java
import java.util.ArrayList;
public interface ServerInt{
public ArrayList<String> getPWMLines();
}
You obviously misuse the method CallHandler#exportObject(Class, Object)
the first parameter must be a class representing an interface and the second parameter must be an instance of a class that implements this interface. 您显然滥用CallHandler#exportObject(Class, Object)
,第一个参数必须是表示接口的类,第二个参数必须是实现此接口的类的实例。 Here you provide an ArrayList
as second parameter which is clearly not an instance of ServerInt
that is why you get this exception. 在这里,您提供了一个ArrayList
作为第二个参数,它显然不是ServerInt
一个实例,这就是您获得此异常的原因。
Here is a good example of how to use this method: 以下是如何使用此方法的一个很好的示例:
MyRemoteListener listenerImplementation = new MyRemoteListenerImpl();
callHandler.exportObject(MyRemoteListener.class, listenerImplementation);
In this case the first parameter is the interface MyRemoteListener
and the second is an instance of MyRemoteListenerImpl
which is an implementation of the interface MyRemoteListener
. 在这种情况下,第一个参数是接口MyRemoteListener
和第二个是一个实例MyRemoteListenerImpl
这是接口的实现MyRemoteListener
。
To expose your List
you can try callHandler.registerGlobal(List.class, list)
要公开你的List
你可以尝试callHandler.registerGlobal(List.class, list)
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.