midpjni: how MIDlets can access native services

最新推荐文章于 2025-09-12 18:08:49 发布

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原文链接：https://yq.aliyun.com/articles/34110

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本博探讨了在MIDP环境下，MIDlet如何通过标准通信协议间接访问本地C++应用的功能，包括建立双向连接进行数据交互，以及权衡此方法对MIDP特性的影响。

Question:
Can I access native functionality from a MIDlet?

Answer:
Not directly since MIDP does not support JNI.

However, it is possible for a MIDlet to communicate with a C++ application running on the host device using a standard communication protocol such as TCP/IP sockets.

For instance the native application can provide a (server) socket listening for incoming connections on a specific port (say 1234). The MIDlet can then use the GCF to opens a client socket connection using the local loopback address to communicate with the native application as follows:

SocketConnection mySocket = (SocketConnection) Connector.open("socket://127.0.0.1:1234");

Once a two way connection has been established the MIDlet client can make requests for data from the native server using a custom protocol understood by both.

Of course this approach relinquishes many of the tradition strengths of MIDP (such as cross platform portability) requiring as it does the implementation, installation and launching of a dedicated native application as well as the MIDlet. However it may provide a route for application developers to leverage existing Java code to a Java implementation with different capabilities, rather than undertake a complete re-write in C++.

For further information see: http://www.symbian.com/developer/techlib/papers/java_MIDP.asp
"Extending the Reach of MIDlets: how MIDlets can access native services"
and
http://midpjni.com/