java调用dll文件需要使用回调函数作为公开函数的参数时，用以下方法实现：

首先，看c++中定义的dll公开函数：

typedef void (*ccback)(char *name ,int length);  
int dllFunction(char *ip, int port, ccback cc); 

引用dll文件方法不再赘述，直接看回调函数的实现，需要通过java的接口实现：

import com.sun.jna.Library;
import com.sun.jna.Native;
import com.sun.jna.Callback;
import com.test.DllCallBackTest.JnaCallBackDll.SCBack_Impl;
 
public class DllCallBackTest {
 
	public interface JnaCallBackDll extends Library {
 
		public static JnaCallBackDll instance = (JnaCallBackDll) Native.loadLibrary("src/main/resources/Dll2.dll",
				JnaCallBackDll.class);
 
		int dllFunction(String host, int port, Callback callback);
 
		public interface SCBack extends Callback {
			public void MessageHandle(String name, int length);
		}
 
		public static class SCBack_Impl implements SCBack {
			public void MessageHandle(String name, int length) {
				// TODO Auto-generated method stub
				System.out.println("回调成功！");
				// 此处添加需要的数据处理操作
			}
		}
	}
 
	public static void main(String[] args) {
 
		DllCallBackTest.JnaCallBackDll.SCBack callback = new SCBack_Impl();
 
		JnaCallBackDll.instance.dllFunction("127.0.0.1", 1234, callback);
	}
 
}

参照：

https://blog.csdn.net/qdqht2009/article/details/50592192
https://www.jb51.net/article/126546.htm
https://blog.csdn.net/qq_31997407/article/details/78247076?locationNum=8&fps=1