java 结构体待数组元素 解析json jna结构体数组返回

一、开发环境

系统、开发环境：win7、eclipse 32位、jdk 32位、jre 32位

1.eclipse，不用安装，解压后即可使用，解压目录：D:\eclipse

Eclipse IDE for Java EE Developers,   247 MB        Windows 32 Bit

http://www.eclipse.org/downloads

2.jdk 32位，安装目录：D:\Program Files\java\jdk32

Windows x86 123.49MB       jdk-7u45-windows-i586.exe

http://www.oracle.com/technetwork/java/javase/downloads/jdk7-downloads-1880260.html

3.jre 32位，安装目录：D:\Program Files\java\jre32

Windows Offline(32-bit)     fileSize:   27.7MB

http://www.java.com/en/download/manual.jsp

        要让32位和64位eclipse共存，需要修改eclipse目录下的文件：eclipse.ini

在原环境变量（JAVA_HOME指向64位目录）不改变的情况下在上面文件内增加两行：

-vm

D:\Program Files\java\jdk32\bin\javaw.exe

以上的作用使32位eclipse指向32位jdk。

4.JNA下载，这里是放在百度云里面的，下载两个文件：jna-3.5.1.jar、platform-3.5.1.jar，放到目录：D:\Program Files\java\JNA_3.5.1

http://pan.baidu.com/s/1iWobp

至于JNA是什么，它本身是基于JNI技术的，然后进行封装以方便dll调用。这里不再详述，网上很多。

二、调用方法

1.简单函数调用

dll提供的接口函数：

int System_Init (int version, char* encoding);

java代码->声明部分：

import com.sun.jna.Library;  
import com.sun.jna.Native;

public class getSDK {
	public interface Function extends Library {
		Function instanceDll  = (Function)Native.loadLibrary("libSDK.dll",Function.class);
		
		public int System_Init(int version, String encoding);
	}
}

java代码->调用部分：

result = getSDK.Function.instanceDll.System_Init(1, "");

参数类型比较简单时，调用也比较容易。

2.回调函数调用

当dll的接口函数需要回调函数作为参数时，使用以下方法实现：

dll接口函数及回调函数类型：

typedef void (*Callback_Status)(char *station_id, char *station_ip, int status);
int Start_Server(char *ip, int port, Callback_Status fun);

java代码->回调函数声明：

import com.sun.jna.win32.StdCallLibrary.StdCallCallback;

public class getSDK {
	public interface Callback_Status extends StdCallCallback {
		public void Status(String station_id, String station_ip, int status);
	}
}

java代码->回调函数实现：

public class getSDK {
	public static class Status_Realize implements Callback_Status{
		public void Status(String station_id, String station_ip, int status) {
			if (status == 2) {
				GUI.Station_online(station_id, station_ip, 1, 0);
			} else if (status == 3) {
				GUI.Station_online(station_id, station_ip, 2, 0);
			}
		}
	}
｝

java代码->dll接口调用：

public static getSDK.Callback_Status callback_status = new getSDK.Status_Realize();

result = getSDK.Function.instanceDll.Start_Server("0.0.0.0", 1234, callback_status);

3.回调函数含有结构体数组参数

当回调函数其中一个参数是结构体数组时的处理方法：

dll接口函数、 回调函数类型，结构体类型 ：

typedef struct result_data {
	char Station_id[3];	
	char Label_id[7];
	int Signal;
	int Power;
	int Status;
}Tstatus, *PTstatus;

typedef void (*Callback_Data)(char *station_id, char *station_ip, Tstatus ret_data[], int count);

int Start_Server (char *server_ip, int listen_port, Callback_Status callback_status, Callback_Data callback_data);

java代码->回调函数、结构体定义：

import com.sun.jna.Structure;
public class getSDK {
	public interface Function extends Library {
		public static class Tstatus extends Structure {
			public byte[] Station_id = new byte[3];
			public byte[] Label_id = new byte[7];
			public int Signal;
			public int Power;
			public int Status;

			 public static class ByReference extends Tstatus implements
			 Structure.ByReference {}
			
			 public static class ByValue extends Tstatus implements
			 Structure.ByValue {}
			
			@SuppressWarnings({ "rawtypes", "unchecked" })
			@Override
			protected List getFieldOrder() {
				List a = new ArrayList();
				a.add("Station_id");
				a.add("Label_id");
				a.add("Signal");
				a.add("Power");
				a.add("Status");
				return a;
			}
		}
		public int Start_Server(String server_ip, int port, getSDK.Callback_Status Callback_Status,getSDK.Callback_Data Callback_Data);
	}
	public interface Callback_Data extends StdCallCallback {
		public void Data(String station_id, String station_ip, Pointer data, int count);
	}
}

java代码->回调函数实现：

public class getSDK {
	public static class Data_Realize implements Callback_Data{
		public void Data(String station_id, String station_ip, Pointer data, int count) {
			int srow, frow;
			
			srow = 0;
			frow = 0;
			
			for (int i = 0; i < count; i++) {
				byte[] stationbuf = new byte[2];
				byte[] labelbuf = new byte[6];
				int[] signal = new int[1];
				int[] power = new int[1];
				int[] status = new int[1];
				
				data.read(0 + i * 24, stationbuf, 0, 2);
				data.read(3 + i * 24, labelbuf, 0, 6);
				data.read(12 + i * 24, signal, 0, 1);
				data.read(16 + i * 24, power, 0, 1);
				data.read(20 + i * 24, status, 0, 1);
				
				String labelID = new String(labelbuf);
				String stationID = new String(stationbuf);

				GUI.message.append(String.valueOf(power[0]));
				GUI.message.append(String.valueOf(signal[0]));
				GUI.message.append(String.valueOf(status[0]));
			}
		}
	}
}

java代码->接口调用：

public static getSDK.Callback_Status callback_status = new getSDK.Status_Realize();	
public static getSDK.Callback_Data callback_data = new getSDK.Data_Realize();

result = getSDK.Function.instanceDll.Start_Server("0.0.0.0", 1234, callback_status, callback_data);

        这里的难点就在处理回调函数的结构体数组参数，参数是从dll传出来的，java里面用指针接收，而获取结构体内部的每个值就需要用读内存的方式读取出来，这里就需要对结构体在内存中的存储方式比较了解才行，因为read函数需要指定：内存起始位置、接收数据数组变量、数组变量的第几个元素、取内存大小，4个参数。

上面源码中i*24作用是取到结构体数组的第二、第三、、、个元素。也就是这里的结构体占内存大小为24，看下面：

         在32位系统中char占1个字节，int占4个字节，算下来结构体TStatus应该是22个字节，实际上还有一个内存对齐的概念，结构体前两个char数组共10个字节（是连续存储的），而结构体分配内存的大小必须是该结构体中占字节最大类型的倍数，所以应该分配4字节的倍数即12字节，所以前两个char数组实际分配了12个字节，在取数据时，第三个int的偏移量是12，整个结构体的大小为12 + 3*4（三个int变量）= 24字节

4.接口函数参数为结构体数组

当接口函数的参数为结构体数组，并且结构体成员也为结构体数组时，调用方法：

dll接口函数 类型，结构体类型 ：

typedef unsigned int UINT;

typedef struct code_word {
	char Feild[8];
	BOOL Inverse;
	UINT Length;
	CHAR Payload[255];	
}Cword, *pCword;

typedef struct label_data {
	char Label_id[7];
	UINT Count;
	Cword NCword[50];
}Ldata, *pLdata;

int Start_Update (char *station_id, int count, Ldata data[]);

public class getSDK {
	public interface Function extends Library {
		public static class Cword extends Structure {
			public byte[] Feild = new byte[8];
			public boolean Inverse;
			public int length;
			public byte[] Payload = new byte[255];

			 public static class ByValue extends Cword implements 
			 Structure.ByValue {}

			@SuppressWarnings({ "rawtypes", "unchecked" })
			@Override
			protected List getFieldOrder() {
				List a = new ArrayList();
				a.add("Feild");
				a.add("X_coord");
				a.add("Y_coord");
				a.add("Font");
				a.add("Inverse");
				a.add("length");
				a.add("Payload");
				return a;
			}
		}

		public static class Ldata extends Structure {
			public byte[] Label_id = new byte[7];
			public int Count;
			public Cword.ByValue[] NCword = new Cword.ByValue[50];

			public static class ByReference extends Ldata implements
					Structure.ByReference {
			}

			public static class ByValue extends Ldata implements
					Structure.ByValue {
			}

			@SuppressWarnings({ "rawtypes", "unchecked" })
			@Override
			protected List getFieldOrder() {
				List a = new ArrayList();
				a.add("Label_id");
				a.add("Patten");
				a.add("Count");
				a.add("NCword");
				return a;
			}
		}
		public int Start_Update(String station_id, int count, Ldata.ByValue[] data);

	}
}

java代码->接口函数调用：

public class GUI {
	public static int labelcount = 5;
	
	public static String[] labellist = new String[]{"000834","000835","041908",
		"041909","04190A","04190B","04190C","04190D","04190E","04190F","041910",
		"041911","041912","041913","041914","041915","041916","041917","041918"};

		bsend.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				int i;
				int result;
			    
				getSDK.Function.Ldata.ByValue tdata = new getSDK.Function.Ldata.ByValue();
				getSDK.Function.Ldata.ByValue[] data = (getSDK.Function.Ldata.ByValue[])tdata.toArray(labelcount);
				
				for (i = 0; i < labelcount; i++) {
					data[i].Label_id = labellist[i].getBytes();
				}
				
				for (i = 0; i < labelcount; i++) {
					data[i].Count = 4;
				}

				getSDK.Function.Cword.ByValue cdata = new getSDK.Function.Cword.ByValue();
				getSDK.Function.Cword.ByValue[] ctdata = (getSDK.Function.Cword.ByValue[])cdata.toArray(50);
				
				ctdata[0].Feild = "Text".getBytes();
				ctdata[0].Inverse = false;
				ctdata[0].length = "test".getBytes().length;
				ctdata[0].Payload = "test".getBytes();
			
				ctdata[1].Feild = "Text".getBytes();
				ctdata[1].Inverse = false;
				ctdata[1].length = "hello".getBytes().length;
				ctdata[1].Payload = "hello".getBytes();
				
				ctdata[2].Feild = "Text".getBytes();
				ctdata[2].Inverse = false;
				ctdata[2].length = "单位".getBytes().length;
				ctdata[2].Payload = "单位".getBytes();
				
				ctdata[3].Feild = "Text".getBytes();
				ctdata[3].Inverse = false;
				ctdata[3].length = "规格".getBytes().length;
				ctdata[3].Payload = "规格".getBytes();
				
				for (i = 0; i < labelcount; i++) {
					data[i].NCword = ctdata;
				}
				
				result = getSDK.Function.instanceDll.Start_Update((String)station.getSelectedItem(), labelcount, data);
			}
		});
}

getSDK.Function.Ldata.ByValue[] tdata = new getSDK.Function.Ldata.ByValue[labelcount];

的方式，得到的内存是不连续的，当你传递这种方式定义的变量给dll时，dll只能取到第一个结构体元素的值，造成数据丢失。