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[英]Trying to use DLL from Java (JNA). Unable to load library exception
[英]Invoking DLL Library with Java JNA
我有一个带有 DLL 库的 SDK。 我正在从 Java 1.8 和 JNA v3.0.9 调用库我在定义结构时遇到问题
SDK 文档指出:
调用 NET_DVR_STDXMLConfig 传递请求 URL: GET /ISAPI/AccessControl/UserInfo/capabilities?format=json 获取人员管理能力,了解配置详情和注意事项。
NET_DVR_STDXMLConfig API 调用定义为:
BOOL NET_DVR_STDXMLConfig(
LONG lUserID,
NET_DVR_XML_CONFIG_INPUT *lpInputParam,
NET_DVR_XML_CONFIG_OUTPUT *lpOutputParam
);
lpInputParam
[IN] Input parameters, refer to the structure NET_DVR_XML_CONFIG_INPUT for details.
lpOutputParam
[IN/OUT] Output parameters, refer to the structure NET_DVR_XML_CONFIG_OUTPUT for details.
NET_DVR_XML_CONFIG_INPUT 结构定义:
struct{
DWORD dwSize;
void *lpRequestUrl;
DWORD dwRequestUrlLen;
void *lpInBuffer;
DWORD dwInBufferSize;
DWORD dwRecvTimeOut;
BYTE byForceEncrpt;
BYTE byNumOfMultiPart;
BYTE byRes[30];
}
dwSize
Structure size.
lpRequestUrl
Request URL (command) for implement different functions, and it is in string format.
dwRequestUrlLen
Request URL size.
lpInBuffer
Buffer for storing input parameters (request messages), see the input content details structure in NET_DVR_MIME_UNIT.
dwInBufferSize
Input buffer size.
dwRecvTimeOut
Receiving timeout, unit: ms, 0-5000ms (default).
byForceEncrpt
Whether to enable force encryption (the messages will be encrypted by AES algorithm for transmission): 0-no, 1-yes.
byNumOfMultiPart
Number of message segments: 0-invalid; other values-number of message segments, which is transmitted by the parameter lpInBuffer in the structure NET_DVR_MIME_UNIT.
NET_DVR_MIME_UNIT 结构的定义是
struct{
char szContentType[32];
char szName[MAX_FILE_PATH_LEN/*256*/];
char szFilename[MAX_FILE_PATH_LEN/*256*/];
DWORD dwContentLen;
char* pContent;
BYTE byRes[16];
}
szContentType
Content type (corresponds to Content-Type field in the message), e.g., text/json. text/xml, and so on. The content format must be supported by HTTP.
zName
Content name (corresponds to name field in the message), e.g., name="upload".
szFilename
Content file name (corresponds to filename field in the message), e.g., filename="C:\Users\test\Desktop\11.txt".
dwContentLen
Content size.
pContent
Data point.
这就是我到目前为止在 Java 中所做的:DLL 调用和结构定义
//DLL native call
boolean NET_DVR_STDXMLConfig(int lUserID, Pointer lpInputParam, Pointer lpOutputParam);
public static class NET_DVR_XML_CONFIG_INPUT extends Structure
{
public int dwSize;
public Pointer lpRequestUrl;
public int dwRequestUrlLen;
public Pointer lpInBuffer;
public int dwInBufferSize;
public int dwRecvTimeOut;
public byte byForceEncrpt;
public byte byNumOfMultiPart;
public byte[] byRes = new byte[30];
@Override
protected List<String> getFieldOrder() {
return Arrays.asList("dwSize", "lpRequestUrl", "dwRequestUrlLen", "lpInBuffer", "dwInBufferSize",
"dwRecvTimeOut","byForceEncrpt","byNumOfMultiPart", "byRes");
}
}
public static class NET_DVR_XML_CONFIG_OUTPUT extends Structure {
public int dwSize;
public Pointer lpOutBuffer;
public int dwOutBufferSize;
public int dwReturnedXMLSize;
public Pointer lpStatusBuffer;
public int dwStatusSize;
public byte[] byRes = new byte[32];
@Override
protected List<String> getFieldOrder() {
return Arrays.asList("dwSize", "lpOutBuffer",
"dwOutBufferSize", "dwReturnedXMLSize", "lpStatusBuffer",
"dwStatusSize", "byRes");
}
}
public static class NET_DVR_MIME_UNIT extends Structure{
public byte[] szContentType = new byte[32];
public byte[] szName = new byte[MAX_FILE_PATH_LEN];
public byte[] szFilename = new byte[MAX_FILE_PATH_LEN];
public int dwContentLen;
public String pContent;
public byte[] byRes = new byte[16];
@Override
protected List<String> getFieldOrder() {
return Arrays.asList("szContentType", "szName", "szFilename", "dwContentLen", "pContent","byRes");
}
}
这是我的图书馆调用
NET_DVR_XML_CONFIG_INPUT struInput = new NET_DVR_XML_CONFIG_INPUT();
NET_DVR_XML_CONFIG_OUTPUT struOuput = new NET_DVR_XML_CONFIG_OUTPUT();
String strInput = new String("GET /ISAPI/AccessControl/UserInfo/capabilities?format=json\r\n\"");
byte[] byInput = strInput.getBytes();
System.arraycopy(byInput, 0, struInput.lpRequestUrl, 0, byInput.length); // Nullpointer exception
struInput.dwRequestUrlLen = byInput.length;
NET_DVR_MIME_UNIT mimeUnit = new NET_DVR_MIME_UNIT();
//mimeUnit.pContent = new Memory(MAX_XML_CONFIG_LEN); // Dont know what to put in here
struInput.lpInBuffer = mimeUnit.getPointer();
struOuput.dwOutBufferSize = MAX_XML_CONFIG_LEN;
struOuput.dwStatusSize = struOuput.dwOutBufferSize;
struInput.write();
struOuput.write();
NET_DVR_STDXMLConfig(userID,struInput.getPointer(), struOuput.getPointer()); // Getting a generic "parameters not valid" error msg
我不确定我的结构。 我在设置 requestURL 时获取了一个空指针我的调用也返回了一个通用的“参数无效”错误消息。
非常感谢任何帮助。
提前致谢
欢迎来到 StackOverflow。
您的结构映射看起来不错。 您没有列出 SDK 结构或NET_DVR_XML_CONFIG_OUTPUT
的文档,所以我对您的期望无能为力。
您的NET_DVR_STDXMLConfig
方法调用可以改进。 虽然它可以传递原始Pointer
值,但最好在那里传递适当的结构。 JNA 会在方法 arguments 中自动将它们视为它们的引用指针,并自动处理read()
和write()
。 所以这是一个更好的映射:
boolean NET_DVR_STDXMLConfig(int lUserID,
NET_DVR_XML_CONFIG_INPUT lpInputParam, NET_DVR_XML_CONFIG_OUTPUT lpOutputParam);
不知道你为什么要这样做new String("string");
而不是只使用原始的"string"
。
您在 arraycopy 上获得了 NPE,因为您还没有为struInput.lpRequestUrl
创建一个数组; 它只是一个Pointer
。 而不是数组副本,您可能希望将该字符串缓冲区定义为Memory
object,然后将字符串复制到其中,例如,
Memory requestUrl = new Memory(strInput.length + 1); // add space for null
requestUrl.clear(); // ensure last byte is null
requestUrl.setString(0, strInput); // set all the other bytes
struInput.lpRequestUrl = requestUrl;
struInput.dwRequestUrlLen = requestUrl.size();
为另一个参数传递结构指针很好,但您需要设置struInput.dwInBufferSize
以匹配该结构的size()
。 正如所写的那样,您在输入结构中为该缓冲区大小传递了一个大小 0 (默认int
),这可能是无效参数的来源。 或者您可能还没有完全初始化NET_DVR_MIME_UNIT
结构,因为您留下了String
null 并且没有设置它的长度。
您还需要为OUTPUT
结构定义您自己的缓冲区,并且由于您不知道字符串的完整大小,因此您需要设置一个最大值(我假设MAX_XML_CONFIG_LEN
基于您的尝试这样做,但我还没有阅读 DLL 文档),您必须在 dll 的 header 文件中找到 的值。
最后一点——您可能应该尝试使用最新版本的 JNA,因为总会有改进和错误修复。
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