| Author |
Message
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| bobbee |
 Posted: Fri Mar 13, 2015 7:32 am Post subject: |
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Knight
Joined: 20 Sep 2001
Posts: 547
Location: Tampa
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Just keeping the dream alive
So this:
public class HelloWorld {
native void helloFromC();
static {
System.load("C:\\IIBShared\\ctest.dll");
/* System.loadLibrary("ctest.dll"); */
/* System.loadLibrary("ctest"); */
}
public static String compress() {
HelloWorld helloWorld = new HelloWorld();
helloWorld.helloFromC();
return "1";
}
}
Got me this:
Text:CHARACTER:Java class not found
Insert
Type:INTEGER:5
Text:CHARACTER:com.cbs.common.HelloWorld.compress |
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| fjb_saper |
| Posted: Fri Mar 13, 2015 8:15 am Post subject: |
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Grand High Poobah
Joined: 18 Nov 2003
Posts: 20768
Location: LI,NY
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bizzarre... My stand alone JMS has no problem with this:
| Code: |
private String module = "C:/MQ/MQ8/Tools/c/samples/mqccred/bin/mqccred.dll";
private String module64 = "C:/MQ/MQ8/Tools/c/samples/mqccred/bin64/mqccred.dll";
.......
String procversion = System.getProperty("sun.arch.data.model");
if (load){
if ("32".equals(procversion)){
System.load(module);
} else if ("64".equals(procversion)){
System.load(module64);
}
} |
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MQ & Broker admin |
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| fjb_saper |
| Posted: Fri Mar 13, 2015 8:20 am Post subject: |
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Grand High Poobah
Joined: 18 Nov 2003
Posts: 20768
Location: LI,NY
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| bobbee wrote: |
you made a statement that has me questioning what I am doing. I have a single C program named ctext. yet you say this:
a C library that has the JNI interface and calls correctly into the existing C library (Which in all likelihood did not have any JNI calls pre-configured.
So it seems you are saying two C programs. I don't get this from the instructions. |
Well it is as simple as this. You want to call a C function from JNI.
Look at the jni call to make, look at the interface it generates.
If the interface does not exist in C you need to create a "pass through" handle. i.e. called from JNI calling the C interface I need to talk to...
If you know what the interfaces are it should not be too complicated yes?
Assumptions
- leaving the original C program / library untouched
- java signature something like: native String funcname(String mystring)
- original c signature string* funcname (string *)
- jni signature JNIEXPORT jString * JNICALL Java_funcname
(JNIEnv * env, jObject jobj, jString * mystring)
So you need a way to translate the JNI call to the C native call, unless the original library already takes care of that, which I doubt....
A few more examples and better explanation: http://en.wikipedia.org/wiki/Java_Native_Interface
And then there is the whole JNA (java native access) project school...
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| tczielke |
| Posted: Fri Mar 13, 2015 9:40 am Post subject: |
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Guardian
Joined: 08 Jul 2010
Posts: 943
Location: Illinois, USA
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For your process address space that is trying to load the dll, are you possibly mixing a 64 bit address space with a 32 bit dll or vice versa?
Also, the SysInternals ProcMon could be helpful here. If you recreate your issue with ProcMon, it should show you all the underlying open calls that are being made to find/open your dll and potentially the underlying issue.
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Working with MQ since 2010. |
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| bobbee |
| Posted: Fri Mar 13, 2015 9:50 am Post subject: |
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Knight
Joined: 20 Sep 2001
Posts: 547
Location: Tampa
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Thanks for the links to JNI programming. Will read
I tried the LD path, i added the directory to the PATH statement and I just tried the code above with System.Load. none of it worked. I will read the links and see what is going on. I know the load is not working. Why, I do not know. |
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| fjb_saper |
| Posted: Fri Mar 13, 2015 10:38 am Post subject: |
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Grand High Poobah
Joined: 18 Nov 2003
Posts: 20768
Location: LI,NY
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Also be careful. You can load the module as many times as you want without error.... so I suggest you use some kind of method that checks if it is already loaded and bypasses the load if it already is... and make sure to synchronize it... 
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