In order to communicate with my serial port I downloaded rxtx for windows 64 bit and pluged into my eclipse. Everything looks fine. But while I'm debugging it when it comes to
SerialPort serialPort = (SerialPort) portIdentifier.open("ListPortClass", 300);
int b = serialPort.getBaudRate();
it goes to class file editor and says rxtxport.class not found. What could be the issue?
The problem sounds like a classpath problem. I'd say check the Eclipse Build Path.
Weirdly, the code snippet you provided did not contain said class, either it's incomplete or you might have the problem that it is a referenced class and a further 3rd party library is needed (ie, your package of rxtx is incomplete).
I'm not familiar with rxtx myself, so I cannot say if this is a definite probability, and on the other hand, this also comes down to the original answer: It is most likely a classpath problem, check whether all required libraries are included in the Eclipse Build Path.
Related
I'm working with some java code wich loads an unmanaged dll, just as the following:
public void Foo(){
System.loadLibrary("absolute_path_to_my_dll.dll")
}
It works fine from eclipse or console.
Next step: I'm using IKVM tools to get a managed dll from my java app (ikvmc.exe). Everything works fine and my dll is built perfectly. In fact, I've imported that library in a Test Solution (and I've add all IKVM refereces needed -IKVM.Core.JDK, IKVM.Runtime.JNI, etc-).
Well, here is the problem: when I run C# code the java call to System.loadLibrary(...) fails and I get an "UnsatisfiedLinkError: Can't load absolute_path_to_my_dll.dll". Absolute path is ok and dll is there.
Any help? Thanks in advance.
Edit 1
I'll try to explain more in detail:
Java step
public void Foo(){
System.loadLibrary("absolute_path_to_my_dll.dll")
}
If path is not correct this call gives the "UnsatisfiedLinkError" mentioned above. This is not the case, everything works well. The dll file is a 32 bit one, so I compiled this java project with jre7 x86 (in 64 bit mode loadLibrary call falis, obviously, saying we can't load 32 bit dll in 64 bit AMD machine).
Ikvm step
Now I compile java code in a managed dll wich can be imported in a .net project. First of all I export my java project to a jar file, "myJar.jar". Then i apply ikvmc.exe to generate a managed dll, let's say "myNewDll.dll".
ikvm.exe -target:library -out:"myNewDll.dll" "myJar.jar"
This step works nicely and i get a new dll I can import in my VS project.
C# step
Now I create a new VS tester solution. I add "myNewDll.dll" as reference so I can use it in my C# code. Also, I add IKVM.Core.JDK reference (if not, project can't compile) and configure project in 32 bit mode. Problems start here:
Running this setup gives "IKVM.Runtime.JNI error". I've added that reference.
Running again gives "can't find ikvm-native". As I can't add ikvm-native-win32-x86.dll or ikvm-native-win32-x64.dll as reference I put both of them in output path (bin/Debug).
Next try it gives the "UnsatisfiedLinkError: Can't load xxx.dll".
How can it be possible if that dll is loaded flawlessly in java step?
Annother try
Just before start crying I tried annother way: I created a java main program that only called Foo(). Then I generated an executable file with ikvmc.exe tool and called it in windows console. It gave me the same error, UnsatisfiedLinkError so maybe it's ikvmc.exe problem but I can't understand why.
Any idea?
Edit 2
Good news. It seems I've solved the problem. First of all, I had to add -platform:x86 to ikvmc.exe call (step 2). The dll generated was succesfully imported in my C# project and it works fine if we run in execution mode (NOT debugging). If I try to debug in VS it gives me System.Runtime.InteropServices.SEHException.
Is there any kind of bug related to debugging native code (dll loaded in java code) under native code (that java code loaded in C# using ikvm)?
Is your dll a 32 bit and you run it on a 64 bit platform?
If yes then the problem is that IKVM is platform independent. This means on a 64 bit system it runs 64 bit process.
To solve this you need a 64 bit version of your dll or mark ikvm.exe as 32 bit process.
Adding an option of reference to IKVM.OpenJDK.Core.dll at ikvm's /bin directory will resolve the error.
Maybe the .jar file needs some native DLLs, which was same as Native library location parameter of JAR in Eclipse. If so, find the native DLLs and copy them to de /bin directory of IKVM, and make ikvmc to load them automatically.
That's all what I've found out. Try and see if it would bring some ideas.
Update: The problem was solved with the help of MathWorks. I've published the answer below.
I need to control a program (Zemax) from Matlab. Unfortunately, Zemax only supports DDE for such control, which Matlab does not support any more. It works, but stops working on 64 bit platform after a few (presumable 63) DDE calls.
I wonder if there are working solutions. I could probably program a DLL with correct DDE support and then use DDE in Matlab via this DLL. This is a major effort for me. A more suitable solution would be to use Java DDE methods. Following another post here, I've discovered the JDDE library. However I cannot make it work: Even if I am in the directory with the DLL and JAR files, executing
import pretty-tools.JDDE-2.0.3.*
works fine but calling
a = com.pretty_tools.dde.client.DDEClientConversation()
afterwards (as done here) results in
Undefined variable "com" or class "com.pretty_tools.dde.client.DDEClientConversation".
I have very limited writing privileges on my PC, so I have added the javaclasspath.txt file with the jar/dll location to the directory indicated by prefdir. The file looks like this:
C:\Users\xxxxxxxx\Documents\matlab toolbox\jdde\pretty-tools-JDDE-2.0.3.jar
Calling javaclasspath shows a long listing with the last lines being:
...
C:\Program Files\MATLAB\R2012b\java\jarext\webservices\ws_client_core\mw-service-client-core.jar
C:\Users\kkarapet\Documents\matlab toolbox\jdde\pretty-tools-JDDE-2.0.3.jar
DYNAMIC JAVA PATH
<empty>
So path seems to be set correctly. What am I doing wrong?
With the help of MathWorks support, I've found the answer. Here is how to make JDDE work with Matlab 2012b, without admin privileges:
Download and unpack JDDE files (DLLs and JAR) into some folder. Let's say it's $path-to-jdde$\.
In Matlab, type prefdir. Open the resulting directory and create two files there, javaclasspath.txt and javalibrarypath.txt.
In javaclasspath.txt, add $path-to-jdde$\pretty-tools-JDDE-2.0.3.jar.
In javalibrarypath.txt, add $path-to-jdde$\.
Restart Matlab.
Now call ddeConv = com.pretty_tools.dde.client.DDEClientConversation; and start using the created object as described in JavaDoc. E.g. to connect to Zemax, run Zemax and then in call ddeConv.connect('Zemax', 'abc').
Step 2 above can only be done starting Matlab version R2012b. With an older version, if you have the write rights on the Matlab installation directory, you should be able to replace step 2 by editing the files librarypath.txt and classpath.txt in $MATLABROOT$\toolbox\local. I could not verify it so if you confirm it please let me know in the comment below.
I'm using JNA and Java but I think this question affects any native-to-nonnative bridge.
I have a Java application which relies on lib1.dylib, and lib1.dylib relies on lib2.dylib.
I want to put everything inside of my .app file on Mac. I can easily put lib1.dylib inside and set java.classpath (or NativeLibrary.addSearchPath()) to tell the JVM where to find lib1.dylib. The trouble is, I don't know how to communicate that lib1.dylib's dependencies are also in the location I provided. The result is that lib1 is loaded fine, but then lib2 can't be found since it's not in the operating system's library path.
Anyone know how I can overcome this problem? I imagine it must come up plenty in big projects with large numbers of shared libraries.
I've come across this problem before, and have just run into it again today. You may be able to get around it by adding the VM argument "-Djava.library.path=/path/to/other/libs", but I seem to remember Java only uses that to search for the intial library and then uses the system PATH to look for any dependencies.
A few solutions I've tried before:
1) Use System.load(absolutePath) on the dependent library before loading your library. Doesn't make your program ultra-portable though, unless you always know where that library is going to be.
2) In a case where lib1 depends on lib2, I actually used SetCurrentDirectory (Windows, not sure of the Mac equivalent) in the native code before it linked to any of the dependent libs, and that seemed to work. Again, requires knowing where the other libs are.
3) On Windows, could dump the dependent libraries in c:\windows\system32, and it finds them.
A few helpful posts on a similar topic (Windows-specific, but I think the problem is the same):
http://www.realityinteractive.com/rgrzywinski/archives/000219.html
http://www.velocityreviews.com/forums/t387618-jni-library-path.html
I've found a solution for MacOSX based on the idea in (2) from Stew:
Using Mac's JarBundler (or the Ant task of the same name) set the workingdirectory variable to $JAVAROOT and make sure your dylibs are in the Contents/Resources/Java part of the .app. If you do this the dynamic linker will find all the dependency dylibs because it will be the present directory. Java will also find the original dylib (the one that has all the dependencies) for the same reason.
Ant code:
<target name="package_mac_app" depends="package_jar, compile_native" description="bundle the runnable jar into a Mac Application -- requires JarBundler ANT Task">
<taskdef name="jarbundler" classname="net.sourceforge.jarbundler.JarBundler"/>
<echo message="CREATING MAC .app EXECUTABLE"/>
<jarbundler dir="${dist}"
name="${appname}"
mainclass="myPackage.myMainClass"
icon="${icon_location}"
jvmversion="1.5+"
infostring="${appname}"
shortname="${appshortname}"
bundleid="${com.mycompany.mydepartment.myprogram}"
jar="${run_jar_location}"
workingdirectory="$JAVAROOT">
<javafilelist dir="${dylib_location}" files="my-lib.dylib"/>
<javafilelist dir="${dylib_location}" files="dependent-lib.dylib"/>
</jarbundler>
</target>
I am working on a team project in Java. One requirement is that we dynamically populate a drop-down menu of all classes that implement a certain interface. New classes can be added after compile time. To accomplish this we are using reflection.
Problem: All of the drop-down menus are blank on my system. I cannot for the life of me figure out why they are not populating. All other 5 team members have it working on their system.
Things I tired that didn't work:
1) Installing most recent eclipse (galileo) because rest team was using it
2) Re-install most recent java release (jdk1.6.0-17 and jre6)
3) Check PATH and JAVA_HOME variables
Any thoughts as to what else I can try or if something I did should have solved it and didn't? It is driving me crazy.
Edit:
I should have been clearer that we are developing in a team. We are using SVN for version control and we are all running the exact same source code. I even tried checking out a fresh copy of the entire tree from SVN, but I had the same issue with reflection on my system while it worked for teammates.
The team created an executable jar and that ran on everyone's system fine except for mine. Everything worked for me except the reflection bit.
You need to debug your application. This means you have to systematically explore possible causes of the problem. Here are some things that come to mind:
Could your GUI be failing rather than reflection? What if you output with System.out.println() rather than your menu?
Is your reflection code throwing an exception, and are you ignoring it?
Is your reflection code actually being called? Toss a println() in there to be sure!
Is the test for the interface suffering from a typo or similar error that's causing it to fail? Try finding classes that implement Serializable instead!
Is your reflection test running in the main thread and trying to update your GUI? You need to use SwingUtilities.invokeAndWait to get an update to the Swing worker thread.
You're working with Eclipse; Eclipse has a fantastic debugger. Set a breakpoint near where your main action is and then single step through the code.
PATH and JAVA_HOME won't help. PATH only affects dynamically-linked libraries ("native code"). JAVA_HOME is a scripting variable that happens to be used by some Java-based utilities like Ant and Tomcat; it means nothing to the Java runtime itself.
You need to be investigating the classpath, which should be specified by the -classpath option to the java command, in the Build Path in your Eclipse project properties, or in the Class-Path attribute of the main section of a JAR file if you're launching java with the -jar option.
From within your code, you should be able to list the contents of your classpath by examining the system property, "java.class.path"
System.out.println(System.getProperty("java.class.path"));
Problem solution:
Classpath leading to source code must have no spaces in it.
I am running windows XP and, for whatever reason, if the classpath that leads to the jar file or source code that is using reflection has any spaces in it, then the reflection fails.
I took the jar file that works for the rest of my team and ran it from C:\ on my system and the reflection worked perfectly fine.
I do not know why this is so please comment if you know what is happening.
Might be a long shot, but look for differences in security settings for you and your team mates. Article describing more details http://www.ibm.com/developerworks/library/j-dyn0603/ heading "Security and reflection"
I have a pci-modem in my laptop and I tried to run a program that opens the port and configures it.I get an excepcion while doing it, I think that it can't see the port, even though it is on COM3. Is there any way of doing it in java?
The error I get is noClassDefFoundError. It says the SerialPortEventListener class isn't found. I'm using rxtxcomm. I tried using javax.comm but it doesn't find the port either.
Thanks a lot
A NoClassDefFoundError indicates that you're missing a JAR file from your classpath, specifically the one that is holding SerialPortEventListener class. Check your classpath.
Have you followed the installation instructions for rxtxcomm ? Note you have to handle a library and a jar file. You need to specify a system library path for the native component.
You may find that you get the 'no class def found' if the appropriate .jar is found, but it can't find the corresponding native library to load.