Is there any way to call the functions which are in a so library from my Java code? Generally, is it possible to use Linux so libraries in Java programs?
The answer is "JNI" :)
Here are a couple of links:
How to compile dynamic library for a JNI application on linux?
http://learn-from-the-guru.blogspot.com/2007/12/java-native-interface-jni-tutorial-hell.html
http://docs.oracle.com/javase/6/docs/technotes/guides/jni/
You cannot use arbitrary .so libraries in your Java code. You can use JNI to write a wrapper around native code to access from Java.
However, be aware that doing so negates many of the advantages of using Java. Your code and deployment system now becomes quite fragile and subject to many types of bugs that cannot happen in Java. I would try quite hard to find a pure-Java solution before resorting to using native code.
Another wayto access libraries form java besides JNI is JNA.
I find that in many cases it's easier to use then JNI, but that's just my personal opinion.
Related
Is there any way to call the functions which are in a so library from my Java code? Generally, is it possible to use Linux so libraries in Java programs?
The answer is "JNI" :)
Here are a couple of links:
How to compile dynamic library for a JNI application on linux?
http://learn-from-the-guru.blogspot.com/2007/12/java-native-interface-jni-tutorial-hell.html
http://docs.oracle.com/javase/6/docs/technotes/guides/jni/
You cannot use arbitrary .so libraries in your Java code. You can use JNI to write a wrapper around native code to access from Java.
However, be aware that doing so negates many of the advantages of using Java. Your code and deployment system now becomes quite fragile and subject to many types of bugs that cannot happen in Java. I would try quite hard to find a pure-Java solution before resorting to using native code.
Another wayto access libraries form java besides JNI is JNA.
I find that in many cases it's easier to use then JNI, but that's just my personal opinion.
I have a java code and created a jar file.
I need to create an Qt application. Can I use this code in that application?
Please help me how can i use that jar file.
Thanks,
Nagaraju.
You could take a look at the capabilities of GCC/GCJ (see http://gcc.gnu.org/ ). IF it's a good idea is a whole other story, and depends on what you have, and what you're trying to accomplish. It should be doable to link SO's created with GCJ in QT applications, but I seriously wonder if you are not better off using either C++ or Java, but not mixing them
If your Java code takes input from stdin or some file and writes output to stdout or some file, then the easiest way is to fork java to run that jar, and parse the output in your Qt code.
Things other than that, you'll need to be a bit specific. Something like "my Java code does painting the screen".
My advice is to use SWT or Swing.
You can use gcj gcj to compile the java code to library and simply call the functions of the java code from your C code.
Yes, you can use your jar file in your Qt application. I've done exactly this myself.
One way is to use the JNI Invocation API. This is part of the Java Native Interface (JNI), which makes it feasible but not pleasant to access Java APIs from C++.
A much more pleasant approach is to use CodeMesh JunC++ion, which wraps the Java APIs in C++ classes. This is a great product, if you can afford it.
If you have very little Java code, it may be easier to port it to C++.
So... I will have a project which will be tested on Win 7 and some Linux server. It will be a web service that will use HSQLDB, Hibernate, Spring, Blaze DS and Flash (Flex RIA) as front end. I need to implement into it some image filtering\editing functionality which will be implemented in cross-platform C++ code (It will use Open-CV) wrapped in Java.
I need some kind of tutorial how to create cross-platform Java projects that use C/C++ libs *(most of all I am intrested in crossplatform compiling issue and what IDEs support such things)
It sounds like you'll benefit from the Java Native Interface. If you've got existing C and C++ code that you'd like to use from Java you may want to seriously consider something like GlueGen. It will save you a lot of time generating the code to access your C code.
You can have a look at the official Java JNI Examples here
Something along these lines?
http://www.javaworld.com/javatips/jw-javatip17.html?page=1
You're going to need to use JNI. The Java will be totally cross-platform and can be one project. For C++, you will need to create the JNI callable interface, and build as a dynamic library. The code should be pretty cross platform, but the actual build will be different.
On Linux, you need to build as a .so and you will probably use gcc. On Windows, you will probably use Visual Studio and build a .dll. The build will be different.
Are there inexpensive or free gateways from .NET to Java? I'm looking at some data acquisition hardware which has drivers for C/C++ and .NET -- I really don't want to do any programming in .NET.
Update: I haven't done what I originally wanted to do, but I've done something similar, using JNA to encapsulate some functions from a DLL, in order to control a USB hardware device from Java. (the DLL comes from the device manufacturer) It works really nicely. Thanks!
You could also try to use JNA for accessing the native library. JNA provides Java programs easy access to native shared libraries (DLLs on Windows) without writing anything but Java code—no JNI or native code is required. If their API is fairly straight foward, this might be the path of least resistance.
See their getting started guide where they call some native code (printf and GetSystemTime).
Well, there's JNBridge and EZ JCom, just from a Google search.
You could also use IKVM which is a slightly different approach.
(Any reason for not wanting to learn .NET, out of interest? It's a nice platform, and C# is a lovely language...)
If they have C++ versions of the drivers then you could write a wrapper around it using JNI and then load that in Java. JNI can be a bit of a pain, but it would let you use the C++ version of their drivers and not have to deal with .Net at all if you don't want.
I am partial to the recommendation to jump in the deep end with C# since it is so similar to Java. I did this and used IKVM to compile my favorite Java libs. to .NET assemblies and you get [nearly] all the core java runtime classes to boot, so if you tire of trying to find just the right C# collection type, you can always go back to java.util. (No generic collections though. Not sure why.)
Depending on what platform you're on, you have several choices for free IDEs too. For windows you can get Visual Studio Express for free but I also use SharpDevelop. You can also get the Mono IDE on Linux (and a few flavours of Unix, I think ?).
The C# learning curve is shallow if you already know Java. I only blew off 1.5 limbs on landmines that came out of nowhere for reasons I still don't understand, but workarounds were easy to come by. The worst thing about it was the darn developer docs which are AWFUL on account of being so slow. I really miss the snappiness of JavaDoc. Not only are the online docs incredibly slow, the problem is compounded by someones's iffy decision to put class summaries, constructors and methods/properties all on seperate pages so it just takes forever. Someone said to get the docs installer and install docs locally for a slightly improved experience. Not a bad idea I suppose.
I am author of jni4net, open source interprocess bridge between JVM and CLR. It's build on top of JNI and PInvoke. No C/C++ code needed. I hope it will help you.
If you have a Java application, the JNI mentioned by the others will be the way to go. You write some wrapper classes, and that's it.
If writing the wrappes is a too big task (depending on the number of methods you have to wrap), have a look at SWIG . I think it generates wrappers automatically, but I never actually used it.
If you want to code in the Java language, but you don't care if your program will run on the JRE/JVM, then you might as well use Microsoft J#. Basically, it's writing Java-Code wich is compiled to .NET-Bytecode and can use the .NET classes of the driver as well as your existing Java classes. With J# you will run into problems if your existing Java-code is newer than Java 1.4, look at this question on how to solve them.
From that point on, you could later add code in J#, C# or any other .NET language. However, you won't get back to the JRE/JVM easily.
I'm wondering if a Java library can be called from a VB.net application.
(A Google search turns up lots of shady answers, but nothing definitive)
No, you can't. Unless you are willing to use some "J#" libraries (which is not nearly the same as Java) or IKVM which is a Java implementation that runs on top of .NET, but as their documentation says:
IKVM.OpenJDK.ClassLibrary.dll: compiled version of the Java class libraries derived from the OpenJDK class library with some parts filled in with code from GNU Classpath and IcedTea, plus some additional IKVM.NET specific code.
So it's not the real deal.
I am author of jni4net, open source intraprocess bridge between JVM and CLR. It's build on top of JNI and PInvoke. No C/C++ code needed. I hope it will help you.
You can call Java from .NET if you wrap it in some form to make it accessable and the easiest way is typically to use a Runtime bridge like
http://www.jnbridge.com/
Other way is to wrap your API with java webservices.
check this also http://www.devx.com/interop/Article/19945
Nothing out of the box.
Most java/.net interop that I know uses web services.
If you can create COM components with Java, you can use tlbimp to create an interop assembly for using in VB.Net.
If can create standard DLLs that can be used from C++ with Java, you can write P/Invoke declarations and call them from VB.Net.
If you can create a web service with Java, you can generate proxy class from the WSDL and call it from VB.Net.
In any case, chances are the Java component will live in a separate process. I doubt you can load both the Java VM and the CLR in the same process.
If you have the source code and compile it using the J# compiler, then the answer is yes. If you want to call any pre-Java 2 (aka 1.2) libraries, then these are included pretty much verbatim with J#. More recent stuff is going to be tricky though (i.e., it's not there).
An example where this is used commercially are the yFiles graph layout algorithms from yWorks. These were originally just a Java library, but for the past few years they've been offering a .NET version, which is just the Java version compiled with Visual J#.
It's not without problems, and there are some limitations that you can't get around, but it can be done. So... unfortunately this answer looks pretty shady as well.
You could use JNI to instantiate a virtual machine and then use Java Classes. It will be some fun, though, because you would need to use C++ as a bridge between VB.Net and Java.
This article in java world has a quick tutorial on how to use Java from C++ and viceversa.
http://www.javaworld.com/javaworld/javatips/jw-javatip17.html
If you have the source, Visual Studio will let you convert Java code into c#.