I want to use this which says to use a particular method I have to include tcutil.h in my java code. Can anybody help me, how to do that ? Another point: we can easily create an header file and include it in to C code but why reverse is so hard (means lots of work have to do) ? May be stupid, but little bit hints will be helpful.
This might be more complicated than you think. The .h files are C language include files which usually describe the methods and data structures of a C-library. You would have to Java Native Interface (JNI) in order to include these libraries in your java code.
You have basically two options
Go through a tutorial like this
Or look for a java implementation.
There're already java-bindings available.
You can't include C/C++ headers into java source code.
Maybe you want to define a native implementation for a java method.
http://java.sun.com/docs/books/jni/
They seem to have a Java API, which you need to download and include in your classpath. You can't include a C header file in Java.
you cannot do it directly in java. You have to include the header files in your C program and use JNI to call the functions that you want to use.
Refer this : JNI reference
To run native code from Java, you need using JNI technology. Try http://java.sun.com/developer/onlineTraining/Programming/JDCBook/jni.html or http://docs.oracle.com/javase/6/docs/technotes/guides/jni/spec/functions.html of google by keywords "JNI, tutorial".
The page mentions that there is an API for Java available, but does not show it. You should ask them for the Java documentation. Preferrably, the API should be a JDBC driver.
Related
I've been trying to find an answer to this for some time, but I think part of my problem is that I don't really know how to phrase my question. I understand the that JVM ultimately preforms all the system calls at run-time that the Java program needs to make, my confusion is about the underlying way that Java classes tell the JVM to do this.
Take for example, the File class in the standard Java library. As far as I know, this is considered the most fundamental API for opening/creating files in Java. But, File is just another class right? So in theory I should be able to write my own File class from scratch which doesn't utilize the pre-exisitng one, right? How would I do that? What is happening inside the File class that tells the VM to actually create the file? I looked at the source code for the File class, and it looks like it calls another class called VMFile, but I could find no explanation of what VMFile is. When I looked at the VMFile source code, it just had function declarations with no definitions.
Thank you for your help.
The Java Native Interface (JNI) is the glue between Java classes and the OS. Native methods have a 'native' attribute (look it up in the JLS).
I'm trying to read a .qm translation files with Java.
.qm files are binary files. I don't have access to the .ts files.
And I don't find much info on these .qm files.
How are they structured ?
Regards,
There's no documentation that I know of, but if you look at QTranslator::load you should be able to follow the format of the QM file.
You will probably need to reimplement QTranslator in Java, as you need not only the ability to load the files, but also to extract and apply translations in Qt fashion.
As per request of OP:
You could use those files by using the Qt libraries and JNI. By using the translator in a c++ dll you can translate strings easily. However, you cannot extract the files or list the contained translations. But if all you need is the actual translation, this solution should work.
I cannot give a real example, because I only now how it works in theory, I haven't tried it, because it's not trivial. But if you are eager to try it out, the general idea would be:
Create a C++ dll and build it against QtCore. The easiest way is to download Qt from their website qt.io. You can for example create a default library project with QtCreator. Note: Besides Qt5Core.dll, Qt requires other libraries to correctly run. They are all included in the installation, but once you deploy your application, those of course have to be includes as well.
Include JNI to the C++ project and link against it. if you're new to this, here is a nice tutorial: Java Programming Tutorial
Create your wrapper methods. Methods in cpp you can call from java that take java strings, convert them to QString, translate them with QTranslator and convert them back.
Load the library in Java and execute those methods
Important:
First, I don't know how java handles dll dependencies. If you encounter errors while loading the dll, it's probably because dependencies of your dll are not present. Second, Qt typically requires a QCoreApplication running in the main thread for most of it's operations. I tested the translator without such an app, and it worked. So apparently for translations only the app is not required. However, depending on what you do in your dll, I think this is important to know.
If you need more details, feel free to ask.
I would like to write toy IDE for Java, so I ask a question about one particular thing that as I hope can help me get started.
I have editor implemented on top of swing and i have some text in there. There is for example:
import java.util.List;
Now I need a way to send "java.util.List" string to a method that returns me all the information I may need including JavaDoc document.
So is there any tool that can set up classpath with libraries, that would parse every string I send and try to find if there is any Class/Interface with documentation to return?
So is there any tool that can set up classpath with libraries, that would parse every string I send and try to find if there is any Class/Interface with documentation to return?
AFAIK, no. There is no such free-standing tool or library. You will need to implement it yourself. (Don't expect that writing a Java IDE is simple ... even a "toy" one.)
Libraries will have class files, which will not have javadocs.. So it is not clear what you want to do.
There are many byte code engineering tools to analyse and extract information from class files. For example asm or bcel. Javassist allows to process both source and byte code, so may be close to what you need.
You could use html parser to get the javadoc and other info from the web using the full path to the class (including package names to construct the correct URL per class). This will of course depend on the version of java you are using.
You can also use the javadoc tool from within java to generate the desired documentation from java source files (which can be downloaded from the web). The source code of the tool could also help you out. See http://java.sun.com/j2se/javadoc/faq/#developingwithjavadoc
Lastly, if you need information based on runtime types in your program, you might want to check reflection capabilities.
First you need to know How to print imported java libraries?. Then download java API documentation here. Once you find out imported libraries, open an inputStream in order to read appropriate HTML file.
Beware! This technic will only work when importing from jdk.
can someone guide me?
Is it possible to get information of .class file (in java) without the use of reflection? Information like class methods,constructors fields etc., and also can we invoke them without using Reflection in Java?
thanks in advance.
You can analyize the .class in terms of bytecode. Either manually or using a library like BCEL
See Java Virtual Machine Spec, Chapter 4 The class File Format.
I'm working on a project where we're doing a lot of remote object transfer between a Java service and clients written in other various languages. Given our current constraints I've decided to see what it would take to generate code based on an existing Java class. Basically I need to take a .class file (or a collection of them) parse the bytecode to determine all of the data members and perhaps getters/setters and then write something that can output code in a different language to create a class with the same structure.
I'm not looking for standard decompilers such as JAD. I need to be able to take a .class file and create an object model of its data members and methods. Is this possible at all?
I've used BCEL and find it really quite awkward. ASM is much better. It very extensively uses visitors (which can be a little confusing) and does not create an object model. Not creating an object model turns out to be a bonus, as any model you do want to create is unlikely to look like a literal interpretation of all the data.
I have used BCEL in the past and it was pretty easy to use. It was a few years ago so there may be something better now.
Apache Jakarta BCEL
From your description, it sounds like simple reflection would suffice. You can discover all of the static structure of the class, as well as accessing the fields of a particular instance.
I would only move on to BCEL if you are trying to translate method instructions. (And if that's what you're trying to automate, good luck!)
I'm shocked that no one has mentioned ASM yet. It's the best bytecode library your money can buy. Well, ok it's free.
JAD is a java decompiler that doesn't allow programmatic access. It isn't readily available anymore, and probably won't work for newer projects with Java7 bytecodes.
I think javassist might help you too.
http://www.jboss.org/javassist/
I have never had the need of using it, but if you give it a try, would you let us know your comments about it?
Although I think it is more for bytecode manipulation than .class inspection.