I have a situation. A device connected to PC(client side) via COM. The vendor provide me a dll to exchange data with the device. I would like to create a java web-app to collect data from many devices(connected to backend through PCs). So how can I call dll from a servlet? Thanks in advanced!
The straight-forward solution is using JNI or JNA. You should learn appropriate tutorial from Oracle to learn how to do this.
But probably you can do it easier. If for example this DLL is ActiveX you can create script (VBScript or JScript) and then run it from java using utility named cscript. Other possibility if this DLL already knows to run as a stand alone application (or you have separate command line app that runs this DLL and provides you CLI.). In this case I'd recommend you to use it unless you have serious performance constraints. It is much easier to run command line application from java than coding JNI.
Related
All of the solutions I found on stackoverflow suggest wrappers to register java application as windows service. My requirement is totally different. Please don't suggest wrappers for the purpose. The question is very simple I have java executable and I want to register it as windows service.
Phyiscal Path
Service Properties
Unfortunately we don't have backup of previous setup that installed it as windows service at the first place. Do I need some setup program or anything like that.
Not necessarily.
It is difficult to advise you on precisely what you need to do without more information on what you actually still have; e.g. an application installer, application JAR files, wrapper scripts, etc. Alternatively, if you told us what the application was, then maybe we could give you some hints on where to get installers, etc.
However, I can tell you definitely that registering java.exe or javaw.exe directly as a Windows Service will not work. These are not the executables for your Java application. Rather they executables for as Java Virtual Machine that will run your (real) Java application.
It is so easy task in case of Visual Studio. I want same support in Eclipse or anything else.
Well Java doesn't work like that. Java compiles to platform independent bytecode files, not to platform-specific native code. Sure, there are third party tools to generate exe's. However, using them is neither necessary, or desirable:
Why is creating an .exe from a java program not recommended?
(And asking for recommendations on what tools to use to do this is off-topic.)
Finally, if you take an arbitrary Java program and turn it into an ".exe" file, it won't necessarily be immediately registerable as a Windows service. This Q&A talks about turning an ".exe" into a Windows Service.
Create Windows service from executable
However, I can't tell you if the advice given there is appropriate for an ".exe" file created from an arbitrary Java app by some unspecified 3rd-part tool.
My recommendation:
If you are starting from scratch, use a Java Service Launcher / Wrapper.
If not, talk with whoever supplied and/or installed this application in the first place.
If you can't find any information about the application and where it came from, or if the vendor has gone out of business ... you need to urgently look for an alternative.
I am trying to develop a HTML5 plugin using NPAPI and firebreath framework. The code which needs to be used, is written in java but I need to convert it into C++. The only way i know is via JNI where i need to convert each .java file into .cpp file. However there are over 200 files in my project. Is there a better way to achieve this??
Any "simple" way would be more of a c++ question than a plugin or firebreath question. My guess is that you'd be far better off just making it an applet rather than a plugin if you want it mainly in java. There is nothing that I'm aware of that will make it easy for you to do what you want to do using FireBreath or NPAPI directly.
JNI doesn't convert Java to C++, it is a technology for calling native code (such as C or C++) from Java code. It doesn't seem relevant to your problem: Either you (manually or robotically) convert all your Java to C++ (which you can then call from Firebreath), or you keep your code in Java and run an applet (with no C/C++ code involved.)
If an applet as suggested by #taxilian isn't a good choice, why not turn your Java project into an application, and have your Firebreath plugin launch that and communicate with it? Your plugin could even download and install the Java app, for example in a temp folder. One limitation: The Java code won't have any direct access to internal browser API's, the Firebreath plugin would have to make any such calls on behalf of the Java app. How hard this all is would mainly depend on the complexity and bandwidth of communication needed between the web page and the Java code.
Is there a way to run a Java Applet in node.js, at server side?
It may sound crazy, but I am looking for a way to run a third party java applet on my node.js app server.
It is used to do a weird calculation that I am not willing to migrate to JavaScript code. Is this possible in any way? Any suggestions? I am in need to send the result of this calculation as a web page to the user, based on a request param.
I was initially thinking of how can I communicate between node.js and an Java Applet running standalone. Googled a bit but no success at all. Can someone suggest how to better google for it or point some good resources???
Using JNI will not help you as applets will not run in a headless environment. Applets are directly dependant on AWT so require a GUI environment to run.
Presuming that the license issues of the applet allow you to reuse the code, then my solution is to decompile the classes for the applet and use the generated java to create a normal java class with main that will run the desired calculations and return the result.
Unless the code is obfuscated, it's relatively simple to understand the decompiled code and should be relatively painless to adapt for what you wish to do.
Once you have your java code working from the command line you can then use the node-java project to call the java code from node.js and get your result.
I have a problem relating my web project.
Previously when my professor ask me on doing a online judge application, I chose to implement it using php rather than Java servlet, as I thought java servlet quite complicated.
Then problem comes. For the online judge, I have to use a backend java program on the server to do the processing of user submitted codes. That is, each time a user submits something, php would call the java virtual machine and invokes the java application. However, to invoke the java application, my own way now is to use command line
popen("start java -jar \"$FILE_ROOT/OnlineJudge.jar\"", "r");
This works fine, but considering loading of java virtual machine, it is actually very slow and error prone. So I was wondering if there is any better ways for PHP to invoke local java programs on the server. Because later I found I still need to invoke more java from php.
Any idea would be appreciated. Thanks.
have you considered php-java bridge, this is quite useful, it uses XML to communicate between php and java.
You'll need to start the JVM once and the bridge component will help with communication.
here are some examples, here you can find a simple example to connect php and java
Depending on how the java application is written, it likely wouldn't be too hard to convert it to a servlet. Once it is a servlet, run it under jetty or tomcat, and then just have your php connect to it via CURL and put/get data from the servlet.
Java servlets are fairly simple. If you are using an external framework like Spring it becomes even easier, but if not, you just need to extend javax.servlet.http.HttpServlet, and then configure it in your web.xml.
It's a bit of a hack, but shouldn't take you too long to accomplish.
Also take a look at the exec for command line executions. I used it to shut down my computer after doing an extensively long task well into the night.
I need to use the logic contained in some java classes. I found JNI, but that project seems not updated recently.
Is there a way to use it in a Delphi native application? I use Delphi 2009.
A newer solution than JNI is JNA, which also supports callbacks from (Delphi) DLLs. I found it easy to use.
You could try j-interop.
The technique I should adopt is to build a COM wrapper of java business logic, and using this COM server from delphi throught interoperability.
Delphi can build a type library of a COM server, and you could istantiate the com server using this typelibrary. Type library is simply a wrapper of the server, exposing its interface to be used by delphi code.
The key to communicating with different platform softwares is called "interoperability".
You can find this also in .net versus win32. Tipically delphi code is win32 (exe or dll), and you can build communication protocol between delphi objects and .net assemblies or java bytecode using interoperability solutions.
With Java 6, it takes only a few lines of code to write a standalone web service server which then can be invoked from Delphi.
small step-by-step tutorial, using the free NetBeans IDE and Delphi:
Delphi and Java Integration using Web Services
more xamples:
http://www.theserverside.de/webservice-in-java/
http://www.torsten-horn.de/techdocs/jee-jax-ws.htm#Minimaler-Webservice
Embed the VM in the native code. This worked for me.
An example with c can be found here. http://java.sun.com/docs/books/jni/html/invoke.html
I very much doubt it. Delphi Code gets compiled into an executable while Java code is executed by a Virtual Machine. So unless you launch a complete Virtual Machine inside Delphi code I see no way to easily include the logics.