I need to write an application for a client that calls a method from a ".dll" file. The ".dll" file was previously executed manually from an ".exe" GUI but now they want to automate the process.
I never worked with .dll files so everything that I found until now is the result of a complete day of research, I also received a small documentation with this tool:
The interface is an ActiveX DLL which provides two functions (GetUnitInfo and SaveResult).
In the moment I just want to run the "GetUnitInfo" method from the Winwdows command line using RUNDLL32.exe.
This is the documentation for the "GetUnitInfo" method:
The interface for GetUnitInfo is as follows:
Public Function GetUnitInfo( _
ByVal strRequest As String, _
ByRef strUnitInfo As String,
Optional ByVal strStationName As String = "") As Long
Sample calling code can be:
Dim lRet As Long
Dim strXML as String
lRet = GetUnitInfo( _“<?xml version=""1.0"" ?><GetUnitInfo
xmlns=""urn:GetUnitInfo-schema"" SerialNumber=""BD3ZZTC8MA"" />", strXML)
So I tried to run this method with some dummy parameters because the method returns an error if the parameters are not OK. The command:
RUNDLL32.EXE FFTester.dll, GetUnitInfo test1, test2
But I receive this error:
I used "Dependency Walker" to list the functions from the dll file:
But this are all the functions, normally I would expected that also "GetUnitInfo" is listed.
Can somebody help? It is not mandatory to use RUNDLL32.
Later edit:
I want to call this DLL from a tool that is written in JAVA, I tried to use JNA but I failed so I was thinking to call the dll functions from the command line because if this works I can use a process builder to execute the command.
I fixed my problem and I will provide a solution, maybe it will help someone else.
I used com4j library to generate the interfaces for my dll. After this you need to register your DLL otherwise most problely your code will throw an "ComException", you can read more in my second question.
To register a DLL:
C:\Windows\SysWOW64>regsvr32.exe "path to your DLL" for 32 bit DLL
Or
C:\Windows\System32>regsvr32.exe "path to your DLL" for 64 bit DLL
Also depending on your DLL type, 32 or 64 bit, you need to use proper Eclipse/JDK.
What's the easiest way to execute a Python script from Java, and receive the output of that script? I've looked for different libraries like Jepp or Jython, but most appear out of date. Another problem with the libraries is that I need to be able to easily include a library with the source code (though I don't need to source for the library itself) if I use a library.
Because of this, would the easiest/most effective way be to simply do something like call the script with runtime.exec, and then somehow capture printed output? Or, even though it would be very painful for me, I could also just have the Python script output to a temporary text file, then read the file in Java.
Note: the actual communication between Java and Python is not a requirement of the problem I am trying to solve. This is, however, the only way I can think of to easily perform what needs to be done.
Not sure if I understand your question correctly, but provided that you can call the Python executable from the console and just want to capture its output in Java, you can use the exec() method in the Java Runtime class.
Process p = Runtime.getRuntime().exec("python yourapp.py");
You can read up on how to actually read the output from this resource:
http://www.devdaily.com/java/edu/pj/pj010016
import java.io.*;
public class JavaRunCommand {
public static void main(String args[]) {
String s = null;
try {
// run the Unix "ps -ef" command
// using the Runtime exec method:
Process p = Runtime.getRuntime().exec("ps -ef");
BufferedReader stdInput = new BufferedReader(new
InputStreamReader(p.getInputStream()));
BufferedReader stdError = new BufferedReader(new
InputStreamReader(p.getErrorStream()));
// read the output from the command
System.out.println("Here is the standard output of the command:\n");
while ((s = stdInput.readLine()) != null) {
System.out.println(s);
}
// read any errors from the attempted command
System.out.println("Here is the standard error of the command (if any):\n");
while ((s = stdError.readLine()) != null) {
System.out.println(s);
}
System.exit(0);
}
catch (IOException e) {
System.out.println("exception happened - here's what I know: ");
e.printStackTrace();
System.exit(-1);
}
}
}
There is also an Apache library (the Apache exec project) that can help you with this. You can read more about it here:
http://www.devdaily.com/java/java-exec-processbuilder-process-1
http://commons.apache.org/exec/
You can include the Jython library in your Java Project. You can download the source code from the Jython project itself.
Jython does offers support for JSR-223 which basically lets you run a Python script from Java.
You can use a ScriptContext to configure where you want to send your output of the execution.
For instance, let's suppose you have the following Python script in a file named numbers.py:
for i in range(1,10):
print(i)
So, you can run it from Java as follows:
public static void main(String[] args) throws ScriptException, IOException {
StringWriter writer = new StringWriter(); //ouput will be stored here
ScriptEngineManager manager = new ScriptEngineManager();
ScriptContext context = new SimpleScriptContext();
context.setWriter(writer); //configures output redirection
ScriptEngine engine = manager.getEngineByName("python");
engine.eval(new FileReader("numbers.py"), context);
System.out.println(writer.toString());
}
And the output will be:
1
2
3
4
5
6
7
8
9
As long as your Python script is compatible with Python 2.5 you will not have any problems running this with Jython.
I met the same problem before, also read the answers here, but doesn't found any satisfy solution can balance the compatibility, performance and well format output, the Jython can't work with extend C packages and slower than CPython. So finally I decided to invent the wheel myself, it took my 5 nights, I hope it can help you too: jpserve(https://github.com/johnhuang-cn/jpserve).
JPserve provides a simple way to call Python and exchange the result by well format JSON, few performance loss. The following is the sample code.
At first, start jpserve on Python side
>>> from jpserve.jpserve import JPServe
>>> serve = JPServe(("localhost", 8888))
>>> serve.start()
INFO:JPServe:JPServe starting...
INFO:JPServe:JPServe listening in localhost 8888
Then call Python from JAVA side:
PyServeContext.init("localhost", 8888);
PyExecutor executor = PyServeContext.getExecutor();
script = "a = 2\n"
+ "b = 3\n"
+ "_result_ = a * b";
PyResult rs = executor.exec(script);
System.out.println("Result: " + rs.getResult());
---
Result: 6
Jep is anther option. It embeds CPython in Java through JNI.
import jep.Jep;
//...
try(Jep jep = new Jep(false)) {
jep.eval("s = 'hello world'");
jep.eval("print(s)");
jep.eval("a = 1 + 2");
Long a = (Long) jep.getValue("a");
}
I've looked for different libraries like Jepp or Jython, but most seem to be very out of date.
Jython is not "a library"; it's an implementation of the Python language on top of the Java Virtual Machine. It is definitely not out of date; the most recent release was Feb. 24 of this year. It implements Python 2.5, which means you will be missing a couple of more recent features, but it is honestly not much different from 2.7.
Note: the actual communication between Java and Python is not a requirement of the aforementioned assignment, so this isn't doing my homework for me. This is, however, the only way I can think of to easily perform what needs to be done.
This seems extremely unlikely for a school assignment. Please tell us more about what you're really trying to do. Usually, school assignments specify exactly what languages you'll be using for what, and I've never heard of one that involved more than one language at all. If it did, they'd tell you if you needed to set up this kind of communication, and how they intended you to do it.
Jython approach
Java is supposed to be platform independent, and to call a native application (like python) isn't very platform independent.
There is a version of Python (Jython) which is written in Java, which allow us to embed Python in our Java programs. As usually, when you are going to use external libraries, one hurdle is to compile and to run it correctly, therefore we go through the process of building and running a simple Java program with Jython.
We start by getting hold of jython jar file:
https://www.jython.org/download.html
I copied jython-2.5.3.jar to the directory where my Java program was going to be. Then I typed in the following program, which do the same as the previous two; take two numbers, sends them to python, which adds them, then python returns it back to our Java program, where the number is outputted to the screen:
import org.python.util.PythonInterpreter;
import org.python.core.*;
class test3{
public static void main(String a[]){
PythonInterpreter python = new PythonInterpreter();
int number1 = 10;
int number2 = 32;
python.set("number1", new PyInteger(number1));
python.set("number2", new PyInteger(number2));
python.exec("number3 = number1+number2");
PyObject number3 = python.get("number3");
System.out.println("val : "+number3.toString());
}
}
I call this file "test3.java", save it, and do the following to compile it:
javac -classpath jython-2.5.3.jar test3.java
The next step is to try to run it, which I do the following way:
java -classpath jython-2.5.3.jar:. test3
Now, this allows us to use Python from Java, in a platform independent manner. It is kind of slow. Still, it's kind of cool, that it is a Python interpreter written in Java.
ProcessBuilder is very easy to use.
ProcessBuilder pb = new ProcessBuilder("python","Your python file",""+Command line arguments if any);
Process p = pb.start();
This should call python. Refer to the process approach here for full example!
https://bytes.com/topic/python/insights/949995-three-ways-run-python-programs-java
You can try using groovy. It runs on the JVM and it comes with great support for running external processes and extracting the output:
http://groovy.codehaus.org/Executing+External+Processes+From+Groovy
You can see in this code taken from the same link how groovy makes it easy to get the status of the process:
println "return code: ${ proc.exitValue()}"
println "stderr: ${proc.err.text}"
println "stdout: ${proc.in.text}" // *out* from the external program is *in* for groovy
First I would recommend to use ProcessBuilder ( since 1.5 )
Simple usage is described here
https://stackoverflow.com/a/14483787
For more complex example refer to
http://www.javaworld.com/article/2071275/core-java/when-runtime-exec---won-t.html
I've encountered problem when launching Python script from Java, script
was producing too much output to standard out and everything went bad.
The best way to achieve would be to use Apache Commons Exec as I use it for production without problems even for Java 8 environment because of the fact that it lets you execute any external process (including python, bash etc) in synchronous and asynchronous way by using watchdogs.
CommandLine cmdLine = new CommandLine("python");
cmdLine.addArgument("/my/python/script/script.py");
DefaultExecuteResultHandler resultHandler = new DefaultExecuteResultHandler();
ExecuteWatchdog watchdog = new ExecuteWatchdog(60*1000);
Executor executor = new DefaultExecutor();
executor.setExitValue(1);
executor.setWatchdog(watchdog);
executor.execute(cmdLine, resultHandler);
// some time later the result handler callback was invoked so we
// can safely request the exit value
resultHandler.waitFor();
Complete source code for a small but complete POC is shared here that addresses another concern in this post;
https://github.com/raohammad/externalprocessfromjava.git
I need to call this MATLAB code from Java code. The code clusters an image according to the specified number of clusters and the specified initial cluster centers (i.e. [176;137] in this code).
nrows = size(a_image,1);
ncols = size(a_image,2);
double_a_2_image = double(reshape(a_image,nrows*ncols,1));
nColors = 2;
[cluster_idx_2_a cluster_center] =
kmeans(double_a_2_image,nColors,'distance','sqEuclidean','start',repmat([176;137],
[1,1,3]));
a_pixel_labels_2 = reshape(cluster_idx_2_a,nrows,ncols);
figure('Name','a* image labeled by cluster index: 2 colors'),imshow(a_pixel_labels_2,
[]);
What is the best tool to convert this code into jar file (or maybe .class file)? Another point: I need to run the resulted jar file on a machine that do not have matlab installed. Is that possible or should I install MATLAB Compiler Runtime (MCR) on this machine?
A simple search on google gives you this link : MATLAB Builder JA, which generate a Java wrapper around your MATLAB code. And for your second question, you won't need it, as the wrapper is taking care of the MATLAB code itself.
I created my own new R library (called "Media"). There is no problem when I try to load it with RGui, and I can call the functions defined in the new package. This is how I load it:
> library(Media)
But, I'm also trying to call that functions from Java/JRI code, and when I load the new R package, Java doesn't seem to find the pacakge, throwing the message "Error in library(Media) : object 'Media' not found"
This is my current code using JRI:
REXP rexpSetFolder = re.eval("setwd('C:/Users/Albert/Documents')");
REXP rexpFolder = re.eval("getwd()");
System.out.println(rexpFolder.asString());
REXP rexpLoad = re.eval("library(Media)"); // fails
It also fails without the 'setwd' command, and simple calls to existing R functions work fine. I'm using R 2.10 and the latest JRI 0.5-0 under Windows.
Any help would be appreciated.
Thank you very much.
Edit:
The parameter lib.loc seems to work, at least this sentence does not return an error:
library("Media", lib.loc = "c:/Users/Albert/Documents")
But after that, calling a function in the package with re.eval("myfunction()"); still fails, as the function is not properly found.
You can modify the library path - see ?.libPaths in R, you simply want to add your private library to the path. The GUI does that for you, but if you are outside it doesn't happen. For example:
re.eval(".libPaths('c:/users/foo/Documents/R')");
Then load your package.
Did you install the library properly first? You might want to try using the lib.loc parameter.
library("Media", lib.loc = "c:/Users/Albert/Documents")
My work-around was to copy the package from my personal library (%USERPROFILE%\Documents\R) to the global library (%R_HOME%\library).
It's not the best because this requires Administrator privileges which not all users will have...
How can I use java to get a js file located on a web server, then execute the function in the js file and get the result and use the result in java.
Can you guys give me some code snippet? Great thanks.
You can use the scripting engine built into Java:
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
public static void main(String[] args) throws Exception {
ScriptEngineManager mgr = new ScriptEngineManager();
ScriptEngine engine = mgr.getEngineByName("JavaScript");
Object result = engine.eval("my-java-script-code")
System.out.println("Result returned by Javascript is: " + result);
}
Here is a more elaborate example.
There's three steps to this process:
Fetch the JS file from the server.
Execute some JS function from the file.
Extract the result.
The first step is fairly simple, there are lots of HTTP libraries in Java that will do this - you effectively want to emulate the simple functionality of something like wget or curl. The exact manner in which you do this will vary depending on what format you want the JS file in for the next step, but the process to get hold of the byte stream is straightforward.
The second step will require executing the JS in a Javascript engine. Java itself cannot interpret Javascript, so you'd need to obtain an engine to run it in - Rhino is a common choice for this. Since you'd need to run this outside of Java, you'll likely have to spawn a process for execution in Rhino using ProcessBuilder. Additionally, depending on the format of the Javascript you might need to create your own "wrapper" javascript that functions like a main class in Java and calls the method in question.
Finally you need to get the result out - obviously you don't have direct access to JavaScript objects from your Java program. The easiest way is going to be for the JS program to print the result to standard out (possibly serialising as something like JSON depending on the complexity of the object), which is being streamed directly to your Java app due to the way you launched the Rhino process. This could be another job for your JS wrapper script, if any. Otherwise, if the JS function has observable side effects (creates a file/modifies a database) then you'll be able to query those directly from Java.
Job done.
I hope you realise this question is far too vague to get full answers. Asking the public to design an entire system goes beyond the point where you'll get useful, actionable responses.
There are plenty of examples on the web of how to download a file from a URL.
Suns version of the JDK and JRE includes the Mozilla Rhino scripting engine.
Assuming you have stored the contents of the javascript file in a string called 'script', you can execute scripts as follows
String result = null;
ScriptEngineManager mgr = new ScriptEngineManager();
ScriptEngine jsEngine = mgr.getEngineByName("JavaScript");
try {
jsEngine.eval(script);
result = jsEngine.get("result")
} catch (ScriptException ex) {
ex.printStackTrace();
}
The result will be extracted from the engine and stored in the 'result' variable.
The is a tutorial on scripting in Java that might be useful.