I want to use matlab function in java application. I create java package from my function by deploytool in matlab. Now, how can i use this package? Can only import the jar file created by deploytool in my java project and use its function?
After a lot of googling, I used this toturial but in the final step, i get error "could not load file".
Also i read about MatlabControl, but in this solution, we should have matlab environment in our system to java code running. But i will run my final app in systems that may not have matlab at all.
So i need a solution to run matlab function in java class even in absence of matlab environment.
Finally I solve my problem. the solution step by step is as follows:
write matlab function:
function y = makesqr(x)
y = magic(x);
Use deploytool in matlab and create java package.
3.create new java application in Eclipse and add main class. import javabuilde.jar and makesqr.jar:
import com.mathworks.toolbox.javabuilder.MWArray;
import com.mathworks.toolbox.javabuilder.MWClassID;
import com.mathworks.toolbox.javabuilder.MWNumericArray;
import makesqr.Class1;
and main.java:
public class main {
public static void main(String[] args) {
MWNumericArray n = null;
Object[] result = null;
Class1 theMagic = null;
try
{
n = new MWNumericArray(Double.valueOf(5),MWClassID.DOUBLE);
theMagic = new Class1();
result = theMagic.makesqr(1, n);
System.out.println(result[0]);
}
catch (Exception e)
{
System.out.println("Exception: " + e.toString());
}
finally
{
MWArray.disposeArray(n);
MWArray.disposeArray(result);
theMagic.dispose();
}
}
}
add javabuilder.jar and makesqr.jar to java build path of your project.
run it.
the Double.valueOf(3), define the input for our function and the output is as follows:
8 1 6
3 5 7
4 9 2
I didn't get properly your problem. Did you already compile the jar file from Matlab code and you are trying to use that, or you are at the last step of the tutorial?
If your answer is the latest case, most probably you forgot the "." before the class path.
From tutorial you linked:
You must be sure to place a dot (.) in the first position of the class path. If it not, you get a message stating that Java cannot load the class.
Also check if the matlab compiler path ("c:\Program Files\MATLAB\MATLAB Compiler Runtime\v82\toolbox\javabuilder\jar\javabuilder.jar" - in the tutorial) is correct for your system.
Related
I am setting up a java framework that should use the Google OR-Tools. The code below compiles successfully, but throws an exception at runtime:
Exception in thread "main" java.lang.UnsatisfiedLinkError: com.google.ortools.linearsolver.operations_research_linear_solverJNI.MPSolver_CLP_LINEAR_PROGRAMMING_get()I
at com.google.ortools.linearsolver.operations_research_linear_solverJNI.MPSolver_CLP_LINEAR_PROGRAMMING_get(Native Method)
at com.google.ortools.linearsolver.MPSolver$OptimizationProblemType.<clinit>(MPSolver.java:221)
at Main.main(Main.java:15)
I am using Intellij 2018.3 on Windows 10. I spent a lot of time trying to get this run, but unsuccessful. Based on what I found on the internet, the exception might be caused by poor linking and/or missing external libraries on which OR-Tools depends. However, I don't have the background to resolve this issue, and also Intellij does not highlight anything. Any idea what the problem is?
For completion, this is the code I run:
import com.google.ortools.linearsolver.MPObjective;
import com.google.ortools.linearsolver.MPSolver;
import com.google.ortools.linearsolver.MPVariable;
public final class Main {
public static void main(String[] args) {
// Create the linear solver with the GLOP backend.
MPSolver solver =
new MPSolver("SimpleLpProgram", MPSolver.OptimizationProblemType.GLOP_LINEAR_PROGRAMMING);
// Create the variables x and y.
MPVariable x = solver.makeNumVar(0.0, 1.0, "x");
MPVariable y = solver.makeNumVar(0.0, 2.0, "y");
System.out.println("Number of variables = " + solver.numVariables());
// Create a linear constraint, 0 <= x + y <= 2.
MPConstraint ct = solver.makeConstraint(0.0, 2.0, "ct");
ct.setCoefficient(x, 1);
ct.setCoefficient(y, 1);
System.out.println("Number of constraints = " + solver.numConstraints());
// Create the objective function, 3 * x + y.
MPObjective objective = solver.objective();
objective.setCoefficient(x, 3);
objective.setCoefficient(y, 1);
objective.setMaximization();
solver.solve();
System.out.println("Solution:");
System.out.println("Objective value = " + objective.value());
System.out.println("x = " + x.solutionValue());
System.out.println("y = " + y.solutionValue());
}
}
In my case solution was simple - I just needed to add this singe line of code:
Loader.loadNativeLibraries();
where loader comes from com.google.ortools.Loader
Disclaimer: more a long comment than an answer...
note: I supposed you are using the github repository of or-tools if you used the binary package it should be more or less the same...
1) You must load the jni library which will load the OR-Tools C++ libraries and its dependencies...
/** Simple linear programming example.*/
public class Main {
static {
System.loadLibrary("jniortools");
}
public static void main(String[] args) throws Exception {
2) Did you manage to run the java samples ?
make run SOURCE=ortools/linear_solver/samples/SimpleLpProgram.java
ref: https://developers.google.com/optimization/introduction/java#simple_example
3) As Kayaman pointed out, you must pass the folder where the java runtime can find the native libraries (i.e. the JNI wrapper jniortools.dll and its dependencies libortools.dll)
if you look at the console log you'll see the full command line:
java -Xss2048k -Djava.library.path=lib -cp lib\sample.jar;lib\com.google.ortools.jar;lib\protobuf.jar ...\sample
Which comes from, the makefiles/Makefile.java file:
JAVAFLAGS = -Djava.library.path=$(LIB_DIR)
...
ifeq ($(SOURCE_SUFFIX),.java) # Those rules will be used if SOURCE contain a .java file
$(CLASS_DIR)/$(SOURCE_NAME): $(SOURCE) $(JAVA_OR_TOOLS_LIBS) | $(CLASS_DIR)
-$(DELREC) $(CLASS_DIR)$S$(SOURCE_NAME)
-$(MKDIR_P) $(CLASS_DIR)$S$(SOURCE_NAME)
"$(JAVAC_BIN)" -d $(CLASS_DIR)$S$(SOURCE_NAME) \
-cp $(LIB_DIR)$Scom.google.ortools.jar$(CPSEP)$(LIB_DIR)$Sprotobuf.jar \
$(SOURCE_PATH)
...
.PHONY: run # Run a Java program.
run: build
"$(JAVA_BIN)" -Xss2048k $(JAVAFLAGS) \
-cp $(LIB_DIR)$S$(SOURCE_NAME)$J$(CPSEP)$(LIB_DIR)$Scom.google.ortools.jar$(CPSEP)$(LIB_DIR)$Sprotobuf.jar \
$(SOURCE_NAME) $(ARGS)
endif
src: https://github.com/google/or-tools/blob/46173008fdb15dae1dca0e8fa42a21ed6190b6e4/makefiles/Makefile.java.mk#L15
and
https://github.com/google/or-tools/blob/46173008fdb15dae1dca0e8fa42a21ed6190b6e4/makefiles/Makefile.java.mk#L328-L333
note: you can run make detect_java to know the flags i.e. value of LIB_DIR
note: if you did use the precompiled package the Makefile is here:
https://github.com/google/or-tools/blob/stable/tools/Makefile.cc.java.dotnet
Then after you can try to add this option in Intellij...
You must understand that or-tools is a set of C++ native libraries which are wrapped to Java using the SWIG generator.
To make it work using Intellij (over a windows machine) you need to:
Install Microsoft Visual C++ Redistributable for Visual Studio
Download and extract the OR-Tools library for Java
In intellij, add jar dependency to the 2 jars under the lib folder of the extracted files (each of the 2 jars separately, do not add to lib folder itself. This is why).
Add the lib library path to VM options. In Intellij edit your run-configuration and add to vm options: -Djava.library.path=<path to the lib folder that hold the jars>
Load the jni library statically by adding the below code to your class (as mentioned here.)
static {
System.loadLibrary("jniortools");
}
I have created the following Java class and saved it as Test.java, then compiled into Test.class on the command line using javac Test.java:
public class Test {
public Test() {
}
public double power(double number) {
System.out.println("calculating...");
return number * number;
}
}
Furthermore, I have created the following R script and saved it as test.R:
library("rJava")
.jinit(classpath = getwd())
test <- .jnew("Test")
.jcall(test, "D", "power", 3)
When I execute it, for example using R CMD BATCH test.R on the command line, I get the following output, which is what I want:
calculating...
[1] 9
However, when I wrap this script in a Markdown document and compile it using knitr, I lose the message that is printed about the calculation taking place. For example, I save the following script in test.Rmd and compile it using RStudio:
```{r echo=TRUE, warning=TRUE, results='show', message=TRUE}
library("rJava")
.jinit(classpath = getwd())
test <- .jnew("Test")
.jcall(test, "D", "power", 3)
```
This only returns the following output, without the message:
## [1] 9
I read somewhere that the reason is that System.out.println in Java writes to stdout, and whether this is shown in the R console or not depends on the interpreter. For example, the output is shown on Unix systems but not on Windows or in knitr.
My questions:
Is the above interpretation correct?
How can I reliably capture or display the output of System.out.println in R, irrespective of operating system or interpreter?
If that's not possible, what is a better way of designing status messages about the current calculations and progress in Java, such that R can display these messages?
Thanks!
I'll take a stab at answering my own question... Looks like the RJava folks actually offer a built-in solution (thanks Simon Urbanek if you read this). On the side of the Java code, there is the LGPL-licensed JRI.jar, which is delivered with rJava (look at the jri sub-directory in the rJava package directory in your local R library path) and which can be copied/extracted into the Java library path. It's only 82kb, so fairly light-weight.
JRI offers a replacement of the default print stream in Java. Essentially, you redirect the system output into an RConsoleOutputStream provided by JRI. The code in my question above can be modified as follows to print to the R console instead of stdout.
import java.io.PrintStream;
import org.rosuda.JRI.RConsoleOutputStream;
import org.rosuda.JRI.Rengine;
public class Test {
public Test() {
Rengine r = new Rengine();
RConsoleOutputStream rs = new RConsoleOutputStream(r, 0);
System.setOut(new PrintStream(rs));
}
public double power(double number) {
System.out.println("calculating...");
return number * number;
}
}
I use the class javax.tools.JavaCompiler (jdk6) to compile a source file, but the source file depends on some jar file. How to set the classpath of the javax.tools.JavaCompiler?
The javax.tools.JavaCompiler#getTask() method takes an options parameter that allows to set compiler options. The following message describes an easy way to set them in order to access the calling program's classpath:
You need to configure the standard
java file manager to know about the
jar files(s) - you use the compiler
options argument to do that.
By default the java compiler object
only seems to know about the default
locations for bootclasspath, extdirs
and endorseddirs directories in terms
of its classpath.
You need to add the calling program's
current classpath to the java compiler
instance's which gets passed on the
the standard file manager, which will
then find classes in the jar files.
Here's how I do it in the compiler
wrapper I wrote
List<String> optionList = new ArrayList<String>();
// set compiler's classpath to be same as the runtime's
optionList.addAll(Arrays.asList("-classpath",System.getProperty("java.class.path")));
// any other options you want
optionList.addAll(Arrays.asList(options));
JavaCompiler.CompilationTask task = compiler.getTask(out,jfm,diagnostics,optionList,null,jfos);
All you'll need then is to get the proper classpath set when running the calling program.
The same problem occurred to me recently, finally I found two workarounds. You can set the class path either by invoke StandardJavaFileManager.setLocation(StandardLocation.CLASS_PATH, "YOUR_CLASS_PATH") or Compiler.getTask(ARG_0, ARG_1, ARG_2, CLASS_PATH_OPTIONS, just as the first answer posted here says.
I needed something simpler than the examples above.
The following is a self-contained example of using the built-in Java compiler, and setting the classpath for the compiler to use.
It is equivalent to creating a source file called HelloPrinter.java and then compiling it as follows:
javac -classpath C:\Users\dab\Testing\a.jar;c:\path\etc org\abc\another\HelloPrinter.java
Note how the classpath can be set using a String[] of options. This should be familiar if you're already used to running javac on the command line (as above).
This code is compatible with Java 6. You will need a JDK, not a JRE, for this to run. This example doesn't actually use the classpath. It all does is print "Hello". You can add an import statement to the generated source and call a method in an external Jar file to test this properly.
import java.io.File;
import java.io.FileOutputStream;
import java.io.PrintStream;
import javax.tools.JavaCompiler;
import javax.tools.ToolProvider;
public class JavaCompilerExample {
public static void main(String[] args) throws Exception {
String className = "HelloPrinter";
String directoryName = "org/abc/another";
new File(directoryName).mkdirs();
FileOutputStream fos = new FileOutputStream(directoryName+"/"+className+".java");
PrintStream ps = new PrintStream(fos);
ps.println(
"package "+directoryName.replace("/", ".") + " ; "
+ "public class " +className +
"{ public static void main(String[] args){System.out.println(\"Hello\");} }");
ps.close();
JavaCompiler javac = ToolProvider.getSystemJavaCompiler();
String javacOpts[] = {"-classpath",
"C:\\Users\\dab\\Testing\\a.jar;c:\\path\\etc;",
directoryName+"/"+className + ".java"};
if ( javac.run(null, null, null, javacOpts)!=0 ) {
System.err.println("Error");
System.exit(1);
}
}
}
I'm trying to run project which uses fannj library, but I'm getting error:
Exception in thread "main" java.lang.UnsatisfiedLinkError: Error looking up function 'fann_create_standard_array':
at com.sun.jna.Function.<init>(Function.java:179)
at com.sun.jna.NativeLibrary.getFunction(NativeLibrary.java:347)
at com.sun.jna.NativeLibrary.getFunction(NativeLibrary.java:327)
at com.sun.jna.Native.register(Native.java:1355)
at com.sun.jna.Native.register(Native.java:1032)
at com.googlecode.fannj.Fann.<clinit>(Fann.java:46)
at javaapplication9.JavaApplication9.main(JavaApplication9.java:14)
Java Result: 1
This is what I did:
I put fannfloat.dll to C:\Windows\System32
I added fannj-0.3.jar to project
I added newest jna.jar to project
here is code:
public static void main(String[] args) {
System.setProperty("jna.library.path", "C:\\Windows\\System32");
System.loadLibrary("fannfloat");
Fann fann=new Fann("D:\\SunSpots.net");
fann.close();
}
SunSpots.net is file from example package. fannfloat.dll: you can get from here.
The "#8" at the end of _fann_create_standard_array indicates that the library is using the stdcall calling convention, so your library interface needs to implement that interface (StdCallLibrary) and it will automatically get the function name mapper applied that converts your simple java name to the decorated stdcall one.
This is covered in the JNA documentation.
It was the first time I had to work with FANN and it took me some time to make it work.
Downloaded Fann 2.2.0. Extract (in my case "C:/FANN-2.2.0-Source") and check the path of the fannfloat.dll file. This is the library that we will use later.
Download fannj-0.6.jar from http://code.google.com/p/fannj/downloads/list.
The dll is compiled for 32 bit environment. So, make sure you have a 32 bit Java installed (even in 64 bit Windows).
I suppose you already have the .net file with your ANN. Write something like this in Java
public class FannTest {
public static void main(String[] args) {
System.setProperty("jna.library.path", "C:/FANN-2.2.0-Source/bin");
Fann fann = new Fann("C:/MySunSpots.net" );
float[] inputs = new float[]{0.686470295f, 0.749375936f, 0.555167249f, 0.816774838f, 0.767848228f, 0.60908637f};
float[] outputs = fann.run( inputs );
fann.close();
for (float f : outputs) {
System.out.print(f + ",");
}
}
}
I use the class javax.tools.JavaCompiler (jdk6) to compile a source file, but the source file depends on some jar file. How to set the classpath of the javax.tools.JavaCompiler?
The javax.tools.JavaCompiler#getTask() method takes an options parameter that allows to set compiler options. The following message describes an easy way to set them in order to access the calling program's classpath:
You need to configure the standard
java file manager to know about the
jar files(s) - you use the compiler
options argument to do that.
By default the java compiler object
only seems to know about the default
locations for bootclasspath, extdirs
and endorseddirs directories in terms
of its classpath.
You need to add the calling program's
current classpath to the java compiler
instance's which gets passed on the
the standard file manager, which will
then find classes in the jar files.
Here's how I do it in the compiler
wrapper I wrote
List<String> optionList = new ArrayList<String>();
// set compiler's classpath to be same as the runtime's
optionList.addAll(Arrays.asList("-classpath",System.getProperty("java.class.path")));
// any other options you want
optionList.addAll(Arrays.asList(options));
JavaCompiler.CompilationTask task = compiler.getTask(out,jfm,diagnostics,optionList,null,jfos);
All you'll need then is to get the proper classpath set when running the calling program.
The same problem occurred to me recently, finally I found two workarounds. You can set the class path either by invoke StandardJavaFileManager.setLocation(StandardLocation.CLASS_PATH, "YOUR_CLASS_PATH") or Compiler.getTask(ARG_0, ARG_1, ARG_2, CLASS_PATH_OPTIONS, just as the first answer posted here says.
I needed something simpler than the examples above.
The following is a self-contained example of using the built-in Java compiler, and setting the classpath for the compiler to use.
It is equivalent to creating a source file called HelloPrinter.java and then compiling it as follows:
javac -classpath C:\Users\dab\Testing\a.jar;c:\path\etc org\abc\another\HelloPrinter.java
Note how the classpath can be set using a String[] of options. This should be familiar if you're already used to running javac on the command line (as above).
This code is compatible with Java 6. You will need a JDK, not a JRE, for this to run. This example doesn't actually use the classpath. It all does is print "Hello". You can add an import statement to the generated source and call a method in an external Jar file to test this properly.
import java.io.File;
import java.io.FileOutputStream;
import java.io.PrintStream;
import javax.tools.JavaCompiler;
import javax.tools.ToolProvider;
public class JavaCompilerExample {
public static void main(String[] args) throws Exception {
String className = "HelloPrinter";
String directoryName = "org/abc/another";
new File(directoryName).mkdirs();
FileOutputStream fos = new FileOutputStream(directoryName+"/"+className+".java");
PrintStream ps = new PrintStream(fos);
ps.println(
"package "+directoryName.replace("/", ".") + " ; "
+ "public class " +className +
"{ public static void main(String[] args){System.out.println(\"Hello\");} }");
ps.close();
JavaCompiler javac = ToolProvider.getSystemJavaCompiler();
String javacOpts[] = {"-classpath",
"C:\\Users\\dab\\Testing\\a.jar;c:\\path\\etc;",
directoryName+"/"+className + ".java"};
if ( javac.run(null, null, null, javacOpts)!=0 ) {
System.err.println("Error");
System.exit(1);
}
}
}