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Google OR-Tools in Intellij: UnsatisfiedLinkError

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");
}

How use openalpr in java project

I want to use openalpr in my java project. What must I include to use the API? What libs must be imported in project properties in Eclipse or Netbeans?
I found the solution
Download openalpr binaries
https://github.com/openalpr/openalpr/releases
Install and configure jdk (java and javac path)
Compile openalpr java source code, start java_test.bat file
Start main.java
java -classpath java Main "us" "openalpr.conf" "runtime_data" "samples/us-1.jpg"

Copy the native libs (DLLs for windows) into the exec dir
Copy the java classes into your project (dir: /src/main/java)
Get started with:
`
Alpr alpr = new Alpr("us", "/path/to/openalpr.conf", "/path/to/runtime_data");
// Set top N candidates returned to 20
alpr.setTopN(20);
// Set pattern to Maryland
alpr.setDefaultRegion("md");
AlprResults results = alpr.recognize("/path/to/image.jpg");
System.out.format(" %-15s%-8s\n", "Plate Number", "Confidence");
for (AlprPlateResult result : results.getPlates())
{
for (AlprPlate plate : result.getTopNPlates()) {
if (plate.isMatchesTemplate())
System.out.print(" * ");
else
System.out.print(" - ");
System.out.format("%-15s%-8f\n", plate.getCharacters(), plate.getOverallConfidence());
}
}
(Source: http://doc.openalpr.com/bindings.html#java)

How to set up classpath of JavaCompiler to multiple .jar files using wildcard

I am using JavaCompiler of javax.tools to compile some java code and I am trying to use wildcard in my classpath in order to include all the .jar files but I fail.
Here is my code:
String classpath = "C:\tomcat6\webapps\myapp/WEB-INF/lib/javax.ws.rs-api-2.0-m10.jar;"
+ "C:\\tomcat6\\webapps\\myapp/WEB-INF/lib/javax.persistence-2.1.0.jar";
Iterable<String> options = Arrays.asList("-d", classesBaseDir,
"-classpath", classpath);
JavaCompiler.CompilationTask task = compiler.getTask(null, fileManager,
diagnostics, options, null, file);
boolean result = task.call();
The code above works just fine. But when I am trying to change the classpath to
String classpath = "C:\\tomcat6\\webapps\\myapp/WEB-INF/lib/*";
it fails with
compiler.err.doesnt.exist|package javax.ws.rs does not exist
...
symbol: class GET
location: class com.my.oasis.resources.TestClass
09/04/2014 14:27:09:030 | COMPILER_DIAGNOSTIC | compileResource() - compiler.err.cant.resolve.location|cannot find symbol
...
I have also tried the following alterations
String classpath = "\"C:\\tomcat6\\webapps\\myapp/WEB-INF/lib/*\"";
String classpath = "'C:\\tomcat6\\webapps\\myapp/WEB-INF/lib/*'";
but none of them worked. Any ideas?
Thanks
Note: the reason why the path includes slashes and backslashes is because the my program identifies the environment in runtime and auto completes the path.
Edit: I am using tomcat 6 and java 1.7.0_21

Wildcards: Since Java 1.6 wildcards are supported when using java/javaw/javac, more information: Windows/Solaris and Linux
example:
javac -cp "lib/*" Test.java
This uses all .jar files (not .class!) in the lib directory as classpath. This should not be confused with the *-expansion of your shell. -cp lib/* gets expanded to -cp lib/a.jar lib/b.jar which is not valid argument syntax. In order to avoid this you have to add quotation marks: -cp "lib/*"
The cause of your Problem: You are trying to call the Java compiler from source directly with its Java API. This source code does not contain the wildcard expansion.
The JDK ships with a wrapper binary (javac,javadoc,javah,javap are all the same binary) which does some things and finally calls the compiler task. This wrapper also expands the wildcards in your classpath and therefore the compiler task doesn't have to do this anymore (and it doesn't). See at Compiler Readme section "build -> Notes -> The launcher". Launcher sourcecode.
Solution:
A very poor solution would be to call javac through a Processbuilder. (This is not recommended since it is a complicated and error prone solution for a simple problem)
Expand the wildcards yourself:
example code:
String classpath = buildClassPath("lib/", "test/", "lib/*");
System.out.println(classpath);
// output: lib/;test/;lib/a.jar;lib/b.jar;
This function takes all classpath entries and builds one classpath. Classpath entries with a wildcard in it will get expanded.
/**
* This function builds a classpath from the passed Strings
*
* #param paths classpath elements
* #return returns the complete classpath with wildcards expanded
*/
private static String buildClassPath(String... paths) {
StringBuilder sb = new StringBuilder();
for (String path : paths) {
if (path.endsWith("*")) {
path = path.substring(0, path.length() - 1);
File pathFile = new File(path);
for (File file : pathFile.listFiles()) {
if (file.isFile() && file.getName().endsWith(".jar")) {
sb.append(path);
sb.append(file.getName());
sb.append(System.getProperty("path.separator"));
}
}
} else {
sb.append(path);
sb.append(System.getProperty("path.separator"));
}
}
return sb.toString();
}

Using backslashes or slashes makes no difference. But you obviously assume that the path is auto-globbed (like a normal command line would). This does not happen. So you run your compiler as you would with a command line arg of
-classpath 'C:\\tomcat6\\webapps\\myapp/WEB-INF/lib/*'
which is not what you want. You may look into the API docs for java.io.File.listFiles(FileFilter) or even java.nio.file.Files.walkFileTree(Path, FileVisitor) to gain a better understanding.
To expand a bit on that, when your shell sees C:\tomcat6\webapps\myapp/WEB-INF/lib/* it expands it into a space-separated list of whatever is in your WEB-INF/lib directory. This is called globbing, or since it's done automatically, auto-globbing.
Now Java doesn't do that, but you can build it yourself in a few lines of code:
StringBuilder sb = new StringBuilder();
String[] filenames = new File("C:\\tomcat6\\webapps\\myapp/WEB-INF/lib/").list();
for(int i = 0; i < filenames.length; i++) {
if(i > 0) sb.append(File.pathSeparatorChar); // separate with ':' or ';' on Win
sb.append(filenames[i]); // append the filename
}
Iterable<String> options = Arrays.asList("-d", classesBaseDir, "-cp", sb.toString())
...
Since Java1.7 you can also use Files.newDirectoryStream(Path) instead of list(File). With 1.8 you could even call join instead of joining manually.

SCons not picking up all class files when creating a jar

SCons neophyte here. I am using it(version 2.0) to create a jar as follows:
compiled_classes = env.Java \
(target = compiled_classes_dir,
source = source_tld,
JAVAVERSION='1.6',
JAVACLASSPATH=['source_tld/libs/' +
file.name
for file in
Glob('source_tld/' +
'libs/*.jar')])
new_jar = env.Jar(target = jar_name,
source = compiled_classes_dir)
I am seeing an issue wherein class files belonging to classes that have inner classes(which when compiled into class files have a $ in the name) are not being handled properly i.e. they do not get included in the generated JAR. Any suggestions to address this would be greatly appreciated. TIA.
PS: This suggestion to add JAVAVERSION didn't seem to help.

Since SCons is incorrectly calculating the output classes I would suggest this workaround.
compiled_classes = env.Java \
(target = compiled_classes_dir,
source = source_tld,
JAVAVERSION='1.6',
JAVACLASSPATH=['source_tld/libs/' +
file.name
for file in
Glob('source_tld/' +
'libs/*.jar')])
#workaround to make sure classes are cleaned
env.Clean(compiled_classes, env.Dir(compiled_classes_dir))
# its important to set the JARCHDIR or the Jar command will not be run
# from the correct location if you want an executable Jar add the manifest here
new_jar = env.Jar(target = jar_name,
source = [compiled_classes_dir], JARCHDIR='$SOURCE')

Running a Java program from Adobe AIR's native process

I've use Adobe native process to run java program from my air app. Here the code and it works fine. But i should write absolute path to java runtime for that:
/System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents/Home/bin/java.
If user installed java runtime in diff folder, or have diff version then this code would not work. How i can detect where java were installed or maybe there is another right way to run java applications from air applications? If i run java library from terminal command line then i could just write "java -jar pdfbox-app-1.6.0.jar" etc. and it runs fine.
private function convertPdf2Txt():void{
var arg:Vector.<String> = new Vector.<String>;
arg.push("-jar");
arg.push(File.applicationDirectory.resolvePath("pdfbox-app-1.6.0.jar").nativePath);
arg.push("ExtractText");
arg.push("-force");
arg.push(File.applicationStorageDirectory.resolvePath("Data/1.pdf").nativePath);
arg.push(File.applicationStorageDirectory.resolvePath("Data/1.txt").nativePath);
var fjava:File = new File("/System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents/Home/bin/java");
if (fjava.exists==false){
Alert.show("Can't find Java Runtime in default folder.","Idea Rover",mx.controls.Alert.OK, null,null,imgInfo);
return;
}
var npInfo:NativeProcessStartupInfo;
npInfo = new NativeProcessStartupInfo();
npInfo.executable = fjava;
npInfo.arguments = arg;
var nativeProcess:NativeProcess;
nativeProcess = new NativeProcess();
nativeProcess.addEventListener(NativeProcessExitEvent.EXIT,onNativeProcessExit);
nativeProcess.start(npInfo);
}

Absolute path is:
Mac OS: /usr/bin/java
Win OS: (default)
64bit : C:\Program Files\Java
32bit : C:\Program Files (x86)\Java

rather than popping up an Alert, you could open a file selection dialog, using File.browseForOpen(). then, the File you want is contained in the event passed by the Event.SELECT handler. this flow seems standard for applications i've used that need to access other applications, but aren't sure where to find their executables.
var npInfo:NativeProcessStartupInfo = new NativeProcessStartupInfo();
// setup npInfo, nativeProcess...
var fjava:File = new File("/System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents/Home/bin/java");
if (!fjava.exists) {
fjava.addEventListener(Event.SELECT, onFileSelected);
fjava.browseForOpen("Where is Java located?");
}
private function onFileSelected (evt:Event) :void {
npInfo.executable = evt.target;
nativeProcess.start(npInfo);
fjava.removeEventListener(Event.SELECT, onFileSelected);
}
of course, you can use the same logic to find the file java needs to launch as well.

You may be able to determine where the Java binaries are by looking at the JAVA_HOME environment variable. I'd like to do the same thing as you're doing, so I'll post more after I do more research.