I have a simple Spring Boot project which loads native libraries. The problem is that I have no idea how to specify the path to the native library when running the application.
I have read tons of posts explaining how to set java.library.path but every single one leads to
java.lang.UnsatisfiedLinkError: /path/to/lib/libconnector.so: libconnector.so: cannot open shared object file: No such file or directory
The project works if I run these two commands in a sequence from command line:
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/path/to/lib
./gradlew bootRun
The library is loaded and works. But I am unable to specify the library path in my gradle file. I tried
run {
systemProperty 'java.library.path', file('/path/to/lib')
}
bootRun {
systemProperty 'java.library.path', file('/path/to/lib')
}
and all sorts of variations of this. Also tried adding VM arguments to my IDE etc. but nothing works. Could someone explain what am I doing wrong?
This is how I load the native library (located in $projectRoot/lib):
static {
// load connector library
File lib = new File("lib/" + System.mapLibraryName("connector"));
System.load(lib.getAbsolutePath());
}
I finally solved my problem. I should be passing LD_LIBRARY_PATH as an environment variable instead of java.library.path as system property when running the application.
The following Gradle modification solved my issue:
tasks.withType(JavaExec) {
environment('LD_LIBRARY_PATH', 'lib')
}
You can write a init method to auto-set java.library.path,
here are some codes:
String path = "/path/to/lib";
String path = System.getProperty("java.library.path");
// if os is windows
path += ";" + classPath.getCanonicalPath();
// if os is linux
path += ":" + classPath.getCanonicalPath();
System.setProperty("java.library.path", path);
Note: run this method first.
try to load the lib from your class ( just to test)
NB : i'am not sure but if you need to use so file you must be on a linux OS.
public class Test {
static {
try {
System.loadLibrary("yourSohere");
// or System.load("/path/to/lib.so");
}
}
}
You can simply use:
dependencies {
compile files('libs/something_local.jar')
}
I have been breaking my head for two days trying to fix the file permissions for my tomcat7 server. I have a library class (.jar file included in myapp/WEB-INF) which needs to run a shell script. The library is written by me and works fine within NetBeans ie. no hassle in creating,reading and deleting files. That is because NetBeans runs the program as blumonkey(my username on my Ubuntu System). But when I import this into tomcat and run it, tomcat "executes" the command, produces no definite output, tries to check for a file(which will be generated when the script succeeds) and throws a FileNotFoundException.
More Details as follows:
Tomcat7 installed using apt-get, has its data in 2 locations - /var/lib/tomcat7 with conf and webapps folders and /usr/share/tomcat7 with the bin and lib folders
The user uploads a .zip file which is stores to /home/blumonkey/data. Rest of the program runs on the documents stored here. All new folders/files uploaded by tomcat have, obviously, tomcat7 as the owner.
I have tried things like changing the ownership to blumonkey, adding tomcat7 to blumonkey user group but none of the methods worked (Somewhere around here I probably messed up changing permissions carelessly :/ ). Apparently tomcat7 is unable to process on the files it owns.(How can this be?).
The script works when I run it in the terminal. But it doesn't work when I do a sudo -u tomcat7 script.sh, ie run it as tomcat7. It just exits with no message. I doubt that this it what is happening as I have tried to debug by redirecting the errors and outputs in ProcessBuilder but they came empty.
Any help regarding how to fix the issue and get the script running would be greatly appreciated. Please comment if you need any more info.
The code for script execution
private static void RunShellCommandFromJava(String command,String fn, String arg1,String arg2) throws Exception
{
try
{
System.out.println(System.getProperty("user.name"));
ProcessBuilder pbuilder = new ProcessBuilder("/bin/bash",command,fn,arg1,arg2);
System.out.println(pbuilder.command());
pbuilder.redirectErrorStream(true);
Process p = pbuilder.start();
p.waitFor();
}
catch(Exception ie)
{
throw ie;
}
}
The command which needs to be executed
"/bin/bash /abs/path/to/script.sh /abs/path/to/doc/in/data-folder maxpages=30 maxsearches=3"
PS : I have followed this question but it didn't help. I also tried other options like Runtime.exec(), bash,/bin/bash/ and /bin/bash/ -c, some of them don't work at all, others give no results.
Try to use Runtime and check standard error to find out what was the problem (probably permissions or paths):
// run command
String[] fixCmd = new String[] { "/bin/bash", "/abs/path/to/script.sh", "/abs/path/to/doc/in/data-folder", "maxpages=30", "maxsearches=3" };
Process start = Runtime.getRuntime().exec(fixCmd);
// monitor standard error to find out what's wrong
BufferedReader r = new BufferedReader(new InputStreamReader(start.getErrorStream()));
String line = null;
while ((line = r.readLine()) != null) {
System.out.println(line);
}
I'm trying to run a java application from a YARN application (in detail: from the ApplicationMaster in the YARN app). All examples I found are dealing with bash scripts that are ran.
My problem seems to be that I distribute the JAR file wrongly to the nodes in my cluster. I specify the JAR as local resource in the YARN client.
Path jarPath2 = new Path("/hdfs/yarn1/08_PrimeCalculator.jar");
jarPath2 = fs.makeQualified(jarPath2);
FileStatus jarStat2 = null;
try {
jarStat2 = fs.getFileStatus(jarPath2);
log.log(Level.INFO, "JAR path in HDFS is "+jarStat2.getPath());
} catch (IOException e) {
e.printStackTrace();
}
LocalResource packageResource = Records.newRecord(LocalResource.class);
packageResource.setResource(ConverterUtils.getYarnUrlFromPath(jarPath2));
packageResource.setSize(jarStat2.getLen());
packageResource.setTimestamp(jarStat2.getModificationTime());
packageResource.setType(LocalResourceType.ARCHIVE);
packageResource.setVisibility(LocalResourceVisibility.PUBLIC);
Map<String, LocalResource> res = new HashMap<String, LocalResource>();
res.put("package", packageResource);
So my JAR is supposed to be distributed to the ApplicationMaster and be unpacked since I specify the ResourceType to be an ARCHIVE. On the AM I try to call a class from the JAR like this:
String command = "java -cp './package/*' de.jofre.prime.PrimeCalculator";
The Hadoop logs tell me when running the application: "Could not find or load main class de.jofre.prime.PrimeCalculator". The class exists at exactly the path that is shown in the error message.
Any ideas what I am doing wrong here?
I found out how to start a java process from an ApplicationMaster. Infact, my problem was based on the command to start the process even if this is the officially documented way provided by the Apache Hadoop project.
What I did no was to specify the packageResource to be a file not an archive:
packageResource.setType(LocalResourceType.FILE);
Now the node manager does not extract the resource but leaves it as file. In my case as JAR.
To start the process I call:
java -jar primecalculator.jar
To start a JAR without specifying a main class in command line you have to specify the main class in the MANIFEST file (Manually or let maven do it for you).
To sum it up: I did NOT added the resource as archive but as file and I did not use the -cp command to add the syslink folder that is created by hadoop for the extracted archive folder. I simply startet the JAR via the -jar parameter and that's it.
Hope it helps you guys!
This question already has answers here:
What does "Could not find or load main class" mean?
(61 answers)
Closed 7 years ago.
I am having trouble compiling and running my Java code, intended to allow me to interface Java with a shared object for Vensim, a simulation modeling package.
The following code compiles without error:
javac -d . -cp ./apache-log4j-1.2.16/log4j-1.2.16.jar:./vensim.jar SpatialModel.java VensimHelper.java VensimException.java VensimContextRepository.java
However, when I try to run the following:
java -cp ./apache-log4j-1.2.16/log4j-1.2.16.jar:./vensim.jar SpatialModel vars
I get the following error: "Error: Could not find or load main class SpatialModel
". My SpatialModel.java code does contain a 'main' method (below), so I'm not sure what the problem is - can anyone please help me out? Thanks.
import java.io.File;
import java.text.NumberFormat;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import org.apache.log4j.Logger;
public class SpatialModel {
private VensimHelper vh;
public static final String DLL_LIBNAME_PARAM = "vensim_lib_nam";
public static final String MODEL_PATH_PARAM = "vensim_model_path";
private final static int VENSIM_CONTEXT_CREATION_MAX_FAILURE_COUNT = 10;
public SpatialModel() throws SpatialException {
String libName = System.getProperty(DLL_LIBNAME_PARAM);
String modelPath = System.getProperty(MODEL_PATH_PARAM);
if(libName == null || libName.trim().equals("")) {
log.error("Vensim library name has to be set with -D" + DLL_LIBNAME_PARAM);
throw new SpatialException("Vensim library name has to be set with -D" + DLL_LIBNAME_PARAM);
}
if(modelPath == null || modelPath.trim().equals("")) {
log.error("Model path has to set with -D" + MODEL_PATH_PARAM);
throw new SpatialException("Model path ahs to be set with -D" + MODEL_PATH_PARAM);
}
for (int i = 0; i < VENSIM_CONTEXT_CREATION_MAX_FAILURE_COUNT && vh == null; i++) {
try {
log.info("creating new vensim helper\n\tdll lib: " + libName + "\n\tmodel path: " + modelPath);
vh = new VensimHelper(libName, modelPath);
} catch (Throwable e) {
log.error("An exception was thrown when initializing Vensim, try: " + i, e);
}
}
if (vh == null) {
throw new SpatialException("Can't initialize Vensim");
}
}
public static void main(String[] args) throws VensimException {
long before = System.currentTimeMillis();
String libName = System.getProperty(DLL_LIBNAME_PARAM);
String modelPath = System.getProperty(MODEL_PATH_PARAM);
if (libName == null) {
libName = "libvensim";
}
if(modelPath == null) {
modelPath = "~/BassModel.vmf";
}
System.setProperty(DLL_LIBNAME_PARAM, libName);
System.setProperty(MODEL_PATH_PARAM, modelPath);
if (args.length > 0 && args[0].equals("info")) {
System.out.println(new VensimHelper(libName, modelPath).getVensimInfo());
} else if (args.length > 0 && args[0].equals("vars")) {
VensimHelper helper = new VensimHelper(libName, modelPath);
String[] vars = helper.getVariables();
for (String var : vars) {
System.out.println(helper.getVariableInfo(var));
}
} else {
File f = new File(".");
System.out.println(f.getAbsolutePath());
SpatialModel sm = new SpatialModel();
}
System.out.println("Execution time: " + (System.currentTimeMillis() - before));
}
}
You must ensure that you add the location of your .class file to your classpath. So, if its in the current folder, add . to your classpath.
Note that the Windows classpath separator is a semi-colon, i.e. a ;.
If the class is in a package
package thepackagename;
public class TheClassName {
public static final void main(String[] cmd_lineParams) {
System.out.println("Hello World!");
}
}
Then calling:
java -classpath . TheClassName
results in Error: Could not find or load main class TheClassName. This is because it must be called with its fully-qualified name:
java -classpath . thepackagename.TheClassName
And this thepackagename directory must exist in the classpath. In this example, ., meaning the current directory, is the entirety of classpath. Therefore this particular example must be called from the directory in which thepackagename exists.
To be clear, the name of this class is not TheClassName, It's thepackagename.TheClassName. Attempting to execute TheClassName does not work, because no class having that name exists. Not on the current classpath anyway.
Finally, note that the compiled (.class) version is executed, not the source code (.java) version. Hence “CLASSPATH.”
You can try these two when you are getting the error: 'could not find or load main class'
If your class file is saved in following directory with HelloWorld program name
d:\sample
java -cp d:\sample HelloWorld
java -cp . HelloWorld
I believe you need to add the current directory to the Java classpath
java -cp .:./apache-log4j-1.2.16/log4j-1.2.16.jar:./vensim.jar SpatialModel vars
You have to include classpath to your javac and java commands
javac -cp . PackageName/*.java
java -cp . PackageName/ClassName_Having_main
suppose you have the following
Package Named: com.test
Class Name: Hello (Having main)
file is located inside "src/com/test/Hello.java"
from outside directory:
$ cd src
$ javac -cp . com/test/*.java
$ java -cp . com/test/Hello
In windows the same thing will be working too, I already tried
If you work in Eclipse, just make a cleanup (project\clean.. clean all projects) of the project.
You have to set the classpath if you get the error:
Could not find or load main class XYZ
For example:
E:\>set path="c:\programfiles\Java\jdk1.7.0_17\bin"
E:\>set classpath=%classpath%;.;
E:\>javac XYZ.java
E:\>java XYZ
I got this error because I was trying to run
javac HelloWorld.java && java HelloWorld.class
when I should have removed .class:
javac HelloWorld.java && java HelloWorld
Check your BuildPath, it could be that you are referencing a library that does not exist anymore.
If you're getting this error and you are using Maven to build your Jars, then there is a good chance that you simply do not have your Java classes in src/main/java/.
In my case I created my project in Eclipse which defaults to src (rather than src/main/java/.
So I ended up with something like mypackage.morepackage.myclass and a directory structure looking like src/mypackage/morepackage/myclass, which inherently has nothing wrong. But when you run mvn clean install it will look for src/main/java/mypackage/morepackage/myclass. It will not find the class but it won't error either. So it will successfully build and you when you run your outputted Jar the result is:
Error: Could not find or load main class mypackage.morepackage.myclass
Because it simply never included your class in the packaged Jar.
I know this question was tagged with linux, but on windows, you might need to separate your cp args with a ; instead of a :.
java -cp ./apache-log4j-1.2.16/log4j-1.2.16.jar;./vensim.jar SpatialModel vars
http://docs.oracle.com/javase/7/docs/technotes/tools/windows/classpath.html
If you try to run a java application which needs JDK 1.6 and you are trying to run on JDK 1.4, you will come across this error. In general, trying to run a Java application on old JRE may fail. Try installing new JRE/JDK.
Problem is not about your main function. Check out for
javac -d . -cp ./apache-log4j-1.2.16/log4j-1.2.16.jar:./vensim.jar SpatialModel.java VensimHelper.java VensimException.java VensimContextRepository.java
output and run it.
Project > Clean and then make sure BuildPath > Libraries has the correct Library.
java -verbose:class HelloWorld might help you understand which classes are being loaded.
Also, as mentioned before, remember to call the full qualified name (i.e. include package).
I was using Java 1.8, and this error suddenly occurred when I pressed "Build and clean" in NetBeans. I switched for a brief moment to 1.7 again, clicked OK, re-opened properties and switched back to 1.8, and everything worked perfectly.
I hope I can help someone out with this, as these errors can be quite time-consuming.
This problem occurred for me when I imported an existing project into eclipse. What happens is it copied all the files not in the package, but outside the package. Hence, when I tried run > run configurations, it couldn't find the main method because it was not in the package. All I did was copy the files into the package and Eclipse was then able to detect the main method. So ultimately make sure that Eclipse can find your main method, by making sure that your java files are in the right package.
If so simple than many people think, me included :)
cd to Project Folder/src/package there you should see yourClass.java then run javac yourClass.java which will create yourClass.class then cd out of the src folder and into the build folder there you can run java package.youClass
I am using the Terminal on Mac or you can accomplish the same task using Command Prompt on windows
If you are using Eclipse... I renamed my main class file and got that error. I went to "Run As" configurator and under the class path for that project, it had listed both files in the class path. I removed old class that I renamed and left the class that had the new name and it compiled and ran just fine.
This solved the issue for me today:
cd /path/to/project
cd build
rm -r classes
Then clean&build it and run the individual files you need.
I have a similar problem in Windows, it's related to the classpath. From the command line, navigate until the directory where it's located your Java file (*.java and *.class), then try again with your commands.
I use Anypoint Studio (an Eclipse based IDE). In my case everything worked well, until I found out that while running the java code, something totally different is executed. Then I have deleted the .class files. After this point I got the error message from this question's title. Cleaning the project didn't solve the problem.
After restarting the IDE everything worked well again.
I tried the code below to run a stand-alone utility app I created from Apple script but, I get a No File or Directory Exists error.
I put identical copies (for testing) in the project, dist, parent directories but, it didn't help.
So, my questions are:
Is my call to run the app bad (perhaps because it's not a Windows exe)?
How to run a mac app from java?
Thanks
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
Runtime r=Runtime.getRuntime();
Process p=null;
String s="MyLineInInput.app";
try {
p = r.exec(s);
} catch (IOException ex) {
Logger.getLogger(AudioSwitcherView.class.getName()).log(Level.SEVERE, null, ex);
}
}
A Mac App Bunde is not an executable file, it's a folder with a special structure. It can be opened using the open command, passing the App Bundle path as an argument: open MyLineInInput.app.
EDIT:
Even better would be using Desktop.getDesktop().open(new File("MyLineInInput.app"));
I used the Runtime.getRuntime().exec() method with the open command mentioned in the selected answer. I didn't use Desktop.getDesktop().open() since it unwantedly opened a terminal in my case and I didn't want to create an extra File object.
Process process = Runtime.getRuntime().exec("open /System/Applications/Books.app");
Reason for adding '/System':
It seems we need to use the /System prefix for System apps. For user-installed apps, that's not required, and it can be like /Applications/Appium.app.
To answer #Pantelis Sopasakis' issue that I also faced initially -
I get the error message: java.lang.IllegalArgumentException: The file: >/Applications/Microsoft Office 2011/Microsoft\ Excel.app doesn't exist.
In this case, it could be simply due to not escaping the space characters in the path.
Environment: JDK 11 Zulu - macOS Monterey 12.2.1 - M1 Silicon