I'm having a little trouble running some Java code, which requires three .jar files to be used. I'm at a lost as to what to do with them--I've tried setting the CLASSPATH (and following the instructions for how to do so in the readme files), but to no avail.
I was wondering if someone could walk me through it? I'd imagine three .jar files would be an easy install for someone who knows what they're doing.
If it helps, I'm using Ubuntu pretty much right out of the box (but I do have JDK and Eclipse installed!)
Runtime library: http://cogcomp.cs.illinois.edu/download/software/20
Additional .jar needed: http://cogcomp.cs.illinois.edu/download/software/23
Program I ultimately need to run: http://cogcomp.cs.illinois.edu/download/software/26
If you're willing to help, I can't thank you enough--you deserve a million kudos!
G
Those are all JAR files. When you execute a JAR file by doubleclicking or using java -jar, the CLASSPATH environment variable and the -cp and -classpath arguments are ignored. The classpath should be defninied in META-INF/MANIFEST.MF file of the JAR. In this particular case, only the second and third JAR have a Class-Path entry in the manifest file:
Class-Path: LBJ2Library.jar
Which is the first JAR. The classpath is telling that it is expecting the LBJ2Library.jar to be in the same folder as the JAR you'd like to execute (either the second or third one).
So, just drop them all in the same folder and execute by java -jar LBJPOS.jar.
If you are using java -jar to run your jar files, then the CLASSPATH variable is ignored. If you are using java -jar, you have two options:
Combine the three jars into one jar.
Run the main class directory and don't use -jar.
Use of the CLASSPATH environment variable is generally discouraged nowadays. This is how it's done (on Linux):
java -cp library1.jar:library2.jar:mainapp.jar <fully qualified name of main class>
You need to set the CLASSPATH .place all the 3 jars in a folder , name it as lib
See below to set classpath
set CLASSPATH=%CLASSPATH%:lib;
Related
What is the difference between running a Java application withjava -cp CLASSPATH and java -jar JAR_FILE_PATH? Is one of them preferred to the other for running a Java application? I mean which one of these ways is more expensive for JVM (according to their machine resources usage)?
Which one will cause JVM to spawn more threads while trying to run the application?
I prefer the first version to start a java application just because it has less pitfalls ("welcome to classpath hell"). The second one requires an executable jar file and the classpath for that application has to be defined inside the jar's manifest (all other classpath declaration will be silently ignored...). So with the second version you'd have to look into the jar, read the manifest and try to find out if the classpath entries are valid from where the jar is stored... That's avoidable.
I don't expect any performance advantages or disadvantages for either version. It's just telling the jvm which class to use for the main thread and where it can find the libraries.
With the -cp argument you provide the classpath i.e. path(s) to additional classes or libraries that your program may require when being compiled or run. With -jar you specify the executable JAR file that you want to run.
You can't specify them both. If you try to run java -cp folder/myexternallibrary.jar -jar myprogram.jar then it won't really work. The classpath for that JAR should be specified in its Manifest, not as a -cp argument.
You can find more about this here and here.
PS: -cp and -classpath are synonyms.
When using java -cp you are required to provide fully qualified main class name, e.g.
java -cp com.mycompany.MyMain
When using java -jar myjar.jar your jar file must provide the information about main class via manifest.mf contained into the jar file in folder META-INF:
Main-Class: com.mycompany.MyMain
java -cp CLASSPATH is necesssary if you wish to specify all code in the classpath. This is useful for debugging code.
The jarred executable format: java -jar JarFile can be used if you wish to start the app with a single short command. You can specify additional dependent jar files in your MANIFEST using space separated jars in a Class-Path entry, e.g.:
Class-Path: mysql.jar infobus.jar acme/beans.jar
Both are comparable in terms of performance.
Like already said, the -cp is just for telling the jvm in the command line which class to use for the main thread and where it can find the libraries (define classpath). In -jar it expects the class-path and main-class to be defined in the jar file manifest. So other is for defining things in command line while other finding them inside the jar manifest. There is no difference in performance. You can't use them at the same time, -jar will override the -cp.
Though even if you use -cp, it will still check the manifest file. So you can define some of the class-paths in the manifest and some in the command line. This is particularly useful when you have a dependency on some 3rd party jar, which you might not provide with your build or don't want to provide (expecting it to be found already in the system where it's to be installed for example). So you can use it to provide external jars. It's location may vary between systems or it may even have a different version on different system (but having the same interfaces). This way you can build the app with other version and add the actual 3rd party dependency to class-path on the command line when running it on different systems.
There won't be any difference in terms of performance.
Using java - cp we can specify the required classes and jar's in the classpath for running a java class file.
If it is a executable jar file . When java -jar command is used, jvm finds the class that it needs to run from /META-INF/MANIFEST.MF file inside the jar file.
This question already has answers here:
NoClassDefFound when trying to run java with external libraries
(4 answers)
Closed 7 years ago.
How do I run a program in Java, with several referenced libraries, .jar files, from a command line?
I have put all my .jars in /lib folder, which is in the root folder of my project, and added those .jars to the build path.
So my project now looks something like this:
Project:
-->/src/Entry.java, ... (all them .java files)
-->/bin/Entry.class, ... (all them other .class files)
-->/lib/commons-codec-1.10./(all them .jars)*
Now when i try to run the program from the cmd:
I locate myself within the /bin folder and execute java Entry, but I get NoClassDefFound exception
How should I run this?
you need to tell JVM where to look for classes while running the program.
the parameter that we use to tell jvm that is known as classpath
there are different ways to achieve that
Recomended Add the classpath location to the run command , alternatively pass the jar locations, assuming you have two jar files a.jar and b.jar under you lib folder, the command should be java -cp".;lib/a.jar;lib/b.jar" Entry
Either put the jar files into a location that is already under classpath (Since current folder is always under classpath, easiest option would be to put the jar under current folder , but this is not a recomended way to achieve)
Modify you classpath variable under environment properties to list the folder containing your jar , which is a trivial way for achieving this.
Create one batch file (.bat) and keep the jars inside that. whenever you want to run then directly run that batch file. I guess its very simple and efficient.
Example:
#echo off
SET PATH=%PATH%;E:\Java\jdk1.6.0_45\bin // JDK path
SET LIB=%cd%\lib
set CP=""
set CP=%CP%;%LIB%\antlr-2.7.6
set CP=%CP%;%LIB%\commons-codec-1.8.jar
set CP=%CP%;%LIB%\opencsv-2.3.jar
javac -classpath %cp% *.java
java -classpath %CP% -Xms256m -Xmx1024m -Xss2m T2DPreProcessing
pause
I hope it will help you. Thanks.
This issue is related to running a Java program (jar) dependent on thirdparty jar library even after setting classpath and trying so many other methods by reading articles in Internet.
I want to use a thirdparty Pack1.jar (it is not a part of jvm) as dependency of my programme.
I do not know where the Pack1.jar file could be in the deployment machine and I want the deployer to specify the path for the thirdparty libraries
I have tried the following alternatives in vain
Setting the java.class.path programatically
String class_path = args[0];
System.setProperty("java.class.path",class_path);
Here I am assuming that deployer would supply the classpath as first argument while running the program
Setting the CLASSPATH env_var to locate the thirdparty directory
While running, using the classpath option
java -classpath /path/to/Pack1.jar -jar Pack2.jar
I think this would not work because documentation says that classpath is ignored when program is run with "java -jar"
Setting the java.ext.dirs programatically.
Setting the java.library.path programatically.
I do not want to specify the Class-Path in manifest because that takes only relative path and I do not know where the thirdparty library would be kept in deployment machine
But I am unable to get the jar running.
How can I fix this problem any help please.
Go for option 3. Put both jars on the classpath like this:
java -classpath '/path/to/Pack1.jar:/path/to/Pack2.jar' com.packagename.yourclassname
Note, that this is for Linux. on Windows, you would separate classpath elements with semicolons:
java -classpath "/path/to/Pack1.jar;/path/to/Pack2.jar" com.packagename.yourclassname
http://en.wikipedia.org/wiki/Classpath_%28Java%29
You can use Pack2.jar without running it using -jar--put it on the classpath and call the entry point listed in its manifest file.
I usually wrap that up in a launcher script to avoid those kinds of problems, and allow jar paths to be set using an argument.
Name the secondary JAR(s) in the Class-path entry of the Manifest.MF of the main JAR file, and use java -jar.
Your objection to this technique doesn't make sense. If you supply and deploy the secondary JAR files, as you should, you have the same degree of control over their location as you do over that of the major JAR file. It doesn't matter where else the user may have copies of them.
Pretty basic problem here. So I have a Java package that I have created that has three classes (one has the main method). I am trying to use a few Apache Jars, and have added these to my build path in Eclipse. However Eclipse wont let me build and run it properly, so I am trying the command line. I have added the env var CLASSPATH and pointed it to my lib directory which hold the Apache Jars. However, when I try to use javac I get a bunch of errors:
package org.apache.xmlrpc does not exist
import org.apache.xmlrpc.client.XmlRpcClient;
I was reading the man page for javac and it said that:
If neither CLASSPATH, -cp nor -classpath is specified, the user class path consists of the current directory.
So I tried copying the Jars to the same location as my three source files, but no change.
Can someone please tell me what I'm doing wrong?
Thanks.
Classpath variable (or command line option of javac) must contain all jars explicitly. It cannot go through jar files stored in specified directory.
You can compile this by specifying the option -cp on the command line:
javac -cp foo.jar:bar.jar foo/bar/Baz.java
You then run it with the same option:
java -cp foo.jar:bar.jar foo.bar.Baz
It sounds like you've just set the classpath to the directory containing the jar files. You need to set it to the individual jar files, or use java.ext.dirs to set an "extension" directory containing jar files. I'd recommend using the specific jar files. Something like:
// Assuming Windows...
CLASSPATH = c:\libs\foo.jar;c:\libs\bar.jar
I'd also personally recommend specifying the classpath on the command line instead of using an environment variable - the latter will work, but it ends up being a bit more fiddly if you want to compile different projects against different libraries.
However, I'd actually recommend getting Eclipse working first, rather than retreating to the command line. It should be fine - if you could give us more information about what's failing in Eclipse, we may be able to help you with that instead.
The jar files in the current directory are not automatically included; that only refers to .class files in normal package/directory hierarchy. Jar files must be added either explicitly, or via a wildcard like javac -cp ./* (Assuming JDK6+)
(Some OSes may require an escape of the * to avoid globbing; OSX does not.)
I agree with previous answers, but I would also recommend to use proper java build tool - like ant (perceived easier to use, but not necessary) or maven ( perceived more difficult to use, but really worth learning )
this will sound silly but i am executing my code from command prompt and have to use a jar in my class.
I have placed my jar in lib folder of JDK..
but i am still getting error of file not found
any explanation??
EDITED : guys tried all but still not working
EDIT 2 :i am trying to work as was told by this link i am using js-1.6R5.jar
Edit 3 : i undestand all the things you ppl have told but nothing working for me.. pls give me a link to upload my example that i can share with you all.
Edit 4 : i am fed up by setting classpaths but its not working... i have SDK installed in my system, do i need an extra JDK to run my programs from command prompt??
You need to add the jar to the class path by doing the following...
java -classpath D:\myprogram;D:\myprogram\lib\supportLib.jar org.mypackage.HelloWorld
Please see Wikipedia - Classpath_(Java)
You can place it anywhere, as long is you include it in your classpath. See Setting the Class Path for how to include jars in the classpath.
Have in mind that adding something in the JDK lib is almost never a good idea.
You can make a lib folder in your application's directory and put jar files there, then make your application find them by adding lib to your application's classpath.
And, don't put your jar files in JDK's lib folder. It's not good practise.
You need to let Java know that you want to include the jar in your classpath (the list of folders and jars it checks for classes). One way to do this is with the -cp command line argument, something like
java -cp ".;pathToMyJar\myJar.jar" MyClass
Another is to edit the CLASSPATH environment variable in your OS to include your jar.
A simple solution will be to place the jar fiel inside the windows folder if you are doing it in a Windows machine.
Unfortunately your question contains a lot of question signs and few information.
If you are using java.io.File to open jar as a regular file this jar should not be in lib directory. You just have to provide correct path in file system.
If however you are just trying to use jar as a part of your application it should be in classpath. Use either command line java -cp myjar.jar MyMainClassor put full path to this jar to global environment variableCLASSPATH`.