I want to create one executable JAR file which contains other JAR libraries. But when I execute the JAR, it gives an error of class path problem.
How do I solve the class-path problem?
I think you can try it like this;
Here is a simple example for you question. First, we assume we have a project directory like D:\javademo. In this working directory we then create a main class HelloWorld.java and thtat contains our other JAR files, like commons-lang.jar. Now, we must archive our main classes HelloWorld and commons-lang.jar into test.jar file.
First we must edit our manifest file so that we can specify our class-path and main-class
like this:
Manifest-Version: 1.0
Created-By: tony example
Class-Path: test.jar commons-lang.jar
Main-Class: org.tony.java.HelloWorld
We named this file test.mf. Now we use the jar command to generate our JAR file like this:
jar -cvfm test.jar test.mf -C ./ .
Then it will generate the JAR file test.jar. You can use this command to run this main class using java command:
java -jar test.jar
That is my solution. I hope it give you something helpful...
You should use third-party libraries for it. For example, OneJar. You'll have to build the final JAR file using the OneJar tool (like Ant task) instead of standard JRE's tools.
On running such a JAR file, OneJar's service class is launched instead of yours. This class then loads JAR files packed inside, as well as your classes, and run your main class.
There are similar questions and answers already. For example: Stack Overflow question Easiest way to merge a release into one JAR file.
Related
I have one JAR named as abc.jar with 15 class files. In JAR file I need to modify xyz.class, so I decompiled to xyz.java and modified it.
How can I update that JAR with the modified Java file? While trying to create (compile) the JAR file I am getting errors.
You can add your newly compiled class to the jar and overwrite the old one, here is how to add xyz.class and xyz.java to the jar :
jar uf abc.jar xyz.class xyz.java
See here for more about updating a jar file.
Or simply you can use any archiving tool, like winrar to open and add files to the jar.
Compile the xyz.java and replace the xyz.class file directly in jar without building the jar again, if the single class has been modified.
I wanted to convert .java file to executable jar file,i did so in the command prompt. But everytime i double click (open) it nothing happens.
jar cf Calculate.jar Calculator.java
This is what i typed in the cmd. How to get an executable file? I use windows
That's not how it works, that way you are creating a jar archive with that .java file in it.
If you want to create the jar manually (if you want to do it one time, instead of using a build tool like ant or maven, it could have some educational value), you have to compile your .java file to a .class with javac, add it to the jar and then modify the META-INF/MANIFEST.MF manifest file to specify Calculator as value for the Main-Class attribute.
See this old guide from Sun.
i have tried to get help me nobody seems to understand my problem. I created a project in netbeans and it produces a jar file when i compiled it. It runs just fine on through the IDE but when i try to launch it from the command prompt it simply does not do anything. It just moves the cursor to the next line for another command? when i echo my classpath this is the result i get
/opt/netbeans-7.1.2/ide/modules/ext/mysql-connector-java-5.1.13-bin.jar:/h/USERS/local/pagola/NetBeansProjects/mylib/dist/mylib.jar:/h/USERS/local/pagola/NetBeansProjects/EOPPrototype/build/classes
i have added the classpath which contains everything that is within the jar. My manifest file contains the main class(entry point) and this is what it looks like
Manifest-Version: 1.0
Ant-Version: Apache Ant 1.8.3
Created-By: 1.6.0_22-b04 (Sun Microsystems Inc.)
Class-Path: lib/mysql-connector-java-5.1.13-bin.jar lib/mylib.jar
X-COMMENT: Main-Class will be added automatically by build
Main-Class: eopprototype.EOPPrototype
and so i cant figure out what i am doing wrong? do i need to add anything to my PATH variable (maybe the java jdk bin stuff) is it not able to locate the java command because it doe not know where to look for that executable?
NOTE: i did not setenv my PATH and LIBRARY PATH -do i need to do this ? this is a c style shell script
Try this first
If your Manifest does not end with a newline it maybe ignored. See manifest requires a newline
Otherwise I have to make assumptions
You don't need lib/mylib.jar in your manifest if that JAR file contains EOPPrototype with a public static void main(String[] args) method that you wish to execute. So remove it so it only lists mysql-connector-java-5.1.13-bin.jar. Your manifest will then look like this
Manifest-Version: 1.0
Ant-Version: Apache Ant 1.8.3
Created-By: 1.6.0_22-b04 (Sun Microsystems Inc.)
Class-Path: lib/mysql-connector-java-5.1.13-bin.jar
X-COMMENT: Main-Class will be added automatically by build
Main-Class: eopprototype.EOPPrototype
Then assuming all your code is in mylib.jar and the only other dependant jar is mysql-connector-java-5.1.13-bin.jar, create a directory structure like this
/h/USERS/temp/mylib.jar
/h/USERS/temp/lib/mysql-connector-java-5.1.13-bin.jar
Then execute like this
cd /h/USERS/temp
java -cp .:mylib.jar eopprototype.EOPPrototype
I created simple Java Servlet: WelcomeServlet.java.
Than, I tried compile this file via:
javac WelcomeServlet.java
In result I see compile error:
package javax.servlet doesn't exit
I try find solution for this error with Google. And I find first part of answer: java compiler doesnt see servlet-api.jar file.
I know, that Apache Tomcat in it lib folder contains servlet-api.jar file.
So, I have this file, but where I must copy this file??
I try different folders:
echo %JAVA_HOME%
C:\Program Files\Java\jdk1.6.0_26
%PATH% contains this line: C:\Program Files\Java\jdk1.6.0_26\bin
So, I copy in:
%JAVA_HOME%\bin
%JAVA_HOME%\lib
%JAVA_HOME%\jre\lib
And in result same error.
And only after I copy servlet-api.jar in directory:
%JAVA_HOME%\jre\lib\ext
compilation complite sucessful.
My question: Why? Why I must copy in folder %JAVA_HOME%\jre\lib\ext ??
Where This moment describe in documentation?
And other question we have some official docs or specifications that describe folder structure for jdk folder??
You'll need to specify the directory or directories you want the compiler to search by using the -classpath command line option when running javac. The reason the compiler found your .jar in %JAVA_HOME%\jre\lib\ext is because it searches the extension directories by default.
This is for Java 1.5, but I believe it is more or less still correct:
http://docs.oracle.com/javase/1.5.0/docs/tooldocs/findingclasses.html
The link Shaun provides is a more complete answer. But in short, using the classpath is the best way to introduce 3rd party or external (to the JDK/JRE) libraries. The classpath is a concept much like the %PATH% or the $PATH variables, but specifies locations for java to use for lookup rather than the shell to use for lookup of executables.
The classpath provides the java compiler or java virtual machine a list of items to use when searching for resources. This "path" may include directories or files. It will typically include jar files and sometimes locations of configuration files. Many Java based lookup schemes for files configuration or otherwise use some variant of what is accomplished by [Class#getResourceAsStream()][1]'s use of walking the Classpath.
I have rarely seen an incident where putting a jar file in the lib/ext location was preferred to utilizing the Classpath.
The classpath is typically an environment variable (%CLASSPATH% or $CLASSPATH) or specified on the command line when running java or javac (e.g. -cp or -classpath see the help from the executable you are running).
Build tools such as Ant and Maven will also provide abstractions to defining the list of jars to be utilized by your applications and are highly recommended to be used for any length of repetitive change code, build, test, run cycles.
I have a bunch of JAR files (from a maven2 project) and maven reports some package could not be found (org.openanzo.client.jena to be exact). I want to dig into the JAR files downloaded as the result of maven dependency resolution and find what packages are thus available from these JAR files. Insights?
UPDATE: Apparently, the only good solution to inspect insides of a jar file is the "jar" utility or one can use the facilities of their IDE to do so.
jar tvf filename.jar will show you the contents of a jar file without requiring you to extract it.
But I think that maybe what you are really trying to do is find the right coordinates for the dependency that you are missing, since obviously none of the ones you have right now are supplying the package you are looking for (in other words, checking their contents is not likely to help you).
I confess that the first place I would suggest to check is Sonatype's public Nexus instance. A search for your example turns up nothing, though. Usually that means the project is not trying to get their stuff into Maven Central or other major repositories (which is okay), so you have to resort to a web search. Usually the first two sections of the package tell you where to look (openanzo.org in your case).
If you are on Linux or a Mac, you could go to the terminal at the root of the folder containing your JARs and type:
# grep -ri "org.openanzo.client.jena" *
It will return a recursive list of all JAR files that contain that package name. If it returns 0 results, then none of those JARS contain that package.
If you wanted to do a more exhaustive search, you could unJAR the JAR files. The directory structure and .class files will be organized by packages in folders.
# jar xvf filename.jar
If you are on Windows, you can unJAR a JAR file using a tool such as 7Zip.
#Carsten
you do not have to rename a .jar file to .zip. You can directly open the jar file in winzip/or other zip utility (assuming windows OS)
#ashy_32bit
try using "jar class finder" eclipse plugin from IBM. Simple plugin for finding classes (if you know the class name)
OR
as carsten suggested... set the jar files as lib files and manually look it up
OR
create a batch file called a.bat (where you have all your jar files directly under a single folder) and paste the following 4 lines
#ECHO OFF
dir /b *.jar > allJarFilesList.txt
FOR /F %%A IN (allJarFilesList.txt) DO jar -tf %%A > list_of_packages.txt
FOR %%B IN (list_of_packages.txt) DO FIND /I "com/sun" %%B
NOTE the "com/sun" in the last line.. it is hard coded, you can pass as argument as well...
I know this is very basic form and can be improved "a lot" like looking up in various sub directories.
hope this helps :-)
.jar files are just ZIP compressed archives, rename it to zip, open it with your favourite unzip programm, and traverse through the directory.
If you add the jar file to a eclipse project, you can traverse through the lib in th project explorer.
HTH
Assuming maven downloaded the jar files,the files will be loaded in to a local repository.
You could use maven browser that comes packaged with Eclipse to browse and search for artifacts in your repository.(usually in userdir/.m2/repository)
Note:You can explore your repository directly if you want. You will understand the packages that were downloaded. But I suggest using the plugin.
If you are using Intellij IDEA, each project contains a tree called External Library that allows you to search and explore your libraries.