I have 2 main classes in the project and i want to merge them into a single jar. because i want to use this jar in another project. so can you please suggest a solution for this.
You would go about this the same you would creating a JAR file from 2 classes which both do not have a main method:
jar -cvf your_jar.jar MainClass1.java MainClass2.java
If you want to choose one of the main methods to be the one which will execute by default when the JAR is run, then you can create a manifest file with the following contents:
Main-Class: MainClass1 (Manifest.txt)
Then you can run the jar tool like this:
jar -cvfm jarfile.jar Manifest.txt MainClass1.java MainClass2.java
Related
I understand how to create a JAR file when there is only a single package in a Java project but don't know how to create a JAR file when there are multiple packages in a Java project.
I have a sample project with the following structure:
I have two packages which you can see in the picture i.e.
academy.learnprogramming
academy.ujjwal
I want to create a jar file for the classes which are in the academy.ujjwal package. I tried multiple ways from the Artifacts option but not sure how to do it right.
It's usually uncommon to create jar file from command, Maven, Gradle like build tools are used but you can try following command.
jar cvp filename.jar /path/to/classes
jar cvf learnprogramming.jar src/academy.learnprogramming
jar cvp abc.jar src/academy.ujjwal
In my project I have this code that tell class loader to load Driver.class like so:
Class.forName(org.gjt.mm.mysql.Driver);
In Eclipse it runs with no problems and I have created the Jar file of the project. But I don't know how to insert the
mysql-connector-java-5.1.7-bin.jar
into a Jar file of my project. The folder structure look like this:
MANIFEST file:
Manifest-Version: 1.0
Main-Class: server.MultiServer
I am assuming that you finally just want to run your code as
java -jar myjar.jar
There are two options.
Keep mysql-connector-java-5.1.7-bin.jar next to your jar in the same folder and add classpath: mysql-connector-java-5.1.7-bin.jar to the manifest.
Copy all the classes in mysql-connector-java-5.1.7-bin.jar to your jar. Do not copy the jar but the classes in the jar. This is called a fat jar or uber jar. You can automate the same using maven shade plugin.
When you invoke your application jar add the -cp or -classpath option and provide the path to the dependent libraries, here the mysql-connector-java-5.1.7-bin.jar.
for example refer the below example
java -jar -classpath C:\myproject\lib\mysql-connector-java-5.1.7-bin.jar myproject.jar
I was wondering how can I turn my program (which I am currently running from Eclipse) into an executable file?
This will make it more feasible as people with JRE can just access it by clicking on a single file.
Any help would be appreciated.
Thank you.
Compile your java code
Create a manifest.txt file.
Specifiy the main class in the manifest file like: Main-Class: com.example.Main
Create a jar by adding the manifest.txt and required .class files: jar cvfm myJar.jar manifest.txt *.class
Note: make sure to add .class files, not .java files.
You may create this as a maven project and then simply run mvn clean package and the jar will be created in target directory.
I'm very new to Java. I have a single class file which is used to do some processing.
That class file is depended on a jar. I'm very new to Java, where I'm passing the jar to my classpath while running the program:
javac -classpath jar MyProgram.java
Now I wish to bundle both the jar and MyProgram into separate jar with dependency resolved.
Are there any ways to do this in Java? Note that it my MyProgram java is only around 50 lines of code, so some simple solution will be good.
Thanks in advance.
You cannot put the library JAR inside another JAR file - Java will not be able to load classes from embedded JAR files.
You could create a JAR file containing just the classes of your application, and have the library JAR alongside it. See Packaging Programs in JAR Files for details on how to do this exactly.
If you really want everything to be in a single JAR file, you could use a tool such as One-JAR to package it.
You should not bundle both your compiled code and the dependency in a separate jar. You should bundle only your compiled classes in a jar and when running the program, you put both your jar and the dependency in the classpath.
Use the jar command to build your jar file and then use the command below to run your program:
java -classpath dependecy.jar;yourjar.jar MyProgram
I am building an assembly in Maven for a command line utility. I can run it as an executable jar, but it fails because I need to load the config file externally. Assuming the following config, how would I run the jar?
Jar is in /opt/myapp/lib/myapp-assembly.jar
Config is in /etc/myapp/config/settings.xml
I'm loading the code from the classpath using ClassPathResource("/settings.xml");
Any help is appreciated!
I see two ways you could do it:
Launch the program using the jar as an archive rather than an executable jar, specifying the main class at run time. In other words, do java -classpath /opt/myapp/lib/myapp-assembly.jar:/etc/myapp/config [name of your main class].
Use the Class-Path field of the jar manifest file. Entries in it are directly added to the run time classpath, and there's nothing stopping you from specifying a filesystem directory rather than another jar file. So your manifest would contain: Class-Path: /etc/myapp/config/