How to create a jar file or war file using the jar command

How to create jar file and war file with jar command

Make a note. The environment in which the sample was created is Windows 10.

How to make a jar file

The sample source file is as follows.

App.java

package sample;
public class App {
	public static void main(String[] arg) {
		System.out.println("Hello World!");
	}
}

The directory structure is as follows. The .class files are placed in the classes folder after compilation. Manifest files to be imported into jar are placed under META-INF.

C:\jar file creation sample>tree /F
List of folder paths:Volume OS
Volume serial number is XXXX-XXXX
C:.
├─classes
├─META-INF
│      MANIFEST.MF
│
└─src
    └─sample
            App.java

The manifest file specifies the Java class in which the main method will be executed when the jar is executed.

MANIFEST.MF

Main-Class: sample.App

Now let's compile before creating the jar. Compile with the javac command. Use -sourcepath to specify the folder where the source files are located. Use -d to specify the folder where the compiled files will be placed.

javac -sourcepath src -d classes src\sample\App.java

Compiling will create a .class file under the classes folder.

C:\jar file creation sample>tree /F
List of folder paths:Volume OS
Volume serial number is XXXX-XXXX
C:.
├─classes
│  └─sample
│          App.class
│
├─META-INF
│      MANIFEST.MF
│
└─src
    └─sample
            App.java

Then use the jar command to create a jar file. Specify the manifest file to be imported into the jar file with m. The subordinates of the folder specified by -C are compressed and imported into the jar file.

jar cvfm sample.jar META-INF\MANIFEST.MF -C classes .

The structure of the created jar file is as follows.

C:\jar file creation sample>jar tf sample.jar
META-INF/
META-INF/MANIFEST.MF
sample/
sample/App.class

The execution result is as follows.

C:\jar file creation sample>java -jar sample.jar
Hello World!

How to make a war file

The sample source file is as follows.

SampleServlet.java

package sample;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet("/sample")
public class SampleServlet extends HttpServlet {
	
	@Override
	public void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		resp.setContentType("text/html");
		resp.setCharacterEncoding("UTF-8");
		ServletOutputStream out = resp.getOutputStream();
		out.println("Hello World!");
		out.flush();
	}
}

The directory structure is as follows. The .class files are placed in the WebContent \ WEB-INF \ classes folder after compilation. The libraries required to compile the above source files are placed under lib.

C:\war file creation sample>tree /F
List of folder paths:Volume OS
Volume serial number is XXXX-XXXX
C:.
├─lib
│      javax.servlet-api-3.1.0.jar
│
├─src
│  └─sample
│          SampleServlet.java
│
└─WebContent
    └─WEB-INF
        └─classes

Now let's compile before creating the war. Compile with the javac command. Use -sourcepath to specify the folder where the source files are located. The library is specified by -classpath. All files under the lib folder can be specified by using *. Use -d to specify the folder where the compiled files will be placed.

javac -sourcepath src -classpath lib\* -d WebContent\WEB-INF\classes src\sample\SampleServlet.java

Compiling will create a .class file under the WebContent \ WEB-INF \ classes folder.

C:\war file creation sample>tree /F
List of folder paths:Volume OS
Volume serial number is XXXX-XXXX
C:.
├─lib
│      javax.servlet-api-3.1.0.jar
│
├─src
│  └─sample
│          SampleServlet.java
│
└─WebContent
    └─WEB-INF
        └─classes
            └─sample
                    SampleServlet.class

Then use the jar command to create a war file. The subordinates of the folder specified by -C are compressed and imported into the war file.

jar cvf sample.war -C WebContent .

The structure of the created war file is as follows.

C:\war file creation sample>jar tf sample.war
META-INF/
META-INF/MANIFEST.MF
WEB-INF/
WEB-INF/classes/
WEB-INF/classes/sample/
WEB-INF/classes/sample/SampleServlet.class

If you deploy the created war file to Tomcat etc. and access it from a browser, Hello World! Will be displayed.