How to fix Failed to load Main-Class manifest attribute from jar in Java? Eclipse Netbeans Tutorial Example

 When encountering the "Failed to load Main-Class manifest attribute from jar" error in Java, it typically means that the manifest file in your JAR (Java Archive) file is missing or incorrectly configured. To resolve this issue, you can follow these steps:

Check your project structure: Make sure that your project is properly structured with the correct folder hierarchy, including the source files and the manifest file.

Ensure the manifest file is in the correct location: In order for the Java Virtual Machine (JVM) to find the manifest file, it needs to be located in the correct directory within your project. By convention, the manifest file named MANIFEST.MF should be placed inside the META-INF folder in your project's root directory.

Verify the manifest file content: Open the manifest file and ensure it contains the required attributes. At a minimum, the manifest file should include the Main-Class attribute, specifying the entry point for your application. Here's an example of a basic manifest file content:

makefile

"Manifest-Version: 1.0"

"Main-Class: com.example.YourMainClass"

Replace com.example.YourMainClass with the fully qualified name of your main class.

Update the build process in your IDE: Depending on the IDE you're using, you'll need to update the build process to ensure that the manifest file is included correctly in your JAR file. Here are the steps for Eclipse and NetBeans:

Eclipse:

• Right-click on your project and select "Properties."
• In the Properties window, navigate to "Java Build Path" -> "Order and Export" tab.
• Make sure the checkbox next to "JRE System Library" is selected.
• If you're using external libraries, make sure their checkboxes are also selected.
• Click "OK" to save the changes.

NetBeans:

• Right-click on your project and select "Properties."
• In the Project Properties window, navigate to "Build" -> "Packaging" -> "Exclude From Packaging" category.
• Ensure that the manifest file (MANIFEST.MF) is not selected/excluded from packaging.
• Click "OK" to save the changes.

Rebuild your project: After making the necessary changes, rebuild your project to generate a new JAR file. Make sure the manifest file is included in the JAR file and is located in the correct directory (META-INF/MANIFEST.MF).

Run the JAR file: Launch the JAR file using the java -jar command. Open a terminal or command prompt, navigate to the directory containing the JAR file, and execute the following command:

"java -jar yourJarFile.jar"

Replace yourJarFile.jar with the actual name of your JAR file.

By following these steps, you should be able to fix the "Failed to load Main-Class manifest attribute from jar" error and run your Java application successfully from the JAR file.