Thread: Run Java Class with External Dependencies from Command Prompt?

I was wondering whether it is possible to run a Java class that uses external libraries using the Windows Command Prompt.

I have the following minimal example Java class, where I just use the "Jackson" library to create a JSON file using the "ObjectMapper" class:

import com.fasterxml.jackson.databind.ObjectMapper;
import java.io.File;
import java.io.IOException;
 
public class Test
{
    public static void main(String[] args) throws IOException
    {
        ObjectMapper objectMapper = new ObjectMapper();
        objectMapper.writeValue(new File("test.json"), "test");
 
        System.out.println("Finished!");
    }
}

I compiled this project originally using Maven in the IntelliJ IDE, and I set the proper dependencies for "Jackson" in the "pom.xml" file.

I then wanted to run the resultant "Test.class" file with the Command Prompt with the following command:

java Test

Resulting in:

Exception in thread "main" java.lang.NoClassDefFoundError: com/fasterxml/jackson/databind/ObjectMapper
        at Test.main(Test.java:9)
Caused by: java.lang.ClassNotFoundException: com.fasterxml.jackson.databind.ObjectMapper
        at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:641)
        at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:188)
        at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:526)
        ... 1 more

I'm not very experienced with Java, and I've only ever used IDEs that handle most of the linking in the background for me. I just know that one can run a Java class in the Windows CMD using the "java" command, and I'm assuming that here it's telling me that it can't link the "Jackson" library properly.

Most of the existing simillar questions out there usually ask about user-made classes, I haven't yet been able to find a solution for external dependencies such as those defined by Maven.

Is it possible to run a Java class that uses external libraries using the Windows Command Prompt?

Thanks for reading my post, any guidance is appreciated.

To run a Java class with external dependencies from the Windows Command Prompt, you need to include the required external libraries (in this case, the Jackson library) in your classpath. Here's how you can do it:

Navigate to the directory containing your compiled Java class file (Test.class) using the Command Prompt.

Use the java command to run your Java class, specifying the classpath using the -cp or -classpath option to include the external dependencies. You'll need to include the paths to both your compiled class and the external JAR files. Assuming your Jackson library JAR file is named jackson-core.jar and is located in a lib directory relative to your class file, the command would look like this:

java -cp .;lib/jackson-core.jar Test

Here, . represents the current directory, and lib/jackson-core.jar specifies the path to the Jackson library JAR file relative to the current directory.

Hit Enter to execute the command. If everything is set up correctly, your Java class should run, utilizing the external dependencies specified in the classpath.

Remember to adjust the paths and filenames in the command according to your project's structure and the actual names of your external dependencies.

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