How to execute main class in java project using maven

Let us say you need to run the main method in class dev.selenium.getting_started.XYZ

Both mvn exec:java -Dexec.mainClass="dev.selenium.getting_started.XYZ" and mvn org.codehaus.mojo:exec-maven-plugin:3.0.0:java -Dexec.mainClass="dev.selenium.getting_started.XYZ" commands can be used to run a Java class with a main method using Maven. However, there are some differences in how they specify the Maven plugin and their level of specificity. Let's break them down:

mvn exec:java -Dexec.mainClass="dev.selenium.getting_started.XYZ"

Overview:

• Command: mvn exec:java -Dexec.mainClass="dev.selenium.getting_started.XYZ"
• Plugin Short Alias: exec:java
• Plugin Configuration: Relies on the default configuration of the exec-maven-plugin specified in the project’s POM file or in the plugin’s default configuration.
• Usage: Simple and convenient when you don't need to specify a specific version of the plugin or other details.

Characteristics:

• Ease of Use: This command is more concise and easier to type.
• Assumes Default Plugin Configuration: Assumes that the exec-maven-plugin is either already defined in the pom.xml or uses a default version specified by Maven’s lifecycle bindings or your settings.
• Version Flexibility: Relies on the version specified in your POM file or the default version.

mvn org.codehaus.mojo:exec-maven-plugin:3.0.0:java -Dexec.mainClass="dev.selenium.getting_started.XYZ"

Overview:

• Command: mvn org.codehaus.mojo:exec-maven-plugin:3.0.0:java -Dexec.mainClass="dev.selenium.getting_started.XYZ"
• Fully Qualified Plugin Invocation: org.codehaus.mojo:exec-maven-plugin:3.0.0:java
• Plugin Configuration: Explicitly specifies the group ID, artifact ID, version, and goal of the plugin.
• Usage: Useful when you need to ensure a specific version of the plugin is used or when the plugin is not configured in your pom.xml.

Characteristics:

• Explicit Version Control: Allows you to specify the exact version of the plugin to use, ensuring consistent behavior across different environments.
• Verbose: The command is more verbose and requires more typing, but offers greater control over the plugin version.
• Plugin Independence: Does not rely on the plugin being declared in the pom.xml, making it more flexible for ad-hoc runs or for use in environments where the POM may not be configured with the plugin.

When to Use Which

Use mvn exec:java -Dexec.mainClass="dev.selenium.getting_started.XYZ":

• When you have the exec-maven-plugin configured in your pom.xml and want a simple, quick command to run your Java class.
• When you are okay with using the default version of the exec-maven-plugin provided by your Maven installation or specified in your project’s pom.xml.

Use mvn org.codehaus.mojo:exec-maven-plugin:3.0.0:java -Dexec.mainClass="dev.selenium.getting_started.XYZ":

• When you need to specify a particular version of the exec-maven-plugin to avoid version conflicts or to ensure compatibility.
• When you want to run the plugin without modifying the pom.xml or if the plugin is not declared in the pom.xml.
• For precise control over the plugin version, which can be important in CI/CD pipelines or in environments with specific plugin requirements.

Example Usage Scenarios

1. Quick Run with Defaults:

   mvn exec:java -Dexec.mainClass="dev.selenium.getting_started.XYZ"
   

   • This command is sufficient for most use cases where the plugin version and configuration are managed in the POM file.

2. Specific Plugin Version:

   mvn org.codehaus.mojo:exec-maven-plugin:3.0.0:java -Dexec.mainClass="dev.selenium.getting_started.XYZ"
   

   • Use this command if you need to ensure you are using version 3.0.0 of the exec-maven-plugin.

By understanding the differences and use cases for these commands, you can choose the most appropriate one for your needs.