Apache Maven Resources Plugin

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The Apache Maven Resources Plugin is essential for copying resources from one directory to another during the build process of your Maven project. This guide will walk you through configuring and using the Maven Resources Plugin with a complete example.

Introduction to Maven Resources Plugin

The Maven Resources Plugin handles the copying of project resources (e.g., configuration files, images, etc.) from the src/main/resources and src/test/resources directories to the target/classes and target/test-classes directories, respectively.

Latest Version

As of this writing, the latest version of the Maven Resources Plugin is 3.2.0. Using the latest version ensures access to the newest features and bug fixes.

Setting Up the Maven Resources Plugin

To use the Maven Resources Plugin, you need to configure it in your project's pom.xml file. Let's go through the steps to set up a complete Maven project with the Resources Plugin.

Step 1: Create a Maven Project

Run the following command to create a new Maven project:

mvn archetype:generate -DgroupId=com.example -DartifactId=resources-plugin-demo -DarchetypeArtifactId=maven-archetype-quickstart -DinteractiveMode=false

This command will generate a simple Maven project with the following structure:

resources-plugin-demo
|-- src
|   |-- main
|   |   |-- java
|   |   |   `-- com
|   |   |       `-- example
|   |   |           `-- App.java
|   |   `-- resources
|   |       `-- config.properties
|   `-- test
|       |-- java
|       |   `-- com
|       |       `-- example
|       |           `-- AppTest.java
|       `-- resources
|           `-- test-config.properties
|-- pom.xml
`-- target

Step 2: Add Maven Resources Plugin Configuration

Navigate to the project directory and open the pom.xml file. Add the Maven Resources Plugin configuration inside the <build> section:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.example</groupId>
    <artifactId>resources-plugin-demo</artifactId>
    <version>1.0-SNAPSHOT</version>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-resources-plugin</artifactId>
                <version>3.2.0</version>
                <executions>
                    <execution>
                        <id>default-resources</id>
                        <phase>process-resources</phase>
                        <goals>
                            <goal>resources</goal>
                        </goals>
                    </execution>
                    <execution>
                        <id>default-testResources</id>
                        <phase>process-test-resources</phase>
                        <goals>
                            <goal>testResources</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

Explanation

  • <groupId>: Specifies the group ID for the Maven Resources Plugin.
  • <artifactId>: Specifies the Maven Resources Plugin.
  • <version>: The version of the plugin you are using. Ensure you use the latest version.
  • <executions>: Defines the plugin executions.
    • <execution>: Specifies an execution of the plugin.
      • <id>: A unique identifier for the execution.
      • <phase>: The build lifecycle phase during which this execution should be run.
      • <goals>: The goals to be executed during this phase.

Step 3: Add Resources to src/main/resources

Create a file named config.properties in the src/main/resources directory with the following content:

app.name=Resources Plugin Demo
app.version=1.0-SNAPSHOT

Step 4: Add Resources to src/test/resources

Create a file named test-config.properties in the src/test/resources directory with the following content:

test.name=Resources Plugin Test
test.version=1.0-SNAPSHOT

Step 5: Modify the App.java to Load Resources

Open src/main/java/com/example/App.java and modify it to load and print the properties from config.properties:

package com.example;

import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;

public class App {
    public static void main(String[] args) {
        Properties properties = new Properties();
        try (InputStream input = App.class.getClassLoader().getResourceAsStream("config.properties")) {
            if (input == null) {
                System.out.println("Sorry, unable to find config.properties");
                return;
            }
            properties.load(input);
            System.out.println("App Name: " + properties.getProperty("app.name"));
            System.out.println("App Version: " + properties.getProperty("app.version"));
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }
}

Step 6: Build and Run the Project

Run the following command to build the project and process the resources:

mvn clean package

Execute the packaged JAR file to see the output from config.properties:

java -jar target/resources-plugin-demo-1.0-SNAPSHOT.jar

You should see the following output:

App Name: Resources Plugin Demo
App Version: 1.0-SNAPSHOT

Complete Example

Here is the complete pom.xml file for the example project:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.example</groupId>
    <artifactId>resources-plugin-demo</artifactId>
    <version>1.0-SNAPSHOT</version>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-resources-plugin</artifactId>
                <version>3.2.0</version>
                <executions>
                    <execution>
                        <id>default-resources</id>
                        <phase>process-resources</phase>
                        <goals>
                            <goal>resources</goal>
                        </goals>
                    </execution>
                    <execution>
                        <id>default-testResources</id>
                        <phase>process-test-resources</phase>
                        <goals>
                            <goal>testResources</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

Conclusion

The Maven Resources Plugin is a crucial tool for managing resources in your Maven projects. This guide provided a complete example of setting up and using the Maven Resources Plugin, helping you efficiently handle resource copying during the build process. By following these steps, you can easily manage resources for your Maven projects.

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