When you develop a stand-alone Java application, Maven can create the executable jar for you, with main-class and classpath manifest entries. You just need the configuration of the maven-jar-plugin shown below.

The sample pom.xml also specifies that we use Java 7 and UTF-8. You can take out the sourceEncoding and maven-compiler-plugin configurations, if you want to go with defaults instead.

<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>net.doepner</groupId>
    <artifactId>executable-jar-sample</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.0</version>
                <configuration>
                    <source>1.7</source>
                    <target>1.7</target>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-jar-plugin</artifactId>
                <version>2.4</version>
                <configuration>
                    <archive>
                        <manifest>
                            <addClasspath>true</addClasspath>
                            <mainClass>net.doepner.sample.Main</mainClass>
                        </manifest>
                    </archive>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>

Here is a matching minimal main class, src/main/java/net/doepner/sample/Main.java:

package net.doepner.sample;

import javax.swing.JOptionPane;

/**
 * The class that has the main method
 */
public class Main {

    public static void main(String[] args) {
        JOptionPane.showMessageDialog(null, "It works!");
    }
}

On all the pages of my webapp I want to see when the WAR was built (i.e. a build timestamp). Here is how I did it:

Add this to the pom.xml of your webapp module:

<build>
  <resources>
    <resource>
      <directory>src/main/resources</directory>
      <filtering>true</filtering>
    </resource>
  </resources>
</build> 

<properties>
  <mavenBuildTimestamp>${maven.build.timestamp}</mavenBuildTimestamp>
</properties>

Create a file src/main/resources/build.properties in  in your webapp module with the following content:

# Build Time Information
build.timestamp=${mavenBuildTimestamp}

The Maven build will replace the Maven property and the resulting file WEB-INF/classes/build.properties will look like this:

# Build Time Information
build.timestamp=20101016-0303

Now we just need a Spring PropertiesFactoryBean definition to make properties available at runtime:

<bean id="appProperties" class="org.springframework.beans.factory.config.PropertiesFactoryBean">
  <property name="locations">
    <list>
      <value>classpath:build.properties</value>
    </list>
  </property>
</bean>

I used a simple Spring bean to make the timestamp easily available in Spring Web Flow / Spring Faces EL expressions:

@Component
public class ViewUtil {

  private Properties appProperties;

  /**
   * @param appProperties Global Application properties
   */
  @Resource
  public void setAppProperties(Properties appProperties) {
    this.appProperties = appProperties;
  }

  /**
   * @return The Build Timestamp as generated by Maven
   */
  public String getBuildTimestamp() {
    return appProperties.getProperty("build.timestamp", "UNKNOWN");
  }
}

The EL expression code in the JSF page is then something like this:

Build timestamp: #{viewUtil.buildTimestamp} 

And this is what the result looks like on the page:

If you want to be able to refer to properties directly by name in your Spring configuration you can define a Spring PropertyPlaceholderConfigurer:

<bean id="propertyConfigurer"
      class="org.springframework.web.context.support.ServletContextPropertyPlaceholderConfigurer">
  <property name="properties" ref="appProperties" />
</bean>

If you use test-jar dependencies in a multi-module Maven project (see my previous posting) you will run into a problem when you run Maven install with the maven.test.skip option turned on.

Problem

Maven looks for dependencies on test-jars even when maven.test.skip is turned on. This posting on the Maven issue tracker site perfectly summarizes the problem.

The maven.test.skip option (which is equivalent to the ‘Skip tests’ checkbox in IntelliJ’s Maven Runner options) prevents test code compilation, packaging and execution.

Hence no test-jars are built and that leads to the dependency error described above.

Solution

Disable the ‘Skip Tests’ checkbox in IntelliJ and INSTEAD add a property skipTests with value true.

This causes all test code to be built (and packaged as test-jars – when configured as described in my last posting) and only disables the execution of the tests.

Maven test execution options

maven.test.skip
Disables both running the tests and compiling the tests.

skipTests
Set this to true to skip running tests, but still compile them

In a multi module Maven project you might want to reuse test-related code (in src/test) across modules.

The recommended way is described here:
http://maven.apache.org/guides/mini/guide-attached-tests.html

You might want to exclude test classes from test-jar, to prevent that they run multiple times. Add this to your maven-jar-plugin definition (right after the <goals>..</goals> section) :

<configuration>
    <excludes>
        <exclude>**/*Test.class</exclude>
    </excludes>
</configuration>

This assumes that your test classes and only your test classes are named “…Test”.

More info on maven-jar-plugin configuration options for the test-jar goal:
http://maven.apache.org/plugins/maven-jar-plugin/test-jar-mojo.html