如何从父pom.xml的配置文件中提取属性数据？

Question

I have a big Java project and each sub-part of the project has a child pom.xml. The parent pom has key data I want, username and password. My question is how can I extract this data from a parent pom.xml in my java program?

The parent pom.xml has numerous profiles in the profile section where the data is that I need. I found a similar example that said to simply code System.getProperty('property.name'); When I tried this the code just returned null though. I think it is because I ran the code from the target directory and not through Maven, but I could be completely wrong about this.

Does anyone know what I am missing?

Regards,

Answer 1

Maven is a build tool (and much more). Your program does not know its existence. The example you probably refer to, uses some system property which is available to both maven and your code. You can refer to system properties in maven. Its easy.

see reference

Any property which can be retrieved from the System.getProperty() method can be referenced as a Maven property.

Answer 2

My answer would clearly oppose the one that @grid suggested. Although Maven is a build tool, but it is also such a goodness that it can afford any functionality when you deeply think about it.

There was once a time where I needed to hook a custom properties file and ask Maven to filter it with project properties then read input that file content within the source code as a java.util.Properties .

Now that part is over I suppose, since all the burden is done for you by the Properties Maven Plugin which has a cutom goal, " set-system-properties ", that can make project properties (those used in by Maven and which are said to be build-time properties) available as runtime-properties and more precisely as System Properties .

You can add a custom plugin configuration snippet within your build section, the one in your child project, that may look as follows:

<project>
  <build>
    <plugins>
      <plugin>
        <groupId>org.codehaus.mojo</groupId>
        <artifactId>properties-maven-plugin</artifactId>
        <version>1.0-alpha-2</version>
        <executions>
          <execution>
            <goals>
              <goal>set-system-properties</goal>
            </goals>
            <configuration>
              <properties>
                <property>
                  <name>property.name</name>
                  <value>${project.version}</value>
                </property>
              </properties>
            </configuration>
          </execution>
        </executions>
      </plugin>
    </plugins>
  </build>
</project>

Although you can have any value set to your property, note the usage of the placeholder ${...} so that Maven resolves the property when the project descriptors are interpolated. You can the reference any property such a way, then have it available at runtime as you suggested in your main post:

package com.github.tmarwen.stackoverflow.maven.properties.showcase;

public Main {
  public static void main( String... args ) {
    String value = System.getProperty( "property.name" );
    System.out.print( value );
  }
}