Specify system property to Maven project

Is there a way ( I mean how do I ) set a system property in a maven project?

I want to access a property from my test and my webapp ( running locally ) and I know I can use a java sys开发者_如何学Ctem property.

Should I put that in ./settings.xml or something like that?

Context

I took an open source project and managed to change the db configuration to use JavaDB

Now, in the jdbc url for JavaDB, the location of the database could be specified as the full path ( see: this other question )

Or a system property: derby.system.home

I have the code working already, but currently it is all hardcoded to:

 jdbc:derby:/Users/oscarreyes/javadbs/mydb

And I want to remove the full path, to leave it like:

 jdbc:derby:mydb

To do that I need to specify the system property ( derby.system.home ) to maven, but I don't know how.

The test are performed using junit ( I don't see any plugin in pom.xml ) and the web app runs with the jetty plugin.

Specifying the system property in the command line seems to work for jetty, but I'm not sure if that's something practical ( granted some other users may run it from eclipse/idea/ whatever )

Is there a way ( I mean how do I ) set a system property in a maven project? I want to access a property from my test [...]

You can set system properties in the Maven Surefire Plugin configuration (this makes sense since tests are forked by default). From Using System Properties:

<project>
  [...]
  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-surefire-plugin</artifactId>
        <version>2.5</version>
        <configuration>
          <systemPropertyVariables>
            <propertyName>propertyValue</propertyName>
            <buildDirectory>${project.build.directory}</buildDirectory>
            [...]
          </systemPropertyVariables>
        </configuration>
      </plugin>
    </plugins>
  </build>
  [...]
</project>

and my webapp ( running locally )

Not sure what you mean here but I'll assume the webapp container is started by Maven. You can pass system properties on the command line using:

mvn -DargLine="-DpropertyName=propertyValue"

Update: Ok, got it now. For Jetty, you should also be able to set system properties in the Maven Jetty Plugin configuration. From Setting System Properties:

<project>
  ...
  <plugins>
    ...
      <plugin>
        <groupId>org.mortbay.jetty</groupId>
        <artifactId>maven-jetty-plugin</artifactId>
        <configuration>
         ...
         <systemProperties>
            <systemProperty>
              <name>propertyName</name>
              <value>propertyValue</value>
            </systemProperty>
            ...
         </systemProperties>
        </configuration>
      </plugin>
  </plugins>
</project>

properties-maven-plugin plugin may help:

<plugin>
    <groupId>org.codehaus.mojo</groupId>
    <artifactId>properties-maven-plugin</artifactId>
    <version>1.0.0</version>
    <executions>
        <execution>
            <goals>
                <goal>set-system-properties</goal>
            </goals>
            <configuration>
                <properties>
                    <property>
                        <name>my.property.name</name>
                        <value>my property value</value>
                    </property>
                </properties>
            </configuration>
        </execution>
    </executions>
</plugin>

I have learned it is also possible to do this with the exec-maven-plugin if you're doing a "standalone" java app.

            <plugin>
            <groupId>org.codehaus.mojo</groupId>
            <artifactId>exec-maven-plugin</artifactId>
            <version>${maven.exec.plugin.version}</version>
            <executions>
                <execution>
                    <goals>
                        <goal>java</goal>
                    </goals>
                </execution>
            </executions>
            <configuration>
                <mainClass>${exec.main-class}</mainClass>
                <systemProperties>
                    <systemProperty>
                        <key>myproperty</key>
                        <value>myvalue</value>
                    </systemProperty>
                </systemProperties>
            </configuration>
        </plugin>

If your test and webapp are in the same Maven project, you can use a property in the project POM. Then you can filter certain files which will allow Maven to set the property in those files. There are different ways to filter, but the most common is during the resources phase - http://books.sonatype.com/mvnref-book/reference/resource-filtering-sect-description.html

If the test and webapp are in different Maven projects, you can put the property in settings.xml, which is in your maven repository folder (C:\Documents and Settings\username.m2) on Windows. You will still need to use filtering or some other method to read the property into your test and webapp.