如何使用属性-maven-插件？

我想使用属性-maven-plugin。我阅读了用法 http://mojohaus.org/properties-maven-plugin/usage.html，但它对我不起作用。

我创建了一个非常简单的项目来测试它。这是我的绒球.xml：

<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>test</groupId>
  <artifactId>MavenTest</artifactId>
  <version>1.0.0</version>
  <name>MavenTest</name>

  <properties>
    <prop1>2.2</prop1>
  </properties>

  <dependencies>
    <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-api</artifactId>
            <version>${log4j.version}</version>
        </dependency>
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-core</artifactId>
            <version>${log4j.version}</version>
        </dependency>
  </dependencies>

  <build>
    <plugins>
            <plugin>
                <groupId>org.codehaus.mojo</groupId>
                <artifactId>properties-maven-plugin</artifactId>
                <version>1.0-alpha-2</version>
                <executions>
                    <execution>
                        <phase>initialize</phase>
                        <goals>
                            <goal>read-project-properties</goal>
                        </goals>
                        <configuration>
                            <files>
                                <file>${basedir}/my.properties</file>
                            </files>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    <pluginManagement>
        <plugins>
            <!--This plugin's configuration is used to store Eclipse m2e settings only. It has no influence on the Maven build itself.-->
            <plugin>
                <groupId>org.eclipse.m2e</groupId>
                <artifactId>lifecycle-mapping</artifactId>
                <version>1.0.0</version>
                <configuration>
                    <lifecycleMappingMetadata>
                        <pluginExecutions>
                            <pluginExecution>
                                <pluginExecutionFilter>
                                    <groupId>
                                        org.codehaus.mojo
                                    </groupId>
                                    <artifactId>
                                        properties-maven-plugin
                                    </artifactId>
                                    <versionRange>
                                        [1.0-alpha-2,)
                                    </versionRange>
                                    <goals>
                                        <goal>
                                            read-project-properties
                                        </goal>
                                    </goals>
                                </pluginExecutionFilter>
                                <action>
                                    <ignore></ignore>
                                </action>
                            </pluginExecution>
                        </pluginExecutions>
                    </lifecycleMappingMetadata>
                </configuration>
            </plugin>
        </plugins>
    </pluginManagement>
  </build>
</project>

如果我运行 mvn 编译，或者 mvn 安装，结果是：

[ERROR] The build could not read 1 project -> [Help 1]
org.apache.maven.project.ProjectBuildingException: Some problems were encountered while processing the POMs:
[ERROR] 'dependencies.dependency.version' for org.apache.logging.log4j:log4j-api:jar must be a valid version but is   '${log4j.version}'. @ line 16, column 13

“my.properties”文件包含以下内容：

 log4j.version=2.2    

正如这里所描述的：mojohaus

如果我使用 prop1 属性，它是在 pom.xml 中定义的，一切都在工作正常。

那么我做错了什么呢？