maven属性表示
属性描述${basedir}项目根目录${version}项目版本${project.build.sourceDirectory}${project.build.testsourceDirectory}${project.build.directory}target${project.outputDirectory}target/classes${project.testOutputDirectory}target/test-classes${project.groupId}${project.artifactId}${project.version}与${version}同${project.build.finalName}