使用Dom4j无法读取pom的版本或其他属性？

Question

我正在尝试使用dom4j读取pom.xml。文档正在被解析并成功创建，但我无法读取标记。

的pom.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>com.cycorax</groupId>
    <artifactId>test-version</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.7</maven.compiler.source>
        <maven.compiler.target>1.7</maven.compiler.target>
    </properties>

    <build>
        <plugins>
            <plugin>
                <groupId>org.codehaus.mojo</groupId>
                <artifactId>exec-maven-plugin</artifactId>
                <version>1.2.1</version>
                <executions>
                    <execution>
                        <goals>
                            <goal>java</goal>
                        </goals>
                    </execution>
                </executions>
                <configuration>
                    <mainClass>com.cycorax.AspenVersionMain</mainClass>
                </configuration>
            </plugin>
        </plugins>
    </build>

    <dependencies>
        <!-- https://mvnrepository.com/artifact/dom4j/dom4j -->
        <dependency>
            <groupId>dom4j</groupId>
            <artifactId>dom4j</artifactId>
            <version>1.6</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/jaxen/jaxen -->
        <dependency>
            <groupId>jaxen</groupId>
            <artifactId>jaxen</artifactId>
            <version>1.1.6</version>
        </dependency>

    </dependencies>

</project>

我的java代码：

private static void updateVersion(String pomFile) throws DocumentException {
        System.out.println(pomFile);
        File inputFile = new File(pomFile);
        SAXReader reader = new SAXReader();
        Document document = reader.read(inputFile);
        System.out.println("Root element : "
                + document.getRootElement().getName());
        Document classElement = document.getRootElement().getDocument();
        System.out.println(classElement.selectNodes("version"));
        System.out.println(classElement.selectSingleNode("version"));
        System.out.println(document.selectNodes("project/version"));
        System.out.println(document.selectSingleNode("project/version"));
    }

代码输出：

H:\Java\test-version\dir\pom.xml
Root element : project
[]
null
[]

请帮助为什么它无法阅读其他标签。