春天单身人士与财产

Question

我想根据提供的网络接口创建一个包含运行系统MAC地址的单例。

我写了以下代码：

public class NodeMac {

    private static final String INSTANCE = getMacAddress();

    private static String networkInterfaceName;

    @Value("${machine.network.interface}")
    public void setNetworkInterfaceName(String networkInterfaceName) {
        NodeMac.networkInterfaceName = networkInterfaceName;
    }

    private NodeMac() { }

    public static String getInstance() {
        return INSTANCE;
    }

    private static String getMacAddress() {
        try {
            NetworkInterface network = NetworkInterface.getByName(networkInterfaceName);

            byte[] mac = network.getHardwareAddress();

            System.out.print("Current MAC address : ");

            StringBuilder sb = new StringBuilder();
            for (int i = 0; i < mac.length; i++) {
                sb.append(String.format("%02X%s", mac[i], (i < mac.length - 1) ? "-" : ""));
            }
            return sb.toString();
        } catch (SocketException | NullPointerException e) {
            throw new RuntimeException(
                    "Failed to extract MAC address for network interface with name " + networkInterfaceName, e);
        }
    }
}

在application.properties中：

machine.network.interface=eno1

但是，我找不到任何方法来获取包含网络接口名称的属性值。无论我如何尝试访问它，它始终为null。

这样做的正确方法是什么？在单身人士中拥有属性是一种反模式吗？

Answer 1

修改

所以你正在努力用注入的@Value创建单实例pojo类。如果你可以使用bean，那么这就是要走的路：

@Component // This will default give you a single ton bean
public class NodeMac {

    @Value("${machine.network.interface}")
    private String networkInterfaceName;

    public String getMacAddress() {
        try {
            NetworkInterface network = NetworkInterface.getByName(networkInterfaceName);

            byte[] mac = network.getHardwareAddress();

            System.out.print("Current MAC address : ");

            StringBuilder sb = new StringBuilder();
            for (int i = 0; i < mac.length; i++) {
                sb.append(String.format("%02X%s", mac[i], (i < mac.length - 1) ? "-" : ""));
            }
            return sb.toString();
        } catch (SocketException | NullPointerException e) {
            throw new RuntimeException(
                    "Failed to extract MAC address for network interface with name " + networkInterfaceName, e);
        }
    }
}

<强> OLD

你怎么想出这个表达方式：

String key = System.getProperty("machine.network.interface");

该机器不太可能只有一个网络接口，因此无法返回单个密钥。

确实，oracle已经写了tutorial here

public static void main(String args[]) throws SocketException {
    Enumeration<NetworkInterface> nets = NetworkInterface.getNetworkInterfaces();
    for (NetworkInterface netint : Collections.list(nets))
        displayInterfaceInformation(netint);
}

static void displayInterfaceInformation(NetworkInterface netint) throws SocketException {
    out.printf("Display name: %s\n", netint.getDisplayName());
    out.printf("Name: %s\n", netint.getName());
    Enumeration<InetAddress> inetAddresses = netint.getInetAddresses();
    for (InetAddress inetAddress : Collections.list(inetAddresses)) {
        out.printf("InetAddress: %s\n", inetAddress);
    }
    out.printf("\n");
 }