如何使用属性文件在web.xml中设置值？

jdbc.url=jdbc:mysql://localhost:3306/mydb
jdbc.username=root
jdbc.password=password

import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;

public class Config {
    private static Properties properties;

    static {
        properties = new Properties();
        try {
            InputStream inputStream = Config.class.getClassLoader().getResourceAsStream("config.properties");
            properties.load(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static String getProperty(String key) {
        return properties.getProperty(key);
    }
}

   <param-name>jdbcUrl</param-name>
   <param-value>${jdbc.url}</param-value>
</context-param><context-param>
   <param-name>jdbcUsername</param-name>
   <param-value>${jdbc.username}</param-value>
</context-param><context-param>
   <param-name>jdbcPassword</param-name>
   <param-value>${jdbc.password}</param-value>
</context-param>

String jdbcUrl = Config.getProperty("jdbc.url");
String jdbcUsername = Config.getProperty("jdbc.username");
String jdbcPassword = Config.getProperty("jdbc.password");