获取系统环境中的变量

import org.apache.log4j.Logger;

public class SystemUtil {
	private static final Logger logger = Logger.getLogger(SystemUtil.class);

	/**
	 * 当前系统环境变量名称
	 */
	public static final String SYSTEM_PROPERTY = "BACK_CONFIG";

	/**
	 * 从当前系统环境变量中获得配置文件路径
	 * 
	 * @return
	 */
	public static String getConfigPath() {
		return SystemUtil
				.resolveSystemProperty(SystemUtil.SYSTEM_PROPERTY);
	}

	public static String resolveSystemProperty(String key) {
		try {
			String value = System.getProperty(key);
			if (value == null) {
				value = System.getenv(key);
			}
			return value;
		} catch (Throwable ex) {
			logger.error("获得系统环境变量失败,key=" + key, ex);
			return null;
		}
	}
}