Java好用的工具类

IP地址获取

public class IPUtil {

    private static final String UNKNOWN = "unknown";

    protected IPUtil(){

    }

    /**
     * 获取 IP地址
     * 使用 Nginx等反向代理软件， 则不能通过 request.getRemoteAddr()获取 IP地址
     * 如果使用了多级反向代理的话，X-Forwarded-For的值并不止一个，而是一串IP地址，
     * X-Forwarded-For中第一个非 unknown的有效IP字符串，则为真实IP地址
     */
    public static String getIpAddr(HttpServletRequest request) {
        String ip = request.getHeader("x-forwarded-for");
        if (StringUtils.isNotEmpty(ip)) {
            ip = ip.split(", ")[0];
        }
        if (ip == null || ip.length() == 0 || UNKNOWN.equalsIgnoreCase(ip)) {
            ip = request.getHeader("Proxy-Client-IP");
        }
        if (ip == null || ip.length() == 0 || UNKNOWN.equalsIgnoreCase(ip)) {
            ip = request.getHeader("WL-Proxy-Client-IP");
        }
        if (ip == null || ip.length() == 0 || UNKNOWN.equalsIgnoreCase(ip)) {
            ip = request.getRemoteAddr();
        }
        return "0:0:0:0:0:0:0:1".equals(ip) ? "127.0.0.1" : ip;
    }

}

 获取上个月月份字符串

public static final String getLastMonth() {
        SimpleDateFormat format = new SimpleDateFormat("yyyy-MM");
        Date date = new Date();
        Calendar calendar = Calendar.getInstance();
        // 设置为当前时间
        calendar.setTime(date);
        // 设置为上一个月
        calendar.add(Calendar.MONTH,-1);
        date = calendar.getTime();
        return format.format(date);
    }