一、随机数值与集合抽样处理器

该组件封装了固定位数验证码的生成逻辑，并提供从数据源中无重复抽取指定样本的高效算法。底层采用洗牌算法替代原有的低效哈希映射方案，显著提升随机采样的准确性与执行效率。

import java.text.DecimalFormat;
import java.util.*;

public class RandomHelper {
    private static final Random GENERATOR = new Random();
    private static final DecimalFormat FMT_4 = new DecimalFormat("0000");
    private static final DecimalFormat FMT_6 = new DecimalFormat("000000");

    public static String createFourDigits() {
        return FMT_4.format(GENERATOR.nextInt(10000));
    }

    public static String createSixDigits() {
        return FMT_6.format(GENERATOR.nextInt(1000000));
    }

    public static <T> List<T> sampleElements(List<T> source, int count) {
        if (source == null || source.isEmpty()) {
            return Collections.emptyList();
        }
        List<T> copy = new ArrayList<>(source);
        Collections.shuffle(copy, GENERATOR);
        int limit = Math.min(count, copy.size());
        return new ArrayList<>(copy.subList(0, limit));
    }
}

二、统一网络请求执行客户端

基于 Apache HttpClient 构建的轻量级通信类，整合了 GET/POST 请求构造、表单数据提交、原始报文发送、连接超时控制以及 HTTPS 证书信任绕过功能。采用资源自动释放机制，避免连接泄漏，适用于常规 API 调用与第三方服务对接。

import org.apache.http.*;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.*;
import org.apache.http.conn.ssl.*;
import org.apache.http.entity.ContentType;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;
import javax.net.ssl.SSLContext;
import java.nio.charset.StandardCharsets;
import java.util.*;

public class NetworkCaller {
    private final RequestConfig requestConf;

    public NetworkCaller(int connectMs, int readMs) {
        this.requestConf = RequestConfig.custom()
                .setConnectTimeout(connectMs)
                .setSocketTimeout(readMs)
                .build();
    }

    public String fetchGet(String endpoint) throws Exception {
        HttpGet req = new HttpGet(endpoint);
        req.setConfig(requestConf);
        try (CloseableHttpClient client = buildClient(endpoint.startsWith("https"))) {
            HttpResponse res = client.execute(req);
            return EntityUtils.toString(res.getEntity(), StandardCharsets.UTF_8);
        }
    }

    public String submitForm(String endpoint, Map<String, String> params) throws Exception {
        HttpPost req = new HttpPost(endpoint);
        req.setConfig(requestConf);
        List<NameValuePair> pairList = new ArrayList<>();
        for (Map.Entry<String, String> entry : params.entrySet()) {
            pairList.add(new BasicNameValuePair(entry.getKey(), entry.getValue()));
        }
        req.setEntity(new UrlEncodedFormEntity(pairList, StandardCharsets.UTF_8));
        try (CloseableHttpClient client = buildClient(endpoint.startsWith("https"))) {
            HttpResponse res = client.execute(req);
            return EntityUtils.toString(res.getEntity(), StandardCharsets.UTF_8);
        }
    }

    public String sendRawPost(String endpoint, String payload, String mime) throws Exception {
        HttpPost req = new HttpPost(endpoint);
        req.setConfig(requestConf);
        if (payload != null && !payload.trim().isEmpty()) {
            ContentType ct = mime != null ? ContentType.create(mime, StandardCharsets.UTF_8) : ContentType.APPLICATION_JSON;
            req.setEntity(new StringEntity(payload, ct));
        }
        try (CloseableHttpClient client = buildClient(endpoint.startsWith("https"))) {
            HttpResponse res = client.execute(req);
            return EntityUtils.toString(res.getEntity(), StandardCharsets.UTF_8);
        }
    }

    private CloseableHttpClient buildClient(boolean bypassCert) throws Exception {
        if (bypassCert) {
            SSLContext ctx = new org.apache.http.ssl.SSLContextBuilder()
                    .loadTrustMaterial(null, (chain, authType) -> true).build();
            SSLConnectionSocketFactory factory = new SSLConnectionSocketFactory(ctx, NoopHostnameVerifier.INSTANCE);
            return HttpClients.custom().setSSLSocketFactory(factory).build();
        }
        return HttpClients.custom().setDefaultRequestConfig(requestConf).build();
    }
}

三、分布式交易流水号生成器

针对订单或交易场景设计的唯一标识构造方法。通过线程安全的日期格式化与伪随机数结合，输出"年月日时分秒+三位随机数"格式的业务主键，有效降低多线程并发下的碰撞概率。

import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.concurrent.ThreadLocalRandom;

public class TradeSequenceUtils {
    private static final ThreadLocal<SimpleDateFormat> FMT =
            ThreadLocal.withInitial(() -> new SimpleDateFormat("yyyyMMddHHmmss"));

    public static String generateOrderSn() {
        String timeStr = FMT.get().format(new Date());
        int randomTail = ThreadLocalRandom.current().nextInt(1000);
        return String.format("%s%03d", timeStr, randomTail);
    }
}

四、日历计算与日期渲染组件

提供标准的日期转字符串功能，支持按天维度的前后推算。内部采用实例化隔离策略，确保在多线程环境下的格式化安全，适用于日志记录、数据过滤与时效性校验。

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

public class TimeProcessor {
    private static final String PATTERN = "yyyy-MM-dd";

    public static String renderDate(Date input) {
        return new SimpleDateFormat(PATTERN).format(input);
    }

    public static Date adjustDays(Date origin, int offset) {
        Calendar cal = Calendar.getInstance();
        cal.setTime(origin);
        cal.add(Calendar.DATE, offset);
        return cal.getTime();
    }
}