前言本文是博主從事後端開發以來，對公司、個人項目的經驗總結，包含代碼編寫、功能推薦、第三方庫使用及優雅配置等，希望大家看到都能有所收穫博主github地址: https://github.com/wayn111 一. 優雅的進行線程池異常處理在Java開發中，線程池的使用必不可少，使用無返回值 ...

前言

本文是博主從事後端開發以來，對公司、個人項目的經驗總結，包含代碼編寫、功能推薦、第三方庫使用及優雅配置等，希望大家看到都能有所收穫

博主github地址: https://github.com/wayn111

一. 優雅的進行線程池異常處理

在Java開發中，線程池的使用必不可少，使用無返回值 execute() 方法時，線程執行發生異常的話，需要記錄日誌，方便回溯，一般做法是線上程執行方法內 try/catch 處理，如下：

@Test
public void test() throws Exception {
    ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(5, 10, 60,
            TimeUnit.SECONDS, new ArrayBlockingQueue<>(100000));
    Future<Integer> submit = threadPoolExecutor.execute(() -> {
        try {
            int i = 1 / 0;
            return i;
        } catch (Exception e) {
            log.error(e.getMessage(), e);
            return null;
        }
    });
}

但是當線程池調用方法很多時，那麼每個線程執行方法內都要 try/catch 處理，這就不優雅了，其實ThreadPoolExecutor類還支持傳入 ThreadFactory 參數，自定義線程工廠，在創建 thread 時，指定 setUncaughtExceptionHandler 異常處理方法，這樣就可以做到全局處理異常了，代碼如下：

ThreadFactory threadFactory = r -> {
    Thread thread = new Thread(r);
    thread.setUncaughtExceptionHandler((t, e) -> {
        // 記錄線程異常
        log.error(e.getMessage(), e);
    });
    return thread;
};
ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(5, 10, 60,
        TimeUnit.SECONDS, new ArrayBlockingQueue<>(100000),
        threadFactory);
threadPoolExecutor.execute(() -> {
    log.info("---------------------");
    int i = 1 / 0;
});

二. 線程池決絕策略設置錯誤導致業務介面執行超時

先介紹下線程池得四種決絕策略

AbortPolicy：丟棄任務並拋出RejectedExecutionException異常，這是線程池預設的拒絕策略
DiscardPolicy：丟棄任務，但是不拋出異常。如果線程隊列已滿，則後續提交的任務都會被丟棄，且是靜默丟棄。
使用此策略，可能會使我們無法發現系統的異常狀態。建議是一些無關緊要的業務採用此策略
DiscardOldestPolicy：丟棄隊列最前面的任務，然後重新提交被拒絕的任務。此拒絕策略，是一種喜新厭舊的拒絕策略。是否要採用此種拒絕策略，還得根據實際業務是否允許丟棄老任務來認真衡量。
CallerRunsPolicy：由調用線程處理該任務

如下是一個線上業務介面使用得線程池配置，決絕策略採用 CallerRunsPolicy

// 某個線上線程池配置如下
ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(
                50, // 最小核心線程數
                50, // 最大線程數，當隊列滿時，能創建的最大線程數
                60L, TimeUnit.SECONDS, // 空閑線程超過核心線程時，回收該線程的最大等待時間
                new LinkedBlockingQueue<>(5000), // 阻塞隊列大小,當核心線程使用滿時，新的線程會放進隊列
            new CustomizableThreadFactory("task"), // 自定義線程名
                new ThreadPoolExecutor.CallerRunsPolicy() // 線程執行的拒絕策略
        );

在某些情況下，子線程任務調用第三方介面超時，導致核心線程數、最大線程數占滿、阻塞隊列占滿的情況下執行拒絕策略時，由於使用 CallerRunsPolicy 策略，導致業務線程執行子任務時繼續超時，進而導致介面執行異常，這種情況下，考慮到子線程任務得重要性，不是很重要得話，可以使用 DiscardPolicy 策略，要是很重要，可以發送到消息隊列中持久化子線程任務數據待後續處理

三. 優雅的單例模式懶載入幫助類代碼實現

博主推薦通過靜態內部類實現單例模式，並實現懶載入效果，代碼如下

// 使用靜態內部類完成單例模式封裝，避免線程安全問題，避免重覆初始化成員屬性  
@Slf4j  
public class FilterIpUtil {  
  
    private FilterIpUtil() {  
    }  
  
    private List<String> strings = new ArrayList<>();  
  
    // 代碼塊在FilterIpUtil實例初始化時才會執行  
    {  
    
        // 在代碼塊中完成文件的第一次讀寫操作，後續不再讀這個文件
        System.out.println("FilterIpUtil init");  
        try (InputStream resourceAsStream = FilterIpUtil.class.getClassLoader().getResourceAsStream("filterIp.txt")) {  
            // 將文件內容放到string集合中  
            IoUtil.readUtf8Lines(resourceAsStream, strings);  
        } catch (IOException e) {  
            log.error(e.getMessage(), e);  
        }  
    }  
  
    public static FilterIpUtil getInstance() {  
        return InnerClassInstance.instance;  
    }  
    // 使用內部類完成單例模式，由jvm保證線程安全  
    private static class InnerClassInstance {  
        private static final FilterIpUtil instance = new FilterIpUtil();  
    }  
  
    // 判斷集合中是否包含目標參數  
    public boolean isFilter(String arg) {  
        return strings.contains(arg);  
    }  
  
}

四. 使用ip2region實現請求地址解析

在博主之前公司得項目中，ip解析是調用淘寶IP還有聚合IP介面獲取結果，通常耗時200毫秒左右，並且介面不穩定時而會掛。都會影響業務介面耗時，後來在 github 上瞭解到 ip2region 這個項目，使用本地ip庫查詢，查詢速度微秒級別，精準度能達到90%，但是ip庫還是有少部分ip信息不准，建議資料庫中把請求ip地址保存下來。簡介如下：

ip2region v2.0 - 是一個離線IP地址定位庫和IP定位數據管理框架，10微秒級別的查詢效率，提供了眾多主流編程語言的 xdb 數據生成和查詢客戶端實現基於 xdb 文件的查詢，下麵是一個 Spring 項目中 ip2region 幫助類來實現ip地址解析

/**
 * ip2region工具類
 */
@Slf4j
@Component
public class Ip2region {

    private Searcher searcher = null;

    @Value("${ip2region.path:}")
    private String ip2regionPath = "";

    @PostConstruct
    private void init() {
        // 1、從 dbPath 載入整個 xdb 到記憶體。
        String dbPath = ip2regionPath;

        // 1、從 dbPath 載入整個 xdb 到記憶體。
        byte[] cBuff;
        try {
            cBuff = Searcher.loadContentFromFile(dbPath);
            searcher = Searcher.newWithBuffer(cBuff);
        } catch (Exception e) {
            log.error("failed to create content cached searcher: {}", e.getMessage(), e);
        }
    }

    public IpInfoBean getIpInfo(String ip) {
        if (StringUtils.isBlank(ip)) {
            return null;
        }

        // 3、查詢
        try {
            long sTime = System.nanoTime();
            // 國家|區域|省份|城市|ISP
            String region = searcher.search(ip);
            long cost = TimeUnit.NANOSECONDS.toMicros((long) (System.nanoTime() - sTime));
            log.info("{region: {}, ioCount: {}, took: {} μs}", region, searcher.getIOCount(), cost);
            if (StringUtils.isNotBlank(region)) {
                String[] split = region.split("\|");
                IpInfoBean ipInfo = new IpInfoBean();
                ipInfo.setIp(ip);
                if (!"".equals(split[0])) {
                    ipInfo.setCountry(split[0]);
                }
                if (!"".equals(split[2])) {
                    ipInfo.setProvince(split[2]);
                }
                if (!"".equals(split[3])) {
                    ipInfo.setCity(split[3]);
                }
                if (!"".equals(split[4])) {
                    ipInfo.setIsp(split[4]);
                }
                return ipInfo;
            }
        } catch (Exception e) {
            log.error("failed to search({}): {}", ip, e);
            return null;
        }

        // 4、關閉資源 - 該 searcher 對象可以安全用於併發，等整個服務關閉的時候再關閉 searcher
        // searcher.close();

        // 備註：併發使用，用整個 xdb 數據緩存創建的查詢對象可以安全的用於併發，也就是你可以把這個 searcher 對象做成全局對象去跨線程訪問。
        return null;
    }
}

要註意得就是 ip2region v2.0 版本使用的xdb文件不建議放在項目 resources 下一起打包，存在編碼格式問題，建議通過指定路徑載入得方式單獨放在伺服器目錄下

五. 優雅得Springboot + mybatis配置多數據源方式

Springboot + mybatis 得項目中一般通過 @MapperScan 註解配置 dao 層包目錄，來實現 dao 層增強，其實項目中配置一個@MapperScan 是指定一個數據源，配置兩個@MapperScan就可以指定兩個數據源，通過不同得 dao 層包目錄區分，來實現不同數據源得訪問隔離。

比如下麵代碼中，com.xxx.dao.master 目錄下為主數據源 dao 文件，com.xxx.dao.slave 為從數據源 dao 文件，這個方式比網上得基於 aop 加註解得方式更加簡潔好用，也沒有單個方法中使用不同數據源切換得問題，因此推薦這種寫法

/**
 * 主數據源
 */
@Slf4j
@Configuration
@MapperScan(basePackages = {"com.xxx.dao.master"},
        sqlSessionFactoryRef = "MasterSqlSessionFactory")
public class MasterDataSourceConfig {

    @Bean(name = "MasterDataSource")
    @Qualifier("MasterDataSource")
    @ConfigurationProperties(prefix = "spring.datasource.master")
    public DataSource clickHouseDataSource() {
        return DruidDataSourceBuilder.create().build();
    }

    @Bean(name = "MasterSqlSessionFactory")
    public SqlSessionFactory getSqlSessionFactory(@Qualifier("MasterDataSource") DataSource dataSource) throws Exception {
        MybatisSqlSessionFactoryBean sessionFactoryBean = new MybatisSqlSessionFactoryBean();
        sessionFactoryBean.setDataSource(dataSource);
        sessionFactoryBean.setMapperLocations(new PathMatchingResourcePatternResolver()
                .getResources("classpath*:mapper/master/*.xml"));
        log.info("------------------------------------------MasterDataSource 配置成功");
        return sessionFactoryBean.getObject();
    }
}

/**
 * 從數據源
 */
@Slf4j
@Configuration
@MapperScan(basePackages = {"com.xxx.dao.slave"},
        sqlSessionFactoryRef = "SlaveSqlSessionFactory")
public class MasterDataSourceConfig {

    @Bean(name = "SlaveDataSource")
    @Qualifier("SlaveDataSource")
    @ConfigurationProperties(prefix = "spring.datasource.slave")
    public DataSource clickHouseDataSource() {
        return DruidDataSourceBuilder.create().build();
    }

    @Bean(name = "SlaveSqlSessionFactory")
    public SqlSessionFactory getSqlSessionFactory(@Qualifier("SlaveDataSource") DataSource dataSource) throws Exception {
        MybatisSqlSessionFactoryBean sessionFactoryBean = new MybatisSqlSessionFactoryBean();
        sessionFactoryBean.setDataSource(dataSource);
        sessionFactoryBean.setMapperLocations(new PathMatchingResourcePatternResolver()
                .getResources("classpath*:mapper/slave/*.xml"));
        log.info("------------------------------------------SlaveDataSource 配置成功");
        return sessionFactoryBean.getObject();
    }
}

數據源yml配置

spring:
  datasource:
    type: com.alibaba.druid.pool.DruidDataSource
    driverClassName: com.mysql.cj.jdbc.Driver
    # 主庫數據源
    master:
      url: jdbc:mysql://localhost:3306/db1?useUnicode=true&characterEncoding=utf8&zeroDateTimeBehavior=convertToNull&useSSL=true&serverTimezone=GMT%2B8
      username: root
      password:
    slave:
      url: jdbc:mysql://localhost:3306/db2?useUnicode=true&characterEncoding=utf8&zeroDateTimeBehavior=convertToNull&useSSL=true&serverTimezone=GMT%2B8
      username: root
      password:

博主剛開始編碼一、兩年得時候一個項目中遇到了多數據源使用得問題，那時候題主便在網上搜索Spring 多數據源得帖子，大多數都是基於Spring提供得AbstractRoutingDataSource + AOP + 註解 來做動態切換，包括現在流行得 Mybatis plus 官方得多數據源解決方案也是這種做法，這種做法解決了博主當時得多數據源使用問題，後來加了一個需求，在一個定時任務中，查詢兩個數據源得數據，才發現動態切換在單個方法中不好用了，最後使用得原生jdbc數據源解決。多年後，博主在另一家公司得項目中又遇到了多數據源問題，但是這次博主在網上搜索得是Mybatis 多數據源，才發現了這個優雅得解決方案，進而推薦給大家

六. Spring Security項目中，使用MDC實現介面請求調用追蹤，以及用戶ID記錄

MDC介紹

MDC(Mapped Diagnostic Context，映射調試上下文)是 log4j 、logback及log4j2 提供的一種方便在多線程條件下記錄日誌的功能。MDC 可以看成是一個與當前線程綁定的哈希表，可以往其中添加鍵值對。MDC 中包含的內容可以被同一線程中執行的代碼所訪問。當前線程的子線程會繼承其父線程中的 MDC 的內容。當需要記錄日誌時，只需要從 MDC 中獲取所需的信息即可。

雖然MDC能夠方便得實現介面請求調用追蹤功能，但是它在子線程中會丟失父線程中添加得鍵值對信息，解決方法是通過父線程中調用線程池前調用 MDC.getCopyOfContextMap() ，然後在子線程中第一個調用 MDC.setConextMap() 獲取鍵值對信息，完整實現代碼如下：

/**
 * 自定義Spring線程池，解決子線程丟失reqest_id問題
 */
public class ThreadPoolExecutorMdcWrapper extends ThreadPoolTaskExecutor {

    @Override
    public void execute(Runnable task) {
        super.execute(ThreadMdcUtil.wrap(task, MDC.getCopyOfContextMap()));
    }

    @Override
    public <T> Future<T> submit(Callable<T> task) {
        return super.submit(ThreadMdcUtil.wrap(task, MDC.getCopyOfContextMap()));
    }

    @Override
    public Future<?> submit(Runnable task) {
        return super.submit(ThreadMdcUtil.wrap(task, MDC.getCopyOfContextMap()));
    }
}

/**
 * MDC幫助類，添加reqest_id
 */
public class ThreadMdcUtil {


    public static final String REQUEST_ID = "request_id";

    /**
     * 設置請求唯一ID
     */
    public static void setTraceIdIfAbsent() {
        if (MDC.get(REQUEST_ID) == null) {
            MDC.put(REQUEST_ID, IdUtil.getUid());
        }
    }

    /**
     * 存在userId則添加到REQUEST_ID中
     * @param userId
     */
    public static void setUserId(String userId) {
        String s = MDC.get(REQUEST_ID);
        if (s != null) {
            MDC.put(REQUEST_ID, s + "_" + userId);
        }
    }

    public static void removeTraceId() {
        MDC.remove(REQUEST_ID);
    }

    public static <T> Callable<T> wrap(final Callable<T> callable, final Map<String, String> context) {
        return () -> {
            if (context == null) {
                MDC.clear();
            } else {
                MDC.setContextMap(context);
            }
            setTraceIdIfAbsent();
            try {
                return callable.call();
            } finally {
                MDC.clear();
            }
        };
    }

    public static Runnable wrap(final Runnable runnable, final Map<String, String> context) {
        return () -> {
            if (context == null) {
                MDC.clear();
            } else {
                MDC.setContextMap(context);
            }
            // 設置traceId
            setTraceIdIfAbsent();
            try {
                runnable.run();
            } finally {
                MDC.clear();
            }
        };
    }
}

在 Spring Security 中添加 token 過濾器

/**
 * token過濾器 驗證token有效性
 *
 * @author ruoyi
 */
@Slf4j
@Component
public class JwtAuthenticationTokenFilter extends OncePerRequestFilter {

    @Autowired
    private TokenService tokenService;


    @Override
    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain chain)
            throws ServletException, IOException {
        try {
            // 入口傳入請求ID
            ThreadMdcUtil.setTraceIdIfAbsent();
            LoginUserDetail loginUser = tokenService.getLoginUser(request);
            if (Objects.nonNull(loginUser) && Objects.isNull(SecurityContextHolder.getContext().getAuthentication())) {
                // 記錄userId
                ThreadMdcUtil.setUserId(String.valueOf(loginUser.getMember().getId()));
                tokenService.verifyToken(loginUser);
                UsernamePasswordAuthenticationToken authenticationToken = new UsernamePasswordAuthenticationToken(loginUser, null, loginUser.getAuthorities());
                authenticationToken.setDetails(new WebAuthenticationDetailsSource().buildDetails(request));
                SecurityContextHolder.getContext().setAuthentication(authenticationToken);
            }
            chain.doFilter(request, response);
        } finally {
            // 出口移除請求ID
            ThreadMdcUtil.removeTraceId();
        }
    }

}

最後在 logback.xml 中添加 %X{request_id}

<property name="pattern"
          value="%d{yyyy-MM-dd HH:mm:ss.SSS} [%X{request_id}] [%thread] [%-5level] %logger{36}:%L %M - %msg%n"/>

日誌列印效果如下：

2022-11-27 21:29:48.008 [86c76336100c414dbe9217aeb099ccd5_12] [http-nio-82-exec-2] [INFO ] c.w.m.a.s.impl.IHomeServiceImpl:56 getHomeIndexDataCompletableFuture - getHomeIndexDataCompletableFuture:com.wayn.common.util.R@701f7b8e[code=200,msg=操作成功,map={bannerList=[{"createTime":"2020-06-26 19:56:03","delFlag":false,"id":14,"imgUrl":"https://m.360buyimg.com/mobilecms/s700x280_jfs/t1/117335/39/13837/263099/5f291a83E8ba761d0/5c0460445cb28248.jpg!cr_1125x449_0_166!q70.jpg.dpg","jumpUrl":"http://82.157.141.70/mall/#/detail/1155015","sort":0,"status":0,"title":"hh2","updateTime":"2022-06-19 09:16:46"},{"createTime":"2020-06-26 19:56:03","delFlag":false,"id":15,"imgUrl":"https://m.360buyimg.com/mobilecms/s700x280_jfs/t1/202096/26/11652/265782/616acb67E4fcdc9ac/8d7cdfbb6c934e67.jpg!cr_1125x449_0_166!q70.jpg.dpg","jumpUrl":"#/detail/1155015","sort":0,"status":0,"title":"hh","updateTime":"2022-06-19 09:04:58"}], newGoodsList=[{"actualSales":0,"brandId":0,"brief":"酥脆奶香，甜酸回味","categoryId":1008015,"counterPrice":56.00,"createTime":"2018-02-01 00:00:00","delFlag":false,"goodsSn":"1116011","id":1116011,"isHot":true,"isNew":true,"isOnSale":true,"keywords":"","name":"蔓越莓曲奇 200克","picUrl":"http://yanxuan.nosdn.127.net/767b370d07f3973500db54900bcbd2a7.png","retailPrice":36.00,"shareUrl":"","sort":5,"unit":"件","updateTime":"2018-02-01 00:00:00","virtualSales":10},{"actualSales":0,"brandId":0,"brief":"粉彩色澤，記錄生活","categoryId":1012003,"counterPrice":49.00,"createTime":"2018-02-01 00:00:00","delFlag":false,"goodsSn":"1127047","id":1127047,"isHot":false,"isNew":true,"isOnSale":true,"keywords":"","name":"趣味粉彩系列筆記本","picUrl":"http://yanxuan.nosdn.127.net/6c03ca93d8fe404faa266ea86f3f1e43.png","retailPrice":29.00,"shareUrl":"","sort":2,"unit":"件","updateTime":"2018-02-01 00:00:00","virtualSales":10},{"actualSales":0,"brandId":0,"brief":"慢回彈海綿，時尚設計。","categoryId":1008002,"counterPrice":66.00,"createTime":"2018-02-01 00:00:00","delFlag":false,"goodsSn":"1134030","id":1134030,"isHot":false,"isNew":true,"isOnSale":true,"keywords":"","name":"簡約知性記憶棉坐墊","picUrl":"http://yanxuan.nosdn.127.net/aa49dfe878becf768eddc4c1636643a6.png","retailPrice":46.00,"shareUrl":"","sort":12,"unit":"件","updateTime":"2018-02-01 00:00:00","virtualSales":10},{"actualSales":0,"brandId":0,"brief":"慢回彈海綿的呵護，萌趣添彩。","categoryId":1008002,"counterPrice":69.00,"createTime":"2018-02-01 00:00:00","delFlag":false,"goodsSn":"1134032","id":1134032,"isHot":false,"isNew":true,"isOnSale":true,"keywords":"","name":"趣味粉彩系列記憶棉坐墊","picUrl":"http://yanxuan.nosdn.127.net/8b30eeb17c831eba08b97bdcb4c46a8e.png","retailPrice":49.00,"shareUrl":"","sort":13,"unit":"件","updateTime":"2018-02-01 00:00:00","virtualSales":10},{"actualSales":0,"brandId":0,"brief":"100%桑蠶絲，絲滑潤膚","categoryId":1008009,"counterPrice":2619.00,"createTime":"2018-02-01 00:00:00","delFlag":false,"goodsSn":"1135002","id":1135002,"isHot":false,"isNew":true,"isOnSale":true,"keywords":"","name":"宮廷奢華真絲四件套","picUrl":"http://yanxuan.nosdn.127.net/45548f26cfd0c7c41e0afc3709d48286.png","retailPrice":2599.00,"shareUrl":"","sort":1,"unit":"件","updateTime":"2018-02-01 00:00:00","virtualSales":10},{"actualSales":0,"brandId":0,"brief":"自由海軍領探索未來夢","categoryId":1020003,"counterPrice":89.00,"createTime":"2018-02-01 00:00:00","delFlag":false,"goodsSn":"1135072","id":1135072,"isHot":false,"isNew":true,"isOnSale":true,"keywords":"","name":"經典海魂紋水手裙（嬰童）","picUrl":"http://yanxuan.nosdn.127.net/43e57d4208cdc78ac9c088f9b3e798f5.png","retailPrice":69.00,"shareUrl":"","sort":3,"unit":"件","updateTime":"2018-02-01 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00:00:00","virtualSales":10},{"actualSales":5,"brandId":0,"brief":"桌面整理神器","categoryId":1032000,"counterPrice":519.00,"createTime":"2018-02-01 00:00:00","delFlag":false,"goodsSn":"1152095","id":1152095,"isHot":false,"isNew":true,"isOnSale":true,"keywords":"","name":"魔獸世界 聯盟·暴風城 堡壘收納盒","picUrl":"http://yanxuan.nosdn.127.net/c86b49f635fa141decebabbd0966a6ef.png","retailPrice":499.00,"shareUrl":"","sort":6,"unit":"件","updateTime":"2018-02-01 00:00:00","virtualSales":10},{"actualSales":0,"brandId":0,"brief":"3重透氣，清爽柔滑","categoryId":1008009,"counterPrice":479.00,"createTime":"2018-02-01 00:00:00","delFlag":false,"goodsSn":"1152161","id":1152161,"isHot":false,"isNew":true,"isOnSale":true,"keywords":"","name":"竹語絲麻印花四件套","picUrl":"http://yanxuan.nosdn.127.net/977401e75113f7c8334c4fb5b4bf6215.png","retailPrice":459.00,"shareUrl":"","sort":6,"unit":"件","updateTime":"2018-02-01 00:00:00","virtualSales":10}], categoryList=[{"createTime":"2020-12-08 23:09:12","delFlag":false,"iconUrl":"http://cdn.wayn.xin/9fc3c52571aa38a1466f114c2dc892fc.png","id":2,"jumpType":0,"name":"大牌手機","picUrl":"http://cdn.wayn.xin/2545dd00ca4575759024af2811949a9d.jpg","sort":1,"status":0,"updateTime":"2020-12-12 19:26:48","valueId":5,"valueUrl":"http://baidu.com"},{"createTime":"2020-12-06 13:27:54","delFlag":false,"iconUrl":"http://82.157.141.70/upload/2022/02/21/a23fa32c8f4004a8c9fbbb1784462163.jpg","id":1,"jumpType":0,"name":"滋補保健2","picUrl":"http://cdn.wayn.xin/d4de7172eb7ae4178ae4dafd6a973d8f.jpg","sort":2,"status":0,"updateTime":"2022-06-19 09:17:20","valueId":2},{"createTime":"2020-12-08 23:26:15","delFlag":false,"iconUrl":"http://cdn.wayn.xin/6bc0f8a131d2d16b8fc2004d4aa4860c.png","id":3,"jumpType":1,"name":"不鏽鋼鍋","picUrl":"http://cdn.wayn.xin/314d87257f7a2ff03d5f4c5183797912.jpg","sort":2,"status":0,"updateTime":"2020-12-12 19:27:24","valueId":1036000},{"createTime":"2020-12-12 19:28:08","delFlag":false,"iconUrl":"http://cdn.wayn.xin/5a90531d901529967885279d7dc826e1.png","id":14,"jumpType":0,"name":"進口牛奶","picUrl":"http://cdn.wayn.xin/0b1f6ab63d5e222c52c83a2d0581e44c.jpg","sort":3,"status":0,"valueId":5},{"createTime":"2020-12-12 19:28:33","delFlag":false,"iconUrl":"http://cdn.wayn.xin/33530951827ca7e59940d51cda537d84.png","id":15,"jumpType":0,"name":"量販囤貨","picUrl":"http://cdn.wayn.xin/bb6daee3b3e51c3008db97585249f513.jpg","sort":4,"status":0,"valueId":2},{"createTime":"2020-12-12 19:28:50","delFlag":false,"iconUrl":"http://cdn.wayn.xin/7d337f25111b263b29d5d12589015c46.png","id":16,"jumpType":0,"name":"清潔用品","picUrl":"http://cdn.wayn.xin/be8995bda39d03b17349b8ec0dcab3d5.jpg","sort":5,"status":0,"valueId":2},{"createTime":"2020-12-12 19:29:10","delFlag":false,"iconUrl":"http://cdn.wayn.xin/2e632ec0173bb477dcdb601495e0412a.png","id":17,"jumpType":0,"name":"洗護用品","picUrl":"http://cdn.wayn.xin/53fb88c9d1245caa882aa3fc29187d0b.jpg","sort":6,"status":0,"valueId":4},{"createTime":"2020-12-12 19:29:28","delFlag":false,"iconUrl":"http://cdn.wayn.xin/942323c0e74677cf2aa15f09a1e63bca.png","id":18,"jumpType":0,"name":"日用百貨","picUrl":"http://cdn.wayn.xin/8587f91db2edcb43e57da9835cc7ec76.jpg","sort":7,"status":0,"valueId":2},{"createTime":"2020-12-12 19:29:46","delFlag":false,"iconUrl":"http://cdn.wayn.xin/18d9d860ba9b8b28522e050f11a8a8e0.png","id":19,"jumpType":0,"name":"明星乳膠","picUrl":"http://cdn.wayn.xin/65273c7fb2273e90958e92626248a90a.jpg","sort":8,"status":0,"valueId":6},{"createTime":"2020-12-12 19:30:15","delFlag":false,"iconUrl":"http://cdn.wayn.xin/7c790577afda91eebc3c95586e190957.png","id":20,"jumpType":0,"name":"口碑好物","picUrl":"http://cdn.wayn.xin/210011b35be4ceee39e6a466b40b8e22.jpg","sort":9,"status":0,"updateTime":"2021-04-01 20:13:08","valueId":5}], expire_time=1669549170235, hotGoodsList=[{"actualSales":1,"brandId":1001045,"brief":"一級桑蠶絲，吸濕透氣柔軟","categoryId":1036000,"counterPrice":719.00,"createTime":"2018-02-01 00:00:00","delFlag":false,"goodsSn":"1006013","id":1006013,"isHot":true,"isNew":false,"isOnSale":true,"keywords":"","name":"雙宮繭桑蠶絲被 空調被","picUrl":"http://yanxuan.nosdn.127.net/583812520c68ca7995b6fac4c67ae2c7.png","retailPrice":699.00,"shareUrl":"","sort":7,"unit":"件","updateTime":"2021-08-08 11:19:36","virtualSales":10},{"actualSales":1,"brandId":1001045,"brief":"雙層子母被，四季皆可使用","categoryId":1008008,"counterPrice":14199.00,"createTime":"2018-02-01 00:00:00","delFlag":false,"goodsSn":"1006014","id":1006014,"isHot":true,"isNew":false,"isOnSale":true,"keywords":"","name":"雙宮繭桑蠶絲被 子母被","picUrl":"http://yanxuan.nosdn.127.net/2b537159f0f789034bf8c4b339c43750.png","retailPrice":1399.00,"shareUrl":"","sort":15,"unit":"件","updateTime":"2018-02-01 00:00:00","virtualSales":10},{"actualSales":6,"brandId":1001000,"brief":"加大加厚，雙色精彩","categoryId":1036000,"counterPrice":219.00,"createTime":"2018-02-01 00:00:00","delFlag":false,"goodsSn":"1011004","id":1011004,"isHot":true,"isNew":false,"isOnSale":true,"keywords":"","name":"色織精梳AB紗格紋空調被","picUrl":"http://yanxuan.nosdn.127.net/0984c9388a2c3fd2335779da904be393.png","retailPrice":199.00,"shareUrl":"","sort":2,"unit":"件","updateTime":"2018-02-01 00:00:00","virtualSales":10},{"actualSales":6,"brandId":0,"brief":"共用親密2人時光","categoryId":1008008,"counterPrice":219.00,"createTime":"2018-02-01 00:00:00","delFlag":false,"goodsSn":"1019002","id":1019002,"isHot":true,"isNew":false,"isOnSale":true,"keywords":"","name":"升級款護頸雙人記憶枕","picUrl":"http://yanxuan.nosdn.127.net/0118039f7cda342651595d994ed09567.png","retailPrice":199.00,"shareUrl":"","sort":10,"unit":"件","updateTime":"2018-02-01 00:00:00","virtualSales":10},{"actualSales":6,"brandId":0,"brief":"健康保護枕","categoryId":1008008,"counterPrice":119.00,"createTime":"2018-02-01 00:00:00","delFlag":false,"goodsSn":"1019006","id":1019006,"isHot":true,"isNew":false,"isOnSale":true,"keywords":"","name":"植物填充護頸夜交藤枕","picUrl":"http://yanxuan.nosdn.127.net/60c3707837c97a21715ecc3986a744ce.png","retailPrice":99.00,"shareUrl":"","sort":7,"unit":"件","updateTime":"2018-02-01 00:00:00","virtualSales":10},{"actualSales":6,"brandId":0,"brief":"厚實舒適","categoryId":1008001,"counterPrice":59.00,"createTime":"2018-02-01 00:00:00","delFlag":false,"goodsSn":"1021000","id":1021000,"isHot":true,"isNew":false,"isOnSale":true,"keywords":"被","name":"埃及進口長絨棉毛巾","picUrl":"http://yanxuan.nosdn.127.net/7191f2599c7fe44ed4cff7a76e853154.png","retailPrice":39.00,"shareUrl":"","sort":7,"unit":"條","updateTime":"2018-02-01 00:00:00","virtualSales":10},{"actualSales":6,"brandId":1001020,"brief":"浪漫毛線繡球，簡約而不簡單","categoryId":1008009,"counterPrice":319.00,"createTime":"2018-02-01 00:00:00","delFlag":false,"goodsSn":"1022000","id":1022000,"isHot":true,"isNew":false,"isOnSale":true,"keywords":"","name":"意式毛線繡球四件套","picUrl":"http://yanxuan.nosdn.127.net/5350e35e6f22165f38928f3c2c52ac57.png","retailPrice":299.00,"shareUrl":"","sort":18,"unit":"件","updateTime":"2018-02-01 00:00:00","virtualSales":10},{"actualSales":32,"brandId":1001000,"brief":"柔軟紗布，嬰童可用","categoryId":1036000,"counterPrice":269.00,"createTime":"2018-02-01 00:00:00","delFlag":false,"goodsSn":"1027004","id":1027004,"isHot":true,"isNew":false,"isOnSale":true,"keywords":"","name":"色織六層紗布夏涼被","picUrl":"http://yanxuan.nosdn.127.net/6252f53aaf36c072b6678f3d8c635132.png","retailPrice":249.00,"shareUrl":"","sort":3,"unit":"件","updateTime":"2018-02-01 00:00:00","virtualSales":10},{"actualSales":32,"brandId":0,"brief":"原生苦蕎，健康護頸","categoryId":1008008,"counterPrice":119.00,"createTime":"2018-02-01 00:00:00","delFlag":false,"goodsSn":"1036002","id":1036002,"isHot":true,"isNew":false,"isOnSale":true,"keywords":"","name":"高山苦蕎麥枕","picUrl":"http://yanxuan.nosdn.127.net/ffd7efe9d5225dff9f36d5110b027caa.png","retailPrice":99.00,"shareUrl":"","sort":5,"unit":"件","updateTime":"2018-02-01 00:00:00","virtualSales":10},{"actualSales":32,"brandId":0,"brief":"5cm記憶綿的親密包裹","categoryId":1008008,"counterPrice":619.00,"createTime":"2018-02-01 00:00:00","delFlag":false,"goodsSn":"1037011","id":1037011,"isHot":true,"isNew":false,"isOnSale":true,"keywords":"","name":"安睡慢回彈記憶綿床墊","picUrl":"http://yanxuan.nosdn.127.net/a03ea6f4509439acdafcb7ceba1debe0.png","retailPrice":599.00,"shareUrl":"","sort":22,"unit":"件","updateTime":"2018-02-01 00:00:00","virtualSales":10}]}]
2022-11-27 21:29:48.336 [9d919fb6d33c4652ba28ff87ae210809_12] [http-nio-82-exec-3] [DEBUG] c.w.c.c.m.s.G.selectGoodsListPage_mpCount:137 debug - ==>  Preparing: SELECT COUNT(*) AS total FROM shop_goods WHERE del_flag = 0 AND is_on_sale = 1
2022-11-27 21:29:48.387 [9d919fb6d33c4652ba28ff87ae210809_12] [http-nio-82-exec-3] [DEBUG] c.w.c.c.m.s.G.selectGoodsListPage_mpCount:137 debug - ==> Parameters: 
2022-11-27 21:29:48.426 [9d919fb6d33c4652ba28ff87ae210809_12] [http-nio-82-exec-3] [DEBUG] c.w.c.c.m.s.G.selectGoodsListPage_mpCount:137 debug - <==      Total: 1
2022-11-27 21:29:48.430 [9d919fb6d33c4652ba28ff87ae210809_12] [http-nio-82-exec-3] [DEBUG] c.w.c.c.m.s.G.selectGoodsListPage:137 debug - ==>  Preparing: select id, goods_sn, name, pic_url, counter_price, retail_price, actual_sales, virtual_sales from shop_goods WHERE del_flag = 0 and is_on_sale = 1 order by create_time desc LIMIT ?
2022-11-27 21:29:48.452 [9d919fb6d33c4652ba28ff87ae210809_12] [http-nio-82-exec-3] [DEBUG] c.w.c.c.m.s.G.selectGoodsListPage:137 debug - ==> Parameters: 6(Long)
2022-11-27 21:29:48.476 [9d919fb6d33c4652ba28ff87ae210809_12] [http-nio-82-exec-3] [DEBUG] c.w.c.c.m.s.G.selectGoodsListPage:137 debug - <==      Total: 6

最後分析上訴日誌：通過86c76336100c414dbe9217aeb099ccd5實現介面調用追蹤，通過12用戶ID，實現用戶調用追蹤

七. alibaba excel導出時自定義格式轉換優雅實現

官網介紹：EasyExcel 是一個基於Java的簡單、省記憶體的讀寫Excel的開源項目。在儘可能節約記憶體的情況下支持讀寫百M的Excel。

EasyExcel 是 alibaba 出的一個基於 java poi 得excel通用處理類庫，他的優勢在於記憶體消耗。對比 easypoi 方案，EasyExcel 在記憶體消耗、知名度（大廠光環）上更出眾些。

博主在使用過程中發現導出excel，官網對自定義格式欄位提供了 converter 介面，但只簡單提供了CustomStringStringConverter 類代碼，達不到博主想要得優雅要求，如下：

public class CustomStringStringConverter implements Converter<String> {
    @Override
    public Class<?> supportJavaTypeKey() {
        return String.class;
    }

    @Override
    public CellDataTypeEnum supportExcelTypeKey() {
        return CellDataTypeEnum.STRING;
    }

    /**
     * 這裡讀的時候會調用
     *
     * @param context
     * @return
     */
    @Override
    public String convertToJavaData(ReadConverterContext<?> context) {
        return "自定義：" + context.getReadCellData().getStringValue();
    }

    /**
     * 這裡是寫的時候會調用 不用管
     *
     * @return
     */
    @Override
    public WriteCellData<?> convertToExcelData(WriteConverterContext<String> context) {
        return new WriteCellData<>(context.getValue());
    }

}

在以上代碼中，打個比方想要實現性別欄位得自定義格式轉換，就需要在convertToExcelData方法中，添加如下代碼

@Override
public WriteCellData<?> convertToExcelData(WriteConverterContext<String> context) {
    String value = context.getValue();
    if ("man".equals(value)) {
        return new WriteCellData<>("男");
    } else {
        return new WriteCellData<>("女");
    }
}

可以看到，非常得不優雅，對於這種類型欄位，博主習慣使用枚舉類來定義欄位所有類型，然後將枚舉類轉換為 map(value,desc) 結構，就可以優雅得實現這個自定義格式得需求

/**
 * 一、先定義int欄位抽象轉換類，實現通用轉換邏輯
 */
public abstract class AbstractIntConverter implements Converter<Integer> {
    abstract List<ConverterDTO> getArr();

    public WriteCellData<?> convertToExcelData(Integer value, ExcelContentProperty contentProperty, GlobalConfiguration globalConfiguration) {
        List<ConverterDTO> values = getArr();
        Map<Integer, String> map = values.stream().collect(toMap(ConverterDTO::getType, ConverterDTO::getDesc));
        String result = map.getOrDefault(value, "");
        return new WriteCellData<>(result);
    }

    static class ConverterDTO {
        private Integer type;
        private String desc;

        public Integer getType() {
            return type;
        }

        public void setType(Integer type) {
            this.type = type;
        }

        public String getDesc() {
            return desc;
        }

        public void setDesc(String desc) {
            this.desc = desc;
        }

        public ConverterDTO(Integer type, String desc) {
            this.type = type;
            this.desc = desc;
        }
    }
}

/**
 * 二、定義通用狀態欄位轉換類
 */
public class StatusConverter extends AbstractIntConverter {

    @Override
    List<ConverterDTO> getArr() {
        StatusEnum[] values = StatusEnum.values();
        return Arrays.stream(values).map(sexEnum -> new ConverterDTO(sexEnum.getType(), sexEnum.getDesc())).toList();
    }

    /**
     * 狀態枚舉
     */
    enum StatusEnum {
        MAN(0, "啟用"),
        WOMAN(1, "禁用");

        private Integer type;
        private String desc;

        StatusEnum(Integer type, String desc) {
            this.type = type;
            this.desc = desc;
        }
        public Integer getType() {
            return type;
        }
        public String getDesc() {
            return desc;
        }
    }
}

最後再導出 ExcelProperty 中甜膩加 StatusConverter ，就優雅得實現了自定義格式得需求

public class User extends BaseEntity {
    ...
    /**
     * 用戶狀態 0 啟用 1 禁用
     */
    @ExcelProperty(value = "用戶狀態", converter = StatusConverter.class)
    private Integer userStatus;
    ...

}

八. Springboot 預設redis客戶端lettuce經常連接超時解決方案

不知道大家有沒有遇到這種情況，線上項目使用 lettuce 客戶端，當操作 redis 得介面一段時間沒有調用後（比如30分鐘），再次調用 redis 操作後，就會遇到連接超時得問題，導致介面異常。博主直接給出分析過程：

通過wireshark抓包工具，發現項目中 redis 連接創建後，一段時間未傳輸數據後，客戶端發送 psh 包，未收到服務端 ack 包，觸發tcp得超時重傳機制，在重傳次數重試完後，最終客戶端主動關閉了連接。

到這裡我們就知道這個問題，主要原因在於服務端沒有回覆客戶端（比如tcp參數設置、防火牆主動關閉等，都是針對一段時間內沒有數據傳輸得tcp連接會做關閉處理），造成了客戶端得連接超時

面對這個問題有三種解決方案：

redis操作異常後進行重試，這篇文章有介紹生產環境Redis連接，長時間無響應被伺服器斷開問題
啟用一個心跳定時任務，定時訪問 redis，保持 redis 連接不被關閉，簡而言之，就是寫一個定時任務，定時調用 redis得 get 命令，進而保活 redis 連接
基於Springboot 提供得 LettuceClientConfigurationBuilderCustomizer 自定義客戶端配置，博主這裡主要針對第三種自定義客戶端配置來講解一種優雅得方式

Springboot 項目中關於 lettuce 客戶端得自動配置是沒有啟用保活配置得，要啟用得話代碼如下：

/**
 * 自定義lettuce客戶端配置
 *
 * @return LettuceClientConfigurationBuilderCustomizer
 */
@Bean
public LettuceClientConfigurationBuilderCustomizer lettuceClientConfigurationBuilderCustomizer() {
    return clientConfigurationBuilder -> {
        LettuceClientConfiguration clientConfiguration = clientConfigurationBuilder.build();
        ClientOptions clientOptions = clientConfiguration.getClientOptions().orElseGet(ClientOptions::create);
        ClientOptions build = clientOptions.mutate().build();
        SocketOptions.KeepAliveOptions.Builder builder = build.getSocketOptions().getKeepAlive().mutate();
        // 保活配置
        builder.enable(true);
        builder.idle(Duration.ofSeconds(30));
        SocketOptions.Builder socketOptionsBuilder = clientOptions.getSocketOptions().mutate();
        SocketOptions.KeepAliveOptions keepAliveOptions = builder.build();
        socketOptionsBuilder.keepAlive(keepAliveOptions);
        SocketOptions socketOptions = socketOptionsBuilder.build();
        ClientOptions clientOptions1 = ClientOptions.builder().socketOptions(socketOptions).build();
        clientConfigurationBuilder.clientOptions(clientOptions1);
    };
}

添加 lettuce 客戶端的自定義配置，在 KeepAliveOptions 中啟用 enable ，這樣 lettuce 客戶端就會在tcp協議規範上啟用 keep alive 機制自動發送心跳包

九. redis客戶端lettuce啟用epoll

直接給官網連接，配置很簡單，添加一個 netty-all 得依賴，lettuce 會自動檢測項目系統是否支持 epoll（linux 系統支持），並且是否有netty-transport-native-epoll依賴（ netty-all 包含 netty-transport-native-epoll ），都滿足得話就會自動啟用 epoll 事件迴圈，進一步提升系統性能

<dependency>
    <groupId>io.netty</groupId>
    <artifactId>netty-all</artifactId>
</dependency>

十. Springboot web項目優雅停機

web項目配置了優雅停機後，在重啟jar包，或者容器時可以防止正在活動得線程被突然停止（ kill -9 無解，請不要使用這個參數殺線上進程，docker compose 項目儘量不要用 docker-compose down 命令關閉項目，使用 docker-compose rm -svf 可以觸發優雅停機），造成用戶請求失敗，在此期間允許完成現有請求但不允許新請求，配置如下：

server: shutdown: "graceful"

十一. nginx配置通用請求尾碼

先說下這個配置產生得前提，博主公司pc客戶項目是基於 electron 打包得網頁項目，每次項目大版本更新時，為了做好相容性，防止客戶端網頁緩存等，會使用一個新網頁地址，打個比方：

老網頁地址，v1.1.0 版本網頁訪問地址：http://api.dev.com/pageV110

新網頁地址，v1.2.0 版本網頁訪問地址：http://api.dev.com/pageV120

那麼項目得nginx配置則則需要新加一個 v1.2.0 得配置如下：

server {
   listen 80;
   server_name api.dev.com;
   client_max_body_size 10m;

   # 老網頁v1.1.0配置
   location ~ ^/pageV110 {
               alias  /home/wwwroot/api.dev.com/pageV110;
               index  index.html index.htm;
       }
       
   # 新網頁v1.2.0配置
   location ~ ^/pageV120 {
               alias  /home/wwwroot/api.dev.com/pageV120;
               index  index.html index.htm;
       }

}

那麼博主在每次項目發佈得時候就需要配合前端發版，配置一個新網頁，故產生了這個通用配置得需求，如下：

server {
   listen 80;
   server_name api.dev.com;
   client_max_body_size 10m;

   # 配置正則localtion
   location ~ ^/pageV(.*) {
               set $s $1; # 定義尾碼變數
               alias  /home/wwwroot/api.dev.com/pageV$s;
               index  index.html index.htm;
       }

}

在 nginx 配置文件語法中，location 語句可以使用正則表達式，定義 set $s $1 變數，實現了通用配置

十二. 關於開發人員的自我提升和突破

博主這裡主要總結了四點：

多和他人溝通，溝通能把複雜問題簡單化，有時候開發階段一個需求多問幾句，可以減少因為個人理解差異導致的需求不一致問題，進而減少開發時間
建立長短期目標，觀看技術視頻、書籍給自己充電，比如7天利用業餘時間看完一本電子書，三十天從零開始一個新項目等
善於總結，對於項目中的疑難bug，踩坑點要有記錄，防止下次遇到再掉坑裡
敢於嘗試、擔責，對項目、代碼里明確不合理的地方要敢於跟他人溝通，修改問題代碼，達到優化目的。對於自己造成的問題要承擔，不要推卸責任。對於線上問題要重視，優先解決線上問題。

十二條後端開發經驗分享，純乾貨，總有一條你不知道

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