簡介

在項目實(shí)際的開發(fā)過程中，有時候會遇到需要在應(yīng)用程序啟動完畢對外提供服務(wù)之前預(yù)先將部分?jǐn)?shù)據(jù)裝載到緩存的需求。本文就總結(jié)了常見的數(shù)據(jù)預(yù)裝載方式及其實(shí)踐。

適用場景

• 預(yù)裝載應(yīng)用級別數(shù)據(jù)到緩存：如字典數(shù)據(jù)、公共的業(yè)務(wù)數(shù)據(jù)
• 系統(tǒng)預(yù)熱
• 心跳檢測：如在系統(tǒng)啟動完畢訪問一個外服務(wù)接口等場景

常用方法

• ApplicationEvent
• CommandLineRunner
• ApplicationRunner

ApplicationEvent

應(yīng)用程序事件，就是發(fā)布訂閱模式。在系統(tǒng)啟動完畢，向應(yīng)用程序注冊一個事件，監(jiān)聽者一旦監(jiān)聽到了事件的發(fā)布，就可以做一些業(yè)務(wù)邏輯的處理了。

既然是發(fā)布-訂閱模式，那么訂閱者既可以是一個，也可以是多個。

定義event

import org.springframework.context.ApplicationEvent;
public class CacheEvent   extends ApplicationEvent {
    public CacheEvent(Object source) {
        super(source);
    }
}

定義listener

import lombok.extern.slf4j.Slf4j;
import org.apache.commons.lang3.StringUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationListener;
import org.springframework.stereotype.Component;
import org.springframework.util.CollectionUtils;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;
@Slf4j
@Component
public class CacheEventListener implements ApplicationListener<CacheEvent> {
    @Autowired
    private MaskingService maskingService;
    @Autowired
    private RedisCache redisCache;
    @Override
    public void onApplicationEvent(CacheEvent cacheEvent) {
        log.debug("CacheEventListener-start");
        List<SysMasking> maskings = maskingService.selectAllSysMaskings();
        if (!CollectionUtils.isEmpty(maskings)) {
            log.debug("CacheEventListener-data-not-empty");
            Map<String, List<SysMasking>> cacheMap = maskings.stream().collect(Collectors.groupingBy(SysMasking::getFieldKey));
            cacheMap.keySet().forEach(x -> {
                if (StringUtils.isNotEmpty(x)) {
                    log.debug("CacheEventListener-x={}", x);
                    List<SysMasking> list = cacheMap.get(x);
                    long count = redisCache.setCacheList(RedisKeyPrefix.MASKING.getPrefix() + x, list);
                    log.debug("CacheEventListener-count={}", count);
                } else {
                    log.debug("CacheEventListener-x-is-empty");
                }
            });
        } else {
            log.debug("CacheEventListener-data-is-empty");
        }
        log.debug("CacheEventListener-end");
    }
}

注冊event

@Slf4j
@SpringBootApplication(exclude = {DataSourceAutoConfiguration.class})
public class BAMSApplication {
    public static void main(String[] args) {
        ConfigurableApplicationContext context = SpringApplication.run(BAMSApplication.class, args);
        log.debug("app-started");
        context.publishEvent(new CacheEvent("處理緩存事件"));
    }
}

CommandLineRunner

通過實(shí)現(xiàn) CommandLineRunner 接口，可以在應(yīng)用程序啟動完畢，回調(diào)到指定的方法中。

package com.ramble.warmupservice.runner;
import lombok.extern.slf4j.Slf4j;
import org.springframework.boot.CommandLineRunner;
import org.springframework.stereotype.Component;
@Slf4j
@Component
public class CacheCommandLineRunner implements CommandLineRunner {
    @Override
    public void run(String... args) throws Exception {
        log.debug("CacheCommandLineRunner-start");
        log.debug("CacheCommandLineRunner-參數(shù)={}", args);
        // 注入業(yè)務(wù) service ，獲取需要緩存的數(shù)據(jù)
        // 注入 redisTemplate ，將需要緩存的數(shù)據(jù)存放到 redis 中
        log.debug("CacheCommandLineRunner-end");
    }
}

ApplicationRunner

同CommandLineRunner 類似，區(qū)別在于，對參數(shù)做了封裝。

package com.ramble.warmupservice.runner;
import com.alibaba.fastjson.JSON;
import lombok.extern.slf4j.Slf4j;
import org.springframework.boot.ApplicationArguments;
import org.springframework.boot.ApplicationRunner;
import org.springframework.stereotype.Component;
@Slf4j
@Component
public class CacheApplicationRunner implements ApplicationRunner {
    @Override
    public void run(ApplicationArguments args) throws Exception {
        log.debug("CacheApplicationRunner-start");
        log.debug("CacheApplicationRunner-參數(shù)={}", JSON.toJSONString(args));
        // 注入業(yè)務(wù) service ，獲取需要緩存的數(shù)據(jù)
        // 注入 redisTemplate ，將需要緩存的數(shù)據(jù)存放到 redis 中
        log.debug("CacheApplicationRunner-end");
    }
}

測試

上述代碼在idea中啟動，若不帶參數(shù)，輸出如下：

2022-04-28 15:44:00.981  INFO 1160 --- [           main] c.r.w.WarmupServiceApplication           : Started WarmupServiceApplication in 1.335 seconds (JVM running for 2.231)
2022-04-28 15:44:00.982 DEBUG 1160 --- [           main] c.r.w.runner.CacheApplicationRunner      : CacheApplicationRunner-start
2022-04-28 15:44:01.025 DEBUG 1160 --- [           main] c.r.w.runner.CacheApplicationRunner      : CacheApplicationRunner-參數(shù)={"nonOptionArgs":[],"optionNames":[],"sourceArgs":[]}
2022-04-28 15:44:01.025 DEBUG 1160 --- [           main] c.r.w.runner.CacheApplicationRunner      : CacheApplicationRunner-end
2022-04-28 15:44:01.025 DEBUG 1160 --- [           main] c.r.w.runner.CacheCommandLineRunner      : CacheCommandLineRunner-start
2022-04-28 15:44:01.026 DEBUG 1160 --- [           main] c.r.w.runner.CacheCommandLineRunner      : CacheCommandLineRunner-參數(shù)={}
2022-04-28 15:44:01.026 DEBUG 1160 --- [           main] c.r.w.runner.CacheCommandLineRunner      : CacheCommandLineRunner-end
2022-04-28 15:44:01.026 DEBUG 1160 --- [           main] c.r.w.listener.CacheEventListener        : CacheEventListener-start
2022-04-28 15:44:01.026 DEBUG 1160 --- [           main] c.r.w.listener.CacheEventListener        : CacheEventListener-參數(shù)=ApplicationEvent-->緩存系統(tǒng)數(shù)據(jù)
2022-04-28 15:44:01.029 DEBUG 1160 --- [           main] c.r.w.listener.CacheEventListener        : CacheEventListener-end
Disconnected from the target VM, address: '127.0.0.1:61320', transport: 'socket'
Process finished with exit code 130

若使用 java -jar xxx.jar --server.port=9009 啟動，則輸入如下：

2022-04-28 16:02:05.327  INFO 9916 --- [           main] c.r.w.WarmupServiceApplication           : Started WarmupServiceApplication in 1.78 seconds (JVM running for 2.116)
2022-04-28 16:02:05.329 DEBUG 9916 --- [           main] c.r.w.runner.CacheApplicationRunner      : CacheApplicationRunner-start
2022-04-28 16:02:05.393 DEBUG 9916 --- [           main] c.r.w.runner.CacheApplicationRunner      : CacheApplicationRunner-參數(shù)={"nonOptionArgs":[],"optionNames":["server.port"],"sourceArgs":["--server.port=9009"]}
2022-04-28 16:02:05.395 DEBUG 9916 --- [           main] c.r.w.runner.CacheApplicationRunner      : CacheApplicationRunner-end
2022-04-28 16:02:05.395 DEBUG 9916 --- [           main] c.r.w.runner.CacheCommandLineRunner      : CacheCommandLineRunner-start
2022-04-28 16:02:05.395 DEBUG 9916 --- [           main] c.r.w.runner.CacheCommandLineRunner      : CacheCommandLineRunner-參數(shù)=--server.port=9009
2022-04-28 16:02:05.395 DEBUG 9916 --- [           main] c.r.w.runner.CacheCommandLineRunner      : CacheCommandLineRunner-end
2022-04-28 16:02:05.395 DEBUG 9916 --- [           main] c.r.w.listener.CacheEventListener        : CacheEventListener-start
2022-04-28 16:02:05.396 DEBUG 9916 --- [           main] c.r.w.listener.CacheEventListener        : CacheEventListener- 參數(shù)=ApplicationEvent-->緩存系統(tǒng)數(shù)據(jù)
2022-04-28 16:02:05.396 DEBUG 9916 --- [           main] c.r.w.listener.CacheEventListener        : CacheEventListener-end

執(zhí)行順序

從上面測試的輸出，可以看到三種方式執(zhí)行的順序為：
ApplicationRunner--->CommandLineRunner--->ApplicationEvent

另外，若同時定義多個runner，可以通過order來指定他們的優(yōu)先級。

代碼

https://gitee.com/naylor_personal/ramble-spring-cloud/tree/master/warmup-service

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