簡介

在項目實際的開發(fā)過程中，有時候會遇到需要在應用程序啟動完畢對外提供服務之前預先將部分數(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)預裝載方式及其實踐。

適用場景

• 預裝載應用級別數(shù)據(jù)到緩存：如字典數(shù)據(jù)、公共的業(yè)務數(shù)據(jù)
• 系統(tǒng)預熱
• 心跳檢測：如在系統(tǒng)啟動完畢訪問一個外服務接口等場景

常用方法

• ApplicationEvent
• CommandLineRunner
• ApplicationRunner

ApplicationEvent

應用程序事件，就是發(fā)布訂閱模式。在系統(tǒng)啟動完畢，向應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

通過實現(xiàn) CommandLineRunner 接口，可以在應用程序啟動完畢，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 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 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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