至於多久從 Redis 取一次資料存到資料庫中，根據專案的實際情況定吧，我是暫時設了兩個小時。
文章分四部分介紹：
Redis 快取設計及實現資料庫設計資料庫操作開啟定時任務持久化儲存到資料庫一、Redis 快取設計及實現1.1 Redis 安裝及執行Redis 安裝請自行查閱相關教程。
說下Docker 安裝執行 Redis
docker run -d -p 6379:6379 redis:4.0.8如果已經安裝了 Redis，開啟命令列，輸入啟動 Redis 的命令
redis-server1.在 pom.xml 中引入依賴
<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-redis</artifactId></dependency>2.在啟動類上添加註釋 @EnableCaching
@SpringBootApplication@EnableDiscoveryClient@EnableSwagger2@EnableFeignClients(basePackages = "com.solo.coderiver.project.client")@EnableCachingpublic class UserApplication { public static void main(String[] args) { SpringApplication.run(UserApplication.class, args); }}3.編寫 Redis 配置類 RedisConfig
import com.fasterxml.jackson.annotation.JsonAutoDetect;import com.fasterxml.jackson.annotation.PropertyAccessor;import com.fasterxml.jackson.databind.ObjectMapper;import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;import org.springframework.data.redis.connection.RedisConnectionFactory;import org.springframework.data.redis.core.RedisTemplate;import org.springframework.data.redis.core.StringRedisTemplate;import org.springframework.data.redis.serializer.Jackson2JsonRedisSerializer;import java.net.UnknownHostException;@Configurationpublic class RedisConfig { @Bean @ConditionalOnMissingBean(name = "redisTemplate") public RedisTemplate<String, Object> redisTemplate( RedisConnectionFactory redisConnectionFactory) throws UnknownHostException { Jackson2JsonRedisSerializer<Object> jackson2JsonRedisSerializer = new Jackson2JsonRedisSerializer<Object>(Object.class); ObjectMapper om = new ObjectMapper(); om.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY); om.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL); jackson2JsonRedisSerializer.setObjectMapper(om); RedisTemplate<String, Object> template = new RedisTemplate<String, Object>(); template.setConnectionFactory(redisConnectionFactory); template.setKeySerializer(jackson2JsonRedisSerializer); template.setValueSerializer(jackson2JsonRedisSerializer); template.setHashKeySerializer(jackson2JsonRedisSerializer); template.setHashValueSerializer(jackson2JsonRedisSerializer); template.afterPropertiesSet(); return template; } @Bean @ConditionalOnMissingBean(StringRedisTemplate.class) public StringRedisTemplate stringRedisTemplate( RedisConnectionFactory redisConnectionFactory) throws UnknownHostException { StringRedisTemplate template = new StringRedisTemplate(); template.setConnectionFactory(redisConnectionFactory); return template; }}至此 Redis 在 SpringBoot 專案中的配置已經完成，可以愉快地使用了。
1.3 Redis 的資料結構型別Redis 可以儲存鍵與5種不同資料結構型別之間的對映，這5種資料結構型別分別為String（字串）、List（列表）、Set（集合）、Hash（雜湊）和 Zset（有序集合）。
下面來對這5種資料結構型別作簡單的介紹：
在視覺化工具 RDM 中看到的是這樣子
1.5 操作 Redis將具體操作方法封裝到了 RedisService 接口裡
RedisService.java
import com.solo.coderiver.user.dataobject.UserLike;import com.solo.coderiver.user.dto.LikedCountDTO;import java.util.List;public interface RedisService { /** * 點贊。狀態為1 * @param likedUserId * @param likedPostId */ void saveLiked2Redis(String likedUserId, String likedPostId); /** * 取消點贊。將狀態改變為0 * @param likedUserId * @param likedPostId */ void unlikeFromRedis(String likedUserId, String likedPostId); /** * 從Redis中刪除一條點贊資料 * @param likedUserId * @param likedPostId */ void deleteLikedFromRedis(String likedUserId, String likedPostId); /** * 該使用者的點贊數加1 * @param likedUserId */ void incrementLikedCount(String likedUserId); /** * 該使用者的點贊數減1 * @param likedUserId */ void decrementLikedCount(String likedUserId); /** * 獲取Redis中儲存的所有點贊資料 * @return */ List<UserLike> getLikedDataFromRedis(); /** * 獲取Redis中儲存的所有點贊數量 * @return */ List<LikedCountDTO> getLikedCountFromRedis();}實現類 RedisServiceImpl.java
import com.solo.coderiver.user.dataobject.UserLike;import com.solo.coderiver.user.dto.LikedCountDTO;import com.solo.coderiver.user.enums.LikedStatusEnum;import com.solo.coderiver.user.service.LikedService;import com.solo.coderiver.user.service.RedisService;import com.solo.coderiver.user.utils.RedisKeyUtils;import lombok.extern.slf4j.Slf4j;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.data.redis.core.Cursor;import org.springframework.data.redis.core.RedisTemplate;import org.springframework.data.redis.core.ScanOptions;import org.springframework.stereotype.Service;import java.util.ArrayList;import java.util.List;import java.util.Map;@Service@Slf4jpublic class RedisServiceImpl implements RedisService { @Autowired RedisTemplate redisTemplate; @Autowired LikedService likedService; @Override public void saveLiked2Redis(String likedUserId, String likedPostId) { String key = RedisKeyUtils.getLikedKey(likedUserId, likedPostId); redisTemplate.opsForHash().put(RedisKeyUtils.MAP_KEY_USER_LIKED, key, LikedStatusEnum.LIKE.getCode()); } @Override public void unlikeFromRedis(String likedUserId, String likedPostId) { String key = RedisKeyUtils.getLikedKey(likedUserId, likedPostId); redisTemplate.opsForHash().put(RedisKeyUtils.MAP_KEY_USER_LIKED, key, LikedStatusEnum.UNLIKE.getCode()); } @Override public void deleteLikedFromRedis(String likedUserId, String likedPostId) { String key = RedisKeyUtils.getLikedKey(likedUserId, likedPostId); redisTemplate.opsForHash().delete(RedisKeyUtils.MAP_KEY_USER_LIKED, key); } @Override public void incrementLikedCount(String likedUserId) { redisTemplate.opsForHash().increment(RedisKeyUtils.MAP_KEY_USER_LIKED_COUNT, likedUserId, 1); } @Override public void decrementLikedCount(String likedUserId) { redisTemplate.opsForHash().increment(RedisKeyUtils.MAP_KEY_USER_LIKED_COUNT, likedUserId, -1); } @Override public List<UserLike> getLikedDataFromRedis() { Cursor<Map.Entry<Object, Object>> cursor = redisTemplate.opsForHash().scan(RedisKeyUtils.MAP_KEY_USER_LIKED, ScanOptions.NONE); List<UserLike> list = new ArrayList<>(); while (cursor.hasNext()){ Map.Entry<Object, Object> entry = cursor.next(); String key = (String) entry.getKey(); //分離出 likedUserId，likedPostId String[] split = key.split("::"); String likedUserId = split[0]; String likedPostId = split[1]; Integer value = (Integer) entry.getValue(); //組裝成 UserLike 物件 UserLike userLike = new UserLike(likedUserId, likedPostId, value); list.add(userLike); //存到 list 後從 Redis 中刪除 redisTemplate.opsForHash().delete(RedisKeyUtils.MAP_KEY_USER_LIKED, key); } return list; } @Override public List<LikedCountDTO> getLikedCountFromRedis() { Cursor<Map.Entry<Object, Object>> cursor = redisTemplate.opsForHash().scan(RedisKeyUtils.MAP_KEY_USER_LIKED_COUNT, ScanOptions.NONE); List<LikedCountDTO> list = new ArrayList<>(); while (cursor.hasNext()){ Map.Entry<Object, Object> map = cursor.next(); //將點贊數量儲存在 LikedCountDT String key = (String)map.getKey(); LikedCountDTO dto = new LikedCountDTO(key, (Integer) map.getValue()); list.add(dto); //從Redis中刪除這條記錄 redisTemplate.opsForHash().delete(RedisKeyUtils.MAP_KEY_USER_LIKED_COUNT, key); } return list; }}RedisKeyUtils, 用於根據一定規則生成 key
public class RedisKeyUtils { //儲存使用者點贊資料的key public static final String MAP_KEY_USER_LIKED = "MAP_USER_LIKED"; //儲存使用者被點贊數量的key public static final String MAP_KEY_USER_LIKED_COUNT = "MAP_USER_LIKED_COUNT"; /** * 拼接被點讚的使用者id和點讚的人的id作為key。格式 222222::333333 * @param likedUserId 被點讚的人id * @param likedPostId 點讚的人的id * @return */ public static String getLikedKey(String likedUserId, String likedPostId){ StringBuilder builder = new StringBuilder(); builder.append(likedUserId); builder.append("::"); builder.append(likedPostId); return builder.toString(); }}LikedStatusEnum 使用者點贊狀態的列舉類
package com.solo.coderiver.user.enums;import lombok.Getter;/** * 使用者點讚的狀態 */@Getterpublic enum LikedStatusEnum { LIKE(1, "點贊"), UNLIKE(0, "取消點贊/未點贊"), ; private Integer code; private String msg; LikedStatusEnum(Integer code, String msg) { this.code = code; this.msg = msg; }}資料庫表中至少要包含三個欄位：被點贊使用者id，點贊使用者id，點贊狀態。再加上主鍵id，建立時間，修改時間就行了。
建表語句
create table `user_like`( `id` int not null auto_increment, `liked_user_id` varchar(32) not null comment '被點讚的使用者id', `liked_post_id` varchar(32) not null comment '點讚的使用者id', `status` tinyint(1) default '1' comment '點贊狀態，0取消，1點贊', `create_time` timestamp not null default current_timestamp comment '建立時間', `update_time` timestamp not null default current_timestamp on update current_timestamp comment '修改時間', primary key(`id`), INDEX `liked_user_id`(`liked_user_id`), INDEX `liked_post_id`(`liked_post_id`)) comment '使用者點贊表';對應的物件 UserLike
import com.solo.coderiver.user.enums.LikedStatusEnum;import lombok.Data;import javax.persistence.Entity;import javax.persistence.GeneratedValue;import javax.persistence.GenerationType;import javax.persistence.Id;/** * 使用者點贊表 */@Entity@Datapublic class UserLike { //主鍵id @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Integer id; //被點讚的使用者的id private String likedUserId; //點讚的使用者的id private String likedPostId; //點讚的狀態.預設未點贊 private Integer status = LikedStatusEnum.UNLIKE.getCode(); public UserLike() { } public UserLike(String likedUserId, String likedPostId, Integer status) { this.likedUserId = likedUserId; this.likedPostId = likedPostId; this.status = status; }}操作資料庫同樣封裝在介面中
LikedService
import com.solo.coderiver.user.dataobject.UserLike;import org.springframework.data.domain.Page;import org.springframework.data.domain.Pageable;import java.util.List;public interface LikedService { /** * 儲存點贊記錄 * @param userLike * @return */ UserLike save(UserLike userLike); /** * 批次儲存或修改 * @param list */ List<UserLike> saveAll(List<UserLike> list); /** * 根據被點贊人的id查詢點贊列表（即查詢都誰給這個人點贊過） * @param likedUserId 被點贊人的id * @param pageable * @return */ Page<UserLike> getLikedListByLikedUserId(String likedUserId, Pageable pageable); /** * 根據點贊人的id查詢點贊列表（即查詢這個人都給誰點贊過） * @param likedPostId * @param pageable * @return */ Page<UserLike> getLikedListByLikedPostId(String likedPostId, Pageable pageable); /** * 透過被點贊人和點贊人id查詢是否存在點贊記錄 * @param likedUserId * @param likedPostId * @return */ UserLike getByLikedUserIdAndLikedPostId(String likedUserId, String likedPostId); /** * 將Redis裡的點贊資料存入資料庫中 */ void transLikedFromRedis2DB(); /** * 將Redis中的點贊數量資料存入資料庫 */ void transLikedCountFromRedis2DB();}LikedServiceImpl 實現類
import com.solo.coderiver.user.dataobject.UserInfo;import com.solo.coderiver.user.dataobject.UserLike;import com.solo.coderiver.user.dto.LikedCountDTO;import com.solo.coderiver.user.enums.LikedStatusEnum;import com.solo.coderiver.user.repository.UserLikeRepository;import com.solo.coderiver.user.service.LikedService;import com.solo.coderiver.user.service.RedisService;import com.solo.coderiver.user.service.UserService;import lombok.extern.slf4j.Slf4j;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.data.domain.Page;import org.springframework.data.domain.Pageable;import org.springframework.stereotype.Service;import org.springframework.transaction.annotation.Transactional;import java.util.List;@Service@Slf4jpublic class LikedServiceImpl implements LikedService { @Autowired UserLikeRepository likeRepository; @Autowired RedisService redisService; @Autowired UserService userService; @Override @Transactional public UserLike save(UserLike userLike) { return likeRepository.save(userLike); } @Override @Transactional public List<UserLike> saveAll(List<UserLike> list) { return likeRepository.saveAll(list); } @Override public Page<UserLike> getLikedListByLikedUserId(String likedUserId, Pageable pageable) { return likeRepository.findByLikedUserIdAndStatus(likedUserId, LikedStatusEnum.LIKE.getCode(), pageable); } @Override public Page<UserLike> getLikedListByLikedPostId(String likedPostId, Pageable pageable) { return likeRepository.findByLikedPostIdAndStatus(likedPostId, LikedStatusEnum.LIKE.getCode(), pageable); } @Override public UserLike getByLikedUserIdAndLikedPostId(String likedUserId, String likedPostId) { return likeRepository.findByLikedUserIdAndLikedPostId(likedUserId, likedPostId); } @Override @Transactional public void transLikedFromRedis2DB() { List<UserLike> list = redisService.getLikedDataFromRedis(); for (UserLike like : list) { UserLike ul = getByLikedUserIdAndLikedPostId(like.getLikedUserId(), like.getLikedPostId()); if (ul == null){ //沒有記錄，直接存入 save(like); }else{ //有記錄，需要更新 ul.setStatus(like.getStatus()); save(ul); } } } @Override @Transactional public void transLikedCountFromRedis2DB() { List<LikedCountDTO> list = redisService.getLikedCountFromRedis(); for (LikedCountDTO dto : list) { UserInfo user = userService.findById(dto.getId()); //點贊數量屬於無關緊要的操作，出錯無需拋異常 if (user != null){ Integer likeNum = user.getLikeNum() + dto.getCount(); user.setLikeNum(likeNum); //更新點贊數量 userService.updateInfo(user); } } }}資料庫的操作就這些，主要還是增刪改查。
四、開啟定時任務持久化儲存到資料庫定時任務 Quartz 很強大，就用它了。
Quartz 使用步驟：1.新增依賴
<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-quartz</artifactId></dependency>2.編寫配置檔案
package com.solo.coderiver.user.config;import com.solo.coderiver.user.task.LikeTask;import org.quartz.*;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;@Configurationpublic class QuartzConfig { private static final String LIKE_TASK_IDENTITY = "LikeTaskQuartz"; @Bean public JobDetail quartzDetail(){ return JobBuilder.newJob(LikeTask.class).withIdentity(LIKE_TASK_IDENTITY).storeDurably().build(); } @Bean public Trigger quartzTrigger(){ SimpleScheduleBuilder scheduleBuilder = SimpleScheduleBuilder.simpleSchedule()// .withIntervalInSeconds(10) //設定時間週期單位秒 .withIntervalInHours(2) //兩個小時執行一次 .repeatForever(); return TriggerBuilder.newTrigger().forJob(quartzDetail()) .withIdentity(LIKE_TASK_IDENTITY) .withSchedule(scheduleBuilder) .build(); }}3.編寫執行任務的類繼承自 QuartzJobBean
package com.solo.coderiver.user.task;import com.solo.coderiver.user.service.LikedService;import lombok.extern.slf4j.Slf4j;import org.apache.commons.lang.time.DateUtils;import org.quartz.JobExecutionContext;import org.quartz.JobExecutionException;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.scheduling.quartz.QuartzJobBean;import java.text.SimpleDateFormat;import java.util.Date;/** * 點讚的定時任務 */@Slf4jpublic class LikeTask extends QuartzJobBean { @Autowired LikedService likedService; private SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); @Override protected void executeInternal(JobExecutionContext jobExecutionContext) throws JobExecutionException { log.info("LikeTask-------- {}", sdf.format(new Date())); //將 Redis 裡的點贊資訊同步到資料庫裡 likedService.transLikedFromRedis2DB(); likedService.transLikedCountFromRedis2DB(); }}在定時任務中直接呼叫 LikedService 封裝的方法完成資料同步。
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