mybatis+redis 註解方式實現二級緩存

1，加入redis依賴

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-redis</artifactId>
</dependency>


spring:
  redis:
    database: 0
    host: localhost
    port: 6379

2，重新定義redis序列化方式

@Bean
    public RedisTemplate<String,Object> redisTemplate(RedisConnectionFactory redisConnectionFactory){
        /**
         * 配置自己的redisTemplate
         * StringRedisTemplate 默認使用使用StringRedisSerializer來序列化
         * RedisTemplate 默認使用JdkSerializationRedisSerializer來序列化
         */
        RedisTemplate<String, Object> redisTemplate = new RedisTemplate<>();
        redisTemplate.setConnectionFactory(redisConnectionFactory);

        //開啓默認類型
        ObjectMapper objectMapper = new ObjectMapper();
        objectMapper.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY);
        objectMapper.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);
        objectMapper.setDateFormat(new SimpleDateFormat("yyyy/MM/dd HH:mm:ss"));
        Jackson2JsonRedisSerializer jackson2JsonRedisSerializer = new Jackson2JsonRedisSerializer(Object.class);
        jackson2JsonRedisSerializer.setObjectMapper(objectMapper);

        redisTemplate.setKeySerializer(new StringRedisSerializer());
        redisTemplate.setValueSerializer(jackson2JsonRedisSerializer);
        redisTemplate.setHashKeySerializer(new StringRedisSerializer());
        redisTemplate.setHashValueSerializer(jackson2JsonRedisSerializer);
        redisTemplate.afterPropertiesSet();
        return redisTemplate;
    }

3，編寫mybatis的自定義緩存類

import org.apache.ibatis.cache.Cache;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.data.redis.core.RedisCallback;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.core.ValueOperations;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

public class RedisCache implements Cache {
    private static final Logger logger = LoggerFactory.getLogger(RedisCache.class);

    private final ReadWriteLock readWriteLock = new ReentrantReadWriteLock();
    private final String id;
    private RedisTemplate redisTemplate;
/**
     * 緩存自動過期時間 24小時
     */
    private static final long EXPIRE_TIME_IN_HOURS = 24;

    public RedisCache(String id) {
        if (id == null) {
            throw new IllegalArgumentException("Cache instances require an ID");
        }
        this.id = id;
    }

    @Override
    public String getId() {
        return id;
    }

    /**
     * Put query result to redis
     *
     * @param key
     * @param value
     */
    @Override
    @SuppressWarnings("unchecked")
    public void putObject(Object key, Object value) {
        try {
            RedisTemplate redisTemplate = getRedisTemplate();
            ValueOperations opsForValue = redisTemplate.opsForValue();
            opsForValue.set(key.toString(), value, EXPIRE_TIME_IN_HOURS, TimeUnit.HOURS);
            logger.debug("Put query result to redis");
        }
        catch (Throwable t) {
            logger.error("Redis put failed", t);
        }
    }

    /**
     * Get cached query result from redis
     *
     * @param key
     * @return
     */
    @Override
    public Object getObject(Object key) {
        try {
            RedisTemplate redisTemplate = getRedisTemplate();
            ValueOperations opsForValue = redisTemplate.opsForValue();
            logger.debug("Get cached query result from redis");
            return opsForValue.get(key.toString());
        }
        catch (Throwable t) {
            logger.error("Redis get failed, fail over to db", t);
            return null;
        }
    }

    /**
     * Remove cached query result from redis
     *
     * @param key
     * @return
     */
    @Override
    @SuppressWarnings("unchecked")
    public Object removeObject(Object key) {
        try {
            RedisTemplate redisTemplate = getRedisTemplate();
            redisTemplate.delete(key);
            logger.debug("Remove cached query result from redis");
        }
        catch (Throwable t) {
            logger.error("Redis remove failed", t);
        }
        return null;
    }

    /**
     * Clears this cache instance
     */
    @Override
    public void clear() {
        RedisTemplate redisTemplate = getRedisTemplate();
        redisTemplate.execute((RedisCallback) connection -> {
            connection.flushDb();
            return null;
        });
        logger.debug("Clear all the cached query result from redis");
    }

    /**
     * This method is not used
     *
     * @return
     */
    @Override
    public int getSize() {
        return 0;
    }

    @Override
    public ReadWriteLock getReadWriteLock() {
        return readWriteLock;
    }

    private RedisTemplate getRedisTemplate() {
        if (redisTemplate == null) {
            redisTemplate = ApplicationContextHolder.getBean("redisTemplate");
        }
        return redisTemplate;
    }
}

4，數據接口層添加緩存註解

啓用二級緩存可在xml文件啓用和mapper上使用@CacheNamespace 這兩種方式
只能有一種生效，不能同時使用
因爲mapper層通常簡單的查詢直接用標籤實現的或者繼承公共方法extends BaseMapper等等，所以推薦使用@CacheNamespace

//開啓緩存，默認所有查詢都緩存，所有修改刪除新增清空緩存
@CacheNamespace(implementation = RedisCache.class)
@Repository
public interface ProductMapper {
    /**
     * 默認緩存
     * @return
     */

    @Select("select code,name from product where code=#{id}")
    Product select(@Param("id")long id);
    /**
     * 自動清空緩存
     * @return
     */
    void update(Product product);
    
    /**
     * 指定禁用緩存
     * @return
     */
    @Options(useCache = false)
    @Select("select code,name from product where code=#{id}")
    Product select2(@Param("id")long id);
    
    
    /**
     * 某些複雜更新寫在xml中的，使用Flush使下次查詢刷新緩存
     * @return
     */
    @Flush
    int batchUpdate(@Param("id")long id);
}

5，所有緩存對象必須序列化，並添加無參構造函數

@Data
public class Product implements Serializable {
    private static final long serialVersionUID = -5035766641884746376L;
    public Product(){}

    private String code;

    private String name;
}

6，ApplicationContextHolder 保存全局上下文，用於獲取bean

import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;

@Component
public class ApplicationContextHolder implements ApplicationContextAware {
    private static ApplicationContext applicationContext;

    @Override
    public void setApplicationContext(ApplicationContext ctx) throws BeansException {
        applicationContext = ctx;
    }

    /**
     * Get application context from everywhere
     *
     * @return
     */
    public static ApplicationContext getApplicationContext() {
        return applicationContext;
    }

    /**
     * Get bean by class
     *
     * @param clazz
     * @param <T>
     * @return
     */
    public static <T> T getBean(Class<T> clazz) {
        return applicationContext.getBean(clazz);
    }

    /**
     * Get bean by class name
     *
     * @param name
     * @param <T>
     * @return
     */
    @SuppressWarnings("unchecked")
    public static <T> T getBean(String name) {
        return (T) applicationContext.getBean(name);
    }
}