MyBatis-Plus中用Redis作为二级缓存,对mapper层操作方法

MyBatis-plus中存在BaseMapper接口，实现了本接口的方法，可以使用QueryWallper进行快速的SQL编写，但是这样会导致一些问题，比如复杂SQL，业务逻辑的需求，这类方面可能会造成一些困扰。本文是将使用MyBatis-Plus的方法添加Redis缓存，一般来说Redis的缓存放置于Service，对于详细的业务来说，更是可以细化至方法，本文为了简化，将其放入了mapper层，使用的是AOP的方式进行Redis的控制，在主启动类加入EnableCache，在对应的mapper层上也加入了相对于注解，起到了简化开发的作用。

一.导入Maven依赖  pom.xml文件

         <!--redis缓存依赖-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-redis</artifactId>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
        </dependency>

 二.更改application.yml文件

 ##redis配置
  # Redis数据库索引（默认为0）
  redis:
    database: 0
    # Redis服务器地址
    host: 127.0.0.1
  # Redis服务器连接端口
    port: 6379
  # Redis服务器连接密码（默认为空）
    password:
  # 连接池最大连接数（使用负值表示没有限制）
    jedis:
      pool:
        max-idle: 8
  # 连接池最大阻塞等待时间（使用负值表示没有限制）
        max-wait: -1
  # 连接池中的最小空闲连接
        min-idle: 0
  # 连接超时时间（毫秒）
    timeout: 5000

mybatis-plus:
    #开启二级缓存，使用redis配置
    cache-enabled: true

三.定义RedisTemplate的bean交给spring管理，这里为了能将对象直接存取到redis中，进行了一些序列化的操作

import com.fasterxml.jackson.annotation.JsonAutoDetect;
import com.fasterxml.jackson.annotation.PropertyAccessor;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.cache.CacheManager;
import org.springframework.context.annotation.Bean;
import org.springframework.data.redis.cache.RedisCacheConfiguration;
import org.springframework.data.redis.cache.RedisCacheManager;
import org.springframework.data.redis.cache.RedisCacheWriter;
import org.springframework.data.redis.connection.RedisConnectionFactory;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.serializer.Jackson2JsonRedisSerializer;
import org.springframework.data.redis.serializer.RedisSerializer;
import org.springframework.data.redis.serializer.StringRedisSerializer;

import java.time.Duration;

/**
 * @class: RedisConfiguration
 * redis的配置文件，template对映序列化规则，以及混村有效时间的设置
 */
public class RedisConfiguration {
    @Bean
    public CacheManager cacheManager(RedisConnectionFactory redisConnectionFactory) {
        RedisCacheConfiguration redisCacheConfiguration = RedisCacheConfiguration.defaultCacheConfig()
                .entryTtl( Duration.ofHours(1)); // 设置缓存有效期一小时
        return RedisCacheManager
                .builder( RedisCacheWriter.nonLockingRedisCacheWriter(redisConnectionFactory))
                .cacheDefaults(RedisCacheConfiguration.defaultCacheConfig(Thread.currentThread().getContextClassLoader())).build();
    }

    @Bean(value = "redisTemplate")
    public RedisTemplate<String, Object> redisTemplate(RedisConnectionFactory connectionFactory) {
        RedisTemplate<String, Object> redisTemplate = new RedisTemplate<>();
        redisTemplate.setConnectionFactory(connectionFactory);
        //Use Jackson 2Json RedisSerializer to serialize and deserialize the value of redis (default JDK serialization)
        Jackson2JsonRedisSerializer jackson2JsonRedisSerializer = new Jackson2JsonRedisSerializer(Object.class);
        ObjectMapper objectMapper = new ObjectMapper();
        objectMapper.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY);
        //将类名称序列化到json串中
        objectMapper.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);
        //设置输入时忽略JSON字符串中存在而Java对象实际没有的属性
        objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
        jackson2JsonRedisSerializer.setObjectMapper(objectMapper);

        //Use String RedisSerializer to serialize and deserialize the key value of redis
        RedisSerializer redisSerializer = new StringRedisSerializer();
        //key
        redisTemplate.setKeySerializer(redisSerializer);
        redisTemplate.setHashKeySerializer(redisSerializer);
        //value
        redisTemplate.setValueSerializer(jackson2JsonRedisSerializer);
        redisTemplate.setHashValueSerializer(jackson2JsonRedisSerializer);

        redisTemplate.afterPropertiesSet();
        return redisTemplate;

    }

}

四.自定义缓存管理

import lombok.extern.slf4j.Slf4j;
import org.apache.ibatis.cache.Cache;
import org.springframework.data.redis.connection.RedisServerCommands;
import org.springframework.data.redis.core.Cursor;
import org.springframework.data.redis.core.RedisCallback;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.core.ScanOptions;
import org.springframework.util.CollectionUtils;

import java.util.HashSet;
import java.util.Set;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

/**
 * @class: MybatisRedisCache
 */
@Slf4j
public class MybatisRedisCache implements Cache {

    // 读写锁
    private final ReadWriteLock readWriteLock = new ReentrantReadWriteLock(true);

    //这里使用了redis缓存，使用springboot自动注入
    private RedisTemplate<String, Object> redisTemplate;

    private String id;

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

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

    @Override
    public void putObject(Object key, Object value) {
        if (redisTemplate == null) {
            //由于启动期间注入失败，只能运行期间注入，这段代码可以删除
            redisTemplate = (RedisTemplate<String, Object>) SpringUtil.getBean("redisTemplate");
        }
        if (value != null) {
            redisTemplate.opsForValue().set(key.toString(), value);
        }
    }

    @Override
    public Object getObject(Object key) {
        if (redisTemplate == null) {
            //由于启动期间注入失败，只能运行期间注入，这段代码可以删除
            redisTemplate = (RedisTemplate<String, Object>) SpringUtil.getBean("redisTemplate");
        }
        try {
            if (key != null) {
                return redisTemplate.opsForValue().get(key.toString());
            }
        } catch (Exception e) {
            e.printStackTrace();
            log.error("缓存出错 ");
        }
        return null;
    }

    @Override
    public Object removeObject(Object key) {
        if (redisTemplate == null) {
            //由于启动期间注入失败，只能运行期间注入，这段代码可以删除
            redisTemplate = (RedisTemplate<String, Object>) SpringUtil.getBean("redisTemplate");
        }
        if (key != null) {
            redisTemplate.delete(key.toString());
        }
        return null;
    }

    @Override
    public void clear() {
        log.debug("清空缓存");
        if (redisTemplate == null) {
            redisTemplate = (RedisTemplate<String, Object>) SpringUtil.getBean("redisTemplate");
        }
        try {
            Set<String> keys = scan(this.id);
            if (!CollectionUtils.isEmpty(keys)) {
                redisTemplate.delete(keys);
            }
        } catch (Exception e) {
            log.error("清空缓存", e);
        }
    }

    public Set<String> scan(String matchKey) {
        if (redisTemplate == null) {
            redisTemplate = (RedisTemplate<String, Object>) SpringUtil.getBean("redisTemplate");
        }
        Set<String> keys = redisTemplate.execute((RedisCallback<Set<String>>) connection -> {
            Set<String> keysTmp = new HashSet<>();
            Cursor<byte[]> cursor = connection.scan(new ScanOptions.ScanOptionsBuilder().match("*" + matchKey + "*").count(1000).build());
            while (cursor.hasNext()) {
                keysTmp.add(new String(cursor.next()));
            }
            return keysTmp;
        });

        return keys;
    }

    @Override
    public int getSize() {
        if (redisTemplate == null) {
            //由于启动期间注入失败，只能运行期间注入，这段代码可以删除
            redisTemplate = (RedisTemplate<String, Object>) SpringUtil.getBean("redisTemplate");
        }
        Long size = redisTemplate.execute((RedisCallback<Long>) RedisServerCommands::dbSize);
        return size.intValue();
    }

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

}

五.编写工具类

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

/**
 * @class: SpringUtil
 * 工具类
 */
@Component
public class SpringUtil implements ApplicationContextAware {

    private static ApplicationContext applicationContext;

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

    public static Object getBean(String name){
        return applicationContext.getBean(name);
    }

    public static <T> T getBean(String name, Class<T> clazz){
        return applicationContext.getBean(name, clazz);
    }

    public static <T> T getBean(Class<T> clazz){
        return applicationContext.getBean(clazz);
    }
}

六.在mapper层中加入注解

//redis缓存注解
@CacheNamespace(implementation= MybatisRedisCache.class,eviction= MybatisRedisCache.class)
public interface ElectronicFenceMapper extends BaseMapper<ElectronicFence> {

}

七.主启动类加入注解

@EnableCaching
public class RedisText{
  
}