Spring与Redis集成

1.引入RedisTemplate

据以前的情况，我们在Java中使用Redis时一般是使用Jedis来操作的，大致的一段代码如下所示

    @Override
    public User findUserById(Integer id) {
        User user = null;
        Jedis jedis = null;
        try {
            jedis = jedisPool.getResource();
            String userStr = jedis.get("user_" + id); // 尝试获取数据
            if (userStr != null && !userStr.isEmpty()) { // 如果获取到有效数据，则转换后返回
                user = JSONObject.parseObject(userStr, User.class);
            } else {// 如果没有获取到数据，则查询数据库返回
                user = userMapper.findUserById(id);
                if (user != null) jedis.set("user_" + id, JSONObject.toJSONString(user)); // 设置到redis中
            }
        } finally {
            // 记得关闭Jedis，因为这里使用的是JedisPool，所以这里的关闭并不是直接关闭连接，而是释放，以供其他的业务使用
            if (jedis != null) jedis.close();
        }
        return user;
    }

上边的这样的一段代码其实是有些臃肿的，但是如果我们引入RedisTemplate，其实会简化不少。

• maven 引入 spring-data-redis

  <dependency>
    <groupId>redis.clients</groupId>
    <artifactId>jedis</artifactId>
    <version>3.9.0</version>
  </dependency>
  <dependency>
    <groupId>org.springframework.data</groupId>
    <artifactId>spring-data-redis</artifactId>
    <version>2.2.13.RELEASE</version>
  </dependency>

• 将RedisTemplate 加入Bean容器中，让Spring进行管理。

  @Bean
  public RedisConnectionFactory redisConnectionFactory() {
      RedisStandaloneConfiguration redisStandaloneConfiguration = new RedisStandaloneConfiguration();
      redisStandaloneConfiguration.setHostName(host);
      redisStandaloneConfiguration.setPort(port);

      RedisConnectionFactory redisConnectionFactory = new JedisConnectionFactory(redisStandaloneConfiguration);
      return redisConnectionFactory;
  }

  @Bean
  public RedisTemplate redisTemplate(RedisConnectionFactory redisConnectionFactory) {
      RedisTemplate redisTemplate = new RedisTemplate();
      redisTemplate.setConnectionFactory(redisConnectionFactory);
      //设置key值的序列化方式，默认是JDK的形式
      redisTemplate.setKeySerializer(StringRedisSerializer.UTF_8);
      return redisTemplate;
  }

• 如果使用RedisTemplate的替换的话，会简洁很多。

  @Autowired
  private RedisTemplate redisTemplate;

  @Override
  public User findUserById(Integer id) {
      Object result = redisTemplate.opsForValue().get("user_" + id);
      if (result != null) return (User) result;

      User user = userMapper.findUserById(id);
      // 设置到redis中
      if (user != null) redisTemplate.opsForValue().set("user_" + id, user);

      return user;
  }

• 大概看一下关于RedisTemplate的方法

看了以上的内容，可以看到引入了RedisTemplate其实已经很简洁了，但是明显还不够，下面我们将考虑引入 “注解”

2. 引入注解

• 开启缓存 @EnableCaching

@Configuration@EnableCachingpublicclassAppConfig{...}

• 引入@Cacheable，表示这个方法将会访问缓存，如果无法命中缓存的话，会将方法返回的值存入redis，假设有注解为 @Cacheable(value="user", key = "#id")，那么生成的key值为 user::{id}，即如果id为1 那么生成的 key就是 user::1

@Override@Cacheable(value="user", key ="#id")// 这里返回的值会被存放到redis，key-value格式，其中生成的key值(假设id为1)： user::1publicUserfindUserById(Integer id){User user = userMapper.findUserById(id);return user;}

但是这样还不够，因为Spring并不清楚缓存的方式是什么，这就涉及到

CacheManager

了

• 设置CacheManager，在AppConfig中加入以下内容

@BeanpublicRedisConnectionFactoryredisConnectionFactory(){RedisStandaloneConfiguration redisStandaloneConfiguration =newRedisStandaloneConfiguration();
    redisStandaloneConfiguration.setHostName(host);// 这里是redis的ip
    redisStandaloneConfiguration.setPort(port);// 这里是redis的端口// 自适应集群变化RedisConnectionFactory redisConnectionFactory =newJedisConnectionFactory(redisStandaloneConfiguration);return redisConnectionFactory;}@BeanpublicRedisCacheConfigurationredisCacheConfiguration(){RedisCacheConfiguration redisCacheConfiguration =RedisCacheConfiguration.defaultCacheConfig().serializeKeysWith(RedisSerializationContext.SerializationPair.fromSerializer(RedisSerializer.string())).serializeValuesWith(RedisSerializationContext.SerializationPair.fromSerializer(RedisSerializer.json()));return redisCacheConfiguration;}@BeanpublicRedisCacheWriterredisCacheWriter(RedisConnectionFactory redisConnectionFactory){RedisCacheWriter redisCacheWriter =RedisCacheWriter.nonLockingRedisCacheWriter(redisConnectionFactory);return redisCacheWriter;}@BeanpublicCacheManagercacheManager(RedisCacheWriter redisCacheWriter,RedisCacheConfiguration redisCacheConfiguration){CacheManager cacheManager =newRedisCacheManager(redisCacheWriter, redisCacheConfiguration);((RedisCacheManager) cacheManager).isTransactionAware();return cacheManager;}

3. 自行通过注解和AOP实现缓存

• 引入AOP相关的包

<dependency><groupId>org.springframework</groupId><artifactId>spring-aop</artifactId><version>5.3.22</version></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-aspects</artifactId><version>5.3.22</version></dependency><!-- Jackson JSON Processor --><dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-core</artifactId><version>2.9.8</version></dependency><dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-databind</artifactId><version>2.9.8</version></dependency><dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-annotations</artifactId><version>2.9.8</version></dependency><dependency><groupId>com.alibaba</groupId><artifactId>fastjson</artifactId><version>1.2.28</version></dependency>

• 创建@CustomCache

@Target(ElementType.METHOD)@Retention(RetentionPolicy.RUNTIME)public@interfaceCustomCache{/**
   * key的规则，可以使用springEL表达式，可以使用方法执行的一些参数
   */Stringkey();/**
   *  类似前缀
   * @return
   */Stringvalue();}

• 修改AppConfig

@EnableAspectJAutoProxy// 开启AOP自动代理publicclassAppConfig{@BeanpublicRedisConnectionFactoryredisConnectionFactory(){RedisStandaloneConfiguration redisStandaloneConfiguration =newRedisStandaloneConfiguration();
        redisStandaloneConfiguration.setHostName(host);
        redisStandaloneConfiguration.setPort(port);// 自适应集群变化RedisConnectionFactory redisConnectionFactory =newJedisConnectionFactory(redisStandaloneConfiguration);return redisConnectionFactory;}@BeanpublicRedisTemplateredisTemplate(RedisConnectionFactory redisConnectionFactory){RedisTemplate redisTemplate =newRedisTemplate();
        redisTemplate.setConnectionFactory(redisConnectionFactory);
        redisTemplate.setKeySerializer(StringRedisSerializer.UTF_8);
        redisTemplate.setValueSerializer(StringRedisSerializer.UTF_8);return redisTemplate;}}

• 创建 CustomCacheAspect

@Component@AspectpublicclassCustomCacheAspect{@AutowiredprivateRedisTemplate redisTemplate;@Pointcut("@annotation(cn.lazyfennec.cache.redis.annotation.CustomCache)")publicvoidcachePointcut(){}@Around("cachePointcut()")publicObjectdoCache(ProceedingJoinPoint joinPoint){Object obj =null;try{MethodSignature signature =(MethodSignature) joinPoint.getSignature();Method method = joinPoint.getTarget().getClass().getMethod(signature.getName(), signature.getMethod().getParameterTypes());CustomCache customCache = method.getAnnotation(CustomCache.class);String cacheKey = customCache.key();String cacheValue = customCache.value();// 创建解析器ExpressionParser parser =newSpelExpressionParser();Expression expression = parser.parseExpression(cacheKey);EvaluationContext context =newStandardEvaluationContext();// 参数// 添加参数Object[] args = joinPoint.getArgs();DefaultParameterNameDiscoverer discover =newDefaultParameterNameDiscoverer();String[] parameterNames = discover.getParameterNames(method);for(int i =0; i < parameterNames.length; i++){
                context.setVariable(parameterNames[i], args[i].toString());}// 解析String key = cacheValue +"::"+ expression.getValue(context).toString();// 1、 判定缓存中是否存在
            obj = redisTemplate.opsForValue().get(key);if(obj !=null)return obj;// 2、不存在则继续行方法
            obj = joinPoint.proceed();// 3、 同步存储value到缓存。
            redisTemplate.opsForValue().set(key, obj);}catch(NoSuchMethodException e){
            e.printStackTrace();}catch(Throwable throwable){
            throwable.printStackTrace();}return obj;}}

• 新建方法 getUserNameById

@RequestMapping("/custom/name/{id}")@ResponseBodypublicStringgetUserNameById(@PathVariableInteger id){return userService.getUserNameById(id);}

• 实际实现方法 getUserNameById，使用方式

@Override@CustomCache(value ="custom_user", key ="#id")publicStringgetUserNameById(Integer id){return userMapper.findUserNameById(id);}