如何使用Spring Cache设置缓存条件操作

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Spring Cache设置缓存条件

原理

从Spring3.1开始，Spring框架提供了对Cache的支持，提供了一个对缓存使用的抽象，通过在既有代码中添加少量它定义的各种 annotation，即能够达到缓存方法的返回对象的作用。

提供的主要注解有@Cacheable、@CachePut、@CacheEvict和@Caching，具体见下表：

当需要在类上或方法上同时使用多个注解时，可以使用@Caching，如：

@Caching(cacheable=@Cacheable("User"), evict = {@CacheEvict("Member"), @CacheEvict(value = "Customer", allEntries = true)})

@Cacheable的常用属性及说明

如下表所示：

Root对象

@CachePut的常用属性同@Cacheable

@CacheEvict的常用属性如下表所示：

示例：设置当 dname 的长度大于3时才缓存

//条件缓存@ResponseBody@GetMapping("/getLocByDname")@Cacheable(cacheNames = "dept", key = "#dname", condition = "#dname.length()>3")public String getLocByDname(@RequestParam("dname") String dname) {//key动态参数    QueryWrapper queryMapper = new QueryWrapper<>();    queryMapper.eq("dname", dname);    Dept dept = deptService.getOne(queryMapper);    return dept.getLoc();}

示例：unless 即条件不成立时缓存

#result 代表返回值，意思是当返回码不等于 200 时不缓存，也就是等于 200 时才缓存。

@ResponseBody@GetMapping("/getDeptByDname")@Cacheable(cacheNames = "dept", key = "#dname", unless = "#result.code != 200")public Result getDeptByDname(@RequestParam("dname") String dname){//key动态参数    QueryWrapper queryMapper = new QueryWrapper<>();    queryMapper.eq("dname", dname);    Dept dept = deptService.getOne(queryMapper);    if (dept == null)        return ResultUtil.error(120, "dept is null");    else        return ResultUtil.success(dept);}

Cache缓存配置

1、pom.xml

 org.springframework.boot spring-boot-starter-cache org.springframework.boot spring-boot-starter-aop    org.reflections    reflections    0.9.11

2、Ehcache配置文件

3、配置类

@Configuration@EnableCachingpublic class CustomConfiguration {    /**     * @see org.springframework.cache.interceptor.SimpleKeyGenerator     * Generate a key based on the specified parameters.     */    public static Object generateKey(Object... params) {        if (params.length == 0) {            return SimpleKey.EMPTY;        }        if (params.length == 1) {            Object param = params[0];            if (param != null && !param.getClass().isArray()) {                return param;            }        }        return new SimpleKey(params);    }/** * 若将target作为key的一部分时，CGLIB动态代理可能导致重复缓存 * 注意：返回的key一定要重写hashCode()和toString()，防止key对象不一致导致的缓存无法命中 * 例如：ehcache 底层存储net.sf.ehcache.store.chm.SelectableConcurrentHashMap#containsKey */    @Bean    public KeyGenerator customKeyGenerator(){        return (target, method, params) -> {            final Object key = generateKey(params);            StringBuffer buffer = new StringBuffer();            buffer.append(method.getName());            buffer.append("::");            buffer.append(key.toString());// 注意一定要转为String,否则ehcache key对象可能不一样，导致缓存无法命中            return buffer.toString();        };    }    /**     * redis缓存管理器     */    @Bean    @ConditionalOnBean(RedisConfiguration.class)    @ConditionalOnProperty(prefix = "spring.cache", name = "type", havingValue = "redis",            matchIfMissing = false)    public CacheManager redisCacheManager(RedisConnectionFactory redisConnectionFactory) {        RedisCacheConfiguration config = RedisCacheConfiguration.defaultCacheConfig()                .serializeKeysWith(RedisSerializationContext.SerializationPair.fromSerializer(new StringRedisSerializer()))                .serializeValuesWith(RedisSerializationContext.SerializationPair.fromSerializer(new GenericJackson2JsonRedisSerializer()))                .entryTtl(Duration.ofMinutes(10));        return RedisCacheManager                .builder(RedisCacheWriter.lockingRedisCacheWriter(redisConnectionFactory))                .cacheDefaults(config).build();    }/** * ehcache缓存管理器(默认) * default XML files {@link net.sf.ehcache.config.ConfigurationFactory#parseConfiguration()} */    @Bean    @ConditionalOnProperty(prefix = "spring.cache", name = "type", havingValue = "ehcache",            matchIfMissing = true)    public CacheManager ehcacheCacheManager() {        net.sf.ehcache.CacheManager cacheManager = net.sf.ehcache.CacheManager.create();        /**         * 包扫描查找指定注解并将cacheNames添加到net.sf.ehcache.CacheManager（单例）         */        Reflections reflections = new Reflections("com.example.demo.service", new TypeAnnotationsScanner()                , new SubTypesScanner(), new MethodAnnotationsScanner());        Set> classesList = reflections.getTypesAnnotatedWith(CacheConfig.class);        for (Class aClass : classesList) {            final CacheConfig config = AnnotationUtils.findAnnotation(aClass, CacheConfig.class);            if (config.cacheNames() != null && config.cacheNames().length > 0) {                for (String cacheName : config.cacheNames()) {                    cacheManager.addCacheIfAbsent(cacheName);                }            }        }        /**         * 方法级别的注解 @Caching、@CacheEvict、@Cacheable、@CachePut,结合实际业务场景仅扫描@Cacheable即可         */        final Set methods = reflections.getMethodsAnnotatedWith(Cacheable.class);        for (Method method : methods) {            final Cacheable cacheable = AnnotationUtils.findAnnotation(method, Cacheable.class);            if (cacheable.cacheNames() != null && cacheable.cacheNames().length > 0) {                for (String cacheName : cacheable.cacheNames()) {                    cacheManager.addCacheIfAbsent(cacheName);                }            }        }        EhCacheCacheManager ehCacheCacheManager = new EhCacheCacheManager();        ehCacheCacheManager.setCacheManager(cacheManager);        return ehCacheCacheManager;    }}

4、示例

@Component@CacheConfig(cacheNames = "XXXServiceImpl", keyGenerator = "customKeyGenerator")public class XXXServiceImpl extends ServiceImpl implements XXXService {    @CacheEvict(allEntries = true)    public void evictAllEntries() {}    @Override    @Cacheable    public List findById(Long id) {        return this.baseMapper.selectList(new QueryWrapper().lambda()                .eq(XXXEntity::getId, id));    }}

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