【spring】自定义缓存注解

为什么要自定义缓存注解？
Spring Cache本身提供@Cacheable、@CacheEvict、@CachePut等缓存注解，为什么还要自定义缓存注解呢？

@Cacheabe不能设置缓存时间，导致生成的缓存始终在redis中，当然这一点可以通过修改RedisCacheManager的配置来设置缓存时间：

@Bean
public RedisCacheManager redisCacheManager(RedisConnectionFactory redisConnectionFactory) {
	RedisCacheConfiguration redisCacheConfiguration = getRedisCacheConfiguration();
	RedisCacheManager cacheManager = RedisCacheManager
			.builder(RedisCacheWriter.nonLockingRedisCacheWriter(redisConnectionFactory))
			.cacheDefaults(redisCacheConfiguration)
			.build();
	return cacheManager;
}
private RedisCacheConfiguration getRedisCacheConfiguration() {
	Jackson2JsonRedisSerializer<Object> jackson2JsonRedisSerializer = new Jackson2JsonRedisSerializer<>(Object.class);
	ObjectMapper om = new ObjectMapper();
	om.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY);
	om.activateDefaultTyping(LaissezFaireSubTypeValidator.instance, ObjectMapper.DefaultTyping.NON_FINAL, JsonTypeInfo.As.WRAPPER_ARRAY);
	jackson2JsonRedisSerializer.setObjectMapper(om);
	RedisCacheConfiguration redisCacheConfiguration = RedisCacheConfiguration.defaultCacheConfig();
	redisCacheConfiguration = redisCacheConfiguration.serializeValuesWith(
			RedisSerializationContext
					.SerializationPair
					.fromSerializer(jackson2JsonRedisSerializer)
	).entryTtl(Duration.ofDays(7)); // 设置全局key的有效事件为7天
	return redisCacheConfiguration;
}

不过这个设置时全局的，所有的key的失效时间都一样，要想实现不同的key不同的失效时间，还得自定义缓存注解。

自定义缓存注解
Cached
类似Spring Cache的@Cacheable。

package com.morris.spring.custom.cache.annotation;

import org.springframework.core.annotation.AliasFor;

import java.lang.annotation.*;
import java.util.concurrent.TimeUnit;

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Documented
public @interface Cached {

	@AliasFor("cacheName")
	String value() default "";

	@AliasFor("value")
	String cacheName() default "";

	int expire() default 0;

	TimeUnit expireUnit() default TimeUnit.SECONDS;

	String key();

	String condition() default "";

	String unless() default "";

	boolean sync() default false;
}

CacheUpdate
类似于Spring Cache的@CachePut。

package com.morris.spring.custom.cache.annotation;

import org.springframework.core.annotation.AliasFor;

import java.lang.annotation.*;
import java.util.concurrent.TimeUnit;

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Documented
public @interface CacheUpdate {

	@AliasFor("cacheName")
	String value() default "";

	@AliasFor("value")
	String cacheName() default "";

	int expire() default 0;

	TimeUnit expireUnit() default TimeUnit.SECONDS;

	String key();

	String condition() default "";

	String unless() default "";
}

acheInvalidate
类似于Spring Cache的@CacheEvict。

package com.morris.spring.custom.cache.annotation;

import org.springframework.core.annotation.AliasFor;

import java.lang.annotation.*;

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Documented
public @interface CacheInvalidate {

	@AliasFor("cacheName")
	String value() default "";

	@AliasFor("value")
	String cacheName() default "";

	String key();

	String condition() default "";

	String unless() default "";
}

CachedAspect
@Cached注解的切面实现。

package com.morris.spring.custom.cache.annotation;

import com.morris.spring.custom.cache.Level2Cache;
import com.morris.spring.custom.cache.Level2CacheManage;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.springframework.cache.Cache;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.EnableAspectJAutoProxy;
import org.springframework.expression.EvaluationContext;

import javax.annotation.Resource;
import java.util.Objects;

@Configuration
@Aspect
@EnableAspectJAutoProxy // 开启AOP
public class CachedAspect {

	@Resource
	private Level2CacheManage cacheManager;

	@Around(value = "@annotation(cached)")
	public Object around(ProceedingJoinPoint joinPoint, Cached cached) throws Throwable {

		Level2Cache cache = cacheManager.getCache(cached.cacheName());

		ExpressionEvaluator evaluator = new ExpressionEvaluator();
		EvaluationContext context = evaluator.createEvaluationContext(joinPoint);

		Object key = evaluator.key(cached.key(), context);

		if(cached.sync()) {
			//
			return cache.get(key, () -> {
				try {
					return joinPoint.proceed();
				} catch (Throwable e) {
					e.printStackTrace();
					return null;
				}
			});
		}

		// 先查缓存
		Cache.ValueWrapper valueWrapper = cache.get(key);
		if (Objects.nonNull(valueWrapper)) {
			return valueWrapper.get();
		}

		Object result = joinPoint.proceed();

		context.setVariable("result", result);
		Boolean condition = evaluator.condition(cached.condition(), context);
		Boolean unless = evaluator.unless(cached.unless(), context);

		if (condition && !unless) {
			if (cached.expire() > 0) {
				cache.put(key, result, cached.expire(), cached.expireUnit());
			} else {
				cache.put(key, result);
			}
		}

		return result;
	}

}

CacheUpdateAspect
@CacheUpdate注解的切面实现类。

package com.morris.spring.custom.cache.annotation;

import com.morris.spring.custom.cache.Level2Cache;
import com.morris.spring.custom.cache.Level2CacheManage;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.springframework.context.annotation.Configuration;
import org.springframework.expression.EvaluationContext;

import javax.annotation.Resource;

@Configuration
@Aspect
public class CacheUpdateAspect {

	@Resource
	private Level2CacheManage cacheManager;

	@Around(value = "@annotation(cacheUpdate)")
	public Object around(ProceedingJoinPoint joinPoint, CacheUpdate cacheUpdate) throws Throwable {

		Level2Cache cache = cacheManager.getCache(cacheUpdate.cacheName());

		ExpressionEvaluator evaluator = new ExpressionEvaluator();
		EvaluationContext context = evaluator.createEvaluationContext(joinPoint);

		Object key = evaluator.key(cacheUpdate.key(), context);

		Object result = joinPoint.proceed();

		context.setVariable("result", result);
		Boolean condition = evaluator.condition(cacheUpdate.condition(), context);
		Boolean unless = evaluator.unless(cacheUpdate.unless(), context);

		if (condition && !unless) {
			if (cacheUpdate.expire() > 0) {
				cache.put(key, result, cacheUpdate.expire(), cacheUpdate.expireUnit());
			} else {
				cache.put(key, result);
			}
		}

		return result;
	}

}

CacheInvalidateAspect
@CacheInvalidate注解的切面实现类。

package com.morris.spring.custom.cache.annotation;

import com.morris.spring.custom.cache.Level2Cache;
import com.morris.spring.custom.cache.Level2CacheManage;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.springframework.context.annotation.Configuration;
import org.springframework.expression.EvaluationContext;

import javax.annotation.Resource;

@Configuration
@Aspect
public class CacheInvalidateAspect {

	@Resource
	private Level2CacheManage cacheManager;

	@Around(value = "@annotation(cacheInvalidate)")
	public Object around(ProceedingJoinPoint joinPoint, CacheInvalidate cacheInvalidate) throws Throwable {

		Level2Cache cache = cacheManager.getCache(cacheInvalidate.cacheName());

		ExpressionEvaluator evaluator = new ExpressionEvaluator();
		EvaluationContext context = evaluator.createEvaluationContext(joinPoint);

		Object key = evaluator.key(cacheInvalidate.key(), context);

		Object result = joinPoint.proceed();

		context.setVariable("result", result);
		Boolean condition = evaluator.condition(cacheInvalidate.condition(), context);
		Boolean unless = evaluator.unless(cacheInvalidate.unless(), context);

		if (condition && !unless) {
			cache.evict(key);
		}

		return result;
	}

}

ExpressionEvaluator
ExpressionEvaluator主要用于解析注解中key、condition、unless属性中的表达式。

package com.morris.spring.custom.cache.annotation;

import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.reflect.MethodSignature;
import org.springframework.aop.support.AopUtils;
import org.springframework.context.expression.MethodBasedEvaluationContext;
import org.springframework.core.DefaultParameterNameDiscoverer;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.Expression;
import org.springframework.expression.spel.standard.SpelExpressionParser;
import org.springframework.util.StringUtils;

import java.lang.reflect.Method;

public class ExpressionEvaluator {

	private final SpelExpressionParser parser = new SpelExpressionParser();

	public EvaluationContext createEvaluationContext(ProceedingJoinPoint joinPoint) {

		MethodSignature methodSignature = (MethodSignature) joinPoint.getSignature();
		Method specificMethod = AopUtils.getMostSpecificMethod(methodSignature.getMethod(), joinPoint.getTarget().getClass());

		MethodBasedEvaluationContext context = new MethodBasedEvaluationContext(joinPoint.getTarget(),
				specificMethod, joinPoint.getArgs(), new DefaultParameterNameDiscoverer());
		return context;
	}

	public Object key(String keyExpression, EvaluationContext evalContext) {
		Expression expression = parser.parseExpression(keyExpression);
		return expression.getValue(evalContext);
	}

	public boolean condition(String conditionExpression, EvaluationContext evalContext) {
		if(!StringUtils.hasText(conditionExpression)) {
			return true;
		}
		Expression expression = parser.parseExpression(conditionExpression);
		return (Boolean.TRUE.equals(expression.getValue(evalContext, Boolean.class)));
	}

	public boolean unless(String unlessExpression, EvaluationContext evalContext) {
		if(StringUtils.hasText(unlessExpression)) {
			return false;
		}
		Expression expression = parser.parseExpression(unlessExpression);
		return (Boolean.TRUE.equals(expression.getValue(evalContext, Boolean.class)));
	}

}

总结
自定义缓存注解使用了AOP的通知功能，所以需要开启AOP，需要在配置类上加上@EnableAspectJAutoProxy注解。
改进：可使用类似@EnableCache注解导入一个入口类，不再需要多个切面，多个注解的处理逻辑放在一起，参考Spring Cache。
扩展：解析表达式可使用缓存，加快解析速度；方法上面支持多个@Cached注解。