多个切面执行顺序（请先看spring cache篇）

代码https://github.com/HiwayChe/zheng/tree/develop/zheng-test

spring cache篇https://www.jianshu.com/p/b9e85a139ea0

Cache切面在事务切面前面，只有事务执行成功才往cache中缓存数据。
代码中共有4个切面，分别为获取缓存失效时间，设置缓存，切换数据源，事务。
执行顺序：CacheExpireAdvice.before->CacheInterceptor.invoke->MultiDataSourceAdvice.before->TransactionInterceptor.invode->MultiDataSourceAdvice.afterReturning->CacheExpireAdvice.afterReturning。
其中CacheInterceptor和TransactionInterceptor没有before,afterReturning之分。
afterReturning只有在方法成功后才执行，如果target中抛了异常，那么afterReturning是不会执行的。如TransactionInterceptor执行失败，CacheInterceptor是不会缓存数据的。

执行CacheTest4测试用例，日志解析如下：

@Test
    public void test(){
        String key = "fafaxxx";
        Account account;
        for(int i=0;i<2;i++){
            account = this.accountService.getAccountByName(key);
            try {
                this.logger.info("sleeping................");
                TimeUnit.SECONDS.sleep(3);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

        this.accountService.update(key);
        this.logger.info("cache evicted....");
        for(int i=0;i<2;i++){
            account = this.accountService.getAccountByName(key);
            try {
                this.logger.info("sleeping................");
                TimeUnit.SECONDS.sleep(3);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

    }

日志：

#执行CacheExpireAdvice.before方法，获取缓存失效时间
01-11 00:35:27 [main] INFO  CacheExpireAdvice.before() | CacheExpireAdvice before, target method:getAccountByName
#切换数据源
01-11 00:35:27 [main] INFO  DataSourceAdvice.before() | DataSourceAdvice before,target method:getAccountByName
#当前数据源是read
01-11 00:35:27 [main] INFO  MultiDataSource.determineCurrentLookupKey() | current database:read
#由于是第一次执行，缓存中没有数据，这里从db中查找
01-11 00:35:27 [main] INFO  AccountService.getFromDB() | =====================real querying db... fafaxxx
#清空数据源设置（到这里说明事务成功了）
01-11 00:35:27 [main] INFO  DataSourceAdvice.afterReturning() | DataSourceAdvice after,target method:getAccountByName
#db中查询的结果缓存起来，有失效时间的
01-11 00:35:27 [main] INFO  MyRedisCache.put() | cache with expire.....
#清空失效时间值
01-11 00:35:27 [main] INFO  CacheExpireAdvice.afterReturning() | CacheExpireAdvice after, target method:getAccountByName
#代码sleeping
01-11 00:35:27 [main] INFO  CacheTest4.test() | sleeping................
#第二次执行（这时缓存中有数据了），获取缓存失效值
01-11 00:35:30 [main] INFO  CacheExpireAdvice.before() | CacheExpireAdvice before, target method:getAccountByName
#由于缓存中有数据了，这里直接在CacheInterceptor中返回，不再走db。清空失效值
01-11 00:35:30 [main] INFO  CacheExpireAdvice.afterReturning() | CacheExpireAdvice after, target method:getAccountByName
#代码sleeping
01-11 00:35:30 [main] INFO  CacheTest4.test() | sleeping................
#进入到update方法（这个方法会清空缓存）。
01-11 00:35:33 [main] INFO  DataSourceAdvice.before() | DataSourceAdvice before,target method:update
#切换数据源到write
01-11 00:35:33 [main] INFO  MultiDataSource.determineCurrentLookupKey() | current database:write
01-11 00:35:33 [main] INFO  AccountService.update() | update or delete account from DB, evict from cache
#清空数据源设置
01-11 00:35:33 [main] INFO  DataSourceAdvice.afterReturning() | DataSourceAdvice after,target method:update
01-11 00:35:33 [main] INFO  CacheTest4.test() | cache evicted....
#再次读取数据，和最上面的一样了
01-11 00:35:33 [main] INFO  CacheExpireAdvice.before() | CacheExpireAdvice before, target method:getAccountByName
01-11 00:35:33 [main] INFO  DataSourceAdvice.before() | DataSourceAdvice before,target method:getAccountByName
01-11 00:35:33 [main] INFO  MultiDataSource.determineCurrentLookupKey() | current database:read
01-11 00:35:33 [main] INFO  AccountService.getFromDB() | =====================real querying db... fafaxxx
01-11 00:35:33 [main] INFO  DataSourceAdvice.afterReturning() | DataSourceAdvice after,target method:getAccountByName
01-11 00:35:33 [main] INFO  MyRedisCache.put() | cache with expire.....
01-11 00:35:33 [main] INFO  CacheExpireAdvice.afterReturning() | CacheExpireAdvice after, target method:getAccountByName
01-11 00:35:33 [main] INFO  CacheTest4.test() | sleeping................
01-11 00:35:36 [main] INFO  CacheExpireAdvice.before() | CacheExpireAdvice before, target method:getAccountByName
01-11 00:35:36 [main] INFO  CacheExpireAdvice.afterReturning() | CacheExpireAdvice after, target method:getAccountByName
01-11 00:35:36 [main] INFO  CacheTest4.test() | sleeping................