/**
* when executing a query operation 1. record this statement's id and it's corresponding Cache
* Object into Global Caching Manager; 2. record this statement's id and
*
* @param invocation
* @return
* @throws Throwable
*/
private Object processQuery(Invocation invocation) throws Throwable {
Object result = invocation.proceed();
if (cachingManager.isCacheEnabled()) {
Object[] args = invocation.getArgs();
MappedStatement mappedStatement = (MappedStatement) args[0];
// 如果本条statementId表示的查询语句配置了 flushCache=true，则清空querCacheOnCommit缓存
if (mappedStatement.isFlushCacheRequired()) {
queryCacheOnCommit.clear();
}
// 如果本条statementId表示的查询语句配置了使用缓存，并且二级缓存不为空，则将StatementId
// 和对应的二级缓存对象映射关系添加到全局缓存映射管理器中
if (mappedStatement.isUseCache() && mappedStatement.getCache() != null) {
cachingManager.appendStatementCacheMap(mappedStatement.getId(), mappedStatement.getCache());
}
Object parameter = args[1];
RowBounds rowBounds = (RowBounds) args[2];
Executor executor = (Executor) invocation.getTarget();
BoundSql boundSql = mappedStatement.getBoundSql(parameter);
// 记录本次查询所产生的CacheKey
CacheKey cacheKey = executor.createCacheKey(mappedStatement, parameter, rowBounds, boundSql);
queryCacheOnCommit.putElement(mappedStatement.getId(), cacheKey);
}
return result;
}
/**
* when the sqlSession has been committed,rollbacked,or closed, session buffer query CacheKeys and
* update Statement collections should be cleared.
*
* <p>当SqlSession 执行了commit()、rollback()、close()方法， Session级别的查询语句产生的CacheKey集合以及 执行的更新语句集合应该被清空
*/
private synchronized void clearSessionData() {
queryCacheOnCommit.clear();
updateStatementOnCommit.clear();
}
