33. BaseExecutor

package com.example.aninbatis.executor;
import com.example.aninbatis.config.Configuration;
import com.example.aninbatis.config.MappedStatement;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
/**
 * 基本执行器，主要处理一级缓存
 */
public abstract class BaseExecutor implements Executor {
    private Map<String, List<Object>> oneLevelCache = new HashMap<>();
    @SuppressWarnings("unchecked")
    @Override
    public <T> List<T> query(MappedStatement mappedStatement, Configuration configuration, Object param) {
        // 获取带有值的sql语句
        String sql = mappedStatement.getSqlSource().getBoundSql(param).getSql();
        // 从一级缓存去根据sql语句获取查询结果
        List<Object> result = oneLevelCache.get(sql);
        if (result != null) {
            return (List<T>) result;
        }
        // 如果没有结果，则调用相应的处理器去处理
        result = queryFromDataBase(mappedStatement, configuration, param);
        oneLevelCache.put(sql, result);
        return (List<T>) result;
    }
    public abstract List<Object> queryFromDataBase(MappedStatement mappedStatement, Configuration configuration,
            Object param);
}