/*
* Copyright 2009-2011 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.ibatis.session;
import java.io.Closeable;
import java.sql.Connection;
import java.util.List;
import java.util.Map;
import org.apache.ibatis.executor.BatchResult;
/**
* The primary Java interface for working with MyBatis.
* Through this interface you can execute commands, get mappers and manage transactions.
*
* @author Clinton Begin
*/
/**
* 这是MyBatis主要的一个类，用来执行SQL，获取映射器，管理事务
*
* 通常情况下，我们在应用程序中使用的Mybatis的API就是这个接口定义的方法。
*
*/
public interface SqlSession extends Closeable {
/**
* Retrieve a single row mapped from the statement key
* 根据指定的SqlID获取一条记录的封装对象
* @param <T> the returned object type 封装之后的对象类型
* @param statement sqlID
* @return Mapped object 封装之后的对象
*/
<T> T selectOne(String statement);
/**
* Retrieve a single row mapped from the statement key and parameter.
* 根据指定的SqlID获取一条记录的封装对象，只不过这个方法容许我们可以给sql传递一些参数
* 一般在实际使用中，这个参数传递的是pojo，或者Map或者ImmutableMap
* @param <T> the returned object type
* @param statement Unique identifier matching the statement to use.
* @param parameter A parameter object to pass to the statement.
* @return Mapped object
*/
<T> T selectOne(String statement, Object parameter);
/**
* Retrieve a list of mapped objects from the statement key and parameter.
* 根据指定的sqlId获取多条记录
* @param <E> the returned list element type
* @param statement Unique identifier matching the statement to use.
* @return List of mapped object
*/
<E> List<E> selectList(String statement);
/**
* Retrieve a list of mapped objects from the statement key and parameter.
* 获取多条记录，这个方法容许我们可以传递一些参数
* @param <E> the returned list element type
* @param statement Unique identifier matching the statement to use.
* @param parameter A parameter object to pass to the statement.
* @return List of mapped object
*/
<E> List<E> selectList(String statement, Object parameter);
/**
* Retrieve a list of mapped objects from the statement key and parameter,
* within the specified row bounds.
* 获取多条记录，这个方法容许我们可以传递一些参数，不过这个方法容许我们进行
* 分页查询。
*
* 需要注意的是默认情况下，Mybatis为了扩展性，仅仅支持内存分页。也就是会先把
* 所有的数据查询出来以后，然后在内存中进行分页。因此在实际的情况中，需要注意
* 这一点。
*
* 一般情况下公司都会编写自己的Mybatis 物理分页插件
* @param <E> the returned list element type
* @param statement Unique identifier matching the statement to use.
* @param parameter A parameter object to pass to the statement.
* @param rowBounds Bounds to limit object retrieval
* @return List of mapped object
*/
<E> List<E> selectList(String statement, Object parameter, RowBounds rowBounds);
/**
* The selectMap is a special case in that it is designed to convert a list
* of results into a Map based on one of the properties in the resulting
* objects.
* Eg. Return a of Map[Integer,Author] for selectMap("selectAuthors","id")
* 将查询到的结果列表转换为Map类型。
* @param <K> the returned Map keys type
* @param <V> the returned Map values type
* @param statement Unique identifier matching the statement to use.
* @param mapKey The property to use as key for each value in the list. 这个参数会作为结果map的key
* @return Map containing key pair data.
*/
<K, V> Map<K, V> selectMap(String statement, String mapKey);
/**
* The selectMap is a special case in that it is designed to convert a list
* of results into a Map based on one of the properties in the resulting
* objects.
* 将查询到的结果列表转换为Map类型。这个方法容许我们传入需要的参数
* @param <K> the returned Map keys type
* @param <V> the returned Map values type
* @param statement Unique identifier matching the statement to use.
* @param parameter A parameter object to pass to the statement.
* @param mapKey The property to use as key for each value in the list.
* @return Map containing key pair data.
*/
<K, V> Map<K, V> selectMap(String statement, Object parameter, String mapKey);
/**
* The selectMap is a special case in that it is designed to convert a list
* of results into a Map based on one of the properties in the resulting
* objects.
* 获取多条记录,加上分页,并存入Map
* @param <K> the returned Map keys type
* @param <V> the returned Map values type
* @param statement Unique identifier matching the statement to use.
* @param parameter A parameter object to pass to the statement.
* @param mapKey The property to use as key for each value in the list.
* @param rowBounds Bounds to limit object retrieval
* @return Map containing key pair data.
*/
<K, V> Map<K, V> selectMap(String statement, Object parameter, String mapKey, RowBounds rowBounds);
/**
* Retrieve a single row mapped from the statement key and parameter
* using a {@code ResultHandler}.
*
* @param statement Unique identifier matching the statement to use.
* @param parameter A parameter object to pass to the statement.
* @param handler ResultHandler that will handle each retrieved row
* @return Mapped object
*/
void select(String statement, Object parameter, ResultHandler handler);
/**
* Retrieve a single row mapped from the statement
* using a {@code ResultHandler}.
* 获取一条记录,并转交给ResultHandler处理。这个方法容许我们自己定义对
* 查询到的行的处理方式。不过一般用的并不是很多
* @param statement Unique identifier matching the statement to use.
* @param handler ResultHandler that will handle each retrieved row
* @return Mapped object
*/
void select(String statement, ResultHandler handler);
/**
* Retrieve a single row mapped from the statement key and parameter
* using a {@code ResultHandler} and {@code RowBounds}
* 获取一条记录,加上分页,并转交给ResultHandler处理
* @param statement Unique identifier matching the statement to use.
* @param rowBounds RowBound instance to limit the query results
* @param handler ResultHandler that will handle each retrieved row
* @return Mapped object
*/
void select(String statement, Object parameter, RowBounds rowBounds, ResultHandler handler);
/**
* Execute an insert statement.
* 插入记录。一般情况下这个语句在实际项目中用的并不是太多，而且更多使用带参数的insert函数
* @param statement Unique identifier matching the statement to execute.
* @return int The number of rows affected by the insert.
*/
int insert(String statement);
/**
* Execute an insert statement with the given parameter object. Any generated
* autoincrement values or selectKey entries will modify the given parameter
* object properties. Only the number of rows affected will be returned.
* 插入记录，容许传入参数。
* @param statement Unique identifier matching the statement to execute.
* @param parameter A parameter object to pass to the statement.
* @return int The number of rows affected by the insert. 注意返回的是受影响的行数
*/
int insert(String statement, Object parameter);
/**
* Execute an update statement. The number of rows affected will be returned.
* 更新记录。返回的是受影响的行数
* @param statement Unique identifier matching the statement to execute.
* @return int The number of rows affected by the update.
*/
int update(String statement);
/**
* Execute an update statement. The number of rows affected will be returned.
* 更新记录
* @param statement Unique identifier matching the statement to execute.
* @param parameter A parameter object to pass to the statement.
* @return int The number of rows affected by the update. 返回的是受影响的行数
*/
int update(String statement, Object parameter);
/**
* Execute a delete statement. The number of rows affected will be returned.
* 删除记录
* @param statement Unique identifier matching the statement to execute.
* @return int The number of rows affected by the delete. 返回的是受影响的行数
*/
int delete(String statement);
/**
* Execute a delete statement. The number of rows affected will be returned.
* 删除记录
* @param statement Unique identifier matching the statement to execute.
* @param parameter A parameter object to pass to the statement.
* @return int The number of rows affected by the delete. 返回的是受影响的行数
*/
int delete(String statement, Object parameter);
//以下是事务控制方法,commit,rollback
/**
* Flushes batch statements and commits database connection.
* Note that database connection will not be committed if no updates/deletes/inserts were called.
* To force the commit call {@link SqlSession#commit(boolean)}
*/
void commit();
/**
* Flushes batch statements and commits database connection.
* @param force forces connection commit
*/
void commit(boolean force);
/**
* Discards pending batch statements and rolls database connection back.
* Note that database connection will not be rolled back if no updates/deletes/inserts were called.
* To force the rollback call {@link SqlSession#rollback(boolean)}
*/
void rollback();
/**
* Discards pending batch statements and rolls database connection back.
* Note that database connection will not be rolled back if no updates/deletes/inserts were called.
* @param force forces connection rollback
*/
void rollback(boolean force);
/**
* Flushes batch statements.
* 刷新批处理语句,返回批处理结果
* @return BatchResult list of updated records
* @since 3.0.6
*/
List<BatchResult> flushStatements();
/**
* Closes the session
* 关闭Session
*/
@Override
void close();
/**
* Clears local session cache
* 清理Session缓存
*/
void clearCache();
/**
* Retrieves current configuration
* 得到配置
* @return Configuration
*/
Configuration getConfiguration();
/**
* Retrieves a mapper.
* 得到映射器
* 这个巧妙的使用了泛型，使得类型安全
* 到了MyBatis 3，还可以用注解,这样xml都不用写了
* @param <T> the mapper type
* @param type Mapper interface class
* @return a mapper bound to this SqlSession
*/
<T> T getMapper(Class<T> type);
/**
* Retrieves inner database connection
* 得到数据库连接
* @return Connection
*/
Connection getConnection();
}