Mybatis3.5.1源码分析
- Mybatis-SqlSessionFactoryBuilder，XMLConfigBuilder，XPathParser源码解析
- Mybatis-Configuration源码解析
- Mybatis-事务对象源码解析
- Mybatis-数据源源码解析
- Mybatis缓存策略源码解析
- Mybatis-DatabaseIdProvider源码解析
- Mybatis-TypeHandler源码解析
- Mybatis-Reflector源码解析
- Mybatis-ObjectFactory，ObjectWrapperFactory源码分析
- Mybatis-Mapper各类标签封装类源码解析
- Mybatis-XMLMapperBuilder,XMLStatmentBuilder源码分析
- Mybatis-MapperAnnotationBuilder源码分析
- [Mybatis-MetaObject,MetaClass源码解析]https://www.jianshu.com/p/f51fa552f30a)
- Mybatis-LanguageDriver源码解析
- Mybatis-SqlSource源码解析
- Mybatis-SqlNode源码解析
- Mybatis-KeyGenerator源码解析
- Mybatis-Executor源码解析
- Mybatis-ParameterHandler源码解析
- Mybatis-StatementHandler源码解析
- Mybatis-DefaultResultSetHandler(一)源码解析
- Mybatis-DefaultResultSetHandler(二)源码解析
- Mybatis-ResultHandler,Cursor,RowBounds 源码分析
- Mybatis-MapperProxy源码解析
- Mybatis-SqlSession源码解析
- Mybatis-Interceptor源码解析
SqlSession
/**
* Copyright 2009-2019 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.cursor.Cursor;
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.
*
* 数据库对话
*
*
* 这个Mybatis的主要Java接口，通过这个接口可以执行命令,映射器和管理事务。
*
*
* Closeable:表示可以关闭的数据的源或目的地。 调用close方法来释放对象持有的资源（如打开的文件）。
*
* @author Clinton Begin
*/
public interface SqlSession extends Closeable {
/**
* Retrieve a single row mapped from the statement key. 返回单个查询结果
* @param the returned object type 结果对象类型
* @param statement 唯一标识匹配的语句.
* @return Mapped object 映射对象
*/
T selectOne(String statement);
/**
* Retrieve a single row mapped from the statement key and parameter. 返回单个查询结果
* @param the returned object type 结果对象类型
* @param statement Unique identifier matching the statement to use. 唯一标识匹配的语句.
* @param parameter A parameter object to pass to the statement. 查询参数对象
* @return Mapped object 映射对象
*/
T selectOne(String statement, Object parameter);
/**
* Retrieve a list of mapped objects from the statement key and parameter. 返回查询结果集合
* @param the returned list element type 结果对象类型
* @param statement Unique identifier matching the statement to use. 唯一标识匹配的语句.
* @return List of mapped object 映射对象集合
*/
List selectList(String statement);
/**
* Retrieve a list of mapped objects from the statement key and parameter. 返回查询结果集合
* @param the returned list element type 结果对象类型
* @param statement Unique identifier matching the statement to use. 唯一标识匹配的语句.
* @param parameter A parameter object to pass to the statement. 查询参数对象
* @return List of mapped object 映射对象集合
*/
List selectList(String statement, Object parameter);
/**
* Retrieve a list of mapped objects from the statement key and parameter,
* within the specified row bounds. 返回集合结果
* @param the returned list element type 结果对象类型
* @param statement Unique identifier matching the statement to use. 唯一标识匹配的语句
* @param parameter A parameter object to pass to the statement. 查询参数对象
* @param rowBounds Bounds to limit object retrieval 返回结果的大小控制
* @return List of mapped object 映射对象集合
*/
List 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.
* 返回Map对象
* Eg. Return a of Map[Integer,Author] for selectMap("selectAuthors","id")
* @param the returned Map keys type Map的Key类型
* @param the returned Map values type Map的Value类型
* @param statement Unique identifier matching the statement to use. 唯一标识匹配的语句.
* @param mapKey The property to use as key for each value in the list. key值，字段的属性别名
* @return Map containing key pair data. 结果对象映射
*/
Map 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. 返回Map对象
* @param the returned Map keys type Map的Key类型
* @param the returned Map values type Map的Value类型
* @param statement Unique identifier matching the statement to use. 唯一标识匹配的语句.
* @param parameter A parameter object to pass to the statement. 查询参数对象
* @param mapKey The property to use as key for each value in the list. key值，字段的属性别名
* @return Map containing key pair data. 结果对象映射
*/
Map 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. 返回Map对象
* @param the returned Map keys type Map的Key类型
* @param the returned Map values type Map的Value类型
* @param statement Unique identifier matching the statement to use. 唯一标识匹配的语句.
* @param parameter A parameter object to pass to the statement. 查询参数对象
* @param mapKey The property to use as key for each value in the list. key值，字段的属性别名
* @param rowBounds Bounds to limit object retrieval 返回结果的大小控制
* @return Map containing key pair data. 结果对象映射
*/
Map selectMap(String statement, Object parameter, String mapKey, RowBounds rowBounds);
/**
* A Cursor offers the same results as a List, except it fetches data lazily using an Iterator. 游标查询
* @param the returned cursor element type. 结果对象类型
* @param statement Unique identifier matching the statement to use. 唯一标识匹配的语句
* @return Cursor of mapped objects 结果对象游标
*/
Cursor selectCursor(String statement);
/**
* A Cursor offers the same results as a List, except it fetches data lazily using an Iterator. 游标查询
* @param the returned cursor element type. 结果对象类型
* @param statement Unique identifier matching the statement to use. 唯一标识匹配的语句
* @param parameter A parameter object to pass to the statement.查询参数对象
* @return Cursor of mapped objects 结果对象游标
*/
Cursor selectCursor(String statement, Object parameter);
/**
* A Cursor offers the same results as a List, except it fetches data lazily using an Iterator. 游标查询
* @param the returned cursor element type. 结果对象类型
* @param statement Unique identifier matching the statement to use. 唯一标识匹配的语句
* @param parameter A parameter object to pass to the statement. 查询参数对象
* @param rowBounds Bounds to limit object retrieval 返回结果的大小控制
* @return Cursor of mapped objects 结果对象游标
*/
Cursor selectCursor(String statement, Object parameter, RowBounds rowBounds);
/**
* Retrieve a single row mapped from the statement key and parameter
* using a {@code ResultHandler}. 查询单条，用ResultHandler接收结果
* @param statement Unique identifier matching the statement to use. 唯一标识匹配的语句
* @param parameter A parameter object to pass to the statement. 查询参数对象
* @param handler ResultHandler that will handle each retrieved row 结果接收处理器
*/
void select(String statement, Object parameter, ResultHandler handler);
/**
* Retrieve a single row mapped from the statement
* using a {@code ResultHandler}. 查询单条，用ResultHandler接收结果
* @param statement Unique identifier matching the statement to use. 唯一标识匹配的语句
* @param handler ResultHandler that will handle each retrieved row 结果接收处理器
*/
void select(String statement, ResultHandler handler);
/**
* Retrieve a single row mapped from the statement key and parameter
* using a {@code ResultHandler} and {@code RowBounds}. 查询单条，用ResultHandler接收结果
* @param statement Unique identifier matching the statement to use. 唯一标识匹配的语句
* @param rowBounds RowBound instance to limit the query results 返回结果的大小控制
* @param handler ResultHandler that will handle each retrieved row 结果接收处理器
*/
void select(String statement, Object parameter, RowBounds rowBounds, ResultHandler handler);
/**
* Execute an insert statement. 执行插入SQL
* @param statement Unique identifier matching the statement to execute. 唯一标识匹配的语句
* @return int The number of rows affected by the insert. 更新记录数
*/
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. 执行插入SQL
* @param statement Unique identifier matching the statement to execute. 唯一标识匹配的语句
* @param parameter A parameter object to pass to the statement. 插入参数对象
* @return int The number of rows affected by the insert. 更新记录数
*/
int insert(String statement, Object parameter);
/**
* Execute an update statement. The number of rows affected will be returned. 执行修改SQL
* @param statement Unique identifier matching the statement to execute. 唯一标识匹配的语句
* @return int The number of rows affected by the update.更新记录数
*/
int update(String statement);
/**
* Execute an update statement. The number of rows affected will be returned. 执行修改SQL
* @param statement Unique identifier matching the statement to execute. 唯一标识匹配的语句
* @param parameter A parameter object to pass to the statement. 修改参数对象
* @return int The number of rows affected by the update. .更新记录数
*/
int update(String statement, Object parameter);
/**
* Execute a delete statement. The number of rows affected will be returned. 执行删除SQL
* @param statement Unique identifier matching the statement to execute.唯一标识匹配的语句
* @return int The number of rows affected by the delete. 更新记录数
*/
int delete(String statement);
/**
* Execute a delete statement. The number of rows affected will be returned. 执行delete语句。将返回受影响的行数;
* @param statement Unique identifier matching the statement to execute. 唯一标识匹配的语句
* @param parameter A parameter object to pass to the statement. 删除参数对象
* @return int The number of rows affected by the delete. 更新记录数
*/
int delete(String statement, Object parameter);
/**
* Flushes batch statements and commits database connection. 事务提交
* Note that database connection will not be committed if no updates/deletes/inserts were called. 注意,数据库连接将不会提交如果没有更新/删除/插入被称为。;
* To force the commit call {@link SqlSession#commit(boolean)} 如果需要强制提交，可以调用 {@link SqlSession#commit(boolean)}
*/
void commit();
/**
* Flushes batch statements and commits database connection. 事务提交
* @param force forces connection commit 强制提交数据库连接
*/
void commit(boolean force);
/**
* Discards pending batch statements and rolls database connection back. 事务回退
* Note that database connection will not be rolled back if no updates/deletes/inserts were called. 注意,数据库连接将不会回退如果没有更新/删除/插入被调用;
* To force the rollback call {@link SqlSession#rollback(boolean)} 如果需要强制回退，可以调用 {@link SqlSession#commit(boolean)}
*/
void rollback();
/**
* Discards pending batch statements and rolls database connection back. 事务回退;
* Note that database connection will not be rolled back if no updates/deletes/inserts were called.注意,数据库连接将不会回退如果没有更新/删除/插入被称为。;
* @param force forces connection rollback 强制回退数据库连接
*/
void rollback(boolean force);
/**
* Flushes batch statements.执行全部等待批处理语句，并将结果封装到BatchResult集合中
* @return BatchResult list of updated records 更新记录的BatchResult集合
* @since 3.0.6
*/
List flushStatements();
/**
* Closes the session. 关闭数据库对话
*/
@Override
void close();
/**
* Clears local session cache. 清空数据库对话缓存
*/
void clearCache();
/**
* 获取Mybatis全局配置信息
* Retrieves current configuration.
* @return Configuration
*/
Configuration getConfiguration();
/**
* Retrieves a mapper. 获取Mapper
* @param the mapper type Mapper对应的Class类型
* @param type Mapper interface class Mapper对应的Class类型
* @return a mapper bound to this SqlSession 一个绑定到这个Sql会话的Mapper;
*/
T getMapper(Class type);
/**
* Retrieves inner database connection. 获取数据库连接
* @return Connection
*/
Connection getConnection();
}
DefaultSqlSession
/**
* Copyright 2009-2019 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.defaults;
import java.io.IOException;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.apache.ibatis.binding.BindingException;
import org.apache.ibatis.cursor.Cursor;
import org.apache.ibatis.exceptions.ExceptionFactory;
import org.apache.ibatis.exceptions.TooManyResultsException;
import org.apache.ibatis.executor.BatchResult;
import org.apache.ibatis.executor.ErrorContext;
import org.apache.ibatis.executor.Executor;
import org.apache.ibatis.executor.result.DefaultMapResultHandler;
import org.apache.ibatis.executor.result.DefaultResultContext;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.session.Configuration;
import org.apache.ibatis.session.ResultHandler;
import org.apache.ibatis.session.RowBounds;
import org.apache.ibatis.session.SqlSession;
/**
* The default implementation for {@link SqlSession}. 这是一个SqlSession接口的默认实现类
* Note that this class is not Thread-Safe. 注意，这个类并不是线程安全的
*
* @author Clinton Begin
*/
public class DefaultSqlSession implements SqlSession {
/**
* mybatis全局配置新
*/
private final Configuration configuration;
/**
* SQL脚本执行器
*/
private final Executor executor;
/**
* 是否自动提交
*/
private final boolean autoCommit;
/**
* 是否有调用更新SQL脚本标记
*/
private boolean dirty;
/**
* 游标集合
*/
private List> cursorList;
/**
*
* @param configuration mybatis全局配置信息
* @param executor SQL脚本执行器
* @param autoCommit 是否自动提交标记
*/
public DefaultSqlSession(Configuration configuration, Executor executor, boolean autoCommit) {
this.configuration = configuration;
this.executor = executor;
this.dirty = false;
this.autoCommit = autoCommit;
}
/**
*
* @param configuration Mybatis全局配置信息
* @param executor SQL脚本执行器
*/
public DefaultSqlSession(Configuration configuration, Executor executor) {
//不设置自动提交
this(configuration, executor, false);
}
/**
* 返回单个查询结果
* @param statement 唯一标识匹配的语句.
* @param 结果对象类型
* @return 映射对象
*/
@Override
public T selectOne(String statement) {
return this.selectOne(statement, null);
}
/**
* 返回单个查询结果
* @param statement Unique identifier matching the statement to use. 唯一标识匹配的语句.
* @param parameter A parameter object to pass to the statement. 查询参数对象
* @param 结果对象类型
* @return 映射对象
*/
@Override
public T selectOne(String statement, Object parameter) {
// Popular vote was to return null on 0 results and throw exception on too many.
// 民众投票 当没有结果对象时，返回null;当超过1条结果对象时，抛出异常
List list = this.selectList(statement, parameter);
//如果一个结果对象在集合中
if (list.size() == 1) {
//返回这个结果对象
return list.get(0);
//如果出现超过一个结果对象在集合中
} else if (list.size() > 1) {
//抛出异常
throw new TooManyResultsException("Expected one result (or null) to be returned by selectOne(), but found: " + list.size());
//如果没有结果对象在集合中
} else {
//返回null
return null;
}
}
/**
* 返回Map对象
* @param statement Unique identifier matching the statement to use. 唯一标识匹配的语句.
* @param mapKey The property to use as key for each value in the list. key值，字段的属性别名
* @param Map的Key类型
* @param Map的Value类型
* @return 结果对象映射
*/
@Override
public Map selectMap(String statement, String mapKey) {
//RowBounds.DEFAULT：从0开始到Integer.MAX_VALUE
return this.selectMap(statement, null, mapKey, RowBounds.DEFAULT);
}
/**
* 返回Map对象
* @param statement Unique identifier matching the statement to use. 唯一标识匹配的语句.
* @param parameter A parameter object to pass to the statement. 查询参数对象
* @param mapKey The property to use as key for each value in the list. key值，字段的属性别名
* @param Map的Key类型
* @param Map的Value类型
* @return 结果对象映射
*/
@Override
public Map selectMap(String statement, Object parameter, String mapKey) {
//RowBounds.DEFAULT：从0开始到Integer.MAX_VALUE
return this.selectMap(statement, parameter, mapKey, RowBounds.DEFAULT);
}
/**
* 返回Map对象
* @param statement Unique identifier matching the statement to use. 唯一标识匹配的语句.
* @param parameter A parameter object to pass to the statement. 查询参数对象
* @param mapKey The property to use as key for each value in the list. key值，字段的属性别名
* @param rowBounds Bounds to limit object retrieval 返回结果的大小控制
* @param Map的Key类型
* @param Map的Value类型
* @return 结果对象映射
*/
@Override
public Map selectMap(String statement, Object parameter, String mapKey, RowBounds rowBounds) {
//执行查询SQL脚本，返回结果对象集合
final List list = selectList(statement, parameter, rowBounds);
//新建一个默认Map形式的ResultHandler
final DefaultMapResultHandler mapResultHandler = new DefaultMapResultHandler<>(mapKey,
configuration.getObjectFactory(), configuration.getObjectWrapperFactory(), configuration.getReflectorFactory());
//新建一个默认结果上下文：这个类封装了结果集个数和当前结果
final DefaultResultContext context = new DefaultResultContext<>();
//遍历结果对象集合
for (V o : list) {
//将结果对象赋值到结果上下文的下一个结果对象中
context.nextResultObject(o);
//接收结果上下文，取出结果对象，添加到mapResultHandler内部维护的Map对象中
mapResultHandler.handleResult(context);
}
//返回mapResultHandler内部维护的Map对象
return mapResultHandler.getMappedResults();
}
/**
* 游标查询
* @param statement Unique identifier matching the statement to use. 唯一标识匹配的语句
* @param 结果对象类型
* @return 结果对象游标
*/
@Override
public Cursor selectCursor(String statement) {
return selectCursor(statement, null);
}
/**
* 游标查询
* @param statement Unique identifier matching the statement to use. 唯一标识匹配的语句
* @param parameter A parameter object to pass to the statement.查询参数对象
* @param 结果对象类型
* @return 结果对象游标
*/
@Override
public Cursor selectCursor(String statement, Object parameter) {
//RowBounds.DEFAULT：从0开始到Integer.MAX_VALUE
return selectCursor(statement, parameter, RowBounds.DEFAULT);
}
/**
* 游标查询
* @param statement Unique identifier matching the statement to use. 唯一标识匹配的语句
* @param parameter A parameter object to pass to the statement. 查询参数对象
* @param rowBounds Bounds to limit object retrieval 返回结果的大小控制
* @param 结果对象类型
* @return 结果对象游标
*/
@Override
public Cursor selectCursor(String statement, Object parameter, RowBounds rowBounds) {
try {
//MappedStatement: Mapper.xml文件的select,delete,update,insert这些DML标签的封装类
//获取statement对应的MappedStatment对象
MappedStatement ms = configuration.getMappedStatement(statement);
/**
* 如果{@code object}是数组，或者是Collection实现类，会将 {@code object} 包装成StrictMap对象，
* 否则直接返回 {@code object},执行查询，返回结果对象游标
*/
Cursor cursor = executor.queryCursor(ms, wrapCollection(parameter), rowBounds);
//注册游标，将cursor添加到cursorList中
registerCursor(cursor);
//返回结果对象游标
return cursor;
} catch (Exception e) {
//如果出现异常，就包装异常对象，并加以描述再抛出
throw ExceptionFactory.wrapException("Error querying database. Cause: " + e, e);
} finally {
//错误上下文实例重置
ErrorContext.instance().reset();
}
}
/**
* 返回查询结果集合
* @param statement Unique identifier matching the statement to use. 唯一标识匹配的语句.
* @param 结果对象类型
* @return 映射对象集合
*/
@Override
public List selectList(String statement) {
return this.selectList(statement, null);
}
/**
* 返回查询结果集合
* @param statement Unique identifier matching the statement to use. 唯一标识匹配的语句.
* @param parameter A parameter object to pass to the statement. 查询参数对象
* @param 结果对象类型
* @return 映射对象集合
*/
@Override
public List selectList(String statement, Object parameter) {
//RowBounds.DEFAULT：从0开始到Integer.MAX_VALUE
return this.selectList(statement, parameter, RowBounds.DEFAULT);
}
/**
* 返回集合结果
* @param statement Unique identifier matching the statement to use. 唯一标识匹配的语句
* @param parameter A parameter object to pass to the statement. 查询参数对象
* @param rowBounds Bounds to limit object retrieval 返回结果的大小控制
* @param 结果对象类型
* @return 结果对象集合
*/
@Override
public List selectList(String statement, Object parameter, RowBounds rowBounds) {
try {
//MappedStatement: Mapper.xml文件的select,delete,update,insert这些DML标签的封装类
//获取statement对应的MappedStatment对象
MappedStatement ms = configuration.getMappedStatement(statement);
/**
* 如果{@code object}是数组，或者是Collection实现类，会将 {@code object} 包装成StrictMap对象，
* 否则直接返回 {@code object},执行查询，返回结果对象集合
*/
return executor.query(ms, wrapCollection(parameter), rowBounds, Executor.NO_RESULT_HANDLER);
} catch (Exception e) {
//如果出现异常，就包装异常对象，并加以描述再抛出
throw ExceptionFactory.wrapException("Error querying database. Cause: " + e, e);
} finally {
//错误上下文实例重置
ErrorContext.instance().reset();
}
}
/**
* 查询单条，用ResultHandler接收结果
* @param statement Unique identifier matching the statement to use. 唯一标识匹配的语句
* @param parameter A parameter object to pass to the statement. 查询参数对象
* @param handler ResultHandler that will handle each retrieved row 结果接收处理器
*/
@Override
public void select(String statement, Object parameter, ResultHandler handler) {
//RowBounds.DEFAULT：从0开始到Integer.MAX_VALUE
select(statement, parameter, RowBounds.DEFAULT, handler);
}
/**
* 查询单条，用ResultHandler接收结果
* @param statement Unique identifier matching the statement to use. 唯一标识匹配的语句
* @param handler ResultHandler that will handle each retrieved row 结果接收处理器
*/
@Override
public void select(String statement, ResultHandler handler) {
//RowBounds.DEFAULT：从0开始到Integer.MAX_VALUE
select(statement, null, RowBounds.DEFAULT, handler);
}
/**
* 查询单条，用ResultHandler接收结果
* @param statement Unique identifier matching the statement to use. 唯一标识匹配的语句
* @param parameter 参数对象
* @param rowBounds RowBound instance to limit the query results 返回结果的大小控制
* @param handler ResultHandler that will handle each retrieved row 结果接收处理器
*/
@Override
public void select(String statement, Object parameter, RowBounds rowBounds, ResultHandler handler) {
try {
//MappedStatement: Mapper.xml文件的select,delete,update,insert这些DML标签的封装类
//获取statement对应的MappedStatment对象
MappedStatement ms = configuration.getMappedStatement(statement);
/**
* 如果parameter是数组，或者是Collection实现类，会将parameter 包装成StrictMap对象，
* 否则直接返回parameter,执行查询，用handler接收结果对象
*/
executor.query(ms, wrapCollection(parameter), rowBounds, handler);
} catch (Exception e) {
//如果出现异常，就包装异常对象，并加以描述再抛出
throw ExceptionFactory.wrapException("Error querying database. Cause: " + e, e);
} finally {
//错误上下文实例重置
ErrorContext.instance().reset();
}
}
/**
* 执行插入SQL
* @param statement Unique identifier matching the statement to execute. 唯一标识匹配的语句
* @return 更新记录数
*/
@Override
public int insert(String statement) {
return insert(statement, null);
}
/**
* 执行插入SQL
* @param statement Unique identifier matching the statement to execute. 唯一标识匹配的语句
* @param parameter A parameter object to pass to the statement. 插入参数对象
* @return 更新记录数
*/
@Override
public int insert(String statement, Object parameter) {
return update(statement, parameter);
}
/**
* 执行修改SQL
* @param statement Unique identifier matching the statement to execute. 唯一标识匹配的语句
* @return 更新记录数
*/
@Override
public int update(String statement) {
return update(statement, null);
}
/**
* 执行修改SQL
* @param statement Unique identifier matching the statement to execute. 唯一标识匹配的语句
* @param parameter A parameter object to pass to the statement. 修改参数对象
* @return 更新记录数
*/
@Override
public int update(String statement, Object parameter) {
try {
//将是否有调用更新SQL标记设置为true，表示有有调用更新SQL
dirty = true;
//MappedStatement: Mapper.xml文件的select,delete,update,insert这些DML标签的封装类
//获取statement对应的MappedStatment对象
MappedStatement ms = configuration.getMappedStatement(statement);
/**
* wrapCollection：如果parameter是数组，或者是Collection实现类，会将parameter 包装成StrictMap对象，
* 否则直接返回parameter
*/
//执行更新SQL脚本
return executor.update(ms, wrapCollection(parameter));
} catch (Exception e) {
//如果出现异常，就包装异常对象，并加以描述再抛出
throw ExceptionFactory.wrapException("Error updating database. Cause: " + e, e);
} finally {
//错误上下文实例重置
ErrorContext.instance().reset();
}
}
/**
* 执行删除SQL
* @param statement Unique identifier matching the statement to execute.唯一标识匹配的语句
* @return 更新记录数
*/
@Override
public int delete(String statement) {
return update(statement, null);
}
/**
* 执行删除SQL
* @param statement Unique identifier matching the statement to execute. 唯一标识匹配的语句
* @param parameter A parameter object to pass to the statement. 删除参数对象
* @return 更新记录数
*/
@Override
public int delete(String statement, Object parameter) {
return update(statement, parameter);
}
/**
* 事务提交
*
* 注意,数据库连接将不会提交如果没有更新/删除/插入被称为。
* 如果需要强制提交，可以调用 {@link SqlSession#commit(boolean)}
*
*/
@Override
public void commit() {
commit(false);
}
/**
* 事务提交
* @param force forces connection commit 强制提交数据库连接
*/
@Override
public void commit(boolean force) {
try {
/**
* isCommitOrRollbackRequired:只要force为true，一定返回ture;如果force
* 为false，如果没有设置自动提交但有执行更新的SQL脚本；否则返回false
*/
//通知执行器提交事务
executor.commit(isCommitOrRollbackRequired(force));
//事务结束，标记还原
dirty = false;
} catch (Exception e) {
//如果出现异常，就包装异常对象，并加以描述再抛出
throw ExceptionFactory.wrapException("Error committing transaction. Cause: " + e, e);
} finally {
//错误上下文实例重置
ErrorContext.instance().reset();
}
}
/**
* 事务回退
*
* 注意,数据库连接将不会回退如果没有更新/删除/插入被调用;
* 如果需要强制回退，可以调用 {@link SqlSession#commit(boolean)}
*
*/
@Override
public void rollback() {
rollback(false);
}
/**
* 事务回退
* @param force forces connection rollback 强制回退数据库连接
*/
@Override
public void rollback(boolean force) {
try {
/**
* isCommitOrRollbackRequired:只要force为true，一定返回ture;如果force
* 为false，如果没有设置自动提交但有执行更新的SQL脚本；否则返回false
*/
//通知执行器回退事务
executor.rollback(isCommitOrRollbackRequired(force));
//事务结束，标记还原
dirty = false;
} catch (Exception e) {
//如果出现异常，就包装异常对象，并加以描述再抛出
throw ExceptionFactory.wrapException("Error rolling back transaction. Cause: " + e, e);
} finally {
//错误上下文实例重置
ErrorContext.instance().reset();
}
}
/**
* 执行全部等待批处理语句，并将结果封装到BatchResult集合中
* @return 更新记录的BatchResult集合
*/
@Override
public List flushStatements() {
try {
//通知执行器执行全部等待批处理语句，并将结果封装到BatchResult集合中
return executor.flushStatements();
} catch (Exception e) {
//如果出现异常，就包装异常对象，并加以描述再抛出
throw ExceptionFactory.wrapException("Error flushing statements. Cause: " + e, e);
} finally {
//错误上下文实例重置
ErrorContext.instance().reset();
}
}
@Override
public void close() {
try {
/**
* isCommitOrRollbackRequired:只要force为true，一定返回ture;如果force
* 为false，如果没有设置自动提交但有执行更新的SQL脚本；否则返回false
*/
//关闭执行器,回退事务，关闭事务
executor.close(isCommitOrRollbackRequired(false));
//关闭游标集合中的所有游标对象，清空游标集合
closeCursors();
//标记还原
dirty = false;
} finally {
//错误上下文实例重置
ErrorContext.instance().reset();
}
}
/**
* 关闭游标集合中的所有游标对象，清空游标集合
*/
private void closeCursors() {
//如果游标集合不为null且游标集合不是空集合
if (cursorList != null && cursorList.size() != 0) {
//遍历游标集合
for (Cursor cursor : cursorList) {
try {
//关闭游标
cursor.close();
} catch (IOException e) {
//如果出现异常，就包装异常对象，并加以描述再抛出
throw ExceptionFactory.wrapException("Error closing cursor. Cause: " + e, e);
}
}
//清空游标集合中的所有游标
cursorList.clear();
}
}
/**
* 获取Mybatis全局配置信息
* @return Mybatis全局配置信息对象
*/
@Override
public Configuration getConfiguration() {
return configuration;
}
/**
* 获取Mapper
* @param type Mapper interface class Mapper对应的Class类型
* @param Mapper对应的Class类型
* @return 一个绑定到这个Sql会话的Mapper;
*/
@Override
public T getMapper(Class type) {
return configuration.getMapper(type, this);
}
/**
* 获取数据库连接
* @return 数据库连接对象
*/
@Override
public Connection getConnection() {
try {
//从执行器中获取事务对象，再从事务对象中获取数据库连接并返回
return executor.getTransaction().getConnection();
} catch (SQLException e) {
////如果出现异常，就包装异常对象，并加以描述再抛出
throw ExceptionFactory.wrapException("Error getting a new connection. Cause: " + e, e);
}
}
/**
* 清空数据库对话缓存
*/
@Override
public void clearCache() {
//清空执行器本地缓存(一级缓存)
executor.clearLocalCache();
}
/**
* 注册游标，将 {@code cursor} 添加到cursorList中
* @param cursor 结果对象游标
* @param 结果对象类型
*/
private void registerCursor(Cursor cursor) {
//如果游标集合为null
if (cursorList == null) {
//实例化cursorList为ArrayList
cursorList = new ArrayList<>();
}
//添加cursor到游标对象集合中
cursorList.add(cursor);
}
/**
* 是否必须提交或者回滚
* @param force 是否强制提交或者强制关闭
* @return 只要force为true，一定返回ture;如果 {@code force} 为false，如果没有设置自动提交但有执行更新的SQL脚本；否则返回false
*/
private boolean isCommitOrRollbackRequired(boolean force) {
//只要force为true，一定返回ture
//如果force为false，如果没有设置自动提交但有执行更新的SQL脚本，返回true；否则返回false
return (!autoCommit && dirty) || force;
}
/**
* 如果{@code object}是数组，或者是Collection实现类，会将 {@code object} 包装成StrictMap对象，否则直接返回 {@code object}
* @param object 参数对象
* @return 如果object是数组，或者是Collection的实现类，就直接返回StrictMap对象；否则直接返回 {@code object}
*/
private Object wrapCollection(final Object object) {
//如果Object是Collection的实现类
if (object instanceof Collection) {
//StrictMap:HashMap的子类，对获取集合没有元素时会抛出异常。
//新建一个Map
StrictMap