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Mybatis源码学习

news 2026/5/26 12:46:55

一、Mybatis核心概念

名称	意义
Configuration	管理 mybatis-config.xml 全局配置关系类
SqlSessionFactory	Session 管理工厂接口
Session	SqlSession 是一个面对用户的接口。SqlSession 提供了很多操作数据库方法
Executor	执行器是一个接口（基本执行器、缓存执行器）。作用：SqlSession 内部通过执行器操作数据库
MappedStatement	底层封装对象。作用对操作数据库存储封装，包括 sql 语句、输入输出参数
StatementHandler	具体操作数据库相关的 handler 接口
ResultSetHandler	具体操作数据库返回结果的 handler 接口

二、Mybatis源码包

文件夹	功能
annotations	注解相关
binding	mapper相关
builder	解析xml相关
cache	缓存相关
cursor	返回结果相关
datasource	数据管理
exceptions	异常
executor	执行器
io	classloader
jdbc	jdbc
lang	jdk7/jdk8
logging	日志相关
mapping	mapper相关的封装
parsing	xml相关解析
plugin	拦截器
reflection	反射相关
scripting	数据厂家
session	session
type	返回类型对应

三、Mybatis操作表数据方式一源码

通过操作xml文件完成对数据库表数据查询

mybatis-conf.xml

<mappers><mapper resource="mybatis/UserMapper.xml"/>
</mappers>

@Test
public void test() throws IOException {String resource = "mybatis-config.xml";InputStream resourceAsStream = Resources.getResourceAsStream(resource);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);SqlSession sqlSession = sqlSessionFactory.openSession();User user = sqlSession.selectOne("com.test.mybaits.UserMappper.selectUserById", 1);System.out.println(user.toString());
}

1.获取mybaits-config中的配置信息解析成Configuration对象，然后将Configuration对象传入DefaultSqlSessionFactory对象并返回DefaultSqlSessionFactory对象
org.apache.ibatis.session.SqlSessionFactoryBuilder#build(java.io.InputStream)>org.apache.ibatis.builder.xml.XMLConfigBuilder#XMLConfigBuilder(java.io.InputStream, java.lang.String, java.util.Properties) 创建构造函数>org.apache.ibatis.builder.xml.XMLConfigBuilder#parse>org.apache.ibatis.builder.xml.XMLConfigBuilder#parseConfiguration  解析mybatis-config.xml成对象>org.apache.ibatis.parsing.XPathParser#evaluate	解析String、Boolean、Double、NodeList、Node类型数据都是调用这个方法处理的>org.apache.ibatis.builder.xml.XMLConfigBuilder#mappersElement >org.apache.ibatis.session.SqlSessionFactoryBuilder#build(org.apache.ibatis.session.Configuration) 将parseConfiguration获取的Configuration传入SqlSessionFactory2.通过 SqlSessionFactory 对执行器初始化然后获取 SqlSession
org.apache.ibatis.session.defaults.DefaultSqlSessionFactory#openSession>org.apache.ibatis.session.defaults.DefaultSqlSessionFactory#openSessionFromDataSource>org.apache.ibatis.transaction.TransactionFactory#newTransaction(javax.sql.DataSource, org.apache.ibatis.session.TransactionIsolationLevel, boolean)>org.apache.ibatis.session.Configuration#newExecutor(org.apache.ibatis.transaction.Transaction, org.apache.ibatis.session.ExecutorType)>org.apache.ibatis.executor.SimpleExecutor 默认执行器>org.apache.ibatis.executor.CachingExecutor 缓存执行器，一级缓存>org.apache.ibatis.plugin.InterceptorChain#pluginAll 责任链模式拦截器3.通过SqlSession找到sql调用JDBC执行
org.apache.ibatis.session.defaults.DefaultSqlSession#selectOne(java.lang.String, java.lang.Object)>org.apache.ibatis.session.defaults.DefaultSqlSession#selectList(java.lang.String, java.lang.Object)>org.apache.ibatis.session.Configuration#getMappedStatement(java.lang.String) MappedStatement对象 就是下面的内容<delete id="deleteConfigByIds" parameterType="Long">delete from sys_config where config_id  = #{configId}</delete>>org.apache.ibatis.executor.CachingExecutor#createCacheKey>org.apache.ibatis.executor.BaseExecutor#createCacheKey 创建一级缓存的Key，由id（namespace+id）+sql+limit+offset等组成>org.apache.ibatis.executor.CachingExecutor#query(org.apache.ibatis.mapping.MappedStatement, java.lang.Object, org.apache.ibatis.session.RowBounds, org.apache.ibatis.session.ResultHandler, org.apache.ibatis.cache.CacheKey, org.apache.ibatis.mapping.BoundSql)>org.apache.ibatis.executor.CachingExecutor#query(org.apache.ibatis.mapping.MappedStatement, java.lang.Object, org.apache.ibatis.session.RowBounds, org.apache.ibatis.session.ResultHandler, org.apache.ibatis.cache.CacheKey, org.apache.ibatis.mapping.BoundSql)	>org.apache.ibatis.executor.BaseExecutor#query(org.apache.ibatis.mapping.MappedStatement, java.lang.Object, org.apache.ibatis.session.RowBounds, org.apache.ibatis.session.ResultHandler, org.apache.ibatis.cache.CacheKey, org.apache.ibatis.mapping.BoundSql)>org.apache.ibatis.executor.BaseExecutor#queryFromDatabase>org.apache.ibatis.executor.SimpleExecutor#doQuery>org.apache.ibatis.executor.statement.PreparedStatementHandler#query>org.apache.ibatis.executor.resultset.DefaultResultSetHandler#handleResultSets

四、Mybatis操作表数据方式二源码

mybatis-config.xml

<mappers><mapper class="com.test.mybaits.UserMappper"></mappers>
</mappers>

@Test
public void test1() throws IOException {String resource = "mybatis-config.xml";InputStream resourceAsStream = Resources.getResourceAsStream(resource);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);SqlSession sqlSession = sqlSessionFactory.openSession();UserMapper userMapper = sqlSession.getMapper(UserMapper.class);User user = userMapper.selectUserById(1);System.out.println(user.toString());
}

1.获取mybaits-config中的配置信息解析成Configuration对象，然后将Configuration对象传入DefaultSqlSessionFactory对象并返回DefaultSqlSessionFactory对象
org.apache.ibatis.session.SqlSessionFactoryBuilder#build(java.io.InputStream)>org.apache.ibatis.builder.xml.XMLConfigBuilder#XMLConfigBuilder(java.io.InputStream, java.lang.String, java.util.Properties) 创建构造函数>org.apache.ibatis.builder.xml.XMLConfigBuilder#parse>org.apache.ibatis.builder.xml.XMLConfigBuilder#parseConfiguration  解析mybatis-config.xml成对象>org.apache.ibatis.parsing.XPathParser#evaluate	解析String、Boolean、Double、NodeList、Node类型数据都是调用这个方法处理的>org.apache.ibatis.builder.xml.XMLConfigBuilder#mappersElement >org.apache.ibatis.session.SqlSessionFactoryBuilder#build(org.apache.ibatis.session.Configuration) 将parseConfiguration获取的Configuration传入SqlSessionFactory2.通过 SqlSessionFactory 对执行器初始化然后获取 SqlSession
org.apache.ibatis.session.defaults.DefaultSqlSessionFactory#openSession>org.apache.ibatis.session.defaults.DefaultSqlSessionFactory#openSessionFromDataSource>org.apache.ibatis.transaction.TransactionFactory#newTransaction(javax.sql.DataSource, org.apache.ibatis.session.TransactionIsolationLevel, boolean)>org.apache.ibatis.session.Configuration#newExecutor(org.apache.ibatis.transaction.Transaction, org.apache.ibatis.session.ExecutorType)>org.apache.ibatis.executor.SimpleExecutor 默认执行器>org.apache.ibatis.executor.CachingExecutor 缓存执行器，一级缓存>org.apache.ibatis.plugin.InterceptorChain#pluginAll 责任链模式拦截器
3.通过getMapper，最后还会调到SqlSession#selectOne
org.apache.ibatis.session.defaults.DefaultSqlSession#getMapper>org.apache.ibatis.session.Configuration#getMapper>org.apache.ibatis.binding.MapperRegistry#getMapper>org.apache.ibatis.binding.MapperProxyFactory#newInstance(org.apache.ibatis.session.SqlSession)>org.apache.ibatis.binding.MapperProxy#invoke>org.apache.ibatis.binding.MapperProxy.MapperMethodInvoker#invoke>org.apache.ibatis.binding.MapperProxy.PlainMethodInvoker#invoke>org.apache.ibatis.binding.MapperMethod#execute>org.apache.ibatis.session.SqlSession#selectOne(java.lang.String, java.lang.Object)

五、Mybaits操作表数据方式三源码

@Select("select * from user where id = #{id}")

<mappers><mapper class="com.test.mybaits.UserMappper"></mappers>
</mappers>

@Test
public void test() throws IOException {String resource = "mybatis-config.xml";InputStream resourceAsStream = Resources.getResourceAsStream(resource);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);SqlSession sqlSession = sqlSessionFactory.openSession();User user = sqlSession.selectOne("com.test.mybaits.UserMappper.selectUserById", 1);System.out.println(user.toString());
}

@Select加载方式
org.apache.ibatis.builder.xml.XMLConfigBuilder#mappersElement>org.apache.ibatis.session.Configuration#addMapper>org.apache.ibatis.binding.MapperRegistry#addMapper>org.apache.ibatis.builder.annotation.MapperAnnotationBuilder#parse>org.apache.ibatis.builder.annotation.MapperAnnotationBuilder#loadXmlResource 先加载xml，看xml是否存在>org.apache.ibatis.builder.annotation.MapperAnnotationBuilder#parseStatement 再查看注解

第一种和第二、三种加载方式不同在于 org.apache.ibatis.builder.xml.XMLConfigBuilder#mappersElement

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