1、读取xml配置文件转换成内存中的流数据 2、流数据在SqlSessionFactoryBuilder中解析封装成Configuration对象 Configuration对象主要包含 DataSource数据源 和 Map<String,MappedStatement> mappedStatementMap存储 SQL语句 3、SqlSessionFactoryBuilder.build(Configuration)创建SqlSessionFactory对象，并将Configuration传给SqlSessionFactory 4、SqlSessionFactory.openSession SqlSessionFactory将Configuration传给SqlSession
最核心流程：解析配置文件封装成Configuration对象并最终传给SqlSession
使用sqlSession封装的API 和 getMapper动态代理方式
使用sqlSession封装的API方式，sqlSession类有两个 属性Executor和Configuration。 内部使用执行器simpleExecutor.simpleExecutor封装了JDBC操作，simpleExecutor主要流程 1、从DataSource数据源获取连接Connection 2、从 Map<String,MappedStatement> mappedStatementMap获取SQL，解析SQL语句 3、获取预处理对象：preparedStatement 4. 设置参数 5. 执行sql 6. 封装返回结果集
去除不重要的代码 1、读取配置文件
InputStream inputStream = Resources.getResourceAsStream("mybatis-config.xml");2、构建SqlSessionFactory
SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(inputStream);3、build()方法
public SqlSessionFactory build(InputStream inputStream, String environment, Properties properties) { XMLConfigBuilder parser = new XMLConfigBuilder(inputStream, environment, properties); return build(parser.parse()); }XMLConfigBuilder专门解析mybatis配置文件的类 parser.parse()返回核心配置对象Configuration
4、parse()方法 看下parse方法，注意返回的就是Configuration
public Configuration parse() { parseConfiguration(parser.evalNode("/configuration")); return configuration; }5、parseConfiguration（）方法 这里就是解析封装到Configuration 对象中
private void parseConfiguration(XNode root) { propertiesElement(root.evalNode("properties")); Properties settings = settingsAsProperties(root.evalNode("settings")); loadCustomVfs(settings); typeAliasesElement(root.evalNode("typeAliases")); pluginElement(root.evalNode("plugins")); objectFactoryElement(root.evalNode("objectFactory")); objectWrapperFactoryElement(root.evalNode("objectWrapperFactory")); reflectorFactoryElement(root.evalNode("reflectorFactory")); settingsElement(settings); environmentsElement(root.evalNode("environments")); databaseIdProviderElement(root.evalNode("databaseIdProvider")); typeHandlerElement(root.evalNode("typeHandlers")); mapperElement(root.evalNode("mappers")); }注意最后一个解析： mapperElement(root.evalNode(“mappers”))，就是解析Mapper.xml文件的SQL，每个SQL封装成一个MappedStatement，看下MappedStatement类：
public final class MappedStatement { private String resource; private Configuration configuration; private String id; private Integer fetchSize; private Integer timeout; private StatementType statementType; private ResultSetType resultSetType; private SqlSource sqlSource; private Cache cache; private ParameterMap parameterMap; private List<ResultMap> resultMaps; private boolean flushCacheRequired; private boolean useCache; private boolean resultOrdered; private SqlCommandType sqlCommandType; private KeyGenerator keyGenerator; private String[] keyProperties; private String[] keyColumns; private boolean hasNestedResultMaps; private String databaseId; private Log statementLog; private LanguageDriver lang; private String[] resultSets; }核心配置类Configuration 类里有个Map：
public class Configuration { protected final Map<String, MappedStatement> mappedStatements = new StrictMap<MappedStatement>("Mapped Statements collection"); }所以Mapper.xml解析的SQL都在这个Map里，key是namespace+sqlID组成，value就是MappedStatement 。
到现在build()将配置文件解析完成，返回Configuration,回到第3步build()方法
public SqlSessionFactory build(InputStream inputStream, String environment, Properties properties) { XMLConfigBuilder parser = new XMLConfigBuilder(inputStream, environment, properties); return build(parser.parse()); }6、build(parser.parse()); parser.parse()解析完成返回的Configuration
public SqlSessionFactory build(Configuration config) { return new DefaultSqlSessionFactory(config); } public DefaultSqlSessionFactory(Configuration configuration) { this.configuration = configuration; }至此，构建完成，返回一个DefaultSqlSessionFactory
