1. 首先Mybatis会加载配置文件mybatis-config.xml， 主要实现在Mybatis的builder模块，包路径org.apache.ibatis.builder，解析入口XMLConfigBuilder

  

  private void settingsElement(Properties props) {
    configuration.setAutoMappingBehavior(AutoMappingBehavior.valueOf(props.getProperty("autoMappingBehavior", "PARTIAL")));
    configuration.setAutoMappingUnknownColumnBehavior(AutoMappingUnknownColumnBehavior.valueOf(props.getProperty("autoMappingUnknownColumnBehavior", "NONE")));
    configuration.setCacheEnabled(booleanValueOf(props.getProperty("cacheEnabled"), true));
    configuration.setProxyFactory((ProxyFactory) createInstance(props.getProperty("proxyFactory")));
    configuration.setLazyLoadingEnabled(booleanValueOf(props.getProperty("lazyLoadingEnabled"), false));
    configuration.setAggressiveLazyLoading(booleanValueOf(props.getProperty("aggressiveLazyLoading"), false));
    configuration.setMultipleResultSetsEnabled(booleanValueOf(props.getProperty("multipleResultSetsEnabled"), true));
    configuration.setUseColumnLabel(booleanValueOf(props.getProperty("useColumnLabel"), true));
    configuration.setUseGeneratedKeys(booleanValueOf(props.getProperty("useGeneratedKeys"), false));
    configuration.setDefaultExecutorType(ExecutorType.valueOf(props.getProperty("defaultExecutorType", "SIMPLE")));
    configuration.setDefaultStatementTimeout(integerValueOf(props.getProperty("defaultStatementTimeout"), null));
    configuration.setDefaultFetchSize(integerValueOf(props.getProperty("defaultFetchSize"), null));
    configuration.setDefaultResultSetType(resolveResultSetType(props.getProperty("defaultResultSetType")));
    configuration.setMapUnderscoreToCamelCase(booleanValueOf(props.getProperty("mapUnderscoreToCamelCase"), false));
    configuration.setSafeRowBoundsEnabled(booleanValueOf(props.getProperty("safeRowBoundsEnabled"), false));
    configuration.setLocalCacheScope(LocalCacheScope.valueOf(props.getProperty("localCacheScope", "SESSION")));
    configuration.setJdbcTypeForNull(JdbcType.valueOf(props.getProperty("jdbcTypeForNull", "OTHER")));
    configuration.setLazyLoadTriggerMethods(stringSetValueOf(props.getProperty("lazyLoadTriggerMethods"), "equals,clone,hashCode,toString"));
    configuration.setSafeResultHandlerEnabled(booleanValueOf(props.getProperty("safeResultHandlerEnabled"), true));
    configuration.setDefaultScriptingLanguage(resolveClass(props.getProperty("defaultScriptingLanguage")));
    configuration.setDefaultEnumTypeHandler(resolveClass(props.getProperty("defaultEnumTypeHandler")));
    configuration.setCallSettersOnNulls(booleanValueOf(props.getProperty("callSettersOnNulls"), false));
    configuration.setUseActualParamName(booleanValueOf(props.getProperty("useActualParamName"), true));
    configuration.setReturnInstanceForEmptyRow(booleanValueOf(props.getProperty("returnInstanceForEmptyRow"), false));
    configuration.setLogPrefix(props.getProperty("logPrefix"));
    configuration.setConfigurationFactory(resolveClass(props.getProperty("configurationFactory")));
    configuration.setShrinkWhitespacesInSql(booleanValueOf(props.getProperty("shrinkWhitespacesInSql"), false));
    configuration.setArgNameBasedConstructorAutoMapping(booleanValueOf(props.getProperty("argNameBasedConstructorAutoMapping"), false));
    configuration.setDefaultSqlProviderType(resolveClass(props.getProperty("defaultSqlProviderType")));
    configuration.setNullableOnForEach(booleanValueOf(props.getProperty("nullableOnForEach"), false));
  }

加载配置入口： org.apache.ibatis.builder.xml.XMLConfigBuilder#parseConfiguration

1. 加载properties节点 ， 将配置中变量加载到mybatis上下文中
2. 加载settings节点， 初始化或者定制化configuration中属性
3. 加载typeAliases节点， 添加类型别名映射器
4. 加载plugins节点， 添加一些插件处理器
5. 加载objectFactory节点，指定对象创建工厂类
6. 加载objectWrapperFactory节点，指定对象创建工厂类
7. 加载reflectorFactory节点，指定对象反射处理工厂类
8. 加载environments节点， 定制化环境配置，例如不同环境不同数据库连接配置
9. 加载databaseIdProvider节点，获取不同数据源的databaseId
10. 加载typeHandlers节点， 添加类型处理器
11. 加载mappers节点，添加Mapper

蒋加载的配置信息统计存储在org.apache.ibatis.session.Configuration

2. Mybatis加载具体的Mapper.xml文件，XMLMapperBuilder

加载配置入口： org.apache.ibatis.builder.xml.XMLMapperBuilder#parse

1. org.apache.ibatis.builder.xml.XMLMapperBuilder#configurationElement 加载Mapper节点配置

• 获取namespace属性， 设置namespace
• 加载cache-ref节点配置， 加载缓存配置
• 加载cache节点配置， 加载缓存配置，MapperBuilderAssistant#useNewCache
• 加载/mapper/parameterMap节点配置， 加载ParameterMapping配置
•  加载ResultMapping配置，MapperBuilderAssistant#buildParameterMapping
• 加载/mapper/resultMap节点配置， 加载ResultMapping配置，MapperBuilderAssistant#buildResultMapping
• 加载/mapper/sql节点配置， 加载sql配置
• 加载select|insert|update|delete节点配置， 构造MappedStatement配置， org.apache.ibatis.builder.xml.XMLStatementBuilder#parseStatementNode

2. org.apache.ibatis.builder.xml.XMLMapperBuilder#bindMapperForNamespace 将xml文件配置的具体java接口注册到MapperRegistry

•  org.apache.ibatis.session.Configuration#addMapper
• org.apache.ibatis.binding.MapperRegistry#addMapper

3. XMLMapperBuilder#parsePendingResultMaps 加载未解析成功的ResultMapping配置

4. XMLMapperBuilder#parsePendingCacheRefs 加载上面为解析成功的Cache配置

5. XMLMapperBuilder#parsePendingStatements 加载上面为解析成功的MappedStatement配置

3. Mybatis加载mapper文件中具体的某个SQL语句，XMLStatementBuilder

解析入口： org.apache.ibatis.builder.xml.XMLStatementBuilder#parseStatementNode

• 构建sql语句即 SqlSource 对象，LanguageDriver#createSqlSource
• 构建MapperStatement， MapperBuilderAssistant#addMappedStatement()

4. Mybatis构建SqlSource对象，org.apache.ibatis.scripting.LanguageDriver

 

接口： org.apache.ibatis.scripting.LanguageDriver

实现：

org.apache.ibatis.scripting.xmltags.XMLLanguageDriver
org.apache.ibatis.scripting.defaults.RawLanguageDriver

接口： org.apache.ibatis.scripting.xmltags.SqlNode sql节点

实现：

org.apache.ibatis.scripting.xmltags.ChooseSqlNode
org.apache.ibatis.scripting.xmltags.ForEachSqlNode
org.apache.ibatis.scripting.xmltags.IfSqlNode
org.apache.ibatis.scripting.xmltags.MixedSqlNode
org.apache.ibatis.scripting.xmltags.SetSqlNode
org.apache.ibatis.scripting.xmltags.TrimSqlNode
org.apache.ibatis.scripting.xmltags.WhereSqlNode 等等

接口： org.apache.ibatis.scripting.xmltags.XMLScriptBuilder.NodeHandler 节点处理器

org.apache.ibatis.scripting.xmltags.XMLScriptBuilder.BindHandler

org.apache.ibatis.scripting.xmltags.XMLScriptBuilder.WhereHandler

org.apache.ibatis.scripting.xmltags.XMLScriptBuilder.SetHandler        

org.apache.ibatis.scripting.xmltags.XMLScriptBuilder.ChooseHandler等等

解析入口：XMLLanguageDriver#createSqlSource

1. org.apache.ibatis.scripting.xmltags.XMLScriptBuilder#parseScriptNode

• org.apache.ibatis.scripting.xmltags.DynamicSqlSource
• org.apache.ibatis.scripting.defaults.RawSqlSource