一、入口

找入口：DefaultSqlSession#getMapper

从Configuration对象中，根据Mapper接口，获取Mapper代理对象

    @Override
    public <T> T getMapper(Class<T> type) {
        // 从Configuration对象中，根据Mapper接口，获取Mapper代理对象
        return configuration.<T>getMapper(type, this);
    }

二、流程图

三、流程分析

• Configuration#getMapper

  获取Mapper代理对象

public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
    return mapperRegistry.getMapper(type, sqlSession);
}

• 1、MapperRegistry#getMapper

  通过代理对象工厂，获取代理对象：

public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
    // 根据Mapper接口的类型，从Map集合中获取Mapper代理对象工厂
    final MapperProxyFactory<T> mapperProxyFactory = (MapperProxyFactory<T>) knownMappers.get(type);
    if (mapperProxyFactory == null) {
      throw new BindingException("Type " + type + " is not known to the MapperRegistry.");
    }
    try {
      // 通过MapperProxyFactory生产MapperProxy，通过MapperProxy产生Mapper代理对象
      return mapperProxyFactory.newInstance(sqlSession);
    } catch (Exception e) {
      throw new BindingException("Error getting mapper instance. Cause: " + e, e);
    }
  }

• 1.1 MapperProxyFactory#newInstance

  调用JDK的动态代理方式，创建Mapper代理

  //1
 protected T newInstance(MapperProxy<T> mapperProxy) {
    // 使用JDK动态代理方式，生成代理对象
    return (T) Proxy.newProxyInstance(mapperInterface.getClassLoader(), new Class[] { mapperInterface }, mapperProxy);
  }

//2
public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
    // 根据Mapper接口的类型，从Map集合中获取Mapper代理对象工厂
    final MapperProxyFactory<T> mapperProxyFactory = (MapperProxyFactory<T>) knownMappers.get(type);
    if (mapperProxyFactory == null) {
      throw new BindingException("Type " + type + " is not known to the MapperRegistry.");
    }
    try {
      // 通过MapperProxyFactory生产MapperProxy，通过MapperProxy产生Mapper代理对象
      return mapperProxyFactory.newInstance(sqlSession);
    } catch (Exception e) {
      throw new BindingException("Error getting mapper instance. Cause: " + e, e);
    }
  }