• mybatis创建代理接口其实在前面已经讲过了，这里以流程的形式加以回顾。可以参考前面的博文：https://www.jianshu.com/p/819a58df1168
• 创建代理接口入口：

UserMapper mapper = sqlSession.getMapper(UserMapper.class);

一、MapperRegistry注册接口类中执行getMapper

• 前面分析了MapperRegistry是Mapper接口的注册管理类，当解析配置文件后会将相应的Mapper接口文件注册进入MapperRegistry中，现在从MapperRegistry根据类对象取出相对应的Mapper接口。

1、SqlSession中执行getMapper
  @Override
  public <T> T getMapper(Class<T> type) {
    return configuration.<T>getMapper(type, this);
  }
2、Configuration中执行getMapper
 public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
    return mapperRegistry.getMapper(type, sqlSession);
  }
3、MapperRegistry中根据type执行getMapper
//代理接口和MapperProxyFactory工厂容器，前面configuration初始化已
//近完成了接口和MapperProxyFactory工厂绑定的
  @SuppressWarnings("unchecked")
  public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
    final MapperProxyFactory<T> mapperProxyFactory = 
(MapperProxyFactory<T>) knownMappers.get(type);
    if (mapperProxyFactory == null) {
      throw new BindingException("Type " + type + " is not known to the MapperRegistry.");
    }
    try {
      return mapperProxyFactory.newInstance(sqlSession);
    } catch (Exception e) {
      throw new BindingException("Error getting mapper instance. Cause: " + e, e);
    }
  }

二、mapperProxyFactory代理工厂创建相应的Mapper对象

//实现InvocationHandler接口，以便完成jdk代理
public class MapperProxy<T> implements InvocationHandler, Serializable {
  private static final long serialVersionUID = -6424540398559729838L;
  private final SqlSession sqlSession;
  private final Class<T> mapperInterface;
  private final Map<Method, MapperMethod> methodCache;
  public MapperProxy(SqlSession sqlSession, Class<T> mapperInterface, Map<Method, MapperMethod> methodCache) {
    this.sqlSession = sqlSession;
    this.mapperInterface = mapperInterface;
    this.methodCache = methodCache;
  }
....
public T newInstance(SqlSession sqlSession) {
    final MapperProxy<T> mapperProxy = new MapperProxy<T>(sqlSession, mapperInterface, methodCache);
    return newInstance(mapperProxy);
  }
//动态代理生成相应的Mapper接口代理接口mapperProxy
  @SuppressWarnings("unchecked")
  protected T newInstance(MapperProxy<T> mapperProxy) {
    return (T) Proxy.newProxyInstance(mapperInterface.getClassLoader(), new Class[] { mapperInterface }, mapperProxy);
  }

三、创建代理接口流程

• 实际返回的是MapperProxy代理对象，代理对象中包含了SqlSession等重要元素，保证能正常执行sql语句，当调用Mapper委托接口的方法的时候，会调用MapperProxy代理对象的invoke方法完成该方法逻辑。

  
  创建代理接口流程