深入MyBatis-运行原理-getMapper获取到接口的代理对象

流程图

1. DefaultSqlSessionF调用getMapper方法，其中为configuration下的getMapper方法
2. configuration下的getMapper方法，其中为mapperRegistry下的getMapper方法
3. mapperRegistry下的getMapper方法下根据接口类型获取MapperProxyFactory
4. MapperProxyFactory调用newInstance生成MapperProxy
5. 创建MapperProxy的代理对象，一路返回到最初调用的DefaultSqlSession

剖析源码

1.DefaultSqlSessionF调用getMapper方法

//传入接口类
sqlSession.getMapper(StudentMapper.class);

2.调用configutaion的getMapper方法

public <T> T getMapper(Class<T> type) {
    return configuration.<T>getMapper(type, this);
  }

3.调用mapperRegistry的getMapper方法

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

  public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
  	//根据接口类型生成代理类工厂
    final MapperProxyFactory<T> mapperProxyFactory = (MapperProxyFactory<T>) knownMappers.get(type);
    if (mapperProxyFactory == null) {
      throw new BindingException("Type " + type + " is not known to the MapperRegistry.");
    }
    try {
     //此处将返回MapperProxy的代理对象
      return mapperProxyFactory.newInstance(sqlSession);
    } catch (Exception e) {
      throw new BindingException("Error getting mapper instance. Cause: " + e, e);
    }
  }

4.创建MapperProxy代理对象

 public T newInstance(SqlSession sqlSession) {
 	//生成MapperProxy
    final MapperProxy<T> mapperProxy = new MapperProxy<T>(sqlSession, mapperInterface, methodCache);
    //生成MapperProxy的代理对象，之后一路返回
    return newInstance(mapperProxy);
  }

小结

DefaultSqlSession下调用getMapper方法，最终根据传入接口的类型生成MapperProxy工厂，创建MapperProxy，最终返回MapperProxy的代理对象。