MyBatis 3源码解析(三)

三、getMapper获取接口的代理对象

1.先调用DefaultSqlSession的getMapper方法。代码如下：

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

2.实际上是调用了configuration的getMapper方法。具体代码如下：

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

3.又是调用了mapperRegistry的getMapper方法。代码如下：

@SuppressWarnings("unchecked") public <T> T getMapper(Class<T> type, SqlSession sqlSession) { // 4.根据接口类型获取mapperProxyFactory 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); } }

4.具体我们可以看这行：return mapperProxyFactory.newInstance(sqlSession);。mapperProxyFactory的该方法如下：

@SuppressWarnings("unchecked") protected T newInstance(MapperProxy<T> mapperProxy) { return (T) Proxy.newProxyInstance(mapperInterface.getClassLoader(), new Class[] { mapperInterface }, mapperProxy); } public T newInstance(SqlSession sqlSession) { final MapperProxy<T> mapperProxy = new MapperProxy<T>(sqlSession, mapperInterface, methodCache); return newInstance(mapperProxy); }