調用getMapper方法
SqlSession#getMapper
->(DefaultSqlSession)configuration#getMapper
–>(Configuration)mapperRegistry#getMapper
//MapperRegistry類
@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 {
//調用工廠方法
return mapperProxyFactory.newInstance(sqlSession);
} catch (Exception e) {
throw new BindingException("Error getting mapper instance. Cause: " + e, e);
}
}
//MapperProxyFactroy類
@SuppressWarnings("unchecked")
//這裏即產生一個mapper接口的代理對象 代理對象的調用在下面類中體現
protected T newInstance(MapperProxy<T> mapperProxy) {
//參數分別爲Mapper接口的類加載器、mapper接口、對應的invocationHandler
return (T) Proxy.newProxyInstance(mapperInterface.getClassLoader(), new Class[] { mapperInterface }, mapperProxy);
}
//MapperRegistry調用的是這個方法 這個方法又調用上面產生代理對象的方法
public T newInstance(SqlSession sqlSession) {
final MapperProxy<T> mapperProxy = new MapperProxy<T>(sqlSession, mapperInterface, methodCache);
return newInstance(mapperProxy);
}
//MapperProxy類
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
try {
//如果該方法是Object中的基本方法 則調用這個循環代碼
if (Object.class.equals(method.getDeclaringClass())) {
return method.invoke(this, args);
} else if (isDefaultMethod(method)) {
//如果接口方法是被Default修飾符修飾 則調用這個循環代碼
return invokeDefaultMethod(proxy, method, args);
}
} catch (Throwable t) {
throw ExceptionUtil.unwrapThrowable(t);
}
//否則該方法即是Mapper中聲明的方法 即調用SqlSession來執行
final MapperMethod mapperMethod = cachedMapperMethod(method);
return mapperMethod.execute(sqlSession, args);
}
綜上可以看出Mapper是基於動態代理產生出來的。