MyBatis源码分析之——面试官问我如何获得Mapper对象？我是这样说的！
MyBatis源码分析之——面试官问我如何获得Mapper对象？我是这样说的！
冰河
发布于 2020-10-29 16:03:06
发布于 2020-10-29 16:03:06
作者个人研发的在高并发场景下，提供的简单、稳定、可扩展的延迟消息队列框架，具有精准的定时任务和延迟队列处理功能。自开源半年多以来，已成功为十几家中小型企业提供了精准定时调度方案，经受住了生产环境的考验。为使更多童鞋受益，现给出开源框架地址：
https://github.com/sunshinelyz/mykit-delay
PS: 欢迎各位Star源码，也可以pr你牛逼哄哄的代码。
咱们直入主题，分析源码吧！从获取Mapper开始吧。
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);public <T> T getMapper(Class<T> type) {
return configuration.getMapper(type, this);
}mapperRegistry.getMapper是从MapperRegistry的knownMappers里面取的,knownMappers里面存的是接口类型(interface mapper.UserMapper)和工厂类(MapperProxyFactory)。
public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
return mapperRegistry.getMapper(type, sqlSession);
}从knownMappers的Map里根据接口类型(interface mapper.UserMapper)取出对应的工厂类
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);
}
}
public T newInstance(SqlSession sqlSession) {
final MapperProxy<T> mapperProxy = new MapperProxy<>(sqlSession, mapperInterface, methodCache);
return newInstance(mapperProxy);
}这里通过JDK动态代理返回代理对象MapperProxy。
protected T newInstance(MapperProxy<T> mapperProxy) {
//mapperInterface是interface mapper.UserMapper
return (T) Proxy.newProxyInstance(mapperInterface.getClassLoader(), new Class[] { mapperInterface }, mapperProxy);
}本文参与 腾讯云自媒体分享计划，分享自微信公众号。
原始发表：2020-06-29，如有侵权请联系 cloudcommunity@tencent.com 删除
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