Mybatis源码分析3--获取mapper

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本文详细解析了Mybatis中如何通过DefaultSqlSession获取Mapper，从Configuration、MapperRegistry到MapperProxyFactory的调用链，以及MapperProxy的实例化过程。深入理解Mapper的查找和创建机制。

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本篇是mybatis执行sql的第三步，获取mapper

调用DefaultSqlSession的getMapper获取mapper

  //org.apache.ibatis.session.defaults.DefaultSqlSession#getMapper
  public <T> T getMapper(Class<T> type) {
    return configuration.getMapper(type, this);
  }

  //org.apache.ibatis.session.Configuration#getMapper
  public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
    return mapperRegistry.getMapper(type, sqlSession);
  }

  //org.apache.ibatis.binding.MapperRegistry#getMapper
  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 {
      //调用MapperProxyFactory来创建mapper
      return mapperProxyFactory.newInstance(sqlSession);
    } catch (Exception e) {
      throw new BindingException("Error getting mapper instance. Cause: " + e, e);
    }
  }

  //org.apache.ibatis.binding.MapperProxyFactory#newInstance
  public T newInstance(SqlSession sqlSession) {
    final MapperProxy<T> mapperProxy = new MapperProxy<T>(sqlSession, mapperInterface, methodCache);
    return newInstance(mapperProxy);
  }

  //org.apache.ibatis.binding.MapperProxyFactory#newInstance
  protected T newInstance(MapperProxy<T> mapperProxy) {
    return (T) Proxy.newProxyInstance(mapperInterface.getClassLoader(), new Class[] { mapperInterface }, mapperProxy);
  }