Who is the founder of China's realistic poetry tradition?

Tracing back to the development of the realistic tradition of China's classical poetry, from The Book of Poetry, the first collection of poems, to the poems of Han Yuefu, from Jian 'an literature to Du Fu's poems, from the new Yuefu movement advocated by Bai Juyi to the inheritance of Lu You and Gong Zizhen's poems, all of them show distinct realistic characteristics with their own unique artistic practice. 1. The Book of Songs initiated the source of China's realistic poetry.