What are Bai Juyi's poetic theories and what are their shortcomings?

Bai Juyi (772-846), born in Xiaguan (now Weinan, Shaanxi), was a scholar in the 16th year of Zhenyuan. Successively Zuo Jinshi, Oriental Palace Doctor, Jiangzhou, Hangzhou, Suzhou secretariat, Taifu. Bai Juyi is a great realistic poet. His poems have a wide range of themes and forms. Deeply exposing social contradictions, he was also the main advocate of the new Yuefu movement in the middle Tang Dynasty. Bai Juyi's narrative poems, such as Song of Eternal Sorrow and Pipa Journey, are delicate, vivid and touching, with unique artistic style and extremely wide influence. On the theory of poetry creation, he put forward the ideas of "combining articles with the times" and "combining poems with phases". There are more than 3,000 existing poems. Peach blossoms in the mountain temple are in full bloom. I hate that spring is nowhere to be found, but I don't know where it becomes spring. Seven wonders, Mujiang songs, a touch of sunset glow in the water, half river rustling, half river red. On the third night of September, the dew is like a pearl and the moon is like a bow. Thinking of the beauty of Jiangnan, the scenery once seemed familiar. At sunrise, the river is red and green as blue as spring. Can I not remember Jiangnan? Five laws have given the ancient grass a farewell to the endless grass on the plain. Arriving at the crumbling gate, my friend's prince, you left again. I heard them sigh behind you. I was saying goodbye to a guest. At night, on the Xunyang River, maple leaves and mature rushes rustled in autumn. I, the master, have dismounted. My guest has boarded his boat. We raised our cups and hope to drink-but, alas, there is no music, because we have already drunk all of us. He secretly asked the player that the pipa was slow to speak. He moved the boat to meet each other, added wine and reopened the banquet. After a long time, he began to come out. There is still half of her face hidden behind her guitar ... She turned the tuning pin, tested several strings, and we can feel her feelings. Even before she played, every string was a meditation, and every note was a profound thought, as if she were telling us the pain of her life. She frowned and bent her fingers, and then started her music and talked about endless things in their hearts. Gently gather together, gently rub, and repeatedly pick, first the air in the rainbow skirt, then six small and big strings hum like rain, and the small strings whisper. The noisy strings scattered and scattered, and the big beads fell on the jade plate. The flowers are slippery and the water flows along the beach. The spring is cold and astringent, and the strings are frozen. Fell into deep sadness and hidden lament, said more in silence than in voice. A silver vase suddenly broke the gushing water and jumped out of the conflict and blow between armored horses and weapons. Before she put down her pick, she ended with a blow. All four strings made a sound, just like tearing silk. The ship in the East was quiet, and the west was quiet. We saw the white autumn moon enter the heart of the river. Put the strings in thoughtfully, tidy up the clothes and gather the guests. She said that she was a woman in Beijing and lived under the frog's tomb. At the age of thirteen, he studied pipa and was awarded the first teaching workshop. She often teaches excellent talents and services. Her beauty is the envy of all the leading dancers. How do the noble young people in Wuling compete generously? Countless red silks are given to a song, the clouds are broken, and the skirts whose blood color is stained by wine are season after season. Joy is followed by joy, and the autumn moon and spring breeze are ignored by her. My brother joined the army and my aunt died. Night passed, and night came. Her beauty faded with fewer and fewer chariots and horses in front of the door. The oldest one married a businessman's wife. Businessmen value profit over parting, and bought tea on the floating beam last month. He went to Jiangkou to see the ships in the air and sailed around the bright moon and the cold river. In the evening, he suddenly dreamed about teenagers. Awaken from my dream by her hot tears, her first guitar note made me sigh. Now, after listening to her story, I am even sadder, and we are all unhappy-until the end of the sky, we met. We understand. What is the relationship between acquaintances? A year ago, I left the capital, and now I am a sick exile in Jiujiang. Jiujiang is so far away that I didn't hear music, silk and bamboo at the end of the year. The land near the Ganjiang River is low and wet, and the bitter bamboo in Huang Lu is around the house. At the same time, when they smell something, azaleas will cry and apes will moan. The spring river is full of flowers and the moon is full of wine. No folk songs and village flutes? Tonight, when I heard you playing the guitar, I felt my hearing was full of wonderful music. Don't leave us. Come, sit down. Play it for us again. I will write a Long song about guitar. Moved by my words, she stood there for a while and then sat on her string-they sounded sadder, although the tune was different from what she had played before, and all the people at the party listened and covered their faces. Who cried the most in the seat, Jiangzhou Sima's blue was wet. Qilv, Qiantang Lake, Spring Tour, Gushan Temple, northwest of Jiating, with low water level. Several early birds compete for warm trees, and their new swallows peck at the soil in spring. These flowers are becoming more and more charming. Only shallow grass can have no horseshoe. I love the lack of eastbound lake, and the white sand embankment is under the shade of green sun. Yueyang Tower Yueyang City is a long water, and the dangerous building is on its own. The spring shore is more dreamy when it is green, and the red waves are near Chang 'an. Why do apes crawl and cry, and it is difficult for geese to fly over the lake? Here, it is only difficult to draw obstacles, and Huatang Zhang and the nobles can see them. Five ancients, look at the wheat fields, and have less leisure at home. Naive children with pot pulp. They went with Tian Xiang, and Ding Zhuang was in Nangang. It is full of rustic heat, and the back is burned by the sun. I don't know about the heat, but I regret the long summer. A poor woman cheated on my son. My right hand holds my ear and my left arm hangs a basket. Listening to his words of concern, I feel sad. I lost all my taxes at home and took them back to satisfy my hunger. Now I have no merit, and I have never served farming and mulberry.