This story is profoundly allegorical:Its a 19th-century version of the myth of Faust,the story of a man who sells his soul to the devil so that all his desires may be satisfied.
One of the most important source of inspiration was The temptation of Saint Antony by Flaubert
This soul becomes the picture,that records the signs of experience,the corruption the horror and the sins concealed under the mask of Dorians beauty and youth.
The picture isnt autonomous:it stands for the dark,evil side of Dorians personality. His double,which he tries to forget by locking the picture in a room.
The moral is that every excess must be punished and reality cannot be escaped;when Dorian destroys the picture,he cannot avoid the punishment for all his sins,that is,death.