Most scholars no longer identify the apostle John as the Beloved Disciple or as the actual author of the fourth Gospel.
No one can claim to have an absolute answer as to how John's Gospel took shape. The following description brings together the varied theories of contemporary scholars, and is intended simply to provide a sample of how this question of authorship might be approached.
The Beloved Disciple was the founding father and leader of a Christian community in Ephesus (the apostle John may have had some contact with this community). The Beloved Disciple lived to be an old man and was much revered by his community. he had been an eyewitness to all that Jesus said and did, and his teachings shaped the community at Ephesus.
From this community emerged what is today called the "Gospel of John." The Beloved Disciple did not actually "write" the Gospel. That was done by a member of his community. However, the Beloved Disciple was the source of the tradition that has gone into this Gospel. While he himself did not do the writing, he, an eyewitness disciple of Jesus, was the author-ity behind it.
- Little White Book, Diocese of Saginaw