“John Chinaman” is a term used to describe someone of Chinese descent that was popular in the 19th century. “John Chinaman” was cited in print in 1826 and “John Chinamen” was cited in 1844.
 
“John Confucius”—after the Chinese teacher Confucius (551-479 BC)—was used by Harper’s Weekly illustrator Thomas Nast (1840-1902) in 1879, but was otherwise rarely used.
 
     
Wikipedia: John Chinaman
John Chinaman was a stock caricature of a Chinese laborer seen in cartoons of the 19th century. Also referenced by Mark Twain and popular American songs of the period, John Chinaman represented, in western society, a typical persona of China. He was typically depicted with a long queue and wearing a coolie hat.
 
American political cartoonist Thomas Nast, who often depicted John Chinaman, created a variant, John Confucius, to represent Chinese political figures.
   
(Oxford English Dictionary)
John, n.
depreciative (now offensive). In full John Chinaman: a Chinese man; Chinese people regarded collectively.
1818   B. Hall Acct. Voy. Corea ii. 92   This interpreter is called ‘John’ by all the parties.
1826   B. Hall Voy. Loo-Choo i. 37   The seamen..not caring, whether John Chinaman, as they called him, understood them or not.
1834   Amer. Railroad Jrnl. 3 189/1   They are required to..ascertain the height of John Chinaman in a breath.
1853   Alta California (San Francisco) 20 Apr. 2/2   The Mary Adams brought 118 ‘Johns’ from the terrestrial kindgom of heaven.
1854   C. A. Corbyn Sydney Revels of Bacchus, Cupid & Momus 125   They came to the determination of giving wretched John Chinaman such a dose that prussic acid is fool to it. They committed John for trial at the Quarter Sessions.
 
25 April 1828, The New-England Galaxy and United States Literary Advertiser, “Letters from a Mariner, No. XII,” pg. 2, col. 6:
“Hi-yah! How can sick man eat gun?” said John Chinaman, and the Dutch were detected too soon to profit by their trick.
 
16 February 1834, The Atlas (London), pg. 107, col. 3:
“Sing then, sing,” exclaimed his lordship; “and I’ll bear a part; and so shall John Chinaman—won’t you, old boy”?
 
27 March 1834, New-York (NY) American, “Backgammon versus Chess,” pg. 1, col. 5:
it is like those “instructive games” invented for children, where they are required to twirl the tee-totum and ascertain the height of John Chinaman in a breath; ...
 
29 December 1834, The York Herald, and General Advertiser (York, England), pg. 2, col. 2:
CHINESE POLITENESS. When John CHinaman wishes to be particularly civil to his friend, he tells him, “Prosperity is painted on your face!”
 
23 March 1840, Caledonian Mercury (Edinburgh, Scotland), pg. 4, col. 4:   
BEAUTIES OF JOHN CHINA-MAN.
 
11 July 1844, Daily National Intelligencer (Washington, DC), pg. 3, col. 4:
When John China-man (as the English tar calls him) had been horribly beaten, in fight after fight, ...
(...)
... every Chinese soldier was to carry one, and a hundred John China-men would speedily put to rout a thousand of the English. 
 
OCLC WorldCat record
John Chinaman : or, Adventures in flowery land
Author: William Dalton
Publisher: Boston : Crosby and Nichols, ©1858.
Edition/Format:   eBook : Document : Fiction : Juvenile audience : English
 
OCLC WorldCat record
—There is a sublime insolence about John Chinaman, unsurpassed
Publisher: VINCENNES, INDIANA
Edition/Format: Article Article
Publication: VINCENNES GAZETTE, (March 2, 1861)
Database: The Civil War: 1855-1869
 
OCLC WorldCat record
INDUSTRIOUS JOHN CHINAMAN
Publisher: Philadelphia, Pennsylvania
Edition/Format: Article Article
Publication: THE CHRISTIAN RECORDER, (September 5, 1863)
Database: African American Newspapers
 
1 March 1879, Cincinnati (OH) Commercial, pg. 6, col. 1:
BLAINE says to himself as he contemplates the Pacific Coast and all that it implies: “We must draw the line one this thing of human rights somewhere, and I draw it on the yellow man with the almond eyes. John Confucius is not a man and a brother, but a Chinaman, and must go.”
 
Google Books
Th. Nast:
His Period and His Pictures
By Albert Bigelow Paine
New York, NY: The Macmillan Company
1904
Pg. 413:
THE CIVILIZATION OF BLAINE
JOHN CONFUCIUS— “Am I not a Man and a Brother!”