首先从/oauth/token入手

@RequestMapping(value = "/oauth/token", method=RequestMethod.POST)
	public ResponseEntity<OAuth2AccessToken> postAccessToken(Principal principal, @RequestParam
	Map<String, String> parameters) throws HttpRequestMethodNotSupportedException {
。。。
		String clientId = getClientId(principal);
		ClientDetails authenticatedClient = getClientDetailsService().loadClientByClientId(clientId);
		TokenRequest tokenRequest = getOAuth2RequestFactory().createTokenRequest(parameters, authenticatedClient);
。。。
		OAuth2AccessToken token = getTokenGranter().grant(tokenRequest.getGrantType(), tokenRequest);
		if (token == null) {
			throw new UnsupportedGrantTypeException("Unsupported grant type: " + tokenRequest.getGrantType());
		}
		return getResponse(token);
	}