web/src/main/java/org/springframework/security/web/authentication/UsernamePasswordAuthenticationFilter.java
public Authentication attemptAuthentication(HttpServletRequest request,
			HttpServletResponse response) throws AuthenticationException {
		if (postOnly && !request.getMethod().equals("POST")) {
			throw new AuthenticationServiceException(
					"Authentication method not supported: " + request.getMethod());
		}

		String username = obtainUsername(request);
		String password = obtainPassword(request);

		if (username == null) {
			username = "";
		}

		if (password == null) {
			password = "";
		}

		username = username.trim();

		UsernamePasswordAuthenticationToken authRequest = new UsernamePasswordAuthenticationToken(
				username, password);

		// Allow subclasses to set the "details" property
		setDetails(request, authRequest);

		return this.getAuthenticationManager().authenticate(authRequest);
	}
public Authentication attemptAuthentication(HttpServletRequest request,
			HttpServletResponse response) throws AuthenticationException {
		if (postOnly && !request.getMethod().equals("POST")) {
			throw new AuthenticationServiceException(
					"Authentication method not supported: " + request.getMethod());
		}

		String username = obtainUsername(request);
		String password = obtainPassword(request);

		if (username == null) {
			username = "";
		}

		if (password == null) {
			password = "";
		}

		username = username.trim();

		UsernamePasswordAuthenticationToken authRequest = new UsernamePasswordAuthenticationToken(
				username, password);

		// Allow subclasses to set the "details" property
		setDetails(request, authRequest);

		return this.getAuthenticationManager().authenticate(authRequest);
	}
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