UsernamePasswordAuthenticationFilter

public class UsernamePasswordAuthenticationFilter extends AbstractAuthenticationProcessingFilter {
    public static final String SPRING_SECURITY_FORM_USERNAME_KEY = "username";
    public static final String SPRING_SECURITY_FORM_PASSWORD_KEY = "password";
    private String usernameParameter = "username";
    private String passwordParameter = "password";
    private boolean postOnly = true;

    public UsernamePasswordAuthenticationFilter() {
        super(new AntPathRequestMatcher("/login", "POST"));
    }

    public Authentication attemptAuthentication(HttpServletRequest request, HttpServletResponse response) throws AuthenticationException {
        if (this.postOnly && !request.getMethod().equals("POST")) {
            throw new AuthenticationServiceException("Authentication method not supported: " + request.getMethod());
        } else {
            String username = this.obtainUsername(request);
            String password = this.obtainPassword(request);
            if (username == null) {
                username = "";
            }

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

            username = username.trim();
            UsernamePasswordAuthenticationToken authRequest = new UsernamePasswordAuthenticationToken(username, password);
            this.setDetails(request, authRequest);
            return this.getAuthenticationManager().authenticate(authRequest);
        }
    }

    protected String obtainPassword(HttpServletRequest request) {
        return request.getParameter(this.passwordParameter);
    }

    protected String obtainUsername(HttpServletRequest request) {
        return request.getParameter(this.usernameParameter);
    }

    protected void setDetails(HttpServletRequest request, UsernamePasswordAuthenticationToken authRequest) {
        authRequest.setDetails(this.authenticationDetailsSource.buildDetails(request));
    }

    public void setUsernameParameter(String usernameParameter) {
        Assert.hasText(usernameParameter, "Username parameter must not be empty or null");
        this.usernameParameter = usernameParameter;
    }

    public void setPasswordParameter(String passwordParameter) {
        Assert.hasText(passwordParameter, "Password parameter must not be empty or null");
        this.passwordParameter = passwordParameter;
    }

    public void setPostOnly(boolean postOnly) {
        this.postOnly = postOnly;
    }

    public final String getUsernameParameter() {
        return this.usernameParameter;
    }

    public final String getPasswordParameter() {
        return this.passwordParameter;
    }
}