spring security未登陆时，不跳转登陆页面改为返回JSON字符串

集成spring security时，因为是前后端分离，所以不能跳转到登陆页面，而是返回未登陆的JSON串。
解决办法如下：

• 重写LoginUrlAuthenticationEntryPoint方法，将该方法里的commence改成返回json串

public class MacLoginUrlAuthenticationEntryPoint implements AuthenticationEntryPoint,
        InitializingBean {
    // ~ Static fields/initializers
    // =====================================================================================

    private static final Log logger = LogFactory
            .getLog(MacLoginUrlAuthenticationEntryPoint.class);

    // ~ Instance fields
    // ================================================================================================

    private PortMapper portMapper = new PortMapperImpl();

    private PortResolver portResolver = new PortResolverImpl();

    private String loginFormUrl;

    private boolean forceHttps = false;

    private boolean useForward = false;

    private final RedirectStrategy redirectStrategy = new DefaultRedirectStrategy();

    /**
     *
     * @param loginFormUrl URL where the login page can be found. Should either be
     * relative to the web-app context path (include a leading {@code /}) or an absolute
     * URL.
     */
    public MacLoginUrlAuthenticationEntryPoint(String loginFormUrl) {
        Assert.notNull(loginFormUrl, "loginFormUrl cannot be null");
        this.loginFormUrl = loginFormUrl;
    }

    // ~ Methods
    // ========================================================================================================

    public void afterPropertiesSet() throws Exception {
        Assert.isTrue(
                StringUtils.hasText(loginFormUrl)
                        && UrlUtils.isValidRedirectUrl(loginFormUrl),
                "loginFormUrl must be specified and must be a valid redirect URL");
        if (useForward && UrlUtils.isAbsoluteUrl(loginFormUrl)) {
            throw new IllegalArgumentException(
                    "useForward must be false if using an absolute loginFormURL");
        }
        Assert.notNull(portMapper, "portMapper must be specified");
        Assert.notNull(portResolver, "portResolver must be specified");
    }

    /**
     * Allows subclasses to modify the login form URL that should be applicable for a
     * given request.
     *
     * @param request the request
     * @param response the response
     * @param exception the exception
     * @return the URL (cannot be null or empty; defaults to {@link #getLoginFormUrl()})
     */
    protected String determineUrlToUseForThisRequest(HttpServletRequest request,
            HttpServletResponse response, AuthenticationException exception) {

        return getLoginFormUrl();
    }

    /**
     * Performs the redirect (or forward) to the login form URL.
     */
    public void commence(HttpServletRequest request, HttpServletResponse response,
            AuthenticationException authException) throws IOException, ServletException {
            // redirect to login page. Use https if forceHttps true
             response.setContentType("application/json;charset=utf-8");
                PrintWriter out = response.getWriter();
                StringBuffer sb = new StringBuffer();
                sb.append("{\"status\":\"error\",\"msg\":\"");
                
                    sb.append("未登陆!");
                
                sb.append("\"}");
                out.write(sb.toString());
                out.flush();
                out.close();


        
    }

    protected String buildRedirectUrlToLoginPage(HttpServletRequest request,
            HttpServletResponse response, AuthenticationException authException) {

        String loginForm = determineUrlToUseForThisRequest(request, response,
                authException);

        if (UrlUtils.isAbsoluteUrl(loginForm)) {
            return loginForm;
        }

        int serverPort = portResolver.getServerPort(request);
        String scheme = request.getScheme();

        RedirectUrlBuilder urlBuilder = new RedirectUrlBuilder();

        urlBuilder.setScheme(scheme);
        urlBuilder.setServerName(request.getServerName());
        urlBuilder.setPort(serverPort);
        urlBuilder.setContextPath(request.getContextPath());
        urlBuilder.setPathInfo(loginForm);

        if (forceHttps && "http".equals(scheme)) {
            Integer httpsPort = portMapper.lookupHttpsPort(Integer.valueOf(serverPort));

            if (httpsPort != null) {
                // Overwrite scheme and port in the redirect URL
                urlBuilder.setScheme("https");
                urlBuilder.setPort(httpsPort.intValue());
            }
            else {
                logger.warn("Unable to redirect to HTTPS as no port mapping found for HTTP port "
                        + serverPort);
            }
        }

        return urlBuilder.getUrl();
    }

    /**
     * Builds a URL to redirect the supplied request to HTTPS. Used to redirect the
     * current request to HTTPS, before doing a forward to the login page.
     */
    protected String buildHttpsRedirectUrlForRequest(HttpServletRequest request)
            throws IOException, ServletException {

        int serverPort = portResolver.getServerPort(request);
        Integer httpsPort = portMapper.lookupHttpsPort(Integer.valueOf(serverPort));

        if (httpsPort != null) {
            RedirectUrlBuilder urlBuilder = new RedirectUrlBuilder();
            urlBuilder.setScheme("https");
            urlBuilder.setServerName(request.getServerName());
            urlBuilder.setPort(httpsPort.intValue());
            urlBuilder.setContextPath(request.getContextPath());
            urlBuilder.setServletPath(request.getServletPath());
            urlBuilder.setPathInfo(request.getPathInfo());
            urlBuilder.setQuery(request.getQueryString());

            return urlBuilder.getUrl();
        }

        // Fall through to server-side forward with warning message
        logger.warn("Unable to redirect to HTTPS as no port mapping found for HTTP port "
                + serverPort);

        return null;
    }

    /**
     * Set to true to force login form access to be via https. If this value is true (the
     * default is false), and the incoming request for the protected resource which
     * triggered the interceptor was not already <code>https</code>, then the client will
     * first be redirected to an https URL, even if <tt>serverSideRedirect</tt> is set to
     * <tt>true</tt>.
     */
    public void setForceHttps(boolean forceHttps) {
        this.forceHttps = forceHttps;
    }

    protected boolean isForceHttps() {
        return forceHttps;
    }

    public String getLoginFormUrl() {
        return loginFormUrl;
    }

    public void setPortMapper(PortMapper portMapper) {
        Assert.notNull(portMapper, "portMapper cannot be null");
        this.portMapper = portMapper;
    }

    protected PortMapper getPortMapper() {
        return portMapper;
    }

    public void setPortResolver(PortResolver portResolver) {
        Assert.notNull(portResolver, "portResolver cannot be null");
        this.portResolver = portResolver;
    }

    protected PortResolver getPortResolver() {
        return portResolver;
    }

    /**
     * Tells if we are to do a forward to the {@code loginFormUrl} using the
     * {@code RequestDispatcher}, instead of a 302 redirect.
     *
     * @param useForward true if a forward to the login page should be used. Must be false
     * (the default) if {@code loginFormUrl} is set to an absolute value.
     */
    public void setUseForward(boolean useForward) {
        this.useForward = useForward;
    }

    protected boolean isUseForward() {
        return useForward;
    }
}

• 设置LoginUrlAuthenticationEntryPoint

 @Override
    protected void configure(HttpSecurity http) throws Exception {
        http.authorizeRequests().antMatchers(loginForm.getAnonList()).permitAll()
                .anyRequest().authenticated() // 任何请求,登录后可以访问
                .and().formLogin().loginProcessingUrl(loginForm.getLoginProcessingUrl()).successForwardUrl(loginForm.getSuccessUrl())
                .permitAll().failureHandler(authenticationFailureHandler()).successHandler(authenticationLogoutSuccessHandler()).and()
                .logout().addLogoutHandler(macLogoutHandler()).permitAll().and().exceptionHandling().authenticationEntryPoint( macLoginUrlAuthenticationEntryPoint())
                .accessDeniedHandler(authenticationAccessDeniedHandler);
        http.addFilterBefore(securityFilterInterceptor, FilterSecurityInterceptor.class).csrf().disable();

    }


    @Bean
    public AuthenticationEntryPoint macLoginUrlAuthenticationEntryPoint() {
        return new MacLoginUrlAuthenticationEntryPoint(loginForm.getLoginPageUrl());
    }

注意，关键是.exceptionHandling().authenticationEntryPoint( macLoginUrlAuthenticationEntryPoint())
经测试，已能正确返回JSON字符串