提供一个实现单点登录的Spring Security的配置类

下面是一个简单的实现基于Spring Security的单点登录的配置类示例：

@Configuration
public class SecurityConfig extends WebSecurityConfigurerAdapter {

    @Autowired
    private CustomUserDetailsService userDetailsService;

    @Autowired
    private JwtAuthenticationEntryPoint unauthorizedHandler;

    @Autowired
    private JwtTokenProvider jwtTokenProvider;

    @Value("${jwt.header}")
    private String jwtHeader;

    @Value("${jwt.prefix}")
    private String jwtPrefix;

    @Value("${jwt.secret}")
    private String jwtSecret;

    @Value("${jwt.expiration}")
    private long jwtExpiration;

    @Bean
    public PasswordEncoder passwordEncoder() {
        return new BCryptPasswordEncoder();
    }

    @Bean
    public JwtAuthenticationFilter jwtAuthenticationFilter() {
        return new JwtAuthenticationFilter(jwtTokenProvider, userDetailsService, jwtHeader, jwtPrefix);
    }

    @Override
    protected void configure(AuthenticationManagerBuilder auth) throws Exception {
        auth.userDetailsService(userDetailsService).passwordEncoder(passwordEncoder());
    }

    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http
                .cors().and().csrf().disable()
                .exceptionHandling().authenticationEntryPoint(unauthorizedHandler).and()
                .sessionManagement().sessionCreationPolicy(SessionCreationPolicy.STATELESS).and()
                .authorizeRequests()
                .antMatchers("/api/auth/**").permitAll()
                .anyRequest().authenticated().and()
                .addFilterBefore(jwtAuthenticationFilter(), UsernamePasswordAuthenticationFilter.class);
    }

    @Bean
    public JwtTokenProvider jwtTokenProvider() {
        return new JwtTokenProvider(jwtSecret, jwtExpiration);
    }

    @Bean
    public SingleSignOutFilter singleSignOutFilter() {
        SingleSignOutFilter filter = new SingleSignOutFilter();
        filter.setCasServerUrlPrefix("https://localhost:8443/cas");
        filter.setIgnoreInitConfiguration(true);
        return filter;
    }

    @Bean
    public CasAuthenticationFilter casAuthenticationFilter(ServiceProperties serviceProperties) throws Exception {
        CasAuthenticationFilter filter = new CasAuthenticationFilter();
        filter.setServiceProperties(serviceProperties);
        filter.setAuthenticationManager(authenticationManager());
        return filter;
    }

    @Bean
    public ServiceProperties serviceProperties() {
        ServiceProperties serviceProperties = new ServiceProperties();
        serviceProperties.setService("https://localhost:8444/login/cas");
        serviceProperties.setSendRenew(false);
        return serviceProperties;
    }

    @Bean
    public CasAuthenticationProvider casAuthenticationProvider() {
        CasAuthenticationProvider provider = new CasAuthenticationProvider();
        provider.setAuthenticationUserDetailsService(new UserDetailsServiceImpl());
        provider.setServiceProperties(serviceProperties());
        provider.setTicketValidator(cas20ServiceTicketValidator());
        provider.setKey("casAuthProviderKey");
        return provider;
    }

    @Bean
    public Cas20ServiceTicketValidator cas20ServiceTicketValidator() {
        return new Cas20ServiceTicketValidator("https://localhost:8443/cas");
    }

    @Bean
    public SingleLogoutFilter singleLogoutFilter() {
        LogoutFilter filter = new LogoutFilter("https://localhost:8443/cas/logout", new SecurityContextLogoutHandler());
        filter.setFilterProcessesUrl("/logout/cas");
        return filter;
    }

    @Override
    protected void configure(AuthenticationManagerBuilder auth) throws Exception {
        auth.authenticationProvider(casAuthenticationProvider());
    }

    @Override
    public void configure(WebSecurity web) throws Exception {
        web.ignoring().antMatchers("/resources/**");
    }

    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http
                .addFilter(singleSignOutFilter())
                .addFilterBefore(casAuthenticationFilter(serviceProperties()), BasicAuthenticationFilter.class)
                .addFilterBefore(singleLogoutFilter(), CasAuthenticationFilter.class);
    }
}

在上述代码中，我们定义了一个`SecurityConfig`配置类，并在其中实现了单点登录的功能。具体的步骤如下：

1. 配置JWT Token的生成和验证。我们使用了`JwtTokenProvider`类来生成和验证JWT Token，其中的`jwtSecret`和`jwtExpiration`参数分别表示JWT Token的秘钥和过期时间。

2. 配置JWT Token的过滤器。我们使用了`JwtAuthenticationFilter`类来实现JWT Token的过滤和校验，其中的`jwtHeader`和`jwtPrefix`参数用于指定JWT Token在请求头中的名称和前缀。

3. 配置CAS单点登录相关的过滤器。我们使用了`SingleSignOutFilter`、`CasAuthenticationFilter`和`LogoutFilter`三个过滤器来实现CAS单点登录的功能。其中的`casServerUrlPrefix`和`serviceProperties`参数分别表示CAS服务器的地址和客户端的服务配置。

4. 配置CAS单点登录的认证和授权。我们使用了`CasAuthenticationProvider`和`UserDetailsServiceImpl`两个类来实现CAS的认证和授权功能。

5. 配置Spring Security的授权规则和安全配置。我们使用了`HttpSecurity`类来配置Spring Security的授权规则和安全配置，其中的`permitAll()`表示对外开放的API接口，而`authenticated()`表示需要认证后才能访问的接口。

通过上述配置，我们就可以实现基于Spring Security的单点登录功能了。具体的实现过程和细节可以根据实际需求进行调整和优化。