@AllArgsConstructor
@Data
public class User {

    private String username;

    private String password;
}

@Component
public class UserMapper {

   public User select(String username) {
        return new User(username, "pass");
    }
}

@Slf4j
@Component
public class UserDetailsServiceImpl implements UserDetailsService {

    public static final UserDetails INVALID_USER =
            new org.springframework.security.core.userdetails.User("invalid_user", "invalid_password", Collections.emptyList());

    private final UserMapper userMapper;

    public UserDetailsServiceImpl(UserMapper userMapper) {
        this.userMapper = userMapper;
    }

    @Override
    public UserDetails loadUserByUsername(String username) throws UsernameNotFoundException {
        // 根據(jù)用戶名從數(shù)據(jù)庫查詢用戶信息
        User user = userMapper.select(username);
        if (user == null) {
            /**
             * 如果沒查詢到這個用戶，考慮兩種選擇：
             * 1. 返回一個標(biāo)記無效用戶的常量對象
             * 2. 返回一個不可能認(rèn)證通過的用戶
             */
            return INVALID_USER;
//            return new User(username, System.currentTimeMillis() + UUID.randomUUID().toString(), Collections.emptyList());
        }
        /**
         * 這里返回的用戶密碼是否為庫里保存的密碼，是明文/密文，取決于認(rèn)證時密碼比對部分的實現(xiàn)，每個人的場景不一樣，
         * 因為使用的是不加密的PasswordEncoder，所以可以返回明文
         */
        return new org.springframework.security.core.userdetails.User(username, user.getPassword(), Collections.emptyList());
    }
}

@Configuration
public class WebConfiguration {

    @Bean
    public PasswordEncoder passwordEncoder() {
        // 示例，不對密碼進行加密處理
        return NoOpPasswordEncoder.getInstance();
    }


    @Bean
    public AuthenticationManager authenticationManager(UserDetailsService userDetailsService, PasswordEncoder passwordEncoder) {
        DaoAuthenticationProvider provider = new DaoAuthenticationProvider();
        // 設(shè)置加載用戶信息的類
        provider.setUserDetailsService(userDetailsService);
        // 比較用戶密碼的時候，密碼加密方式
        provider.setPasswordEncoder(passwordEncoder);
        return new ProviderManager(Arrays.asList(provider));
    }

}

	@Override
	@SuppressWarnings("deprecation")
	protected void additionalAuthenticationChecks(UserDetails userDetails,
			UsernamePasswordAuthenticationToken authentication) throws AuthenticationException {
		if (authentication.getCredentials() == null) {
			this.logger.debug("Failed to authenticate since no credentials provided");
			throw new BadCredentialsException(this.messages
					.getMessage("AbstractUserDetailsAuthenticationProvider.badCredentials", "Bad credentials"));
		}
		String presentedPassword = authentication.getCredentials().toString();
		// 就是比對下請求傳過來的密碼和根據(jù)該用戶查詢的密碼是否一致，passwordEncoder是根據(jù)不同的加密算法進行加密，示例我們用的是NoOpPasswordEncoder，也就是原始明文比對
		if (!this.passwordEncoder.matches(presentedPassword, userDetails.getPassword())) {
			this.logger.debug("Failed to authenticate since password does not match stored value");
			throw new BadCredentialsException(this.messages
					.getMessage("AbstractUserDetailsAuthenticationProvider.badCredentials", "Bad credentials"));
		}
	}

@RequestMapping("/login")
@RestController
public class LoginController {

    private final AuthenticationManager authenticationManager;

    public LoginController(AuthenticationManager authenticationManager) {
        this.authenticationManager = authenticationManager;
    }

    @PostMapping()
    public Object login(@RequestBody User user) {
        try {
            // 使用定義的AuthenticationManager進行認(rèn)證處理
            Authentication authenticate = authenticationManager.authenticate(new UsernamePasswordAuthenticationToken(user.getUsername(), user.getPassword()));
            // 認(rèn)證通過，設(shè)置到當(dāng)前上下文，如果當(dāng)前認(rèn)證過程后續(xù)還有處理的邏輯需要的話。這個示例是沒有必要了
            SecurityContextHolder.getContext().setAuthentication(authenticate);
            return "login success";
        }catch (Exception e) {
            return "login failed";
        }
    }

    /**
     * 獲取驗證碼，需要的話，可以提供一個驗證碼獲取的接口，在上面的login里把驗證碼傳進來進行比對
     */
    @GetMapping("/captcha")
    public Object captcha() {
        return "1234";
    }
}

@Component
public class WebSecurityConfigurer extends WebSecurityConfigurerAdapter {

    @Override
    protected void configure(HttpSecurity http) throws Exception {
        // 在這里自定義配置
        http.authorizeRequests()
                // 登錄相關(guān)接口都允許訪問
                .antMatchers("/login/**").permitAll()
                .anyRequest()
                .authenticated()
                .and()
                .exceptionHandling()
                // 認(rèn)證失敗返回401狀態(tài)碼，前端頁面可以根據(jù)401狀態(tài)碼跳轉(zhuǎn)到登錄頁面
                .authenticationEntryPoint((request, response, authException) ->
                        response.sendError(HttpStatus.UNAUTHORIZED.value(), HttpStatus.UNAUTHORIZED.getReasonPhrase()))
                .and().cors()
                // csrf是否決定禁用，請自行考量
                .and().csrf().disable()
                // 采用http 的基本認(rèn)證.
                .httpBasic();
    }
}