UserPrincipal user = (UserPrincipal) SecurityContextHolder.getContext().getAuthentication().getPrincipal();

这段代码是使用Spring Security获取当前已认证的用户的信息。具体来说，它从SecurityContextHolder（安全上下文持有者）中获取Authentication（认证信息），再从认证信息中获取Principal（主体）。由于我们通常使用UserDetailsService来验证用户身份，因此在这种情况下，Principal通常是UserDetails或其子类的实例。在这里，代码将Principal强制转换为UserPrincipal类型，以便访问自定义的用户属性。

相关问题

spring boot+token实现登录的代码

可以使用Spring Security框架来实现token登录，具体代码如下：

1. 添加依赖：

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-security</artifactId>
</dependency>

2. 配置Spring Security：

@Configuration
@EnableWebSecurity
public class SecurityConfig extends WebSecurityConfigurerAdapter {

    @Autowired
    private UserDetailsService userDetailsService;

    @Autowired
    private JwtAuthenticationEntryPoint unauthorizedHandler;

    @Bean
    public JwtAuthenticationFilter authenticationTokenFilterBean() throws Exception {
        return new JwtAuthenticationFilter();
    }

    @Override
    public void configure(AuthenticationManagerBuilder authenticationManagerBuilder) throws Exception {
        authenticationManagerBuilder
                .userDetailsService(userDetailsService)
                .passwordEncoder(passwordEncoder());
    }

    @Bean(BeanIds.AUTHENTICATION_MANAGER)
    @Override
    public AuthenticationManager authenticationManagerBean() throws Exception {
        return super.authenticationManagerBean();
    }

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

    @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();

        // Add our custom JWT security filter
        http.addFilterBefore(authenticationTokenFilterBean(), UsernamePasswordAuthenticationFilter.class);
    }
}

3. 实现JwtAuthenticationFilter：

public class JwtAuthenticationFilter extends OncePerRequestFilter {

    @Autowired
    private JwtTokenProvider tokenProvider;

    @Autowired
    private CustomUserDetailsService customUserDetailsService;

    @Override
    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {
        try {
            String jwt = getJwtFromRequest(request);

            if (StringUtils.hasText(jwt) && tokenProvider.validateToken(jwt)) {
                Long userId = tokenProvider.getUserIdFromJWT(jwt);

                UserDetails userDetails = customUserDetailsService.loadUserById(userId);
                UsernamePasswordAuthenticationToken authentication = new UsernamePasswordAuthenticationToken(userDetails, null, userDetails.getAuthorities());
                authentication.setDetails(new WebAuthenticationDetailsSource().buildDetails(request));
                SecurityContextHolder.getContext().setAuthentication(authentication);
            }
        } catch (Exception ex) {
            logger.error("Could not set user authentication in security context", ex);
        }

        filterChain.doFilter(request, response);
    }

    private String getJwtFromRequest(HttpServletRequest request) {
        String bearerToken = request.getHeader("Authorization");
        if (StringUtils.hasText(bearerToken) && bearerToken.startsWith("Bearer ")) {
            return bearerToken.substring(7);
        }
        return null;
    }
}

4. 实现JwtTokenProvider：

@Component
public class JwtTokenProvider {

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

    @Value("${app.jwtExpirationInMs}")
    private int jwtExpirationInMs;

    public String generateToken(Authentication authentication) {
        UserPrincipal userPrincipal = (UserPrincipal) authentication.getPrincipal();

        Date now = new Date();
        Date expiryDate = new Date(now.getTime() + jwtExpirationInMs);

        return Jwts.builder()
                .setSubject(Long.toString(userPrincipal.getId()))
                .setIssuedAt(new Date())
                .setExpiration(expiryDate)
                .signWith(SignatureAlgorithm.HS512, jwtSecret)
                .compact();
    }

    public Long getUserIdFromJWT(String token) {
        Claims claims = Jwts.parser()
                .setSigningKey(jwtSecret)
                .parseClaimsJws(token)
                .getBody();

        return Long.parseLong(claims.getSubject());
    }

    public boolean validateToken(String authToken) {
        try {
            Jwts.parser().setSigningKey(jwtSecret).parseClaimsJws(authToken);
            return true;
        } catch (SignatureException ex) {
            logger.error("Invalid JWT signature");
        } catch (MalformedJwtException ex) {
            logger.error("Invalid JWT token");
        } catch (ExpiredJwtException ex) {
            logger.error("Expired JWT token");
        } catch (UnsupportedJwtException ex) {
            logger.error("Unsupported JWT token");
        } catch (IllegalArgumentException ex) {
            logger.error("JWT claims string is empty.");
        }
        return false;
    }
}

5. 实现CustomUserDetailsService：

@Service
public class CustomUserDetailsService implements UserDetailsService {

    @Autowired
    private UserRepository userRepository;

    @Override
    @Transactional
    public UserDetails loadUserByUsername(String usernameOrEmail) throws UsernameNotFoundException {
        // Let people login with either username or email
        User user = userRepository.findByUsernameOrEmail(usernameOrEmail, usernameOrEmail)
                .orElseThrow(() ->
                        new UsernameNotFoundException("User not found with username or email : " + usernameOrEmail)
                );

        return UserPrincipal.create(user);
    }

    @Transactional
    public UserDetails loadUserById(Long id) {
        User user = userRepository.findById(id).orElseThrow(
                () -> new ResourceNotFoundException("User", "id", id)
        );

        return UserPrincipal.create(user);
    }
}

6. 实现UserPrincipal：

public class UserPrincipal implements UserDetails {

    private Long id;

    private String name;

    private String username;

    private String email;

    @JsonIgnore
    private String password;

    private Collection<? extends GrantedAuthority> authorities;

    public UserPrincipal(Long id, String name, String username, String email, String password, Collection<? extends GrantedAuthority> authorities) {
        this.id = id;
        this.name = name;
        this.username = username;
        this.email = email;
        this.password = password;
        this.authorities = authorities;
    }

    public static UserPrincipal create(User user) {
        List<GrantedAuthority> authorities = user.getRoles().stream().map(role ->
                new SimpleGrantedAuthority(role.getName().name())
        ).collect(Collectors.toList());

        return new UserPrincipal(
                user.getId(),
                user.getName(),
                user.getUsername(),
                user.getEmail(),
                user.getPassword(),
                authorities
        );
    }

    public Long getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public String getEmail() {
        return email;
    }

    @Override
    public String getUsername() {
        return username;
    }

    @Override
    public String getPassword() {
        return password;
    }

    @Override
    public Collection<? extends GrantedAuthority> getAuthorities() {
        return authorities;
    }

    @Override
    public boolean isAccountNonExpired() {
        return true;
    }

    @Override
    public boolean isAccountNonLocked() {
        return true;
    }

    @Override
    public boolean isCredentialsNonExpired() {
        return true;
    }

    @Override
    public boolean isEnabled() {
        return true;
    }
}

springboot实现登录注册代码

以下是使用Spring Boot实现登录注册的示例代码：

User.java

@Entity
@Table(name = "users")
public class User {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @NotBlank
    @Size(max = 50)
    @Email
    private String email;

    @NotBlank
    @Size(min = 6, max = 100)
    private String password;

    // constructors, getters and setters
}

UserRepository.java

@Repository
public interface UserRepository extends JpaRepository<User, Long> {
    Optional<User> findByEmail(String email);
    Boolean existsByEmail(String email);
}

UserService.java

@Service
public class UserService implements UserDetailsService {

    @Autowired
    private UserRepository userRepository;

    @Override
    @Transactional
    public UserDetails loadUserByUsername(String email) throws UsernameNotFoundException {
        User user = userRepository.findByEmail(email)
                .orElseThrow(() ->
                        new UsernameNotFoundException("User Not Found with email: " + email)
                );

        return UserPrincipal.create(user);
    }

    @Transactional
    public User createUser(SignUpRequest signUpRequest) {
        User user = new User();
        user.setEmail(signUpRequest.getEmail());
        user.setPassword(signUpRequest.getPassword());

        return userRepository.save(user);
    }

    public Boolean isEmailAvailable(String email) {
        return !userRepository.existsByEmail(email);
    }
}

UserPrincipal.java

public class UserPrincipal implements UserDetails {
    private Long id;
    private String email;
    private String password;
    private Collection<? extends GrantedAuthority> authorities;

    public UserPrincipal(Long id, String email, String password, Collection<? extends GrantedAuthority> authorities) {
        this.id = id;
        this.email = email;
        this.password = password;
        this.authorities = authorities;
    }

    public static UserPrincipal create(User user) {
        List<GrantedAuthority> authorities = Collections.singletonList(new SimpleGrantedAuthority("USER"));

        return new UserPrincipal(
                user.getId(),
                user.getEmail(),
                user.getPassword(),
                authorities
        );
    }

    public Long getId() {
        return id;
    }

    @Override
    public String getUsername() {
        return email;
    }

    @Override
    public String getPassword() {
        return password;
    }

    @Override
    public Collection<? extends GrantedAuthority> getAuthorities() {
        return authorities;
    }

    @Override
    public boolean isAccountNonExpired() {
        return true;
    }

    @Override
    public boolean isAccountNonLocked() {
        return true;
    }

    @Override
    public boolean isCredentialsNonExpired() {
        return true;
    }

    @Override
    public boolean isEnabled() {
        return true;
    }
}

SignUpRequest.java

public class SignUpRequest {
    @NotBlank
    @Size(max = 50)
    @Email
    private String email;

    @NotBlank
    @Size(min = 6, max = 100)
    private String password;

    // constructors, getters and setters
}

AuthController.java

@RestController
@RequestMapping("/api/auth")
public class AuthController {

    @Autowired
    private AuthenticationManager authenticationManager;

    @Autowired
    private UserService userService;

    @Autowired
    private JwtTokenProvider tokenProvider;

    @PostMapping("/signin")
    public ResponseEntity<?> authenticateUser(@Valid @RequestBody LoginRequest loginRequest) {

        Authentication authentication = authenticationManager.authenticate(
                new UsernamePasswordAuthenticationToken(
                        loginRequest.getEmail(),
                        loginRequest.getPassword()
                )
        );

        SecurityContextHolder.getContext().setAuthentication(authentication);

        String jwt = tokenProvider.generateToken(authentication);
        return ResponseEntity.ok(new JwtAuthenticationResponse(jwt));
    }

    @PostMapping("/signup")
    public ResponseEntity<?> registerUser(@Valid @RequestBody SignUpRequest signUpRequest) {
        if(!userService.isEmailAvailable(signUpRequest.getEmail())) {
            return new ResponseEntity(new ApiResponse(false, "Email Address already in use!"),
                    HttpStatus.BAD_REQUEST);
        }

        User user = userService.createUser(signUpRequest);

        URI location = ServletUriComponentsBuilder
                .fromCurrentContextPath().path("/api/users/{username}")
                .buildAndExpand(user.getEmail()).toUri();

        return ResponseEntity.created(location).body(new ApiResponse(true, "User registered successfully"));
    }
}

LoginRequest.java

public class LoginRequest {
    @NotBlank
    @Size(max = 50)
    @Email
    private String email;

    @NotBlank
    @Size(min = 6, max = 100)
    private String password;

    // constructors, getters and setters
}

JwtTokenProvider.java

@Component
public class JwtTokenProvider {

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

    @Value("${app.jwtExpirationInMs}")
    private int jwtExpirationInMs;

    public String generateToken(Authentication authentication) {
        UserPrincipal userPrincipal = (UserPrincipal) authentication.getPrincipal();

        Date now = new Date();
        Date expiryDate = new Date(now.getTime() + jwtExpirationInMs);

        return Jwts.builder()
                .setSubject(Long.toString(userPrincipal.getId()))
                .setIssuedAt(new Date())
                .setExpiration(expiryDate)
                .signWith(SignatureAlgorithm.HS512, jwtSecret)
                .compact();
    }

    public Long getUserIdFromJWT(String token) {
        Claims claims = Jwts.parser()
                .setSigningKey(jwtSecret)
                .parseClaimsJws(token)
                .getBody();

        return Long.parseLong(claims.getSubject());
    }

    public boolean validateToken(String authToken) {
        try {
            Jwts.parser().setSigningKey(jwtSecret).parseClaimsJws(authToken);
            return true;
        } catch (SignatureException ex) {
            logger.error("Invalid JWT signature");
        } catch (MalformedJwtException ex) {
            logger.error("Invalid JWT token");
        } catch (ExpiredJwtException ex) {
            logger.error("Expired JWT token");
        } catch (UnsupportedJwtException ex) {
            logger.error("Unsupported JWT token");
        } catch (IllegalArgumentException ex) {
            logger.error("JWT claims string is empty.");
        }
        return false;
    }
}

JwtAuthenticationResponse.java

public class JwtAuthenticationResponse {
    private String accessToken;
    private String tokenType = "Bearer";

    public JwtAuthenticationResponse(String accessToken) {
        this.accessToken = accessToken;
    }

    public String getAccessToken() {
        return accessToken;
    }

    public void setAccessToken(String accessToken) {
        this.accessToken = accessToken;
    }

    public String getTokenType() {
        return tokenType;
    }

    public void setTokenType(String tokenType) {
        this.tokenType = tokenType;
    }
}

ApiResponse.java

public class ApiResponse {
    private Boolean success;
    private String message;

    public ApiResponse(Boolean success, String message) {
        this.success = success;
        this.message = message;
    }

    public Boolean getSuccess() {
        return success;
    }

    public void setSuccess(Boolean success) {
        this.success = success;
    }

    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }
}

以上代码实现了基本的用户注册和登录功能，并使用了JWT进行身份验证。