面试题：安全认证之JWT用户角色权限控制的实现细节

1. 引入依赖

在pom.xml中添加JWT和Spring Security相关依赖：

<dependency>
    <groupId>io.jsonwebtoken</groupId>
    <artifactId>jjwt-api</artifactId>
    <version>0.11.2</version>
</dependency>
<dependency>
    <groupId>io.jsonwebtoken</groupId>
    <artifactId>jjwt-impl</artifactId>
    <version>0.11.2</version>
    <scope>runtime</scope>
</dependency>
<dependency>
    <groupId>io.jsonwebtoken</groupId>
    <artifactId>jjwt-jackson</artifactId>
    <version>0.11.2</version>
    <scope>runtime</scope>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-security</artifactId>
</dependency>

2. 配置Spring Security

创建一个SecurityConfig类，继承WebSecurityConfigurerAdapter：

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.security.config.annotation.web.builders.HttpSecurity;
import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
import org.springframework.security.config.annotation.web.configuration.WebSecurityConfigurerAdapter;
import org.springframework.security.config.http.SessionCreationPolicy;
import org.springframework.security.web.authentication.UsernamePasswordAuthenticationFilter;

@Configuration
@EnableWebSecurity
public class SecurityConfig extends WebSecurityConfigurerAdapter {

    @Bean
    public JwtFilter jwtFilter() {
        return new JwtFilter();
    }

    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http
           .csrf().disable()
           .sessionManagement().sessionCreationPolicy(SessionCreationPolicy.STATELESS)
           .and()
           .authorizeRequests()
               .antMatchers("/auth/login").permitAll()
               .anyRequest().authenticated()
               .and()
           .addFilterBefore(jwtFilter(), UsernamePasswordAuthenticationFilter.class);
    }
}

3. JWT生成

创建一个JwtUtil类来生成和验证JWT：

import io.jsonwebtoken.Claims;
import io.jsonwebtoken.Jwts;
import io.jsonwebtoken.SignatureAlgorithm;
import io.jsonwebtoken.security.Keys;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.stereotype.Service;

import java.security.Key;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;
import java.util.function.Function;

@Service
public class JwtUtil {

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

    public String extractUsername(String token) {
        return extractClaim(token, Claims::getSubject);
    }

    public Date extractExpiration(String token) {
        return extractClaim(token, Claims::getExpiration);
    }

    public <T> T extractClaim(String token, Function<Claims, T> claimsResolver) {
        final Claims claims = extractAllClaims(token);
        return claimsResolver.apply(claims);
    }
    private Claims extractAllClaims(String token) {
        return Jwts.parserBuilder().setSigningKey(getSignInKey()).build()
               .parseClaimsJws(token).getBody();
    }

    private Boolean isTokenExpired(String token) {
        return extractExpiration(token).before(new Date());
    }

    public String generateToken(UserDetails userDetails) {
        Map<String, Object> claims = new HashMap<>();
        return createToken(claims, userDetails.getUsername());
    }

    private String createToken(Map<String, Object> claims, String subject) {

        return Jwts.builder().setClaims(claims)
               .setSubject(subject)
               .setIssuedAt(new Date(System.currentTimeMillis()))
               .setExpiration(new Date(System.currentTimeMillis() + 10 * 60 * 1000))
               .signWith(getSignInKey(), SignatureAlgorithm.HS256)
               .compact();
    }

    public Boolean validateToken(String token, UserDetails userDetails) {
        final String username = extractUsername(token);
        return (username.equals(userDetails.getUsername()) &&!isTokenExpired(token));
    }

    private Key getSignInKey() {
        byte[] keyBytes = SECRET_KEY.getBytes();
        return Keys.hmacShaKeyFor(keyBytes);
    }
}

4. JWT验证和权限校验

创建一个JwtFilter类，继承OncePerRequestFilter：

import io.jsonwebtoken.Claims;
import io.jsonwebtoken.Jwts;
import io.jsonwebtoken.security.Keys;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
import org.springframework.security.core.context.SecurityContextHolder;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.security.core.userdetails.UserDetailsService;
import org.springframework.security.web.authentication.WebAuthenticationDetailsSource;
import org.springframework.stereotype.Component;
import org.springframework.web.filter.OncePerRequestFilter;

import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.security.Key;

@Component
public class JwtFilter extends OncePerRequestFilter {

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

    private final UserDetailsService userDetailsService;

    public JwtFilter(UserDetailsService userDetailsService) {
        this.userDetailsService = userDetailsService;
    }

    @Override
    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {
        final String authorizationHeader = request.getHeader("Authorization");

        String username = null;
        String jwt = null;

        if (authorizationHeader != null && authorizationHeader.startsWith("Bearer ")) {
            jwt = authorizationHeader.substring(7);
            username = extractUsername(jwt);
        }

        if (username != null && SecurityContextHolder.getContext().getAuthentication() == null) {
            UserDetails userDetails = this.userDetailsService.loadUserByUsername(username);

            if (validateToken(jwt, userDetails)) {
                UsernamePasswordAuthenticationToken usernamePasswordAuthenticationToken = new UsernamePasswordAuthenticationToken(
                        userDetails, null, userDetails.getAuthorities());
                usernamePasswordAuthenticationToken.setDetails(new WebAuthenticationDetailsSource().buildDetails(request));
                SecurityContextHolder.getContext().setAuthentication(usernamePasswordAuthenticationToken);
            }
        }
        filterChain.doFilter(request, response);
    }

    private String extractUsername(String token) {
        Claims claims = Jwts.parserBuilder().setSigningKey(getSignInKey()).build().parseClaimsJws(token).getBody();
        return claims.getSubject();
    }

    private Boolean validateToken(String token, UserDetails userDetails) {
        final String username = extractUsername(token);
        return (username.equals(userDetails.getUsername()));
    }

    private Key getSignInKey() {
        byte[] keyBytes = SECRET_KEY.getBytes();
        return Keys.hmacShaKeyFor(keyBytes);
    }
}

5. 登录生成JWT

在登录接口中，使用JwtUtil生成JWT：

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.security.authentication.AuthenticationManager;
import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
import org.springframework.security.core.Authentication;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class AuthController {

    @Autowired
    private AuthenticationManager authenticationManager;

    @Autowired
    private UserDetailsService userDetailsService;

    @Autowired
    private JwtUtil jwtUtil;

    @PostMapping("/auth/login")
    public ResponseEntity<String> createToken(@RequestBody AuthRequest authRequest) throws Exception {
        Authentication authentication = authenticationManager.authenticate(
                new UsernamePasswordAuthenticationToken(authRequest.getUsername(), authRequest.getPassword())
        );
        SecurityContextHolder.getContext().setAuthentication(authentication);
        final UserDetails userDetails = userDetailsService.loadUserByUsername(authRequest.getUsername());
        final String jwt = jwtUtil.generateToken(userDetails);
        return new ResponseEntity<>(jwt, HttpStatus.OK);
    }
}

class AuthRequest {
    private String username;
    private String password;

    // getters and setters
}

通过上述步骤，在Spring Boot项目中实现了基于JWT的用户角色权限控制，包括JWT的生成、验证以及权限校验。

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