Spring Boot 应用如何实现 JWT 认证？

JSON Web Token (JWT) 是一种开放标准 (RFC 7519)，用于在网络应用之间安全地传输信息。JWT 通常用于身份验证和信息交换，因为它可以包含声明（claims），这些声明可以用于验证用户的身份和权限。在 Spring Boot 应用中实现 JWT 认证可以帮助我们构建安全的 RESTful API。本文将详细介绍如何在 Spring Boot 应用中实现 JWT 认证。

1. 什么是 JWT？

JWT 是一种紧凑且自包含的方式，用于在网络应用之间安全地传输信息。JWT 包含三个部分：头部（Header）、载荷（Payload）和签名（Signature）。每个部分都是 Base64 编码的字符串，中间用点（.）分隔。

• Header：包含令牌类型（通常是 JWT）和哈希算法（如 HMAC SHA-256 或 RSA）。
• Payload：包含声明，这些声明可以是预定义的（如 iss、sub、aud 等）或自定义的。
• Signature：用于验证消息在传输过程中没有被篡改，并且对于使用私钥签名的令牌，还可以验证发送方的身份。

2. 添加依赖

首先，我们需要在项目中添加 JWT 相关的依赖。这里我们使用 jjwt 库来处理 JWT 的生成和解析。如果你使用的是 Maven，可以在 pom.xml 文件中添加以下依赖：

<dependency>
    <groupId>io.jsonwebtoken</groupId>
    <artifactId>jjwt</artifactId>
    <version>0.9.1</version>
</dependency>

如果你使用 Gradle，可以在 build.gradle 文件中添加：

implementation 'io.jsonwebtoken:jjwt:0.9.1'

3. 创建 JWT 工具类

接下来，我们创建一个工具类来生成和解析 JWT。

import io.jsonwebtoken.Claims;
import io.jsonwebtoken.Jwts;
import io.jsonwebtoken.SignatureAlgorithm;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;

public class JwtUtil {

    private String secret = "yourSecretKey";

    public String generateToken(String username) {
        Map<String, Object> claims = new HashMap<>();
        return createToken(claims, username);
    }

    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() + 1000 * 60 * 60 * 10)) // 10 hours
                .signWith(SignatureAlgorithm.HS256, secret)
                .compact();
    }

    public Boolean validateToken(String token, String username) {
        final String extractedUsername = getUsernameFromToken(token);
        return (extractedUsername.equals(username) && !isTokenExpired(token));
    }

    public String getUsernameFromToken(String token) {
        return getClaimFromToken(token, Claims::getSubject);
    }

    public Date getExpirationDateFromToken(String token) {
        return getClaimFromToken(token, Claims::getExpiration);
    }

    public <T> T getClaimFromToken(String token, Function<Claims, T> claimsResolver) {
        final Claims claims = getAllClaimsFromToken(token);
        return claimsResolver.apply(claims);
    }

    private Claims getAllClaimsFromToken(String token) {
        return Jwts.parser()
                .setSigningKey(secret)
                .parseClaimsJws(token)
                .getBody();
    }

    private Boolean isTokenExpired(String token) {
        final Date expiration = getExpirationDateFromToken(token);
        return expiration.before(new Date());
    }
}

4. 配置 Spring Security

为了实现 JWT 认证，我们需要配置 Spring Security。首先，添加 Spring Security 的依赖：

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

然后，创建一个 SecurityConfig 类来配置安全设置。

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.security.authentication.AuthenticationManager;
import org.springframework.security.config.annotation.authentication.builders.AuthenticationManagerBuilder;
import org.springframework.security.config.annotation.method.configuration.EnableGlobalMethodSecurity;
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.core.userdetails.UserDetailsService;
import org.springframework.security.crypto.bcrypt.BCryptPasswordEncoder;
import org.springframework.security.crypto.password.PasswordEncoder;
import org.springframework.security.web.authentication.UsernamePasswordAuthenticationFilter;

@Configuration
@EnableWebSecurity
@EnableGlobalMethodSecurity(prePostEnabled = true)
public class SecurityConfig extends WebSecurityConfigurerAdapter {

    private final UserDetailsService userDetailsService;
    private final JwtRequestFilter jwtRequestFilter;

    public SecurityConfig(UserDetailsService userDetailsService, JwtRequestFilter jwtRequestFilter) {
        this.userDetailsService = userDetailsService;
        this.jwtRequestFilter = jwtRequestFilter;
    }

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

    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http.csrf().disable()
            .authorizeRequests()
            .antMatchers("/authenticate").permitAll()
            .anyRequest().authenticated()
            .and()
            .sessionManagement()
            .sessionCreationPolicy(SessionCreationPolicy.STATELESS);

        http.addFilterBefore(jwtRequestFilter, UsernamePasswordAuthenticationFilter.class);
    }

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

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

5. 创建 JWT 过滤器

我们需要创建一个过滤器来拦截请求并验证 JWT。

import org.springframework.beans.factory.annotation.Autowired;
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;

@Component
public class JwtRequestFilter extends OncePerRequestFilter {

    private final UserDetailsService userDetailsService;
    private final JwtUtil jwtUtil;

    @Autowired
    public JwtRequestFilter(UserDetailsService userDetailsService, JwtUtil jwtUtil) {
        this.userDetailsService = userDetailsService;
        this.jwtUtil = jwtUtil;
    }

    @Override
    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain chain)
            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 = jwtUtil.getUsernameFromToken(jwt);
        }

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

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

6. 创建认证控制器

最后，我们创建一个控制器来处理用户的认证请求。

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.security.authentication.AuthenticationManager;
import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.security.core.userdetails.UserDetailsService;
import org.springframework.web.bind.annotation.*;

@RestController
public class AuthenticateController {

    private final AuthenticationManager authenticationManager;
    private final JwtUtil jwtUtil;
    private final UserDetailsService userDetailsService;

    @Autowired
    public AuthenticateController(AuthenticationManager authenticationManager, JwtUtil jwtUtil, UserDetailsService userDetailsService) {
        this.authenticationManager = authenticationManager;
        this.jwtUtil = jwtUtil;
        this.userDetailsService = userDetailsService;
    }

    @PostMapping("/authenticate")
    public ResponseEntity<?> createAuthenticationToken(@RequestBody AuthenticationRequest authenticationRequest) throws Exception {
        try {
            authenticationManager.authenticate(
                    new UsernamePasswordAuthenticationToken(authenticationRequest.getUsername(), authenticationRequest.getPassword())
            );
        } catch (Exception e) {
            throw new Exception("Incorrect username or password", e);
        }

        final UserDetails userDetails = userDetailsService.loadUserByUsername(authenticationRequest.getUsername());
        final String jwt = jwtUtil.generateToken(userDetails.getUsername());

        return ResponseEntity.ok(new AuthenticationResponse(jwt));
    }
}

class AuthenticationRequest {
    private String username;
    private String password;

    // Getters and Setters
}

class AuthenticationResponse {
    private final String token;

    public AuthenticationResponse(String token) {
        this.token = token;
    }

    // Getters
}

7. 总结

通过以上步骤，我们成功地在 Spring Boot 应用中实现了 JWT 认证。JWT 认证不仅可以提高应用的安全性，还可以简化认证流程，减少服务器的负载。希望本文对你理解如何在 Spring Boot 应用中实现 JWT 认证有所帮助。如果你有任何疑问或建议，欢迎留言交流。