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Spring Boot JWT（JSON Web Token）：无状态认证

在现代 Web 开发中，无状态认证是一种重要的安全机制，它允许服务器在不存储会话信息的情况下验证用户身份。JSON Web Token（JWT）是一种常用的无状态认证技术，它通过一个紧凑的 URL 安全令牌来传递用户身份信息。Spring Boot 与 JWT 的结合可以为应用提供强大的安全保护。本文将详细介绍如何在 Spring Boot 中集成 JWT 实现无状态认证。

一、JWT 概述

1.1 什么是 JWT

JWT 是一种基于 JSON 的开放标准（RFC 7519），用于在各方之间传递声明信息。它由三部分组成：头部（Header）、载荷（Payload）和签名（Signature）。JWT 的主要特点是无状态、自包含和安全，非常适合用于分布式系统和微服务架构中的身份验证和信息交换。

1.2 JWT 的工作原理

当用户使用用户名和密码登录系统时，认证服务器会验证用户的身份。如果验证成功，服务器会生成一个 JWT，并将其返回给客户端。客户端在后续的请求中，将 JWT 放在请求头的 Authorization 字段中，格式为 Bearer <token>。服务器接收到请求后，会验证 JWT 的合法性，如果验证通过，则允许用户访问受保护的资源。

二、Spring Boot 集成 JWT

2.1 添加依赖

在 Spring Boot 项目中，需要在 pom.xml 文件中添加 JWT 和 Spring Security 的依赖。

<!-- Spring Security -->
<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-security</artifactId>
</dependency><!-- JWT -->
<dependency><groupId>io.jsonwebtoken</groupId><artifactId>jjwt</artifactId><version>0.9.1</version>
</dependency>

2.2 配置 JWT 工具类

创建一个工具类 JwtUtil，用于生成和验证 JWT。

import io.jsonwebtoken.*;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;import java.util.Date;
import java.util.HashMap;
import java.util.Map;@Component
public class JwtUtil {@Value("${jwt.secret}")private String secret;public String generateToken(String username) {Map<String, Object> claims = new HashMap<>();return Jwts.builder().setClaims(claims).setSubject(username).setIssuedAt(new Date(System.currentTimeMillis())).setExpiration(new Date(System.currentTimeMillis() + 1000 * 60 * 60 * 10)) // 10 小时有效期.signWith(SignatureAlgorithm.HS256, secret).compact();}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 = Jwts.parser().setSigningKey(secret).parseClaimsJws(token).getBody();return claimsResolver.apply(claims);}public Boolean isTokenExpired(String token) {return extractExpiration(token).before(new Date());}public Boolean validateToken(String token, String username) {final String extractedUsername = extractUsername(token);return (extractedUsername.equals(username) && !isTokenExpired(token));}
}

2.3 配置 Spring Security

创建一个 SecurityConfig 类，配置 Spring Security 以支持 JWT 认证。

import org.springframework.beans.factory.annotation.Autowired;
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.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;@Configuration
@EnableWebSecurity
public class SecurityConfig extends WebSecurityConfigurerAdapter {@Autowiredprivate JwtRequestFilter jwtRequestFilter;@Autowiredprivate UserDetailsService userDetailsService;@Overrideprotected void configure(AuthenticationManagerBuilder auth) throws Exception {auth.userDetailsService(userDetailsService).passwordEncoder(passwordEncoder());}@Overrideprotected void configure(HttpSecurity http) throws Exception {http.csrf().disable().authorizeRequests().antMatchers("/api/authenticate").permitAll().anyRequest().authenticated().and().sessionManagement().sessionCreationPolicy(SessionCreationPolicy.STATELESS);http.addFilterBefore(jwtRequestFilter, UsernamePasswordAuthenticationFilter.class);}@Override@Beanpublic AuthenticationManager authenticationManagerBean() throws Exception {return super.authenticationManagerBean();}@Beanpublic PasswordEncoder passwordEncoder() {return new BCryptPasswordEncoder();}
}

2.4 创建 JWT 请求过滤器

创建一个 JwtRequestFilter 类，用于在每个请求中解析 JWT，并将其设置到 Spring Security 上下文中。

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
import org.springframework.security.core.context.SecurityContextHolder;
import org.springframework.security.core.userdetails.UserDetails;
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 {@Autowiredprivate JwtUtil jwtUtil;@Autowiredprivate UserDetailsService userDetailsService;@Overrideprotected 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.extractUsername(jwt);}if (username != null && SecurityContextHolder.getContext().getAuthentication() == null) {UserDetails userDetails = userDetailsService.loadUserByUsername(username);if (jwtUtil.validateToken(jwt, userDetails)) {UsernamePasswordAuthenticationToken usernamePasswordAuthenticationToken = new UsernamePasswordAuthenticationToken(userDetails, null, userDetails.getAuthorities());usernamePasswordAuthenticationToken.setDetails(new WebAuthenticationDetailsSource().buildDetails(request));SecurityContextHolder.getContext().setAuthentication(usernamePasswordAuthenticationToken);}}chain.doFilter(request, response);}
}

2.5 创建认证和授权接口

创建一个 AuthenticationController 类，用于处理用户登录和生成 JWT。

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.ResponseEntity;
import org.springframework.security.authentication.AuthenticationManager;
import org.springframework.security.authentication.BadCredentialsException;
import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.web.bind.annotation.*;@RestController
@RequestMapping("/api")
public class AuthenticationController {@Autowiredprivate AuthenticationManager authenticationManager;@Autowiredprivate JwtUtil jwtUtil;@Autowiredprivate UserDetailsService userDetailsService;@PostMapping("/authenticate")public ResponseEntity<?> createAuthenticationToken(@RequestBody AuthenticationRequest authenticationRequest) throws Exception {try {authenticationManager.authenticate(new UsernamePasswordAuthenticationToken(authenticationRequest.getUsername(), authenticationRequest.getPassword()));} catch (BadCredentialsException 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));}
}

2.6 创建用户详情服务

创建一个 UserDetailsService 实现类，用于加载用户信息。

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.security.core.userdetails.UserDetailsService;
import org.springframework.security.core.userdetails.UsernameNotFoundException;
import org.springframework.stereotype.Service;import java.util.ArrayList;@Service
public class CustomUserDetailsService implements UserDetailsService {@Autowiredprivate UserRepository userRepository;@Overridepublic UserDetails loadUserByUsername(String username) throws UsernameNotFoundException {User user = userRepository.findByUsername(username).orElseThrow(() -> new UsernameNotFoundException("User not found with username: " + username));return new org.springframework.security.core.userdetails.User(user.getUsername(), user.getPassword(), new ArrayList<>());}
}

2.7 配置 application.properties

在 application.properties 文件中配置 JWT 密钥。

jwt.secret=yourSecretKey

2.8 测试

启动应用后，可以通过发送 POST 请求到 /api/authenticate 接口进行登录，获取 JWT。然后在请求头中添加 Authorization: Bearer <token>，即可访问受保护的接口。

三、总结

通过本文的介绍，我们详细学习了如何在 Spring Boot 中集成 JWT 实现无状态认证。我们添加了必要的依赖，配置了 JWT 工具类、Spring Security、JWT 请求过滤器、认证和授权接口以及用户详情服务。希望这些内容能够帮助你在实际开发中更好地应用 JWT，提升应用的安全性。