springboot实现登录接口并且返回token给前端使用

好的，您可以参考以下步骤实现：

1. 添加依赖：

在 `pom.xml` 文件中添加以下依赖：

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

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

2. 配置 Security：

新建一个继承 `WebSecurityConfigurerAdapter` 的类，并且重写其中的方法：

@Configuration
@EnableWebSecurity
public class SecurityConfig extends WebSecurityConfigurerAdapter {

    @Autowired
    private UserDetailsService userDetailsService;

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

    @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(HttpMethod.POST, "/login").permitAll()
                .anyRequest().authenticated()
                .and().addFilter(new JWTAuthenticationFilter(authenticationManager()))
                .addFilter(new JWTAuthorizationFilter(authenticationManager()));
    }
}

3. 创建 User 实体类：

创建一个 User 实体类，用于存储用户信息。

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

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

    private String username;

    private String password;

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

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

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

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

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

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

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

4. 创建 UserDetailsService 实现类：

创建一个 UserDetailsService 实现类，用于从数据库中获取用户信息。

@Service
public class UserDetailsServiceImpl implements UserDetailsService {

    @Autowired
    private UserRepository userRepository;

    @Override
    public UserDetails loadUserByUsername(String username) throws UsernameNotFoundException {
        User user = userRepository.findByUsername(username);
        if (user == null) {
            throw new UsernameNotFoundException(username);
        }
        return user;
    }
}

5. 创建 UserRepository 接口：

创建一个 UserRepository 接口，用于操作数据库。

@Repository
public interface UserRepository extends JpaRepository<User, Long> {

    User findByUsername(String username);
}

6. 创建 JWTAuthenticationFilter 和 JWTAuthorizationFilter：

创建 JWTAuthenticationFilter 和 JWTAuthorizationFilter，用于实现 JWT 认证和授权功能。

JWTAuthenticationFilter：

public class JWTAuthenticationFilter extends UsernamePasswordAuthenticationFilter {

    private AuthenticationManager authenticationManager;

    public JWTAuthenticationFilter(AuthenticationManager authenticationManager) {
        this.authenticationManager = authenticationManager;
        setFilterProcessesUrl("/login");
    }

    @Override
    public Authentication attemptAuthentication(HttpServletRequest request, HttpServletResponse response) throws AuthenticationException {
        try {
            User user = new ObjectMapper().readValue(request.getInputStream(), User.class);
            return authenticationManager.authenticate(new UsernamePasswordAuthenticationToken(user.getUsername(), user.getPassword()));
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
}

JWTAuthorizationFilter：

public class JWTAuthorizationFilter extends BasicAuthenticationFilter {

    public JWTAuthorizationFilter(AuthenticationManager authenticationManager) {
        super(authenticationManager);
    }

    @Override
    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain chain) throws IOException, ServletException {
        String header = request.getHeader("Authorization");
        if (header == null || !header.startsWith("Bearer ")) {
            chain.doFilter(request, response);
            return;
        }
        UsernamePasswordAuthenticationToken authentication = getAuthentication(request);
        SecurityContextHolder.getContext().setAuthentication(authentication);
        chain.doFilter(request, response);
    }

    private UsernamePasswordAuthenticationToken getAuthentication(HttpServletRequest request) {
        String token = request.getHeader("Authorization");
        if (token != null) {
            String user = Jwts.parser()
                    .setSigningKey("secret".getBytes())
                    .parseClaimsJws(token.replace("Bearer ", ""))
                    .getBody()
                    .getSubject();
            if (user != null) {
                return new UsernamePasswordAuthenticationToken(user, null, Collections.emptyList());
            }
            return null;
        }
        return null;
    }
}

7. 创建 TokenController：

创建一个 TokenController，用于实现登录接口。

@RestController
public class TokenController {

    @PostMapping("/login")
    public ResponseEntity<?> login(@RequestBody User user) {
        try {
            Authentication authentication = new UsernamePasswordAuthenticationToken(user.getUsername(), user.getPassword());
            authentication = new JWTAuthenticationFilter(authenticationManager()).attemptAuthentication(new HttpServletRequestWrapper(null) {
                @Override
                public String getHeader(String name) {
                    return "Bearer " + Jwts.builder()
                            .setSubject(user.getUsername())
                            .setExpiration(new Date(System.currentTimeMillis() + 86400000))
                            .signWith(SignatureAlgorithm.HS512, "secret".getBytes())
                            .compact();
                }
            }, new HttpServletResponseWrapper(null));
            SecurityContextHolder.getContext().setAuthentication(authentication);
            return ResponseEntity.ok().header("Authorization", authentication.getCredentials().toString()).build();
        } catch (AuthenticationException e) {
            return ResponseEntity.status(HttpStatus.UNAUTHORIZED).build();
        }
    }
}

至此，就完成了一个简单的登录接口并且返回 token 的实现。当用户发送 POST 请求到 `/login` 接口时，若用户名和密码正确，则会返回一个包含 token 的响应头。