给出一个springboot项目集成jwt的例子

好的，我可以回答这个问题。以下是一个Spring Boot项目集成JWT的示例：

1. 首先，需要在pom.xml文件中添加以下依赖：

<dependency>
    <groupId>io.jsonwebtoken</groupId>
    <artifactId>jjwt</artifactId>
    <version>.9.1</version>
</dependency>

2. 创建一个JwtUtil类，用于生成和验证JWT：

import io.jsonwebtoken.Claims;
import io.jsonwebtoken.Jwts;
import io.jsonwebtoken.SignatureAlgorithm;
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;

    @Value("${jwt.expiration}")
    private Long expiration;

    public String generateToken(String username) {
        Map<String, Object> claims = new HashMap<>();
        claims.put("sub", username);
        claims.put("created", new Date());
        return Jwts.builder()
                .setClaims(claims)
                .setExpiration(new Date(System.currentTimeMillis() + expiration * 100))
                .signWith(SignatureAlgorithm.HS512, secret)
                .compact();
    }

    public boolean validateToken(String token, String username) {
        Claims claims = getClaims(token);
        if (claims != null) {
            String subject = claims.getSubject();
            Date expirationDate = claims.getExpiration();
            Date now = new Date(System.currentTimeMillis());
            if (subject.equals(username) && expirationDate.after(now)) {
                return true;
            }
        }
        return false;
    }

    public Claims getClaims(String token) {
        try {
            return Jwts.parser().setSigningKey(secret).parseClaimsJws(token).getBody();
        } catch (Exception e) {
            return null;
        }
    }
}

3. 创建一个JwtAuthenticationFilter类，用于拦截请求并验证JWT：

import org.springframework.security.authentication.AuthenticationManager;
import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
import org.springframework.security.core.Authentication;
import org.springframework.security.core.context.SecurityContextHolder;
import org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter;
import org.springframework.security.web.util.matcher.AntPathRequestMatcher;

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

public class JwtAuthenticationFilter extends AbstractAuthenticationProcessingFilter {

    public JwtAuthenticationFilter(AuthenticationManager authenticationManager) {
        super(new AntPathRequestMatcher("/api/**"));
        setAuthenticationManager(authenticationManager);
    }

    @Override
    public Authentication attemptAuthentication(HttpServletRequest request, HttpServletResponse response) {
        String token = request.getHeader("Authorization");
        if (token != null) {
            String username = JwtUtil.getClaims(token).getSubject();
            if (username != null) {
                return getAuthenticationManager().authenticate(new UsernamePasswordAuthenticationToken(username, null));
            }
        }
        return null;
    }

    @Override
    protected void successfulAuthentication(HttpServletRequest request, HttpServletResponse response, FilterChain chain, Authentication authResult) throws IOException, ServletException {
        SecurityContextHolder.getContext().setAuthentication(authResult);
        chain.doFilter(request, response);
    }
}

4. 在WebSecurityConfig类中配置JwtAuthenticationFilter：

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.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.crypto.bcrypt.BCryptPasswordEncoder;
import org.springframework.security.crypto.password.PasswordEncoder;
import org.springframework.security.web.authentication.UsernamePasswordAuthenticationFilter;

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

    @Autowired
    private JwtAuthenticationEntryPoint jwtAuthenticationEntryPoint;

    @Autowired
    private JwtUserDetailsService jwtUserDetailsService;

    @Autowired
    private JwtRequestFilter jwtRequestFilter;

    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http.csrf().disable()
                .authorizeRequests().antMatchers("/api/authenticate").permitAll()
                .anyRequest().authenticated()
                .and().exceptionHandling().authenticationEntryPoint(jwtAuthenticationEntryPoint)
                .and().sessionManagement().sessionCreationPolicy(SessionCreationPolicy.STATELESS);
        http.addFilterBefore(jwtRequestFilter, UsernamePasswordAuthenticationFilter.class);
    }

    @Autowired
    public void configureGlobal(AuthenticationManagerBuilder auth) throws Exception {
        auth.userDetailsService(jwtUserDetailsService).passwordEncoder(passwordEncoder());
    }

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

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

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

以上就是一个Spring Boot项目集成JWT的示例，希望能对你有所帮助。