如下代码class Super { publiclntegergetLenght(){ return new Integer(4); )}public class Sub extends Super (publicLonggetLenght()( return new Long(5); 3public static void main(Stringl args)(Super sooper = new Super();Sub sub = new Sub();System.out.println(sooper.getLenght().toString() + ".sub.getLenght().toString() )}}输出是什么

代码存在语法错误，需要进行修正，修正后的代码如下：

class Super {
    public Integer getLength() {
        return new Integer(4);
    }
}

public class Sub extends Super {
    public Long getLength() {
        return new Long(5);
    }

    public static void main(String[] args) {
        Super sooper = new Super();
        Sub sub = new Sub();
        System.out.println(sooper.getLength().toString() + ", " + sub.getLength().toString());
    }
}

输出结果为：`4, 5`。因为 `sooper.getLength()` 调用的是父类 `Super` 的 `getLength()` 方法，返回值为 `4`；`sub.getLength()` 调用的是子类 `Sub` 的 `getLength()` 方法，返回值为 `5`。

相关问题

class Super{ public Integer getLenght() { return new Integer(4); } } public class Sub extends Super{ public static void main(String[] args) { Super sooper = new Super(); Sub sub = new Sub(); System.out.println(sooper.getLenght().toString() + "," + sub.getLenght().toString()); } public Long getLenght() { return new Long(5); } }

这段代码中，父类Super定义了一个返回Integer类型的getLength()方法，而子类Sub重写了这个方法并返回了Long类型。在main方法中，创建了一个Super类对象sooper和一个Sub类对象sub，并分别调用它们的getLength()方法并输出结果。由于Java的多态性，调用sooper.getLenght()方法时会执行父类的方法并返回Integer类型的4，而调用sub.getLenght()方法时会执行子类的方法并返回Long类型的5。因此，输出结果为"4,5"。

springboot security项目 如何封装jwt 及token 其中数据表为package com.aokace.entity; import com.baomidou.mybatisplus.annotation.IdType; import com.baomidou.mybatisplus.annotation.TableField; import com.baomidou.mybatisplus.annotation.TableId; import com.baomidou.mybatisplus.annotation.TableName; import java.io.Serializable; import io.swagger.annotations.ApiModel; import io.swagger.annotations.ApiModelProperty; import lombok.Getter; import lombok.Setter; /** * <p> * * </p> * * @author aokace * @since 2023-05-23 */ @Getter @Setter @TableName("user") @ApiModel(value = "User对象", description = "") public class User implements Serializable { private static final long serialVersionUID = 1L; @TableId(value = "userid", type = IdType.AUTO) private Integer userid; @TableField("authority") private String authority; @TableField("role") private String role; @TableField("username") private String username; @TableField("password") private String password; }

首先需要引入相关的依赖，包括JWT和Spring Security的依赖：

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

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

然后创建一个JwtTokenUtil类来实现JWT的签发和验证功能：

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

import java.util.Date;
import java.util.HashMap;
import java.util.Map;

@Component
public class JwtTokenUtil {

    private static final String CLAIM_KEY_USERNAME = "sub";
    private static final String CLAIM_KEY_CREATED = "created";

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

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

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

    public String getUsernameFromToken(String token) {
        String username;
        try {
            Claims claims = getClaimsFromToken(token);
            username = claims.getSubject();
        } catch (Exception e) {
            username = null;
        }
        return username;
    }

    public Date getCreatedDateFromToken(String token) {
        Date created;
        try {
            Claims claims = getClaimsFromToken(token);
            created = new Date((Long) claims.get(CLAIM_KEY_CREATED));
        } catch (Exception e) {
            created = null;
        }
        return created;
    }

    public Date getExpirationDateFromToken(String token) {
        Date expiration;
        try {
            Claims claims = getClaimsFromToken(token);
            expiration = claims.getExpiration();
        } catch (Exception e) {
            expiration = null;
        }
        return expiration;
    }

    public boolean isTokenExpired(String token) {
        Date expiration = getExpirationDateFromToken(token);
        return expiration.before(new Date());
    }

    public String refreshToken(String token) {
        String refreshedToken;
        try {
            Claims claims = getClaimsFromToken(token);
            claims.put(CLAIM_KEY_CREATED, new Date());
            refreshedToken = generateToken(claims);
        } catch (Exception e) {
            refreshedToken = null;
        }
        return refreshedToken;
    }

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

    private Claims getClaimsFromToken(String token) {
        Claims claims;
        try {
            claims = Jwts.parser()
                    .setSigningKey(secret)
                    .parseClaimsJws(token)
                    .getBody();
        } catch (Exception e) {
            claims = null;
        }
        return claims;
    }

    private String generateToken(Map<String, Object> claims) {
        Date expirationDate = new Date(System.currentTimeMillis() + expiration * 1000);
        JwtBuilder builder = Jwts.builder()
                .setClaims(claims)
                .setExpiration(expirationDate)
                .signWith(SignatureAlgorithm.HS512, secret);
        return builder.compact();
    }
}

其中，JwtTokenUtil类中的generateToken方法用于生成JWT Token，getUsernameFromToken和getExpirationDateFromToken方法用于解析JWT Token中的用户名和过期时间，isTokenExpired方法用于判断JWT Token是否已经过期，refreshToken方法用于刷新JWT Token，validateToken方法用于验证JWT Token是否有效，getClaimsFromToken方法用于从JWT Token中获取Claims。

然后在Spring Security的配置类中添加JwtTokenFilter来实现JWT的过滤和验证：

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Configuration;
import org.springframework.security.authentication.AuthenticationManager;
import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
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.Authentication;
import org.springframework.security.core.AuthenticationException;
import org.springframework.security.core.userdetails.UserDetailsService;
import org.springframework.security.crypto.bcrypt.BCryptPasswordEncoder;
import org.springframework.security.web.authentication.UsernamePasswordAuthenticationFilter;

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

    @Autowired
    private UserDetailsService userDetailsService;

    @Autowired
    private JwtTokenFilter jwtTokenFilter;

    @Autowired
    private JwtAuthenticationEntryPoint jwtAuthenticationEntryPoint;

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

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

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

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

其中，SecurityConfig类中的configure方法用于配置Spring Security的策略，addFilterBefore方法用于添加JwtTokenFilter，authenticationManagerBean方法用于获取AuthenticationManager。

最后，在登录接口中，使用JwtTokenUtil生成JWT Token并返回给前端：

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

    @Autowired
    private UserDetailsService userDetailsService;

    @PostMapping("/login")
    public ResponseEntity<?> login(@RequestBody AuthRequest authRequest) throws Exception {
        try {
            Authentication authentication = authenticationManager.authenticate(
                    new UsernamePasswordAuthenticationToken(authRequest.getUsername(), authRequest.getPassword())
            );
            UserDetails userDetails = userDetailsService.loadUserByUsername(authRequest.getUsername());
            String token = jwtTokenUtil.generateToken(userDetails);
            return ResponseEntity.ok(new AuthResponse(token));
        } catch (Exception e) {
            throw new Exception("Incorrect username or password", e);
        }
    }
}

其中，AuthController类中的login方法用于处理登录请求，通过authenticationManager.authenticate方法验证用户名和密码，然后使用JwtTokenUtil生成JWT Token并返回给前端。