记录Threadlocal使用

编写ThreadLocal工具类

package com.jjking.jplan.context;


public class BaseContext<T> {
    public static final ThreadLocal threadLocal = new ThreadLocal();

    //存储用户
    public static void set(Object t) {
        threadLocal.set(t);
    }

    //获取用户
    public static <T> T get() {
        return (T) threadLocal.get();
    }

    //移除用户
    public static void remove() {
        threadLocal.remove();
    }
}

搭配拦截器使用

package com.jjking.jplan.interceptors;

import com.jjking.jplan.context.BaseContext;
import com.jjking.jplan.pojo.User;
import com.jjking.jplan.utils.JwtUtil;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import org.springframework.stereotype.Component;
import org.springframework.web.servlet.HandlerInterceptor;

import java.util.Map;

@Component
public class LoginInterceptors implements HandlerInterceptor {

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {

        //获取token
        String token = request.getHeader("Authorization");

        try {
            //解析token
            Map<String, Object> clamis = JwtUtil.parseToken(token);

            //将当前信息装入ThreadLocal

            User user = User.builder()
                    .id((Integer) clamis.get("id"))
                    .username((String) clamis.get("username"))
                    .build();

            BaseContext.set(user);
            return true;
        } catch (Exception e) {
            response.setStatus(401);
            //回去把孩子
            return false;
        }
    }


    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        //清空ThreadLoacl信息
        BaseContext.remove();
    }
}

我们在请求发送到服务器前,判断是否带着token,如果token解析正确,写入ThreadLocal

并且在请求完成之后,清空ThreadLocal

附录

jwt工具类

package com.jjking.jplan.utils;

import com.auth0.jwt.JWT;
import com.auth0.jwt.algorithms.Algorithm;

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

public class JwtUtil {

    //秘钥
    private static final String KEY = "itheima";
	
	//接收业务数据,生成token并返回
    public static String genToken(Map<String, Object> claims) {
        return JWT.create()
                .withClaim("claims", claims) //载荷
                .withExpiresAt(new Date(System.currentTimeMillis() + 1000 * 60 * 60 * 12)) //过期时间
                .sign(Algorithm.HMAC256(KEY));  //加密算法
    }

	//接收token,验证token,并返回业务数据
    public static Map<String, Object> parseToken(String token) {
        return JWT.require(Algorithm.HMAC256(KEY))
                .build()
                .verify(token)
                .getClaim("claims")
                .asMap();
    }

}

Md5工具类

package com.jjking.jplan.utils;


import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class Md5Util {
    /**
     * 默认的密码字符串组合，用来将字节转换成 16 进制表示的字符,apache校验下载的文件的正确性用的就是默认的这个组合
     */
    protected static char hexDigits[] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};

    protected static MessageDigest messagedigest = null;

    static {
        try {
            messagedigest = MessageDigest.getInstance("MD5");
        } catch (NoSuchAlgorithmException nsaex) {
            System.err.println(Md5Util.class.getName() + "初始化失败，MessageDigest不支持MD5Util。");
            nsaex.printStackTrace();
        }
    }

    /**
     * 生成字符串的md5校验值
     *
     * @param s
     * @return
     */
    public static String getMD5String(String s) {
        return getMD5String(s.getBytes());
    }

    /**
     * 判断字符串的md5校验码是否与一个已知的md5码相匹配
     *
     * @param password  要校验的字符串
     * @param md5PwdStr 已知的md5校验码
     * @return
     */
    public static boolean checkPassword(String password, String md5PwdStr) {
        String s = getMD5String(password);
        return s.equals(md5PwdStr);
    }


    public static String getMD5String(byte[] bytes) {
        messagedigest.update(bytes);
        return bufferToHex(messagedigest.digest());
    }

    private static String bufferToHex(byte bytes[]) {
        return bufferToHex(bytes, 0, bytes.length);
    }

    private static String bufferToHex(byte bytes[], int m, int n) {
        StringBuffer stringbuffer = new StringBuffer(2 * n);
        int k = m + n;
        for (int l = m; l < k; l++) {
            appendHexPair(bytes[l], stringbuffer);
        }
        return stringbuffer.toString();
    }

    private static void appendHexPair(byte bt, StringBuffer stringbuffer) {
        char c0 = hexDigits[(bt & 0xf0) >> 4];// 取字节中高 4 位的数字转换, >>>
        // 为逻辑右移，将符号位一起右移,此处未发现两种符号有何不同
        char c1 = hexDigits[bt & 0xf];// 取字节中低 4 位的数字转换
        stringbuffer.append(c0);
        stringbuffer.append(c1);
    }

}