小程序java解密

        <dependency>
            <groupId>org.bouncycastle</groupId>
            <artifactId>bcprov-jdk16</artifactId>
            <version>1.46</version>
        </dependency>

package com.qmtt.service;

import java.security.AlgorithmParameters;
import java.security.Security;
import java.util.Arrays;
import java.util.Base64;
import java.util.Map;

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.stereotype.Service;

import com.qmtt.tools.JsonUtils;

@Service
public class WxService {
    private static final Logger log = LoggerFactory.getLogger(WxService.class);
    @Autowired
    RedisTemplate redisTemplate;

    @Autowired
    QuestionService questionService;

    public String getGroupid(String openid, String encryptedData, String iv) {
        String key = redisTemplate.opsForValue().get("sessionKey_" + openid).toString();
        log.info("密钥:<{}>", key);
        Base64.Decoder decoder = Base64.getDecoder();
        byte[] dataByte = decoder.decode(encryptedData);
        byte[] keyByte = decoder.decode(key);
        byte[] ivByte = decoder.decode(iv);
        try {
            // 如果密钥不足16位，那么就补足. 这个if 中的内容很重要
            int base = 16;
            if (keyByte.length % base != 0) {
                int groups = keyByte.length / base + (keyByte.length % base != 0 ? 1 : 0);
                byte[] temp = new byte[groups * base];
                Arrays.fill(temp, (byte) 0);
                System.arraycopy(keyByte, 0, temp, 0, keyByte.length);
                keyByte = temp;
            }
            // 初始化
            Security.addProvider(new BouncyCastleProvider());
            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS7Padding", "BC");
            SecretKeySpec spec = new SecretKeySpec(keyByte, "AES");
            AlgorithmParameters parameters = AlgorithmParameters.getInstance("AES");
            parameters.init(new IvParameterSpec(ivByte));
            cipher.init(Cipher.DECRYPT_MODE, spec, parameters);// 初始化
            byte[] resultByte = cipher.doFinal(dataByte);
            if (null != resultByte && resultByte.length > 0) {
                String result = new String(resultByte, "UTF-8");
                log.info(result);
                Map map = JsonUtils.json2map(result);
                String gid = map.get("openGId").toString();
                questionService.addGroup(openid, gid);
                return gid;
            }
        } catch (Exception e) {
            log.error("", e);
        }
        return null;
    }

}