第四 创建工具类解密加密数据(encryptedData)

在pom中引入的依赖

		<dependency>
				<groupId>org.bouncycastle</groupId>
				<artifactId>bcprov-jdk16</artifactId>
				<version>1.46</version>
		</dependency>
		
	  <dependency>
	        <groupId>com.alibaba</groupId>
	        <artifactId>fastjson</artifactId>
	        <version>1.2.4</version>
    </dependency>

import java.io.UnsupportedEncodingException;
import java.security.AlgorithmParameters;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.NoSuchProviderException;
import java.security.Security;
import java.security.Key;
import java.security.spec.InvalidParameterSpecException;
import java.util.Arrays;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

import org.bouncycastle.jce.provider.BouncyCastleProvider;

import com.alibaba.fastjson.util.Base64;
import com.alibaba.fastjson.JSONObject;

/**
 * 
 * AES-128-CBC 加密方式
 * 注：
 * AES-128-CBC可以自己定义“密钥”和“偏移量“。
 * AES-128是jdk自动生成的“密钥”。
 * @Description: 解密加密数据(encryptedData) 
 */
public class AesCbcUtil {
	/**
     * 获取信息
     */
    public static JSONObject decrypt(String encryptedData,String sessionkey,String iv){
        // 被加密的数据
        byte[] dataByte = Base64.decodeFast(encryptedData);
        // 加密秘钥
        byte[] keyByte = Base64.decodeFast(sessionkey);
        // 偏移量
        byte[] ivByte = Base64.decodeFast(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");
                return JSONObject.parseObject(result);
            }
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        } catch (NoSuchPaddingException e) {
            e.printStackTrace();
        } catch (InvalidParameterSpecException e) {
            e.printStackTrace();
        } catch (IllegalBlockSizeException e) {
            e.printStackTrace();
        } catch (BadPaddingException e) {
            e.printStackTrace();
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (InvalidKeyException e) {
            e.printStackTrace();
        } catch (InvalidAlgorithmParameterException e) {
            e.printStackTrace();
        } catch (NoSuchProviderException e) {
            e.printStackTrace();
        }
        return null;
    }
}