Add WXBizDataCrypt for WeChat Mini Program.

weixin4j-wxa/src/main/java/com/foxinmy/weixin4j/wxa/AESUtils.java

@@ -0,0 +1,58 @@
+package com.foxinmy.weixin4j.wxa;
+
+import java.security.AlgorithmParameters;
+import java.security.InvalidAlgorithmParameterException;
+import java.security.Key;
+import java.security.NoSuchProviderException;
+import java.security.Security;
+
+import javax.crypto.Cipher;
+import javax.crypto.spec.IvParameterSpec;
+import javax.crypto.spec.SecretKeySpec;
+
+import org.bouncycastle.jce.provider.BouncyCastleProvider;
+
+final class AESUtils {
+
+	private static boolean initialized = false;
+
+	private AESUtils() {
+	}
+
+	/**
+	 * AES解密
+	 *
+	 * @param content 密文
+	 * @return 明文
+	 * @throws InvalidAlgorithmParameterException
+	 * @throws NoSuchProviderException
+	 */
+	static byte[] decrypt(byte[] content, byte[] keyByte, byte[] ivByte)
+			throws InvalidAlgorithmParameterException {
+		initialize();
+		try {
+			Cipher cipher = Cipher.getInstance("AES/CBC/PKCS7Padding");
+			Key sKeySpec = new SecretKeySpec(keyByte, "AES");
+
+			cipher.init(Cipher.DECRYPT_MODE, sKeySpec, generateIV(ivByte)); // 初始化
+			byte[] result = cipher.doFinal(content);
+			return result;
+		} catch (Exception e) {
+			throw new RuntimeException(e);
+		}
+	}
+
+	private static void initialize() {
+		if (initialized)
+			return;
+		Security.addProvider(new BouncyCastleProvider());
+		initialized = true;
+	}
+
+	private static AlgorithmParameters generateIV(byte[] iv) throws Exception {
+		AlgorithmParameters params = AlgorithmParameters.getInstance("AES");
+		params.init(new IvParameterSpec(iv));
+		return params;
+	}
+
+}

weixin4j-wxa/src/main/java/com/foxinmy/weixin4j/wxa/WXBizDataCrypt.java

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+package com.foxinmy.weixin4j.wxa;
+
+import java.nio.charset.Charset;
+import java.security.InvalidAlgorithmParameterException;
+
+import org.apache.commons.codec.binary.Base64;
+
+import com.alibaba.fastjson.JSON;
+import com.alibaba.fastjson.JSONObject;
+
+/**
+ * @see <a href="https://developers.weixin.qq.com/miniprogram/dev/api/signature.html#wxchecksessionobject">加密数据解密算法</a>
+ */
+public class WXBizDataCrypt {
+
+	private final String appid;
+
+	private final String sessionKey;
+
+	public WXBizDataCrypt(String appid, String sessionKey) {
+		this.appid = appid;
+		this.sessionKey = sessionKey;
+	}
+
+	public JSONObject decryptData(final String encryptedData, final String iv) {
+		final byte[] aesKey = Base64.decodeBase64(sessionKey);
+		final byte[] aesCipher = Base64.decodeBase64(encryptedData);
+		final byte[] aesIV = Base64.decodeBase64(iv);
+
+		final byte[] resultByte;
+		try {
+			resultByte = AESUtils.decrypt(aesCipher, aesKey, aesIV);
+		} catch (InvalidAlgorithmParameterException e) {
+			throw new RuntimeException(e);
+		}
+
+		final String decryptedText = new String(resultByte, Charset.forName("UTF-8"));
+		final JSONObject decrypted = JSON.parseObject(decryptedText);
+
+		final String appId = decrypted.getJSONObject("watermark").getString("appid");
+		if (!appId.equals(this.appid)) {
+			throw new IllegalArgumentException("Invalid Buffer");
+		}
+
+		return decrypted;
+	}
+
+}

weixin4j-wxa/src/main/java/com/foxinmy/weixin4j/wxa/package-info.java

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+/**
+ * <a href="https://developers.weixin.qq.com/miniprogram/dev/api/">WeChat Mini Program</a> support library.
+ */
+package com.foxinmy.weixin4j.wxa;