支付宝APP支付之Java后台生成签名具体步骤

   /**
    *支付宝支付
    * @param orderId 订单编号
    * @param actualPay 实际支付金额
    * @return
    */
 private String getOrderInfoByAliPay(String orderId,float actualPay) {

      //回调页面
      String ali_call_back_url = propertiesService.ALI_CALL_BACK_URL;
      String seller_id = propertiesService.SELLER_ID;//商户编号
      String[] parameters={
            "service=\"mobile.securitypay.pay\"",//固定值（手机快捷支付）
            "partner=\"2088421544444\"",//合作身份者ID（16位）

            "_input_charset=\"utf-8\"",
            "notify_url=\""+ali_call_back_url+"\"",//通知地址
            "out_trade_no=\""+orderId+"\"",//商户内部订单号
            "subject=\"测试\"",//测试
            "payment_type=\"1\"",//固定值
            "seller_id=\""+seller_id+"\"",//账户邮箱
           "total_fee=\""+"0.01"+"\"",//支付金额（元）

            "body=\"订单说明\"",//订单说明            

            "it_b_pay=\"30m\""（订单过期时间 30分钟过期无效）
      };
      String signOrderUrl = signAllString(parameters);
      return signOrderUrl;
   }

/**
 * 支付宝签名
 * @param array
 * @return
 */
private String signAllString(String [] array){
   StringBuffer sb = new StringBuffer("");
   for (int i = 0; i < array.length; i++) {
      if(i==(array.length-1)){
         sb.append(array[i]);
      }else{
         sb.append(array[i]+"&");
      }
   }
   System.out.println(sb.toString());
   String sign = "";
   try {
      sign = URLEncoder.encode(RSA.sign(sb.toString(), AlipayConfig.private_key, "utf-8"), "utf-8");//private_key私钥
   } catch (UnsupportedEncodingException e) {
      e.printStackTrace();
   }
   sb.append("&sign=\""+sign+"\"&");
   sb.append("sign_type=\"RSA\"");
   return sb.toString();
}

package com.alipay.sign;

import javax.crypto.Cipher;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.security.KeyFactory;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;

public class RSA{

   public static final String  SIGN_ALGORITHMS = "SHA1WithRSA";

   /**
   * RSA签名
   * @param content 待签名数据
   * @param privateKey 商户私钥
   * @param input_charset 编码格式
   * @return 签名值
   */
   public static String sign(String content, String privateKey, String input_charset)
   {
        try 
        {
         byte[] decode = Base64.decode(privateKey);
         PKCS8EncodedKeySpec priPKCS8   = new PKCS8EncodedKeySpec(decode );
           KeyFactory keyf= KeyFactory.getInstance("RSA");
           PrivateKey priKey= keyf.generatePrivate(priPKCS8);

            java.security.Signature signature = java.security.Signature.getInstance(SIGN_ALGORITHMS);

            signature.initSign(priKey);
            signature.update( content.getBytes(input_charset) );

            byte[] signed = signature.sign();

            return Base64.encode(signed);
        }
        catch (Exception e) 
        {
           e.printStackTrace();
        }

        return null;
    }

   /**
   * RSA验签名检查
   * @param content 待签名数据
   * @param sign 签名值
   * @param ali_public_key 支付宝公钥
   * @param input_charset 编码格式
   * @return 布尔值
   */
   public static boolean verify(String content, String sign, String ali_public_key, String input_charset)
   {
      try 
      {
         KeyFactory keyFactory = KeyFactory.getInstance("RSA");
           byte[] encodedKey = Base64.decode(ali_public_key);
           PublicKey pubKey = keyFactory.generatePublic(new X509EncodedKeySpec(encodedKey));
         java.security.Signature signature = java.security.Signature
         .getInstance(SIGN_ALGORITHMS);

         signature.initVerify(pubKey);
         signature.update( content.getBytes(input_charset) );

         boolean bverify = signature.verify( Base64.decode(sign) );
         return bverify;

      } 
      catch (Exception e) 
      {
         e.printStackTrace();
      }

      return false;
   }

   /**
   * 解密
   * @param content 密文
   * @param private_key 商户私钥
   * @param input_charset 编码格式
   * @return 解密后的字符串
   */
   public static String decrypt(String content, String private_key, String input_charset) throws Exception {
        PrivateKey prikey = getPrivateKey(private_key);

        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.DECRYPT_MODE, prikey);

        InputStream ins = new ByteArrayInputStream(Base64.decode(content));
        ByteArrayOutputStream writer = new ByteArrayOutputStream();
        //rsa解密的字节大小最多是128，将需要解密的内容，按128位拆开解密
        byte[] buf = new byte[128];
        int bufl;

        while ((bufl = ins.read(buf)) != -1) {
            byte[] block = null;

            if (buf.length == bufl) {
                block = buf;
            } else {
                block = new byte[bufl];
                for (int i = 0; i < bufl; i++) {
                    block[i] = buf[i];
                }
            }

            writer.write(cipher.doFinal(block));
        }

        return new String(writer.toByteArray(), input_charset);
    }

   /**
   * 得到私钥
   * @param key 密钥字符串（经过base64编码）
   * @throws Exception
   */
   public static PrivateKey getPrivateKey(String key) throws Exception {

      byte[] keyBytes;

      keyBytes = Base64.decode(key);

      PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(keyBytes);

      KeyFactory keyFactory = KeyFactory.getInstance("RSA");

      PrivateKey privateKey = keyFactory.generatePrivate(keySpec);

      return privateKey;
   }
}

支付宝参数里面为什么要进行转义？主要是因为返回给移动的参数结果是springmvc进行返回的给移动端时，会认为"为结束，所以需要\"进行转义！

支付宝APP支付开发- IOException : DerInputStream.getLength(): lengthTag=127, too big.

支付宝APP支付Java开发报错:

1 IOException : DerInputStream.getLength(): lengthTag=127, too big.

后来排查是因为没有设置私钥.