详解Java通过JsApi方式实现微信支付方法

要使用JsApi进行微信支付，首先要从微信获得一个prepay_id，然后通过调用微信的jsapi完成支付，JS API的返回结果get_brand_wcpay_request:ok仅在用户成功完成支付时返回。由于前端交互复杂，get_brand_wcpay_request:cancel或者get_brand_wcpay_request:fail可以统一处理为用户遇到错误或者主动放弃，不必细化区分。
示例代码如下：

function onBridgeReady(){
 WeixinJSBridge.invoke(
 &＃39;getBrandWCPayRequest&＃39;, {
  "appId" : "wx2421b1c4370ec43b", //公众号名称，由商户传入 
  "timeStamp":" 1395712654",  //时间戳，自1970年以来的秒数 
  "nonceStr" : "e61463f8efa94090b1f366cccfbbb444", //随机串 
  "package" : "u802345jgfjsdfgsdg888", 
  "signType" : "MD5",  //微信签名方式: 
  "paySign" : "70EA570631E4BB79628FBCA90534C63FF7FADD89" //微信签名 
 },
 function(res){ 
  if(res.err_msg == "get_brand_wcpay_request:ok" ) {} // 使用以上方式判断前端返回,微信团队郑重提示：res.err_msg将在用户支付成功后返回 ok，但并不保证它绝对可靠。 
 }
 ); 
}
if (typeof WeixinJSBridge == "undefined"){
 if( document.addEventListener ){
 document.addEventListener(&＃39;WeixinJSBridgeReady&＃39;, onBridgeReady, false);
 }else if (document.attachEvent){
 document.attachEvent(&＃39;WeixinJSBridgeReady&＃39;, onBridgeReady); 
 document.attachEvent(&＃39;onWeixinJSBridgeReady&＃39;, onBridgeReady);
 }
}else{
 onBridgeReady();
}

以上传入的参数package，即为prepay_id

下面讲的是获得参数来调用jsapi
我们调用JSAPI时，必须获得用户的openid，（trade_type=JSAPI，openid为必填参数。）
首先定义一个请求的对象：

package com.unstoppedable.protocol;
import com.unstoppedable.common.Configure;
import com.unstoppedable.common.HttpService;
import com.unstoppedable.common.RandomStringGenerator;
import com.unstoppedable.common.Signature;
import java.lang.reflect.Field;
import java.util.HashMap;
import java.util.Map;
public class UnifiedOrderReqData {
 private String appid;
 private String mch_id;
 private String device_info;
 private String nonce_str;
 private String sign;
 private String body;
 private String detail;
 private String attach;
 private String out_trade_no;
 private String fee_type;
 private int total_fee;
 private String spbill_create_ip;
 private String time_start;
 private String time_expire;
 private String goods_tag;
 private String notify_url;
 private String trade_type;
 private String product_id;
 private String limit_pay;
 private String openid;
 private UnifiedOrderReqData(UnifiedOrderReqDataBuilder builder) {
 this.appid = builder.appid;
 this.mch_id = builder.mch_id;
 this.device_info = builder.device_info;
 this.nonce_str = RandomStringGenerator.getRandomStringByLength(32);
 this.body = builder.body;
 this.detail = builder.detail;
 this.attach = builder.attach;
 this.out_trade_no = builder.out_trade_no;
 this.fee_type = builder.fee_type;
 this.total_fee = builder.total_fee;
 this.spbill_create_ip = builder.spbill_create_ip;
 this.time_start = builder.time_start;
 this.time_expire = builder.time_expire;
 this.goods_tag = builder.goods_tag;
 this.notify_url = builder.notify_url;
 this.trade_type = builder.trade_type;
 this.product_id = builder.product_id;
 this.limit_pay = builder.limit_pay;
 this.openid = builder.openid;
 this.sign = Signature.getSign(toMap());
 }
 public void setAppid(String appid) {
 this.appid = appid;
 }
 public void setMch_id(String mch_id) {
 this.mch_id = mch_id;
 }
 public void setDevice_info(String device_info) {
 this.device_info = device_info;
 }
 public void setNonce_str(String nonce_str) {
 this.nonce_str = nonce_str;
 }
 public void setSign(String sign) {
 this.sign = sign;
 }
 public void setBody(String body) {
 this.body = body;
 }
 public void setDetail(String detail) {
 this.detail = detail;
 }
 public void setAttach(String attach) {
 this.attach = attach;
 }
 public void setOut_trade_no(String out_trade_no) {
 this.out_trade_no = out_trade_no;
 }
 public void setFee_type(String fee_type) {
 this.fee_type = fee_type;
 }
 public void setTotal_fee(int total_fee) {
 this.total_fee = total_fee;
 }
 public void setSpbill_create_ip(String spbill_create_ip) {
 this.spbill_create_ip = spbill_create_ip;
 }
 public void setTime_start(String time_start) {
 this.time_start = time_start;
 }
 public void setTime_expire(String time_expire) {
 this.time_expire = time_expire;
 }
 public void setGoods_tag(String goods_tag) {
 this.goods_tag = goods_tag;
 }
 public void setNotify_url(String notify_url) {
 this.notify_url = notify_url;
 }
 public void setTrade_type(String trade_type) {
 this.trade_type = trade_type;
 }
 public void setProduct_id(String product_id) {
 this.product_id = product_id;
 }
 public void setLimit_pay(String limit_pay) {
 this.limit_pay = limit_pay;
 }
 public void setOpenid(String openid) {
 this.openid = openid;
 }
 public Map toMap() {
 Map map = new HashMap();
 Field[] fields = this.getClass().getDeclaredFields();
 for (Field field : fields) {
  Object obj;
  try {
  obj = field.get(this);
  if (obj != null) {
   map.put(field.getName(), obj);
  }
  } catch (IllegalArgumentException e) {
  e.printStackTrace();
  } catch (IllegalAccessException e) {
  e.printStackTrace();
  }
 }
 return map;
 }
 public static class UnifiedOrderReqDataBuilder {
 private String appid;
 private String mch_id;
 private String device_info;
 private String body;
 private String detail;
 private String attach;
 private String out_trade_no;
 private String fee_type;
 private int total_fee;
 private String spbill_create_ip;
 private String time_start;
 private String time_expire;
 private String goods_tag;
 private String notify_url;
 private String trade_type;
 private String product_id;
 private String limit_pay;
 private String openid;
 public UnifiedOrderReqDataBuilder(String appid, String mch_id, String body, String out_trade_no, Integer total_fee,
      String spbill_create_ip, String notify_url, String trade_type) {
  if (appid == null) {
  throw new IllegalArgumentException("传入参数appid不能为null");
  }
  if (mch_id == null) {
  throw new IllegalArgumentException("传入参数mch_id不能为null");
  }
  if (body == null) {
  throw new IllegalArgumentException("传入参数body不能为null");
  }
  if (out_trade_no == null) {
  throw new IllegalArgumentException("传入参数out_trade_no不能为null");
  }
  if (total_fee == null) {
  throw new IllegalArgumentException("传入参数total_fee不能为null");
  }
  if (spbill_create_ip == null) {
  throw new IllegalArgumentException("传入参数spbill_create_ip不能为null");
  }
  if (notify_url == null) {
  throw new IllegalArgumentException("传入参数notify_url不能为null");
  }
  if (trade_type == null) {
  throw new IllegalArgumentException("传入参数trade_type不能为null");
  }
  this.appid = appid;
  this.mch_id = mch_id;
  this.body = body;
  this.out_trade_no = out_trade_no;
  this.total_fee = total_fee;
  this.spbill_create_ip = spbill_create_ip;
  this.notify_url = notify_url;
  this.trade_type = trade_type;
 }
 public UnifiedOrderReqDataBuilder setDevice_info(String device_info) {
  this.device_info = device_info;
  return this;
 }
 public UnifiedOrderReqDataBuilder setDetail(String detail) {
  this.detail = detail;
  return this;
 }
 public UnifiedOrderReqDataBuilder setAttach(String attach) {
  this.attach = attach;
  return this;
 }
 public UnifiedOrderReqDataBuilder setFee_type(String fee_type) {
  this.fee_type = fee_type;
  return this;
 }
 public UnifiedOrderReqDataBuilder setTime_start(String time_start) {
  this.time_start = time_start;
  return this;
 }
 public UnifiedOrderReqDataBuilder setTime_expire(String time_expire) {
  this.time_expire = time_expire;
  return this;
 }
 public UnifiedOrderReqDataBuilder setGoods_tag(String goods_tag) {
  this.goods_tag = goods_tag;
  return this;
 }
 public UnifiedOrderReqDataBuilder setProduct_id(String product_id) {
  this.product_id = product_id;
  return this;
 }
 public UnifiedOrderReqDataBuilder setLimit_pay(String limit_pay) {
  this.limit_pay = limit_pay;
  return this;
 }
 public UnifiedOrderReqDataBuilder setOpenid(String openid) {
  this.openid = openid;
  return this;
 }
 public UnifiedOrderReqData build() {
  if("JSAPI".equals(this.trade_type) && this.openid == null) {
  throw new IllegalArgumentException("当传入trade_type为JSAPI时，openid为必填参数");
  }
  if("NATIVE".equals(this.trade_type) && this.product_id == null) {
  throw new IllegalArgumentException("当传入trade_type为NATIVE时，product_id为必填参数");
  }
  return new UnifiedOrderReqData(this);
 }
 }
}

因为有些参数为必填，有些参数为选填。而且sign要等所有参数传入之后才能计算的出，所以这里用了builder模式。关于builder模式。

我们选用httpclient进行网络传输。

package com.unstoppedable.common;
import com.thoughtworks.xstream.XStream;
import com.thoughtworks.xstream.io.xml.DomDriver;
import com.thoughtworks.xstream.io.xml.XmlFriendlyNameCoder;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.ResponseHandler;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.conn.ConnectTimeoutException;
import org.apache.http.conn.ConnectionPoolTimeoutException;
import org.apache.http.conn.ssl.SSLConnectionSocketFactory;
import org.apache.http.conn.ssl.SSLContexts;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;
import javax.net.ssl.SSLContext;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.net.SocketTimeoutException;
import java.security.KeyStore;
/**
 * Created by hupeng on 2015/7/28.
 */
public class HttpService {
 private static Log logger = LogFactory.getLog(HttpService.class);
 private static CloseableHttpClient httpClient = buildHttpClient();
 //连接超时时间，默认10秒
 private static int socketTimeout = 5000;
 //传输超时时间，默认30秒
 private static int cOnnectTimeout= 5000;
 private static int requestTimeout = 5000;
 public static CloseableHttpClient buildHttpClient() {
 try {
  KeyStore keyStore = KeyStore.getInstance("PKCS12");
  FileInputStream instream = new FileInputStream(new File(Configure.getCertLocalPath()));//加载本地的证书进行https加密传输
  try {
  keyStore.load(instream, Configure.getCertPassword().toCharArray());//设置证书密码
  } finally {
  instream.close();
  }
  // Trust own CA and all self-signed certs
  SSLContext sslcOntext= SSLContexts.custom()
   .loadKeyMaterial(keyStore, Configure.getCertPassword().toCharArray())
   .build();
  // Allow TLSv1 protocol only
  SSLConnectionSocketFactory sslsf = new SSLConnectionSocketFactory(
   sslcontext,
   new String[]{"TLSv1"},
   null,
   SSLConnectionSocketFactory.BROWSER_COMPATIBLE_HOSTNAME_VERIFIER);
  RequestConfig requestCOnfig= RequestConfig.custom()
   .setConnectTimeout(connectTimeout)
   .setConnectionRequestTimeout(requestTimeout)
   .setSocketTimeout(socketTimeout).build();
  httpClient = HttpClients.custom()
   .setDefaultRequestConfig(requestConfig)
   .setSSLSocketFactory(sslsf)
   .build();
  return httpClient;
 } catch (Exception e) {
  throw new RuntimeException("error create httpclient......", e);
 }
 }
 public static String doGet(String requestUrl) throws Exception {
 HttpGet httpget = new HttpGet(requestUrl);
 try {
  logger.debug("Executing request " + httpget.getRequestLine());
  // Create a custom response handler
  ResponseHandler respOnseHandler= new ResponseHandler() {
  @Override
  public String handleResponse(
   final HttpResponse response) throws ClientProtocolException, IOException {
   int status = response.getStatusLine().getStatusCode();
   if (status >= 200 && status <300) {
   HttpEntity entity = response.getEntity();
   return entity != null ? EntityUtils.toString(entity) : null;
   } else {
   throw new ClientProtocolException("Unexpected response status: " + status);
   }
  }
  };
  return httpClient.execute(httpget, responseHandler);
 } finally {
  httpget.releaseConnection();
 }
 }
 public static String doPost(String url, Object object2Xml) {
 String result = null;
 HttpPost httpPost = new HttpPost(url);
 //解决XStream对出现双下划线的bug
 XStream xStreamForRequestPostData = new XStream(new DomDriver("UTF-8", new XmlFriendlyNameCoder("-_", "_")));
 //将要提交给API的数据对象转换成XML格式数据Post给API
 String postDataXML = xStreamForRequestPostData.toXML(object2Xml);
 logger.info("API，POST过去的数据是：");
 logger.info(postDataXML);
 //得指明使用UTF-8编码，否则到API服务器XML的中文不能被成功识别
 StringEntity postEntity = new StringEntity(postDataXML, "UTF-8");
 httpPost.addHeader("Content-Type", "text/xml");
 httpPost.setEntity(postEntity);
 //设置请求器的配置
 logger.info("executing request" + httpPost.getRequestLine());
 try {
  HttpResponse respOnse= httpClient.execute(httpPost);
  HttpEntity entity = response.getEntity();
  result = EntityUtils.toString(entity, "UTF-8");
 } catch (ConnectionPoolTimeoutException e) {
  logger.error("http get throw ConnectionPoolTimeoutException(wait time out)", e);
 } catch (ConnectTimeoutException e) {
  logger.error("http get throw ConnectTimeoutException", e);
 } catch (SocketTimeoutException e) {
  logger.error("http get throw SocketTimeoutException", e);
 } catch (Exception e) {
  logger.error("http get throw Exception", e);
 } finally {
  httpPost.abort();
 }
 return result;
 }
}

然后是我们的总入口：

package com.unstoppedable.service;
import com.unstoppedable.common.Configure;
import com.unstoppedable.common.HttpService;
import com.unstoppedable.common.XMLParser;
import com.unstoppedable.protocol.UnifiedOrderReqData;
import org.xml.sax.SAXException;
import javax.xml.parsers.ParserConfigurationException;
import java.io.IOException;
import java.util.Map;
/**
 * Created by hupeng on 2015/7/28.
 */
public class WxPayApi {
 public static Map UnifiedOrder(UnifiedOrderReqData reqData) throws IOException, SAXException, ParserConfigurationException {
 String res = HttpService.doPost(Configure.UNIFIED_ORDER_API, reqData);
 return XMLParser.getMapFromXML(res);
 }
 public static void main(String[] args) throws Exception {
 UnifiedOrderReqData reqData = new UnifiedOrderReqData.UnifiedOrderReqDataBuilder("appid", "mch_id", "body", "out_trade_no", 1, "spbill_create_ip", "notify_url", "JSAPI").setOpenid("openid").build();
 System.out.println(UnifiedOrder(reqData));
 }
}

返回的xml为：

return_code 和result_code都为SUCCESS的时候会返回我们需要的prepay_id。。。，然后在jsapi中使用他就可以了。。

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