本文解釋了Java如何實現(xiàn)JsApi方式的微信支付，代碼內(nèi)容詳細(xì)，文章思路清晰,需要的朋友可以參考下

要使用JsApi進行微信支付，首先要從微信獲得一個prepay_id，然後透過呼叫微信的jsapi完成支付，JS API的回傳結(jié)果get_brand_wcpay_request:ok僅在使用者成功完成支付時傳回。由於前端互動複雜，get_brand_wcpay_request:cancel或get_brand_wcpay_request:fail可以統(tǒng)一處理為使用者遇到錯誤或主動放棄，不必細(xì)化區(qū)分。
範(fàn)例程式碼如下：

function?onBridgeReady(){
?WeixinJSBridge.invoke(
?'getBrandWCPayRequest',?{
??"appId"?:?"wx2421b1c4370ec43b",?//公眾號名稱，由商戶傳入?
??"timeStamp":"?1395712654",??//時間戳，自1970年以來的秒數(shù)?
??"nonceStr"?:?"e61463f8efa94090b1f366cccfbbb444",?//隨機串?
??"package"?:?"u802345jgfjsdfgsdg888",?
??"signType"?:?"MD5",??//微信簽名方式:?
??"paySign"?:?"70EA570631E4BB79628FBCA90534C63FF7FADD89"?//微信簽名?
?},
?function(res){?
??if(res.err_msg?==?"get_brand_wcpay_request:ok"?)?{}?//?使用以上方式判斷前端返回,微信團隊鄭重提示：res.err_msg將在用戶支付成功后返回?ok，但并不保證它絕對可靠。?
?}
?);?
}
if?(typeof?WeixinJSBridge?==?"undefined"){
?if(?document.addEventListener?){
?document.addEventListener('WeixinJSBridgeReady',?onBridgeReady,?false);
?}else?if?(document.attachEvent){
?document.attachEvent('WeixinJSBridgeReady',?onBridgeReady);?
?document.attachEvent('onWeixinJSBridgeReady',?onBridgeReady);
?}
}else{
?onBridgeReady();
}

以上傳入的參數(shù)package，也就是為prepay_id

下面講的是取得參數(shù)來呼叫jsapi
我們呼叫JSAPI時，必須取得用戶的openid，（trade_type=JSAPI，openid為必填參數(shù)。）
先定義一個請求的物件：

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<String, Object>?toMap()?{
?Map<String, Object>?map?=?new?HashMap<String, Object>();
?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("傳入?yún)?shù)appid不能為null");
??}
??if?(mch_id?==?null)?{
??throw?new?IllegalArgumentException("傳入?yún)?shù)mch_id不能為null");
??}
??if?(body?==?null)?{
??throw?new?IllegalArgumentException("傳入?yún)?shù)body不能為null");
??}
??if?(out_trade_no?==?null)?{
??throw?new?IllegalArgumentException("傳入?yún)?shù)out_trade_no不能為null");
??}
??if?(total_fee?==?null)?{
??throw?new?IllegalArgumentException("傳入?yún)?shù)total_fee不能為null");
??}
??if?(spbill_create_ip?==?null)?{
??throw?new?IllegalArgumentException("傳入?yún)?shù)spbill_create_ip不能為null");
??}
??if?(notify_url?==?null)?{
??throw?new?IllegalArgumentException("傳入?yún)?shù)notify_url不能為null");
??}
??if?(trade_type?==?null)?{
??throw?new?IllegalArgumentException("傳入?yún)?shù)trade_type不能為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("當(dāng)傳入trade_type為JSAPI時，openid為必填參數(shù)");
??}
??if("NATIVE".equals(this.trade_type)?&&?this.product_id?==?null)?{
??throw?new?IllegalArgumentException("當(dāng)傳入trade_type為NATIVE時，product_id為必填參數(shù)");
??}
??return?new?UnifiedOrderReqData(this);
?}
?}
}

因為有些參數(shù)為必填，有些參數(shù)為選填。而且sign要等所有參數(shù)傳入之後才能計算的出，所以這裡用了builder模式。關(guān)於builder模式。

我們選用httpclient進行網(wǎng)路傳輸。

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();
?//連接超時時間，默認(rèn)10秒
?private?static?int?socketTimeout?=?5000;
?//傳輸超時時間，默認(rèn)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()));//加載本地的證書進行https加密傳輸
??try?{
??keyStore.load(instream,?Configure.getCertPassword().toCharArray());//設(shè)置證書密碼
??}?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<String>?responseHandler?=?new?ResponseHandler<String>()?{
??@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);
 //解決XStream對出現(xiàn)雙下劃線的bug
 XStream xStreamForRequestPostData = new XStream(new DomDriver("UTF-8", new XmlFriendlyNameCoder("-_", "_")));
 //將要提交給API的數(shù)據(jù)對象轉(zhuǎn)換成XML格式數(shù)據(jù)Post給API
 String postDataXML = xStreamForRequestPostData.toXML(object2Xml);
 logger.info("API，POST過去的數(shù)據(jù)是：");
 logger.info(postDataXML);
 //得指明使用UTF-8編碼，否則到API服務(wù)器XML的中文不能被成功識別
 StringEntity postEntity = new StringEntity(postDataXML, "UTF-8");
 httpPost.addHeader("Content-Type", "text/xml");
 httpPost.setEntity(postEntity);
 //設(shè)置請求器的配置
 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;
 }
}

然後是我們的總?cè)肟冢?/p>

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<String,Object>?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));
?}
}

回傳的xml為：

<xml>
?<return_code><![CDATA[SUCCESS]]></return_code>
?<return_msg><![CDATA[OK]]></return_msg>
?<appid><![CDATA[wx2421b1c4370ec43b]]></appid>
?<mch_id><![CDATA[10000100]]></mch_id>
?<nonce_str><![CDATA[IITRi8Iabbblz1Jc]]></nonce_str>
?<sign><![CDATA[7921E432F65EB8ED0CE9755F0E86D72F]]></sign>
?<result_code><![CDATA[SUCCESS]]></result_code>
?<prepay_id><![CDATA[wx201411101639507cbf6ffd8b0779950874]]></prepay_id>
?<trade_type><![CDATA[JSAPI]]></trade_type>
</xml>

return_code 和result_code都為SUCCESS的時候會回傳我們需要的prepay_id。 。 。 ，然後在jsapi中使用他就可以了。 。

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