对微信支付开发者文档中给出的API进行了封装。
com.github.wxpay.sdk.WXPay类下提供了对应的方法:
| 方法名 | 说明 | 
|---|---|
| microPay | 刷卡支付 | 
| unifiedOrder | 统一下单 | 
| orderQuery | 查询订单 | 
| reverse | 撤销订单 | 
| closeOrder | 关闭订单 | 
| refund | 申请退款 | 
| refundQuery | 查询退款 | 
| downloadBill | 下载对账单 | 
| report | 交易保障 | 
| shortUrl | 转换短链接 | 
| authCodeToOpenid | 授权码查询openid | 
- 参数为
Map<String, String>对象,返回类型也是Map<String, String>。 - 方法内部会将参数会转换成含有
appid、mch_id、nonce_str、sign\_type和sign的XML; - 默认使用MD5进行签名;
 - 通过HTTPS请求得到返回数据后会对其做必要的处理(例如验证签名,签名错误则抛出异常)。
 - 对于downloadBill,无论是否成功都返回Map,且都含有
return_code和return_msg。若成功,其中return_code为SUCCESS,另外data对应对账单数据。 
maven:
<dependency>
    <groupId>com.github.wxpay</groupId>
    <artifactId>wxpay-sdk</artifactId>
    <version>0.0.3</version>
</dependency>
配置类MyConfig:
import com.github.wxpay.sdk.WXPayConfig;
import java.io.*;
public class MyConfig implements WXPayConfig{
    private byte[] certData;
    public MyConfig() throws Exception {
        String certPath = "/path/to/apiclient_cert.p12";
        File file = new File(certPath);
        InputStream certStream = new FileInputStream(file);
        this.certData = new byte[(int) file.length()];
        certStream.read(this.certData);
        certStream.close();
    }
    public String getAppID() {
        return "wx8888888888888888";
    }
    public String getMchID() {
        return "12888888";
    }
    public String getKey() {
        return "88888888888888888888888888888888";
    }
    public InputStream getCertStream() {
        ByteArrayInputStream certBis = new ByteArrayInputStream(this.certData);
        return certBis;
    }
    public int getHttpConnectTimeoutMs() {
        return 8000;
    }
    public int getHttpReadTimeoutMs() {
        return 10000;
    }
}统一下单:
import com.github.wxpay.sdk.WXPay;
import java.util.HashMap;
import java.util.Map;
public class WXPayExample {
    public static void main(String[] args) throws Exception {
        MyConfig config = new MyConfig();
        WXPay wxpay = new WXPay(config);
        Map<String, String> data = new HashMap<String, String>();
        data.put("body", "腾讯充值中心-QQ会员充值");
        data.put("out_trade_no", "2016090910595900000012");
        data.put("device_info", "");
        data.put("fee_type", "CNY");
        data.put("total_fee", "1");
        data.put("spbill_create_ip", "123.12.12.123");
        data.put("notify_url", "http://www.example.com/wxpay/notify");
        data.put("trade_type", "NATIVE");  // 此处指定为扫码支付
        data.put("product_id", "12");
        try {
            Map<String, String> resp = wxpay.unifiedOrder(data);
            System.out.println(resp);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}订单查询:
import com.github.wxpay.sdk.WXPay;
import java.util.HashMap;
import java.util.Map;
public class WXPayExample {
    public static void main(String[] args) throws Exception {
        MyConfig config = new MyConfig();
        WXPay wxpay = new WXPay(config);
        Map<String, String> data = new HashMap<String, String>();
        data.put("out_trade_no", "2016090910595900000012");
        try {
            Map<String, String> resp = wxpay.orderQuery(data);
            System.out.println(resp);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}退款查询:
import com.github.wxpay.sdk.WXPay;
import java.util.HashMap;
import java.util.Map;
public class WXPayExample {
    public static void main(String[] args) throws Exception {
        MyConfig config = new MyConfig();
        WXPay wxpay = new WXPay(config);
        Map<String, String> data = new HashMap<String, String>();
        data.put("out_trade_no", "2016090910595900000012");
        try {
            Map<String, String> resp = wxpay.refundQuery(data);
            System.out.println(resp);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}下载对账单:
import com.github.wxpay.sdk.WXPay;
import java.util.HashMap;
import java.util.Map;
public class WXPayExample {
    public static void main(String[] args) throws Exception {
        MyConfig config = new MyConfig();
        WXPay wxpay = new WXPay(config);
        Map<String, String> data = new HashMap<String, String>();
        data.put("bill_date", "20140603");
        data.put("bill_type", "ALL");
        try {
            Map<String, String> resp = wxpay.downloadBill(data);
            System.out.println(resp);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}其他API的使用和上面类似。
暂时不支持下载压缩格式的对账单,但可以使用该SDK生成请求用的XML数据:
import com.github.wxpay.sdk.WXPay;
import com.github.wxpay.sdk.WXPayUtil;
import java.util.HashMap;
import java.util.Map;
public class WXPayExample {
    public static void main(String[] args) throws Exception {
        MyConfig config = new MyConfig();
        WXPay wxpay = new WXPay(config);
        Map<String, String> data = new HashMap<String, String>();
        data.put("bill_date", "20140603");
        data.put("bill_type", "ALL");
        data.put("tar_type", "GZIP");
        try {
            data = wxpay.fillRequestData(data);
            System.out.println(WXPayUtil.mapToXml(data));
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}收到支付结果通知时,需要验证签名,可以这样做:
import com.github.wxpay.sdk.WXPay;
import com.github.wxpay.sdk.WXPayUtil;
import java.util.Map;
public class WXPayExample {
    public static void main(String[] args) throws Exception {
        String notifyData = "...."; // 支付结果通知的xml格式数据
        MyConfig config = new MyConfig();
        WXPay wxpay = new WXPay(config);
        Map<String, String> notifyMap = WXPayUtil.xmlToMap(notifyData);  // 转换成map
        if (wxpay.isPayResultNotifySignatureValid(notifyMap)) {
            // 签名正确
            // 进行处理。
            // 注意特殊情况:订单已经退款,但收到了支付结果成功的通知,不应把商户侧订单状态从退款改成支付成功
        }
        else {
            // 签名错误,如果数据里没有sign字段,也认为是签名错误
        }
    }
}HTTPS请求默认使用MD5算法签名,若需要使用HMAC-SHA256:
import com.github.wxpay.sdk.WXPay;
import com.github.wxpay.sdk.WXPayConstants;
public class WXPayExample {
    public static void main(String[] args) throws Exception {
        MyConfig config = new MyConfig();
        WXPay wxpay = new WXPay(config, WXPayConstants.SignType.HMACSHA256);
        // ......
    }
}
若需要使用sandbox环境:
import com.github.wxpay.sdk.WXPay;
import com.github.wxpay.sdk.WXPayConstants;
public class WXPayExample {
    public static void main(String[] args) throws Exception {
        MyConfig config = new MyConfig();
        WXPay wxpay = new WXPay(config, WXPayConstants.SignType.MD5, true);
        // ......
    }
}
BSD