微信小程序请求微信api授权登录(Java后端)

1.小程序端调用wx.login(),获取到微信返回的code临时凭证.
2.小程序端调用我方的后台接口,Java后端调用微信的api,需要appId,appSecret,js_code,grant_type:authorization_code
代码如下:

private JSONObject getUserWXLoginInfo(String wxCode) {
		String requestUrl = "https://api.weixin.qq.com/sns/jscode2session";
		Map requestUrlParam = new HashMap();
		requestUrlParam.put("appid", GameConstants.AppID);	//开发者设置中的appId
		requestUrlParam.put("secret", GameConstants.AppSecret);	//开发者设置中的appSecret
		requestUrlParam.put("js_code", wxCode);	//小程序调用wx.login返回的code
		requestUrlParam.put("grant_type", "authorization_code");	//默认参数
		//发送post请求读取调用微信 https://api.weixin.qq.com/sns/jscode2session 接口获取openid用户唯一标识
		JSONObject jsonObject = JSON.parseObject(UrlUtil.sendPost(requestUrl, requestUrlParam));
		return jsonObject;
	}
public String login(String wxCode) throws ParseException {
		//请求微信api获取用户的openid和sessionKey
		JSONObject jsonObject = getUserWXLoginInfo(wxCode);
		if(jsonObject!=null&&!jsonObject.containsKey("openid")) {
			return Common.getErrorReturn(GameMsg.CANSHU_ERROR);
		}
		String openid = (String)jsonObject.get("openid");
		String sessionKey = (String)jsonObject.get("session_key");
		//通过openid查询数据库是否有此用户
		List userList = getUserByOpenId(openid);
		if(userList!=null&&userList.size()!=0) {//用户已存在	
			if(userList.get(0).getPhone()==null) {
				jsonObject.put("phone", "");
			}else {
				jsonObject.put("phone", userList.get(0).getPhone());
			}
			RedisSetter.setRedisStringDuration(openid, sessionKey, 60*60);//存到redis中,设置失效时间
			jsonObject.put("userId", userList.get(0).getUserId());
			jsonObject.put("dateTime",DatetimeUtil.dateToStamp(new Date()));
			return Common.getReturn(jsonObject);
		}
		User user = new User();
		user.setOpenid(openid);
		userDao.insertUser(user);
		List newUser = getUserByOpenId(openid);
		if(newUser.get(0).getPhone()==null) {
			jsonObject.put("phone", "");
		}else {
			jsonObject.put("phone", newUser.get(0).getPhone());
		}
		RedisSetter.setRedisStringDuration(openid, sessionKey, 60*60);//存到redis中,设置失效时间
		jsonObject.put("userId", newUser.get(0).getUserId());
		jsonObject.put("dateTime",DatetimeUtil.dateToStamp(new Date()));
		return Common.getReturn(jsonObject);
	}

http请求的工具类:
package com.king.util;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.URL;
import java.net.URLConnection;
import java.util.Iterator;
import java.util.Map;

import org.apache.log4j.LogManager;
import org.apache.log4j.Logger;

public class UrlUtil {
	private final Logger LOG = LogManager.getLogger(this.getClass());

	/**
	 * 向指定 URL 发送POST方法的请求
	 * 
	 * @param url 发送请求的 URL
	 * @param param 请求参数
	 * @return 所代表远程资源的响应结果
	 */
	public static String sendPost(String url, Map paramMap) {
        PrintWriter out = null;
        BufferedReader in = null;
        String result = "";
        
        String param = "";
		Iterator it = paramMap.keySet().iterator();
		
		while(it.hasNext()) {
			String key = it.next();
			param += key + "=" + paramMap.get(key) + "&";
		}
		
        try {
            URL realUrl = new URL(url);
            // 打开和URL之间的连接
            URLConnection conn = realUrl.openConnection();
            // 设置通用的请求属性
            conn.setRequestProperty("accept", "*/*");
            conn.setRequestProperty("connection", "Keep-Alive");
            conn.setRequestProperty("Accept-Charset", "utf-8");
            conn.setRequestProperty("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
            // 发送POST请求必须设置如下两行
            conn.setDoOutput(true);
            conn.setDoInput(true);
            // 获取URLConnection对象对应的输出流
            out = new PrintWriter(conn.getOutputStream());
            // 发送请求参数
            out.print(param);
            // flush输出流的缓冲
            out.flush();
            // 定义BufferedReader输入流来读取URL的响应
            in = new BufferedReader(new InputStreamReader(conn.getInputStream(), "UTF-8"));
            String line;
            while ((line = in.readLine()) != null) {
                result += line;
            }
        } catch (Exception e) {
        	e.printStackTrace();
        }
        //使用finally块来关闭输出流、输入流
        finally{
            try{
                if(out!=null){
                    out.close();
                }
                if(in!=null){
                    in.close();
                }
            }
            catch(IOException ex){
                ex.printStackTrace();
            }
        }
        return result;
    }
}

返回给小程序所需要的参数即可