用java对接一下微信登陆

要使用Java对接微信登陆，需要使用微信开放平台提供的OAuth2.0授权登录接口。下面是一个使用Java实现微信登陆的示例代码：

import java.io.IOException;
import java.net.URLEncoder;
import java.util.HashMap;
import java.util.Map;

import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.JSONObject;

import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;

public class WeChatLogin {
    // 应用ID
    private static final String APP_ID = "your_app_id";
    // 应用密钥
    private static final String APP_SECRET = "your_app_secret";
    // 授权回调地址
    private static final String REDIRECT_URI = "your_redirect_uri";

    /**
     * 获取微信授权链接
     * 
     * @return
     */
    public static String getAuthorizeUrl() {
        String url = "https://open.weixin.qq.com/connect/oauth2/authorize";
        String encodedUri = URLEncoder.encode(REDIRECT_URI);
        String params = String.format("appid=%s&redirect_uri=%s&response_type=code&scope=snsapi_userinfo&state=STATE#wechat_redirect", APP_ID, encodedUri);
        return url + "?" + params;
    }

    /**
     * 通过code换取网页授权access_token
     * 
     * @param code
     * @return
     * @throws IOException
     */
    public static String getAccessToken(String code) throws IOException {
        String url = "https://api.weixin.qq.com/sns/oauth2/access_token";
        String params = String.format("appid=%s&secret=%s&code=%s&grant_type=authorization_code", APP_ID, APP_SECRET, code);
        String requestUrl = url + "?" + params;
        OkHttpClient client = new OkHttpClient();
        Request request = new Request.Builder().url(requestUrl).get().build();
        Response response = client.newCall(request).execute();
        String json = response.body().string();
        JSONObject jsonObject = JSON.parseObject(json);
        return jsonObject.getString("access_token");
    }

    /**
     * 获取微信用户信息
     * 
     * @param accessToken
     * @param openId
     * @return
     * @throws IOException
     */
    public static Map<String, String> getUserInfo(String accessToken, String openId) throws IOException {
        String url = "https://api.weixin.qq.com/sns/userinfo";
        String params = String.format("access_token=%s&openid=%s&lang=zh_CN", accessToken, openId);
        String requestUrl = url + "?" + params;
        OkHttpClient client = new OkHttpClient();
        Request request = new Request.Builder().url(requestUrl).get().build();
        Response response = client.newCall(request).execute();
        String json = response.body().string();
        JSONObject jsonObject = JSON.parseObject(json);
        Map<String, String> userInfo = new HashMap<>();
        userInfo.put("openId", jsonObject.getString("openid"));
        userInfo.put("nickname", jsonObject.getString("nickname"));
        userInfo.put("sex", jsonObject.getString("sex"));
        userInfo.put("province", jsonObject.getString("province"));
        userInfo.put("city", jsonObject.getString("city"));
        userInfo.put("country", jsonObject.getString("country"));
        userInfo.put("headImgUrl", jsonObject.getString("headimgurl"));
        return userInfo;
    }

    public static void main(String[] args) {
        // 1. 获取微信授权链接
        String authorizeUrl = getAuthorizeUrl();
        System.out.println("授权链接：" + authorizeUrl);

        // 2. 用户同意授权后，获取code
        String code = "your_code";

        try {
            // 3. 通过code获取access_token
            String accessToken = getAccessToken(code);
            System.out.println("access_token：" + accessToken);

            // 4. 获取用户信息
            Map<String, String> userInfo = getUserInfo(accessToken, "your_openid");
            System.out.println("用户信息：" + userInfo);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

其中，`getAuthorizeUrl()`方法用于获取微信授权链接，`getAccessToken()`方法用于通过code换取网页授权access_token，`getUserInfo()`方法用于获取微信用户信息。在main方法中，你需要将`your_code`和`your_openid`替换成实际的值。

需要注意的是，示例代码中使用了OkHttp库来发送HTTP请求，需要在项目中添加OkHttp库的依赖。