微信小程序使用code换openid的方法（JAVA、SpringBoot）

淡淡的烟草味﹌ 2022-04-06 13:28 804阅读 0赞

微信小程序序的代码中提示，使用code换取openid，但官方文档中没有给出进一步的说明。  
　　换取openid的要点：由于安全的原因，必须由自己小程序的服务器端完成。知道了这个要点，实现起来就简单了，服务器端写一个RestController，接收code参数，使用httpclient向微信的服务端换openid就行了。  
　　代码使用了SpringBoot，不会也不难理解。主要代码如下：

package com.wallimn.iteye.sp.asset.common.controller;
    
    import java.util.Map;
    
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    import org.springframework.beans.factory.annotation.Value;
    import org.springframework.web.bind.annotation.RequestBody;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RequestMethod;
    import org.springframework.web.bind.annotation.RequestParam;
    import org.springframework.web.bind.annotation.RestController;
    
    import com.fasterxml.jackson.databind.ObjectMapper;
    import com.wallimn.iteye.sp.asset.common.util.AesUtil;
    import com.wallimn.iteye.sp.asset.common.util.HttpUtil;
    
    @RestController
    @RequestMapping("/api/wx")
    public class WeixinController {
       
    
    	private static Logger log = LoggerFactory.getLogger(WeixinController.class);
    
    	@Value("${wx.appId}")
    	private String appId;
    
    	@Value("${wx.appSecret}")
    	private String appSecret;
    
    	@Value("${wx.grantType}")
    	private String grantType;
    	// wx.grantType=authorization_code
    
    	@Value("${wx.requestUrl}")
    	private String requestUrl;
    	// wx.requestUrl=https://api.weixin.qq.com/sns/jscode2session
    
    	@RequestMapping("/session")
    	public Map<String, Object> getSession(@RequestParam(required = true) String code) {
       
    		return this.getSessionByCode(code);
    	}
    
    	@SuppressWarnings("unchecked")
    	private Map<String, Object> getSessionByCode(String code) {
       
    		String url = this.requestUrl + "?appid=" + appId + "&secret=" + appSecret + "&js_code=" + code + "&grant_type="
    				+ grantType;
    		// 发送请求
    		String data = HttpUtil.get(url);
    		log.debug("请求地址：{}", url);
    		log.debug("请求结果：{}", data);
    		ObjectMapper mapper = new ObjectMapper();
    		Map<String, Object> json = null;
    		try {
       
    			json = mapper.readValue(data, Map.class);
    		} catch (Exception e) {
       
    			e.printStackTrace();
    		}
    		// 形如{"session_key":"6w7Br3JsRQzBiGZwvlZAiA==","openid":"oQO565cXXXXXEvc4Q_YChUE8PqB60Y"}的字符串
    		return json;
    	}
    }

用到了一个httpclient封闭的工具类，代码如下：

package com.wallimn.iteye.sp.asset.common.util;
    
    import java.io.BufferedReader;
    import java.io.InputStream;
    import java.io.InputStreamReader;
    import java.net.URI;
    import java.util.ArrayList;
    import java.util.List;
    import java.util.Map;
    
    import org.apache.http.HttpResponse;
    import org.apache.http.NameValuePair;
    import org.apache.http.client.HttpClient;
    import org.apache.http.client.entity.UrlEncodedFormEntity;
    import org.apache.http.client.methods.HttpGet;
    import org.apache.http.client.methods.HttpPost;
    import org.apache.http.entity.StringEntity;
    import org.apache.http.impl.client.HttpClientBuilder;
    import org.apache.http.message.BasicNameValuePair;
    
    public class HttpUtil {
       
    
    	private static final String Charset = "utf-8";
    
    
    	/**
    	 * 发送请求，如果失败，会返回null
    	 * @param url
    	 * @param map
    	 * @return
    	 */
    	public static String post(String url, Map<String, String> map) {
       
    		// 处理请求地址
    		try {
       
    			HttpClient client = HttpClientBuilder.create().build();
    			URI uri = new URI(url);
    			HttpPost post = new HttpPost(uri);
    
    			// 添加参数
    			List<NameValuePair> params = new ArrayList<NameValuePair>();
    			for (String str : map.keySet()) {
       
    				params.add(new BasicNameValuePair(str, map.get(str)));
    			}
    			post.setEntity(new UrlEncodedFormEntity(params, Charset));
    			// 执行请求
    			HttpResponse response = client.execute(post);
    
    			if (response.getStatusLine().getStatusCode() == 200) {
       
    				// 处理请求结果
    				StringBuffer buffer = new StringBuffer();
    				InputStream in = null;
    				try {
       
    					in = response.getEntity().getContent();
    					BufferedReader reader = new BufferedReader(new InputStreamReader(in,Charset));
    					String line = null;
    					while ((line = reader.readLine()) != null) {
       
    						buffer.append(line);
    					}
    
    				} catch (Exception e) {
       
    					e.printStackTrace();
    				} finally {
       
    					// 关闭流
    					if (in != null)
    						try {
       
    							in.close();
    						} catch (Exception e) {
       
    							e.printStackTrace();
    						}
    				}
    
    				return buffer.toString();
    			} else {
       
    				return null;
    			}
    		} catch (Exception e1) {
       
    			e1.printStackTrace();
    		}
    		return null;
    
    	}
    
    	/**
    	 * 发送请求，如果失败会返回null
    	 * @param url
    	 * @param str
    	 * @return
    	 */
    	public static String post(String url, String str) {
       
    		// 处理请求地址
    		try {
       
    			HttpClient client = HttpClientBuilder.create().build();
    			URI uri = new URI(url);
    			HttpPost post = new HttpPost(uri);
    			post.setEntity(new StringEntity(str, Charset));
    			// 执行请求
    			HttpResponse response = client.execute(post);
    
    			if (response.getStatusLine().getStatusCode() == 200) {
       
    				// 处理请求结果
    				StringBuffer buffer = new StringBuffer();
    				InputStream in = null;
    				try {
       
    					in = response.getEntity().getContent();
    					BufferedReader reader = new BufferedReader(new InputStreamReader(in,"utf-8"));
    					String line = null;
    					while ((line = reader.readLine()) != null) {
       
    						buffer.append(line);
    					}
    
    				} finally {
       
    					// 关闭流
    					if (in != null)
    						in.close();
    				}
    
    				return buffer.toString();
    			} else {
       
    				return null;
    			}
    		} catch (Exception e) {
       
    			e.printStackTrace();
    		}
    		return null;
    
    	}
    
    	/**
    	 * 发送GET方式的请求，并返回结果字符串。
    	 * <br>
    	 * 时间：2017年2月27日，作者：http://wallimn.iteye.com
    	 * @param url
    	 * @return 如果失败，返回为null
    	 */
    	public static String get(String url) {
       
    		try {
       
    			HttpClient client = HttpClientBuilder.create().build();
    			URI uri = new URI(url);
    			HttpGet get = new HttpGet(uri);
    			HttpResponse response = client.execute(get);
    			if (response.getStatusLine().getStatusCode() == 200) {
       
    				StringBuffer buffer = new StringBuffer();
    				InputStream in = null;
    				try {
       
    					in = response.getEntity().getContent();
    					BufferedReader reader = new BufferedReader(new InputStreamReader(in,Charset));
    					String line = null;
    					while ((line = reader.readLine()) != null) {
       
    						buffer.append(line);
    					}
    
    				} finally {
       
    					if (in != null)
    						in.close();
    				}
    
    				return buffer.toString();
    			} else {
       
    				return null;
    			}
    		} catch (Exception e) {
       
    			e.printStackTrace();
    		}
    		return null;
    
    	}
    }

小程序中，使用wx.request(url:'https://域名/api/wx/session',....)，就可以拿到一个JSON对象，其中有openid。