服务端调用接口实例

前言：

　　在做小程序的开发时需要获取用户的openId用来做唯一标识，来获取对应用户的相关数据

　　官方的文档说明上有四个必须传的参数

　　其中appId和appSecret可在自己的微信公众号平台上获取，同时这些也是属于私密信息，应该妥善保管的，因为微信手机客户端是很容易反编译获取到这些信息的，所以在前端的ajax请求将这些参数传到后台是不可取的，最好的方式是将这两个参数在后台传入，然后发送请求至官方接口

1.模拟Http请求

package com.btw.util;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.io.Reader;
import java.net.HttpURLConnection;
import java.net.ProtocolException;
import java.net.URL;
import java.util.Map;

public class HttpUtil {
    /**
     * 请求类型： GET
     */
    public final static String GET = "GET";
    /**
     * 请求类型： POST
     */
    public final static String POST = "POST";

    /**
     * 模拟Http Get请求
     * @param urlStr
     *             请求路径
     * @param paramMap
     *             请求参数
     * @return
     * @throws Exception
     */
    public static String get(String urlStr, Map<String, String> paramMap) throws Exception{
        urlStr = urlStr + "?" + getParamString(paramMap);
        HttpURLConnection conn = null;
        try{
            //创建URL对象
            URL url = new URL(urlStr);
            //获取URL连接
            conn = (HttpURLConnection) url.openConnection();
            //设置通用的请求属性
            setHttpUrlConnection(conn, GET);
            //建立实际的连接
            conn.connect();
            //获取响应的内容
            return readResponseContent(conn.getInputStream());
        }finally{
            if(null!=conn) conn.disconnect();
        }
    }

    /**
     * 模拟Http Post请求
     * @param urlStr
     *             请求路径
     * @param paramMap
     *             请求参数
     * @return
     * @throws Exception
     */
    public static String post(String urlStr, Map<String, String> paramMap) throws Exception{
        HttpURLConnection conn = null;
        PrintWriter writer = null;
        try{
            //创建URL对象
            URL url = new URL(urlStr);
            //获取请求参数
            String param = getParamString(paramMap);
            //获取URL连接
            conn = (HttpURLConnection) url.openConnection();
            //设置通用请求属性
            setHttpUrlConnection(conn, POST);
            //建立实际的连接
            conn.connect();
            //将请求参数写入请求字符流中
            writer = new PrintWriter(conn.getOutputStream());
            writer.print(param);
            writer.flush();
            //读取响应的内容
            return readResponseContent(conn.getInputStream());
        }finally{
            if(null!=conn) conn.disconnect();
            if(null!=writer) writer.close();
        }
    }

    /**
     * 读取响应字节流并将之转为字符串
     * @param in
     *         要读取的字节流
     * @return
     * @throws IOException
     */
    private static String readResponseContent(InputStream in) throws IOException{
        Reader reader = null;
        StringBuilder content = new StringBuilder();
        try{
            reader = new InputStreamReader(in);
            char[] buffer = new char[1024];
            int head = 0;
            while( (head=reader.read(buffer))>0 ){
                content.append(new String(buffer, 0, head));
            }
            return content.toString();
        }finally{
            if(null!=in) in.close();
            if(null!=reader) reader.close();
        }
    }

    /**
     * 设置Http连接属性
     * @param conn
     *             http连接
     * @return
     * @throws ProtocolException
     * @throws Exception
     */
    private static void setHttpUrlConnection(HttpURLConnection conn, String requestMethod) throws ProtocolException{
        conn.setRequestMethod(requestMethod);
        conn.setRequestProperty("accept", "*/*");
        conn.setRequestProperty("Accept-Language", "zh-CN");
        conn.setRequestProperty("User-Agent", "Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; WOW64; Trident/5.0)");
        conn.setRequestProperty("Proxy-Connection", "Keep-Alive");
        if(null!=requestMethod && POST.equals(requestMethod)){
            conn.setDoOutput(true);
            conn.setDoInput(true);
        }
    }

    /**
     * 将参数转为路径字符串
     * @param paramMap
     *             参数
     * @return
     */
    private static String getParamString(Map<String, String> paramMap){
        if(null==paramMap || paramMap.isEmpty()){
            return "";
        }
        StringBuilder builder = new StringBuilder();
        for(String key : paramMap.keySet() ){
            builder.append("&")
                    .append(key).append("=").append(paramMap.get(key));
        }
        return builder.deleteCharAt(0).toString();
    }
}

其中请求参数已经封装成map的形式，非常方便

2.请求接口

在这个接口我们只需要接收一个code的参数，然后用String类型接收Util类返回的数据即可，其中的url为官方接口地址

package com.btw.controller;

import com.btw.util.AppConstant;
import com.btw.util.HttpUtil;
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 javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.util.HashMap;
import java.util.Map;

@RestController
@RequestMapping("/system")
public class SecretController {
    @RequestMapping(value = "/getOpenId",method = RequestMethod.GET)
    public String getOpenid(HttpServletRequest request,HttpServletResponse response, @RequestParam String code){
        Map<String,String> paramMap=new HashMap<>();
        paramMap.put("appid", AppConstant.AppId);
        paramMap.put("secret",AppConstant.AppSecret);
        paramMap.put("js_code",code);
        paramMap.put("grant_type","authorization_code");
        String url="https://api.weixin.qq.com/sns/jscode2session";
        String res=null;
        try {
            res=HttpUtil.post(url,paramMap);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return res;
    }
}

3.前端Ajax请求

原文地址：https://www.cnblogs.com/wutongshu-master/p/11660552.html