HttpURLConnection的用法

为了使用这个类，我们模拟来发送请求。

我们在京东万象中申请了一个免费的api接口，来模拟这个请求。

代码示例如下：

package cn.xiaomin.http;

import java.net.HttpURLConnection;
import java.net.URL;
import java.nio.charset.Charset;

import org.springframework.util.StreamUtils;

/**
* HttpURLConnection的用法
* 模拟http请求
* @author Administrator
*
*/
public class HttpTest {
   public static void main(String[] args) throws Exception {
       //定义需要访问的地址
       URL url = new URL("https://way.jd.com/jisuapi/search");
       //2.与服务器建立连接
       HttpURLConnection conn =(HttpURLConnection) url.openConnection();
       //3.设置请求的方式
       conn.setRequestMethod("POST");
       //4.需要输出的参数,默认为false，不输出，我们让他输出
       conn.setDoOutput(true);
       //5.拼接参数信息
       StringBuffer param = new StringBuffer();
       param.append("keyword=").append("土豆");
       param.append("&num=").append("1");
       param.append("&appkey=").append("c57af9eadd710aaf6025bd64672e47c4");
       //6.写出参数
       conn.getOutputStream().write(param.toString().getBytes("UTF-8"));
       //7.发起请求
       conn.connect();
       //8.接受对方响应的信息 StreamUtils是spring中的包
       String str=StreamUtils.copyToString(conn.getInputStream(), Charset.forName("UTF-8"));
       System.out.println(str);
   }
}

返回结果：

{"code":"10000","charge":false,"msg":"查询成功","result":{"status":"0","msg":"ok","result":{"num":"1","list":[{"id":"2","classid":"2","name":"开心土豆泥","peoplenum":"3-4人","preparetime":"10分钟内","cookingtime":"30分钟-1小时","content":"粉粉绵绵的土豆泥，加入玉米粒、青豆点缀，色彩亮丽清新，而火腿肠更是增加了口感，造型圆圆的，十分的可爱哦！","pic":"http://api.jisuapi.com/recipe/upload/20160719/115137_58878.jpg","tag":"下午茶,减肥,家常菜,春季,甜,甜品,私房菜,素菜,蒸","material":[{"mname":"火腿肠","type":"0","amount":"50g"},{"mname":"玉米粒","type":"0","amount":"30g"},{"mname":"青豆","type":"0","amount":"30g"},{"mname":"沙拉酱","type":"0","amount":"适量"},{"mname":"牛奶","type":"0","amount":"少许"},{"mname":"盐","type":"0","amount":"1勺"},{"mname":"土豆","type":"1","amount":"2个"}],"process":[{"pcontent":"首先将去皮土豆切成块，泡入清水，火腿肠切粒。","pic":"http://api.jisuapi.com/recipe/upload/20160719/162542_28654.jpg"},{"pcontent":"将土豆放入蒸锅，隔水蒸十分钟，取出。","pic":"http://api.jisuapi.com/recipe/upload/20160719/162542_65552.jpg"},{"pcontent":"将玉米粒、青豆，放入蒸锅，隔水蒸十分钟，取出。","pic":"http://api.jisuapi.com/recipe/upload/20160719/162543_51629.jpg"},{"pcontent":"将土豆压成泥，放入火腿、青豆、玉米粒，挤入适量沙拉酱，再淋入少量牛奶，放入半勺盐，搅拌均匀，用模具压成心形，就可以享用了。","pic":"http://api.jisuapi.com/recipe/upload/20160719/162543_43692.jpg"}]}]}}}

为了以后方便的使用，我把这个封装了成一个工具类

package cn.xiaomin.http;

import java.net.HttpURLConnection;
import java.net.URL;
import java.nio.charset.Charset;
import java.util.Map;
import java.util.Map.Entry;

import org.springframework.util.StreamUtils;

public class HttpUtil {
   /**
   * 模拟浏览器的请求
   * @param httpURL 发送请求的地址
   * @param params 请求参数
   * @return
   * @throws Exception
   */
   public static String sendHttpRequest(String httpURL,Map<String,String> params) throws Exception{
       //建立URL连接对象
       URL url = new URL(httpURL);
       //创建连接
       HttpURLConnection conn = (HttpURLConnection) url.openConnection();
       //设置请求的方式(需要是大写的)
       conn.setRequestMethod("POST");
       //设置需要输出
       conn.setDoOutput(true);
       //判断是否有参数.
       if(params!=null&&params.size()>0){
           StringBuilder sb = new StringBuilder();
           for(Entry<String,String> entry:params.entrySet()){
               sb.append("&").append(entry.getKey()).append("=").append(entry.getValue());
           }
           //sb.substring(1)去除最前面的&
           conn.getOutputStream().write(sb.substring(1).toString().getBytes("utf-8"));
       }
       //发送请求到服务器
       conn.connect();
       //获取远程响应的内容.
       String responseContent = StreamUtils.copyToString(conn.getInputStream(),Charset.forName("utf-8"));
       conn.disconnect();
       return responseContent;
   }
   /**
   * 模拟浏览器的请求
   * @param httpURL 发送请求的地址
   * @param jesssionId 会话Id
   * @return
   * @throws Exception
   */
   public static void sendHttpRequest(String httpURL,String jesssionId) throws Exception{
       //建立URL连接对象
       URL url = new URL(httpURL);
       //创建连接
       HttpURLConnection conn = (HttpURLConnection) url.openConnection();
       //设置请求的方式(需要是大写的)
       conn.setRequestMethod("POST");
       //设置需要输出
       conn.setDoOutput(true);
       conn.addRequestProperty("Cookie","JSESSIONID="+jesssionId);
       //发送请求到服务器
       conn.connect();
       conn.getInputStream();
       conn.disconnect();
   }
}

工具类的用法

package cn.xiaomin.http;

import java.util.HashMap;
import java.util.Map;

public class HttpTest2 {
   public static void main(String[] args) throws Exception {
       Map<String, String> map = new HashMap<String, String>();
       map.put("keyword", "梅菜扣肉");
       map.put("num", "1");
       map.put("appkey", "c57af9eadd710aaf6025bd64672e47c4");

       String str=HttpUtil.sendHttpRequest("https://way.jd.com/jisuapi/search", map);
       System.out.println(str);


   }
}

返回结果：