转：https://www.cnblogs.com/brokencolor/p/8575440.html

Java的URL类(二)

实例：

Java 通过HttpURLConnection Post方式提交json，并从服务端返回json数据

package Demo.Test;

import java.io.ByteArrayOutputStream;

import java.io.InputStream;

import java.io.OutputStream;

import java.net.HttpURLConnection;

import java.net.URL;

public class App {

    public static void readParse(String urlPath,String str) throws Exception {

        System.out.println(str);

        ByteArrayOutputStream outStream = new ByteArrayOutputStream();

        byte[] data = new byte[1024];

        int len = 0;

        URL url = new URL(urlPath);

        HttpURLConnection conn = (HttpURLConnection) url.openConnection();

        // 设置传递方式

        conn.setRequestMethod("POST");

        //代理

        conn.addRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 5.0; Windows NT; DigExt)");

        conn.setRequestProperty("Content-Type", "application/json");

        conn.setDoOutput(true);

        conn.setDoInput(true);

        // 设置不用缓存

        conn.setUseCaches(false);

        //权限

        conn.setRequestProperty("Authorization", " Bearer fc58be57c46b32f9a2c32e5393684ac0");

         // 开始连接请求

        conn.connect();

        OutputStream  out = conn.getOutputStream();

        // 写入请求的字符串

        out.write((str).getBytes());

        out.flush();

        out.close();

        // 请求返回的状态

        if (conn.getResponseCode() == 200) {

            System.out.println("连接成功");

            // 请求返回的数据

            InputStream in = conn.getInputStream();

            String a = null;

            try {

                byte[] data1 = new byte[in.available()];

                in.read(data1);

                // 转成字符串

                a = new String(data1);

                System.out.println(a);

            } catch (Exception e1) {

                // TODO Auto-generated catch block

                e1.printStackTrace();

            }

        } else {

            System.out.println(conn.getResponseCode()+":no++");

        }

    }

    public static void main(String[] args) throws Exception {//地址

        String url = "http://...";

        //查询参数

        String str = "{\"ids\":[15410,15402]}";

        readParse(url,str);

    }

}

注：如果你的代码报错：java.io.IOException: Server returned HTTP response code: 403 for URL https://...... 访问被拒绝

　　你需要在代码中加入请求头信息

// 设置允许输出

conn.setDoOutput(true);

conn.setDoInput(true);

// 设置不用缓存

conn.setUseCaches(false);

// 设置传递方式

conn.setRequestMethod("POST");

// 设置维持长连接

conn.setRequestProperty("Connection", "Keep-Alive");

// 设置文件字符集:

conn.setRequestProperty("Charset", "UTF-8");

// 设置文件长度

conn.setRequestProperty("Content-Length", String.valueOf(data.length));

// 设置文件类型:

conn.setRequestProperty("contentType", "application/json");

//代理

conn.addRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 5.0; Windows NT; DigExt)");

//权限---需要根据自己情况进行修改

conn.setRequestProperty("Authorization", " Bearer fc58be57c46b32f9a2c32e5393684ac0");

GET方式访问weatherAPI接口实例

 1 import java.io.InputStream;

 2 import java.net.URL;

 3 import java.net.URLConnection;

 4

 5 public class WeatherAPI {

 6

 7     public static void main(String[] args) throws Exception {

 8         // TODO Auto-generated method stub

 9         WeatherAPI.json("北京");

10         //3秒后继续执行

11         Thread.sleep(3000);

12         WeatherAPI.xml("东京");

13     }

14     public static void json(String strcity) throws Exception{

15         //参数url化

16         String city = java.net.URLEncoder.encode(strcity, "utf-8");

17         //拼地址

18         String apiUrl = String.format("https://www.sojson.com/open/api/weather/json.shtml?city=%s",city);

19         //开始请求

20         URL url= new URL(apiUrl);

21         URLConnection open = url.openConnection();

22         InputStream input = open.getInputStream();

23         //这里转换为String，带上包名，怕你们引错包

24         String result = org.apache.commons.io.IOUtils.toString(input,"utf-8");

25         //输出

26         System.out.println(result);

27     }

28

29     public static void xml(String strcity) throws Exception{

30         //参数url化

31         String city = java.net.URLEncoder.encode(strcity, "utf-8");

32         //拼地址

33         String apiUrl = String.format("https://www.sojson.com/open/api/weather/xml.shtml?city=%s",city);

34         //开始请求

35         URL url= new URL(apiUrl);

36         URLConnection open = url.openConnection();

37         InputStream input = open.getInputStream();

38         //这里转换为String，带上包名，怕你们引错包

39         String result = org.apache.commons.io.IOUtils.toString(input,"utf-8");

40         //输出

41         System.out.println(result);

42     }

43 }