请求参数，请求参数应该是 name1=value1&name2=value2 的形式。
1 import java.io.BufferedReader;
2 import java.io.IOException;
3 import java.io.InputStreamReader;
4 import java.io.PrintWriter;
5 import java.net.URL;
6 import java.net.URLConnection;
7 import java.util.List;
8 import java.util.Map;
9 import java.util.Set;
10
11 public class HttpRequest {
12 /**
13 * 向指定URL发送GET方法的请求
14 *
15 * @param url 发送请求的URL
16 * @param param 请求参数，请求参数应该是 name1=value1&name2=value2 的形式。
17 * @return URL 所代表远程资源的响应结果
18 */
19 public static String sendGet(String url, String param) {
20 String result = "";
21 BufferedReader in = null;
22 try {
23 String urlNameString = url + "?" + param;
24 URL realUrl = new URL(urlNameString);
25 // 打开和URL之间的连接
26 URLConnection connection = realUrl.openConnection();
27 // 设置通用的请求属性
28 connection.setRequestProperty("accept", "*/*");
29 connection.setRequestProperty("connection", "Keep-Alive");
30 connection.setRequestProperty("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
31 // 建立实际的连接
32 connection.connect();
33 // 获取所有响应头字段
34 Map<String, List<String>> map = connection.getHeaderFields();
35 // 遍历所有的响应头字段
36 for (String key : map.keySet()) {
37 System.out.println(key + "--->" + map.get(key));
38 }
39 // 定义 BufferedReader输入流来读取URL的响应
40 in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
41 String line;
42 while ((line = in.readLine()) != null) {
43 result += line;
44 }
45 } catch (Exception e) {
46 System.out.println("发送GET请求出现异常！" + e);
47 e.printStackTrace();
48 }
49 // 使用finally块来关闭输入流
50 finally {
51 try {
52 if (in != null) {
53 in.close();
54 }
55 } catch (Exception e2) {
56 e2.printStackTrace();
57 }
58 }
59 return result;
60 }
61
62 /**
63 * 向指定 URL 发送POST方法的请求
64 *
65 * @param url 发送请求的 URL
66 * @param map/param 请求参数
67 *
68 * 请求参数，请求参数应该是 name1=value1&name2=value2 的形式。
69 * @return 所代表远程资源的响应结果
70 */
71 public static String sendPost(String url, String param) {
72 // public static String sendPost(String url, Map<String, String> map) {
73 // String param = getKeyVAlueSting(map); //如果是参数是String 就不需要再转换成name1=value1&name2=value2 的形式
74 System.out.println(param);
75 PrintWriter out = null;
76 BufferedReader in = null;
77 String result = "";
78 try {
79 URL realUrl = new URL(url);
80 // 打开和URL之间的连接
81 URLConnection conn = realUrl.openConnection();
82 // 设置通用的请求属性
83 conn.setRequestProperty("accept", "*/*");
84 conn.setRequestProperty("connection", "Keep-Alive");
85 conn.setRequestProperty("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
86 // 发送POST请求必须设置如下两行
87 conn.setDoOutput(true);
88 conn.setDoInput(true);
89 // 1.获取URLConnection对象对应的输出流
90 out = new PrintWriter(conn.getOutputStream());
91 // 2.中文有乱码的需要将PrintWriter改为如下
92 // out=new OutputStreamWriter(conn.getOutputStream(),"UTF-8")
93 // 发送请求参数
94 out.print(param);
95 // flush输出流的缓冲
96 out.flush();
97 // 定义BufferedReader输入流来读取URL的响应
98 in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
99 String line;
100 while ((line = in.readLine()) != null) {
101 result += line;
102 }
103 } catch (Exception e) {
104 System.out.println("发送 POST 请求出现异常！" + e);
105 e.printStackTrace();
106 }
107 // 使用finally块来关闭输出流、输入流
108 finally {
109 try {
110 if (out != null) {
111 out.close();
112 }
113 if (in != null) {
114 in.close();
115 }
116 } catch (IOException ex) {
117 ex.printStackTrace();
118 }
119 }
120 return result;
121 }
122
123 /**
124 * 获取key=value格式字符串
125 *
126 * @param map
127 * @return
128 */
129 public static String getKeyVAlueSting(Map<String, String> map) {
130 String sign = "";
131
132 Set<String> set = map.keySet();
133 for (String key : set) {
134 sign += key + "=" + map.get(key) + "&";
135 }
136
137 sign = sign.substring(0, sign.length() - 1);
138
139 return sign;
140 }
141
142 public static void main(String[] args) {
143 HttpRequest httpRequest = new HttpRequest();
144
145 //测试微信项目中通过post请求获取access token
146 String url = "https://api.weixin.qq.com/cgi-bin/token";
147 String param = "grant_type=client_credential&appid=wxfc27805daac56d9b&secret=12d853529003c68d0d2c9d4f87dd8b57";
148 String sr=HttpRequest.sendPost(url, param);
149 System.out.println(sr);
150 }
151 }
Json格式、Post请求：
1 /**Map转json post请求*/
2 public void a(){
3 Map<String, String> map = new LinkedHashMap<>();
4 map.put("type",type)
5 Map<String, String> requestMap = new LinkedHashMap<>();
6 requestMap.put("bg_url", bg_url);
7 requestMap.put("biz_code", biz_code);
8 requestMap.put("sign", sign);
9 map.put("data",requestMap);
10 // 组装请求参数,JSON格式
11 JSONObject json = new JSONObject(map);
12
13 String result=sendPostJson("请求地址url",json.toJSONString());
14 }
15
16 /**
17 * Post请求、 Json格式
18 * @param strURL
19 * @param params
20 * @return
21 */
22 public static String sendPostJson(String strURL, String params) {
23 BufferedReader reader = null;
24 try {
25 URL url = new URL(strURL);// 创建连接
26 HttpURLConnection connection = (HttpURLConnection) url.openConnection();
27 connection.setDoOutput(true);
28 connection.setDoInput(true);
29 connection.setUseCaches(false);
30 connection.setInstanceFollowRedirects(true);
31 connection.setRequestMethod("POST"); // 设置请求方式
32 connection.setRequestProperty("Content-Type", "application/json"); // 设置发送数据的格式
33 connection.connect();
34 OutputStreamWriter out = new OutputStreamWriter(connection.getOutputStream(), "UTF-8"); // utf-8编码
35 out.append(params);
36 out.flush();
37 out.close();
38 // 读取响应
39 reader = new BufferedReader(new InputStreamReader(connection.getInputStream(), "UTF-8"));
40 String line;
41 String res = "";
42 while ((line = reader.readLine()) != null) {
43 res += line;
44 }
45 reader.close();
46 return res;
47 } catch (IOException e) {
48 // TODO Auto-generated catch block
49 e.printStackTrace();
50 }
51 return ""; // 自定义错误信息
52 }
来源：https://www.cnblogs.com/shenjiangwei/p/11348678.html