介绍
HttpURLConnection类从java.net包可以用来编程发送Java HTTP请求. 在本文中,您将学习如何在Java程序中使用HttpURLConnection发送GET和POST请求,然后打印响应。
前提条件
对于这个HttpURLConnection示例,你应该已经完成了春季MVC教程(社区/教程/春季mvc教程),因为它有GET和POSTHTTP方法的URL。
考虑部署到一个本地主机的Tomcat服务器。
春天总结
Java HTTP GET 请求
localhost:8080/SpringMVCExample/
Java HTTP 请求登录页面
localhost:8080/SpringMVCExample/login
Java HTTP POST 请求
localhost:8080/SpringMVCExample?userName=Pankajlocalhost:8080/SpringMVCExample/login?userName=Pankaj&pwd=apple123- 用于多个参数
从形式中提取参数
登录页面的HTML包含以下形式:
1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "https://www.w3.org/TR/html4/loose.dtd">
2<html>
3<head>
4<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
5<title>Login Page</title>
6</head>
7<body>
8<form action="home" method="post">
9<input type="text" name="userName"><br>
10<input type="submit" value="Login">
11</form>
12</body>
13</html>
*「方法」為「POST」。 *「行動」為「主頁」。
- 「localhost:8080/SpringMVCExample/home」 *「用戶名」為「文字」。
您可以构建一个POST请求到:
1localhost:8080/SpringMVCExample/home?userName=Pankaj
这将作为HttpURLConnection示例的基础。
「HttpURLConnection」示例
以下是使用HttpURLConnection类来发送Java HTTP请求的步骤:
从GET或POST URL 字符串中创建一个URL对象
2.在HttpURLConnection的实例中返回的 URL 对象上调用openConnection()方法
3.在HttpURLConnection实例中设置请求方法(默认值为GET)
4.在HttpURLConnection实例中调用setRequestProperty()方法以设置请求标题值(如User-Agent、Accept-Language等)。
5.我们可以调用getResponseCode()来获取响应的 HTTP 代码。这样,我们
以下是使用HttpURLConnection发送JavaGET和POST请求的示例程序:
1[label HttpURLConnectionExample.java]
2package com.journaldev.utils;
3
4import java.io.BufferedReader;
5import java.io.IOException;
6import java.io.InputStreamReader;
7import java.io.OutputStream;
8import java.net.HttpURLConnection;
9import java.net.URL;
10
11public class HttpURLConnectionExample {
12
13 private static final String USER_AGENT = "Mozilla/5.0";
14
15 private static final String GET_URL = "https://localhost:9090/SpringMVCExample";
16
17 private static final String POST_URL = "https://localhost:9090/SpringMVCExample/home";
18
19 private static final String POST_PARAMS = "userName=Pankaj";
20
21 public static void main(String[] args) throws IOException {
22 sendGET();
23 System.out.println("GET DONE");
24 sendPOST();
25 System.out.println("POST DONE");
26 }
27
28 private static void sendGET() throws IOException {
29 URL obj = new URL(GET_URL);
30 HttpURLConnection con = (HttpURLConnection) obj.openConnection();
31 con.setRequestMethod("GET");
32 con.setRequestProperty("User-Agent", USER_AGENT);
33 int responseCode = con.getResponseCode();
34 System.out.println("GET Response Code :: " + responseCode);
35 if (responseCode == HttpURLConnection.HTTP_OK) { // success
36 BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));
37 String inputLine;
38 StringBuffer response = new StringBuffer();
39
40 while ((inputLine = in.readLine()) != null) {
41 response.append(inputLine);
42 }
43 in.close();
44
45 // print result
46 System.out.println(response.toString());
47 } else {
48 System.out.println("GET request did not work.");
49 }
50
51 }
52
53 private static void sendPOST() throws IOException {
54 URL obj = new URL(POST_URL);
55 HttpURLConnection con = (HttpURLConnection) obj.openConnection();
56 con.setRequestMethod("POST");
57 con.setRequestProperty("User-Agent", USER_AGENT);
58
59 // For POST only - START
60 con.setDoOutput(true);
61 OutputStream os = con.getOutputStream();
62 os.write(POST_PARAMS.getBytes());
63 os.flush();
64 os.close();
65 // For POST only - END
66
67 int responseCode = con.getResponseCode();
68 System.out.println("POST Response Code :: " + responseCode);
69
70 if (responseCode == HttpURLConnection.HTTP_OK) { //success
71 BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));
72 String inputLine;
73 StringBuffer response = new StringBuffer();
74
75 while ((inputLine = in.readLine()) != null) {
76 response.append(inputLine);
77 }
78 in.close();
79
80 // print result
81 System.out.println(response.toString());
82 } else {
83 System.out.println("POST request did not work.");
84 }
85 }
86
87}
编译并运行代码. 它将产生以下输出:
1[secondary_label Output]
2GET Response Code :: 200
3<html><head> <title>Home</title></head><body><h1> Hello world! </h1><P> The time on the server is March 6, 2015 9:31:04 PM IST. </P></body></html>
4GET DONE
5POST Response Code :: 200
6<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "https://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>User Home Page</title></head><body><h3>Hi Pankaj</h3></body></html>
7POST DONE
将此输出与浏览器 HTTP 响应进行比较。
如果你必须通过HTTPS协议发送GET和POST请求,那么你需要使用javax.net.ssl.HttpsURLConnection而不是java.net.HttpURLConnection。
结论
在本文中,您了解如何在Java程序中使用HttpURLConnection发送GET和POST请求,然后打印响应。
继续学习更多的Java教程(https://andsky.com/tags/java)。