可以使用ApacheHttpClient将HTTP请求从客户端代码发送到服务器。在上一个教程中,我们了解了如何使用HttpURLConnection 从Java程序本身执行GET和POST HTTP请求操作。今天我们将以相同的示例项目为例,但使用** Apache HttpClient** 来执行GET和POST请求操作。
Apache HttpClient
为了了解GET和POST请求的详细信息,我强烈建议您也看看早期的example ]。** ApacheHttpClient** 非常广泛地用于从Java程序本身发送HTTP请求。如果您使用的是Maven,那么您可以添加以下依赖项,它将包括使用Apache HttpClient所需的所有其他依赖项。
1<dependency>
2 <groupId>org.apache.httpcomponents</groupId>
3 <artifactId>httpclient</artifactId>
4 <version>4.4</version>
5</dependency>
但是,如果您没有使用Maven,则需要在项目构建路径中添加以下jar文件才能使其工作。
1.HTTPCLIENT-4.4.jar 2.HTTPcore-4.4.jar 3.Commons-Logging-1.2.jar 4.Commons-codec-1.9.jar
如果您使用的是其他版本的ApacheHttpClient,而不是Maven,那么只需创建一个临时Maven项目来获取兼容JAR的列表,如下图所示。现在只需将JAR复制到您的项目库目录中,它将使您避免任何兼容性问题,并将节省查找JAR和从互联网下载的时间。现在我们有了所有必需的依赖项,下面是使用ApacheHttpClient发送GET和POST请求的步骤。
1.使用helper类HttpClients
创建CloseableHttpClient
的实例。
2.根据HTTP请求类型创建HttpGet
或HttpPost
实例。
3.使用_addHeader_method添加必需的头部,如User-Agent、Accept-Ending等。
4.POST创建NameValuePair
列表,添加所有表单参数。然后将其设置为HttpPost实体。
5.通过执行HttpGet或HttpPost请求获取CloseableHttpResponse
。
6.从响应中获取需要的状态码、错误信息、响应html等详细信息。
7.最后关闭ApacheHttpClient
资源。
下面是我们拥有的最后一个程序,展示了如何在Java程序本身中使用Apache HttpClient 执行HTTP GET和POST请求。
1package com.journaldev.utils;
2
3import java.io.BufferedReader;
4import java.io.IOException;
5import java.io.InputStreamReader;
6import java.util.ArrayList;
7import java.util.List;
8
9import org.apache.http.HttpEntity;
10import org.apache.http.NameValuePair;
11import org.apache.http.client.entity.UrlEncodedFormEntity;
12import org.apache.http.client.methods.CloseableHttpResponse;
13import org.apache.http.client.methods.HttpGet;
14import org.apache.http.client.methods.HttpPost;
15import org.apache.http.impl.client.CloseableHttpClient;
16import org.apache.http.impl.client.HttpClients;
17import org.apache.http.message.BasicNameValuePair;
18
19public class ApacheHttpClientExample {
20
21 private static final String USER_AGENT = "Mozilla/5.0";
22
23 private static final String GET_URL = "https://localhost:9090/SpringMVCExample";
24
25 private static final String POST_URL = "https://localhost:9090/SpringMVCExample/home";
26
27 public static void main(String[] args) throws IOException {
28 sendGET();
29 System.out.println("GET DONE");
30 sendPOST();
31 System.out.println("POST DONE");
32 }
33
34 private static void sendGET() throws IOException {
35 CloseableHttpClient httpClient = HttpClients.createDefault();
36 HttpGet httpGet = new HttpGet(GET_URL);
37 httpGet.addHeader("User-Agent", USER_AGENT);
38 CloseableHttpResponse httpResponse = httpClient.execute(httpGet);
39
40 System.out.println("GET Response Status:: "
41 + httpResponse.getStatusLine().getStatusCode());
42
43 BufferedReader reader = new BufferedReader(new InputStreamReader(
44 httpResponse.getEntity().getContent()));
45
46 String inputLine;
47 StringBuffer response = new StringBuffer();
48
49 while ((inputLine = reader.readLine()) != null) {
50 response.append(inputLine);
51 }
52 reader.close();
53
54 // print result
55 System.out.println(response.toString());
56 httpClient.close();
57 }
58
59 private static void sendPOST() throws IOException {
60
61 CloseableHttpClient httpClient = HttpClients.createDefault();
62 HttpPost httpPost = new HttpPost(POST_URL);
63 httpPost.addHeader("User-Agent", USER_AGENT);
64
65 List<NameValuePair> urlParameters = new ArrayList<NameValuePair>();
66 urlParameters.add(new BasicNameValuePair("userName", "Pankaj Kumar"));
67
68 HttpEntity postParams = new UrlEncodedFormEntity(urlParameters);
69 httpPost.setEntity(postParams);
70
71 CloseableHttpResponse httpResponse = httpClient.execute(httpPost);
72
73 System.out.println("POST Response Status:: "
74 + httpResponse.getStatusLine().getStatusCode());
75
76 BufferedReader reader = new BufferedReader(new InputStreamReader(
77 httpResponse.getEntity().getContent()));
78
79 String inputLine;
80 StringBuffer response = new StringBuffer();
81
82 while ((inputLine = reader.readLine()) != null) {
83 response.append(inputLine);
84 }
85 reader.close();
86
87 // print result
88 System.out.println(response.toString());
89 httpClient.close();
90
91 }
92
93}
当我们运行上面的程序时,我们得到与浏览器中接收到的类似的输出html。
1GET Response Status:: 200
2<html><head> <title>Home</title></head><body><h1> Hello world! </h1><P> The time on the server is March 7, 2015 1:01:22 AM IST. </P></body></html>
3GET DONE
4POST Response Status:: 200
5<!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 Kumar</h3></body></html>
6POST DONE
以上就是ApacheHttpClient示例,它包含了许多您可以使用的实用程序方法。所以我建议你去看看,以便更好地了解。